Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia
Identifieur interne : 001246 ( Istex/Corpus ); précédent : 001245; suivant : 001247Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia
Auteurs : Ville T. Peltola ; K. Gopal Murti ; Jonathan A. MccullersSource :
- The Journal of Infectious Diseases [ 0022-1899 ] ; 2005.
Abstract
Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of Streptococcus pneumoniae and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality
Url:
DOI: 10.1086/430954
Links to Exploration step
ISTEX:D587CC152DC4685067505883F679482ED1939AE2Le document en format XML
<record><TEI wicri:istexFullTextTei="biblStruct"><teiHeader><fileDesc><titleStmt><title>Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia</title><author><name sortKey="Peltola, Ville T" sort="Peltola, Ville T" uniqKey="Peltola V" first="Ville T." last="Peltola">Ville T. Peltola</name><affiliation><mods:affiliation>Infectious Diseases and</mods:affiliation></affiliation></author><author><name sortKey="Murti, K Gopal" sort="Murti, K Gopal" uniqKey="Murti K" first="K. Gopal" last="Murti">K. Gopal Murti</name><affiliation><mods:affiliation>Molecular Biotechnology, St. Jude Children’s Research Hospital, Memphis, Tennessee</mods:affiliation></affiliation></author><author><name sortKey="Mccullers, Jonathan A" sort="Mccullers, Jonathan A" uniqKey="Mccullers J" first="Jonathan A." last="Mccullers">Jonathan A. Mccullers</name><affiliation><mods:affiliation>Infectious Diseases and</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: jon.mccullers@stjude.org</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:D587CC152DC4685067505883F679482ED1939AE2</idno><date when="2005" year="2005">2005</date><idno type="doi">10.1086/430954</idno><idno type="url">https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/fulltext.pdf</idno><idno type="wicri:Area/Istex/Corpus">001246</idno><idno type="wicri:explorRef" wicri:stream="Istex" wicri:step="Corpus" wicri:corpus="ISTEX">001246</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a" type="main" xml:lang="en">Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia<ref type="fn" target="#fn1"></ref></title><author><name sortKey="Peltola, Ville T" sort="Peltola, Ville T" uniqKey="Peltola V" first="Ville T." last="Peltola">Ville T. Peltola</name><affiliation><mods:affiliation>Infectious Diseases and</mods:affiliation></affiliation></author><author><name sortKey="Murti, K Gopal" sort="Murti, K Gopal" uniqKey="Murti K" first="K. Gopal" last="Murti">K. Gopal Murti</name><affiliation><mods:affiliation>Molecular Biotechnology, St. Jude Children’s Research Hospital, Memphis, Tennessee</mods:affiliation></affiliation></author><author><name sortKey="Mccullers, Jonathan A" sort="Mccullers, Jonathan A" uniqKey="Mccullers J" first="Jonathan A." last="Mccullers">Jonathan A. Mccullers</name><affiliation><mods:affiliation>Infectious Diseases and</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: jon.mccullers@stjude.org</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j" type="main">The Journal of Infectious Diseases</title><title level="j" type="abbrev">The Journal of Infectious Diseases</title><idno type="ISSN">0022-1899</idno><idno type="eISSN">1537-6613</idno><imprint><publisher>The University of Chicago Press</publisher><date when="2005-07-15">2005</date><biblScope unit="vol">192</biblScope><biblScope unit="issue">2</biblScope><biblScope unit="page" from="249">249</biblScope><biblScope unit="page" to="257">257</biblScope></imprint><idno type="ISSN">0022-1899</idno></series></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0022-1899</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract">Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of Streptococcus pneumoniae and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality</div></front></TEI><istex><corpusName>oup</corpusName><keywords><teeft><json:string>pneumoniae</json:string><json:string>viral</json:string><json:string>neuraminidase</json:string><json:string>recombinant</json:string><json:string>secondary bacterial pneumonia</json:string><json:string>recombinant virus</json:string><json:string>sialic</json:string><json:string>virion</json:string><json:string>oseltamivir</json:string><json:string>gure</json:string><json:string>streptococcus pneumoniae</json:string><json:string>pneumoniae strain</json:string><json:string>sialic acid</json:string><json:string>july</json:string><json:string>pneumonia</json:string><json:string>pneumococcal</json:string><json:string>hemagglutinin</json:string><json:string>virus</json:string><json:string>datum</json:string><json:string>mouse model</json:string><json:string>bacterial pneumonia</json:string><json:string>streptococcus</json:string><json:string>higher mortality</json:string><json:string>gold particle</json:string><json:string>human virus</json:string><json:string>pandemic</json:string><json:string>jude research hospital</json:string><json:string>mdck cell</json:string><json:string>gene segment</json:string><json:string>virus neuraminidase</json:string><json:string>other virus</json:string><json:string>high level</json:string><json:string>human population</json:string><json:string>substrate concentration</json:string><json:string>monoclonal antibody</json:string><json:string>lung viral titer</json:string><json:string>embryonated egg</json:string><json:string>immunoelectron microscopy</json:string><json:string>excess mortality</json:string><json:string>cell culture</json:string><json:string>adherence assay</json:string><json:string>mouse</json:string><json:string>high mortality</json:string><json:string>viral stock</json:string><json:string>parental strain</json:string><json:string>internal gene segment</json:string><json:string>standard method</json:string><json:string>parental virus</json:string><json:string>higher level</json:string><json:string>thiobarbituric acid assay</json:string><json:string>interpandemic period</json:string><json:string>bacterial superinfection</json:string><json:string>positive staining</json:string><json:string>viral strain</json:string><json:string>other factor</json:string><json:string>infectious disease</json:string><json:string>next pandemic</json:string><json:string>virus infectious</json:string><json:string>weight loss</json:string><json:string>respiratory tract</json:string><json:string>anesthetized mouse</json:string><json:string>relative light unit</json:string><json:string>bacterial adherence</json:string><json:string>chicken virus</json:string><json:string>gene sequence</json:string><json:string>xenogen corp</json:string><json:string>common background</json:string><json:string>viral protein</json:string><json:string>embryonated chicken egg</json:string><json:string>representative virus</json:string><json:string>substrate preference</json:string><json:string>oseltamivir treatment</json:string><json:string>highest level</json:string><json:string>pneumococcal pneumonia</json:string><json:string>survival curve</json:string><json:string>representative mouse</json:string><json:string>virus infection</json:string><json:string>excess death</json:string><json:string>different virus</json:string><json:string>viral infection</json:string><json:string>viral titer</json:string><json:string>previous study</json:string><json:string>public health</json:string><json:string>lethal synergism</json:string><json:string>microb pathog</json:string><json:string>cell surface carbohydrate</json:string><json:string>chinchilla tubotympanum</json:string><json:string>proc natl acad</json:string><json:string>mortality</json:string></teeft></keywords><author><json:item><name>Ville T. Peltola</name><affiliations><json:string>Infectious Diseases and</json:string></affiliations></json:item><json:item><name>K. Gopal Murti</name><affiliations><json:string>Molecular Biotechnology, St. Jude Children’s Research Hospital, Memphis, Tennessee</json:string></affiliations></json:item><json:item><name>Jonathan A. McCullers</name><affiliations><json:string>Infectious Diseases and</json:string><json:string>E-mail: jon.mccullers@stjude.org</json:string></affiliations></json:item></author><arkIstex>ark:/67375/HXZ-XXR113JR-N</arkIstex><language><json:string>unknown</json:string></language><originalGenre><json:string>research-article</json:string></originalGenre><abstract>Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of Streptococcus pneumoniae and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality</abstract><qualityIndicators><score>7.443</score><pdfWordCount>5800</pdfWordCount><pdfCharCount>35306</pdfCharCount><pdfVersion>1.4</pdfVersion><pdfPageCount>9</pdfPageCount><pdfPageSize>612 x 792 pts (letter)</pdfPageSize><pdfWordsPerPage>644</pdfWordsPerPage><pdfText>true</pdfText><refBibsNative>true</refBibsNative><abstractWordCount>148</abstractWordCount><abstractCharCount>1057</abstractCharCount><keywordCount>0</keywordCount></qualityIndicators><title>Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia</title><pmid><json:string>15962219</json:string></pmid><genre><json:string>research-article</json:string></genre><host><title>The Journal of Infectious Diseases</title><language><json:string>unknown</json:string></language><issn><json:string>0022-1899</json:string></issn><eissn><json:string>1537-6613</json:string></eissn><publisherId><json:string>jid</json:string></publisherId><volume>192</volume><issue>2</issue><pages><first>249</first><last>257</last></pages><genre><json:string>journal</json:string></genre></host><namedEntities><unitex><date><json:string>1968</json:string><json:string>2005</json:string><json:string>1957</json:string><json:string>1997</json:string><json:string>1990s</json:string><json:string>50s</json:string><json:string>1918</json:string><json:string>1986 or 1997</json:string><json:string>2003</json:string></date><geogName></geogName><orgName><json:string>Jude Children’s Research Hospital Animal Care and Use</json:string><json:string>University of Oklahoma Health Sciences Center</json:string><json:string>Jude Children’s Research Hospital</json:string><json:string>Jude Children’s Research Hospital, Memphis, Tennessee Secondary</json:string><json:string>Xenogen Corp.</json:string><json:string>Centers for Disease Control and Prevention</json:string></orgName><orgName_funder></orgName_funder><orgName_provider></orgName_provider><persName><json:string>Jonathan A. McCullers</json:string><json:string>Hong Kong</json:string><json:string>D. R. Perez</json:string><json:string>R. G. Webster</json:string><json:string>L. Widjaja</json:string><json:string>Jackson Laboratory</json:string><json:string>K. Gopal</json:string><json:string>G. Air</json:string><json:string>E. Hoffmann</json:string><json:string>C. Controls</json:string><json:string>E. I. Tuomanen</json:string><json:string>R. McKeon</json:string><json:string>Mice</json:string><json:string>Gillian Air</json:string><json:string>Jun Yu</json:string><json:string>Kevin Francis</json:string><json:string>Robert Webster</json:string></persName><placeName><json:string>Singapore</json:string><json:string>Puerto Rico</json:string><json:string>Japan</json:string><json:string>Leningrad</json:string><json:string>Tokyo</json:string></placeName><ref_url></ref_url><ref_bibl><json:string>[34]</json:string><json:string>[30, 32]</json:string><json:string>Thompson et al. [2]</json:string><json:string>[29]</json:string><json:string>[33]</json:string><json:string>[39]</json:string><json:string>[21]</json:string><json:string>[38]</json:string><json:string>Housworth et al. [34]</json:string><json:string>[31]</json:string><json:string>[13, 14]</json:string><json:string>[37]</json:string><json:string>Liu et al. [35]</json:string><json:string>[41]</json:string><json:string>[25]</json:string><json:string>[2, 34, 36]</json:string><json:string>[9]</json:string><json:string>[40]</json:string><json:string>[2]</json:string><json:string>[13]</json:string><json:string>Peltola et al.</json:string><json:string>[19]</json:string></ref_bibl><bibl></bibl></unitex></namedEntities><ark><json:string>ark:/67375/HXZ-XXR113JR-N</json:string></ark><categories><wos><json:string>1 - science</json:string><json:string>2 - microbiology</json:string><json:string>2 - infectious diseases</json:string><json:string>2 - immunology</json:string></wos><scienceMetrix><json:string>1 - health sciences</json:string><json:string>2 - biomedical research</json:string><json:string>3 - microbiology</json:string></scienceMetrix><scopus><json:string>1 - Health Sciences</json:string><json:string>2 - Medicine</json:string><json:string>3 - Infectious Diseases</json:string><json:string>1 - Health Sciences</json:string><json:string>2 - Medicine</json:string><json:string>3 - Immunology and Allergy</json:string></scopus><inist><json:string>1 - sciences appliquees, technologies et medecines</json:string><json:string>2 - sciences biologiques et medicales</json:string><json:string>3 - sciences medicales</json:string></inist></categories><publicationDate>2005</publicationDate><copyrightDate>2005</copyrightDate><doi><json:string>10.1086/430954</json:string></doi><id>D587CC152DC4685067505883F679482ED1939AE2</id><score>1</score><fulltext><json:item><extension>pdf</extension><original>true</original><mimetype>application/pdf</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/fulltext.pdf</uri></json:item><json:item><extension>zip</extension><original>false</original><mimetype>application/zip</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/bundle.zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/fulltext.tei"><teiHeader><fileDesc><titleStmt><title level="a" type="main">Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia
</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>The University of Chicago Press</publisher><availability><licence>© 2005 by the Infectious Diseases Society of America</licence></availability><date type="Copyright" when="2005">2005</date><date when="2005-07-15">2005</date></publicationStmt><notesStmt><note type="content-type" source="research-article" scheme="https://content-type.data.istex.fr/ark:/67375/XTP-1JC4F85T-7">research-article</note><note type="publication-type" scheme="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</note></notesStmt><sourceDesc><biblStruct type="article"><analytic><title level="a" type="main" xml:lang="en">Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia<ref type="fn" target="#fn1"></ref></title><author xml:id="author-0000"><persName><surname>Peltola</surname><forename type="first">Ville T.</forename></persName><affiliation><orgName type="">Infectious Diseases and</orgName></affiliation></author><author xml:id="author-0001"><persName><surname>Murti</surname><forename type="first">K. Gopal</forename></persName><affiliation><orgName type="department">Molecular Biotechnology</orgName><address><addrLine>St Jude Children’s Research Hospital, Memphis, Tennessee</addrLine></address></affiliation></author><author xml:id="author-0002" role="corresp"><persName><surname>McCullers</surname><forename type="first">Jonathan A.</forename></persName><affiliation><orgName type="">Infectious Diseases and</orgName></affiliation></author><idno type="istex">D587CC152DC4685067505883F679482ED1939AE2</idno><idno type="ark">ark:/67375/HXZ-XXR113JR-N</idno><idno type="DOI">10.1086/430954</idno></analytic><monogr><title level="j" type="main">The Journal of Infectious Diseases</title><title level="j" type="abbrev">The Journal of Infectious Diseases</title><idno type="hwp">jinfdis</idno><idno type="publisher-id">jid</idno><idno type="pISSN">0022-1899</idno><idno type="eISSN">1537-6613</idno><imprint><publisher>The University of Chicago Press</publisher><date when="2005-07-15">2005</date><biblScope unit="vol">192</biblScope><biblScope unit="issue">2</biblScope><biblScope unit="page" from="249">249</biblScope><biblScope unit="page" to="257">257</biblScope></imprint></monogr></biblStruct></sourceDesc></fileDesc><encodingDesc><schemaRef type="ODD" url="https://xml-schema.delivery.istex.fr/tei-istex.odd"></schemaRef><appInfo><application ident="pub2tei" version="1.0.10" when="2019-12-09"><label>pub2TEI-ISTEX</label><desc>A set of style sheets for converting XML documents encoded in various scientific publisher formats into a common TEI format.
<ref target="http://www.tei-c.org/">We use TEI</ref></desc></application></appInfo></encodingDesc><profileDesc><abstract><p>Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of <hi rend="italic">Streptococcus pneumoniae</hi> and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality</p></abstract><textClass ana="subject"><keywords scheme="heading"><term>Major Articles and Brief Reports</term></keywords></textClass><langUsage><language ident="EN"></language></langUsage></profileDesc><revisionDesc><change when="2019-12-09" who="#istex" xml:id="pub2tei">formatting</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><extension>txt</extension><original>false</original><mimetype>text/plain</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/fulltext.txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="corpus oup, element #text not found" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0" encoding="utf-8"</istex:xmlDeclaration><istex:docType PUBLIC="-//NLM//DTD Journal Publishing DTD v2.3 20070202//EN" URI="journalpublishing.dtd" name="istex:docType"></istex:docType><istex:document><article article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="hwp">jinfdis</journal-id>
<journal-id journal-id-type="publisher-id">jid</journal-id>
<journal-title>The Journal of Infectious Diseases</journal-title>
<abbrev-journal-title>The Journal of Infectious Diseases</abbrev-journal-title>
<issn pub-type="ppub">0022-1899</issn>
<issn pub-type="epub">1537-6613</issn>
<publisher>
<publisher-name>The University of Chicago Press</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1086/430954</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Major Articles and Brief Reports</subject>
<subj-group subj-group-type="heading">
<subject>Viruses</subject>
<subj-group subj-group-type="heading">
<subject>Major Articles</subject>
</subj-group>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia<xref ref-type="fn" rid="fn1"></xref>
</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Peltola</surname>
<given-names>Ville T.</given-names>
</name>
<xref ref-type="aff" rid="aff1">1</xref>
<xref ref-type="fn" rid="fn2">a</xref>
</contrib>
<contrib contrib-type="author">
<name>
<surname>Murti</surname>
<given-names>K. Gopal</given-names>
</name>
<xref ref-type="aff" rid="aff2">2</xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name>
<surname>McCullers</surname>
<given-names>Jonathan A.</given-names>
</name>
<xref ref-type="aff" rid="aff1">1</xref>
</contrib>
<aff>Departments of</aff>
<aff id="aff1">
<label>1</label>Infectious Diseases and</aff>
<aff id="aff2">
<label>2</label>Molecular Biotechnology, St. Jude Children’s Research Hospital, Memphis, Tennessee</aff>
</contrib-group>
<author-notes>
<corresp id="cor1">Reprints or correspondence: Dr. Jonathan A. McCullers, Dept. of Infectious Diseases, St. Jude Children’s Research Hospital, 332 N. Lauderdale St., Memphis, TN 38105-2794 (<email>jon.mccullers@stjude.org</email>)</corresp>
</author-notes>
<pub-date pub-type="ppub">
<day>15</day>
<month>7</month>
<year>2005</year>
</pub-date>
<volume>192</volume>
<issue>2</issue>
<fpage>249</fpage>
<lpage>257</lpage>
<history>
<date date-type="received">
<day>19</day>
<month>1</month>
<year>2005</year>
</date>
<date date-type="accepted">
<day>24</day>
<month>2</month>
<year>2005</year>
</date>
</history>
<copyright-statement>© 2005 by the Infectious Diseases Society of America</copyright-statement>
<copyright-year>2005</copyright-year>
<abstract>
<p>Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of <italic>Streptococcus pneumoniae</italic> and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality</p>
</abstract>
</article-meta>
</front>
<body>
<p>Influenza A virus causes epidemics annually and pandemics several times a century. Two subtypes of influenza A virus, H3N2 and H1N1, are presently circulating in the human population. Epidemics caused by H3N2 are associated with higher mortality in human populations than are epidemics caused by H1N1 or influenza B virus [<xref ref-type="bibr" rid="ref1">1</xref>, <xref ref-type="bibr" rid="ref2">2</xref>]. Viruses that cause pandemics are defined as those that acquire a new hemagglutinin (HA), have a high attack rate, and spread globally. Infection with them is generally considered to result in high mortality. Understanding what factors are associated with increased mortality will help us prepare for the next influenza pandemic</p>
<p>It has been suggested that antigenic novelty accounts for increased mortality during pandemics, but a comparison of mortality estimates between different pandemic years and between interpandemic years indicates that other factors are also involved. The capability of influenza viral strains to predispose to bacterial superinfection may be a factor that determines mortality during an epidemic. Secondary bacterial pneumonia is an important cause of influenza-associated death during both pandemic and interpandemic periods. Results of studies performed during the influenza pandemics of 1957 and 1968 revealed that there was a bacterial etiology in ∼70% of patients with fatal or life-threatening pneumonia [<xref ref-type="bibr" rid="ref3">3</xref>, <xref ref-type="bibr" rid="ref4">4</xref>]. During interpandemic periods, 44%–57% of patients hospitalized with influenza have bacterial pneumonia [<xref ref-type="bibr" rid="ref5">5</xref>
<xref ref-type="bibr" rid="ref6"></xref>
<xref ref-type="bibr" rid="ref7"></xref>–<xref ref-type="bibr" rid="ref8">8</xref>], and—although the estimate varies from year to year, depending on the viral strain that is circulating—on average, 25% of all influenza-associated deaths are due to secondary bacterial pneumonia [<xref ref-type="bibr" rid="ref9">9</xref>]</p>
<p>
<italic>Streptococcus pneumoniae</italic> is the leading cause of community-acquired pneumonia [<xref ref-type="bibr" rid="ref10">10</xref>] and is a major cause of pneumonia and other bacterial complications of influenza. We developed a mouse model of synergism between influenza virus and <italic>S. pneumoniae</italic> [<xref ref-type="bibr" rid="ref11">11</xref>, <xref ref-type="bibr" rid="ref12">12</xref>], and, using this model, we established that viral neuraminidase (NA) is an important factor in viral-bacterial synergism [<xref ref-type="bibr" rid="ref13">13</xref>, <xref ref-type="bibr" rid="ref14">14</xref>]. NA activity is needed by an influenza virus to release newly synthesized virus by cleaving sialic acid both from host cell glycoconjugates and from oligosaccharides of viral HA and NA. This action of NA also promotes adherence and invasion of <italic>S. pneumoniae</italic> because cleavage of sialic acid from the surface of host cells exposes cryptic receptors for <italic>S. pneumoniae</italic> [<xref ref-type="bibr" rid="ref15">15</xref>
<xref ref-type="bibr" rid="ref16"></xref>
<xref ref-type="bibr" rid="ref17"></xref>–<xref ref-type="bibr" rid="ref18">18</xref>]. Bacteria that can successfully invade the lower respiratory tract typically express NA for this purpose. That generally higher levels of NA activity are found in modern H3N2 than in H1N1 viruses [<xref ref-type="bibr" rid="ref19">19</xref>] is consistent with the hypothesis that high levels of NA activity lead to higher mortality from secondary bacterial pneumonia. We sought to define the viral-specific NA activity in several influenza viruses within a subtype and correlate it with the biological characteristics of secondary bacterial pneumonia</p>
<sec id="S1">
<title>Materials and Methods</title>
<p>
<bold>
<italic>Generation of recombinant influenza viruses</italic>
</bold>Recombinant influenza viruses were produced using an established 8-plasmid reverse-genetics system [<xref ref-type="bibr" rid="ref20">20</xref>] in a coculture of 293T and MDCK cells and parental viruses from the influenza virus repository at St. Jude Children’s Research Hospital. Internal gene segments of A/Puerto Rico/8/34 (subtype H1N1; hereafter referred to as “PR8”) [<xref ref-type="bibr" rid="ref21">21</xref>], the HA gene segment of the human influenza virus A/Hong Kong/1/68 (subtype H3N2; hereafter referred to as “HK68”), and the HA and NA gene segments of the human influenza virus A/Fujian/411/02 (subtype H3N2; hereafter referred to as “Fuj02”) had been cloned into the pHW2000 plasmid previously. NA gene segments of the human H2N2 influenza viruses A/Singapore/1/57 (Sing57) and A/England/12/62 (Eng62); the human H3N2 influenza viruses HK68, A/Memphis/102/72 (Mem72), A/Leningrad/516/86 (Len86), and A/Sydney/5/97 (Syd97); and the chicken H9N2 influenza virus A/Chicken/Hong Kong/WF2/99 (WF2) were amplified by polymerase chain reaction (PCR) and cloned into the pHW2000 plasmid. HA and NA genes were sequenced, and their identities were confirmed by comparison of their sequences with those of the parental strain. Viral stocks were grown in embryonated chicken eggs, centrifuged on a 25%/75% sucrose cushion, pelleted, and resuspended in PBS</p>
<p>
<bold>
<italic>Pneumococci</italic>
</bold>A type 3 strain of <italic>S. pneumoniae</italic> that had been transformed with the <italic>lux</italic> operon (provided by Kevin Francis and Jun Yu, Xenogen Corp.) was used in mouse studies. R6T, an unencapsulated laboratory strain of <italic>S. pneumoniae</italic>, was used in adherence assays</p>
<p>
<bold>
<italic>Characterization of recombinant influenza viruses in cell culture, embryonated eggs, and mice</italic>
</bold>Allantoic fluid and concentrated viral stocks were titrated in MDCK cells and embryonated chicken eggs by standard methods to obtain the TCID<sub>50</sub> and EID<sub>50</sub>. Groups of 4 mice were infected with serial dilutions of the allantoic fluid stocks to obtain an MLD<sub>50</sub> by the method of Reed and Muench [<xref ref-type="bibr" rid="ref22">22</xref>]. For lung viral titers, mouse lung homogenates were titrated in MDCK cells as described elsewhere [<xref ref-type="bibr" rid="ref12">12</xref>]</p>
<p>
<bold>
<italic>NA activity</italic>
</bold>The total level of NA activity in concentrated influenza virus diluted in calcium saline buffer to a final substrate concentration of 10 μmol/L was determined by measuring the fluorescence of 4-methylumbelliferone cleaved from 2′-(4-methylumbelliferyl)-<italic>N-</italic>acetylneuraminic acid (Mu-NANA; Sigma) as described elsewhere [<xref ref-type="bibr" rid="ref23">23</xref>]. The relative linkage specificity of NA was determined using <italic>N-</italic>acetylneuraminic acid (NANA) bound to lactose through either α(2–3) or α(2–6) linkage as a substrate. Fetuin was used as a substrate to measure the level of NA activity against a large molecule with both α(2–3) and α(2–6) sialic acid linkages. The amount of sialic acid released from NANA-lactose (substrate concentration, 0.1 mmol/L) or fetuin (substrate concentration, 6.1 mmol/L) was measured by the thiobarbituric acid assay, as described elsewhere [<xref ref-type="bibr" rid="ref24">24</xref>]. All reactions were performed for 30 min at 37°C. To relate NA activity to the predominant viral proteins, virus concentrates were run on 10% Tris-HCl gels. After staining with Sypro orange (Amersham Pharmacia), HA and nucleoprotein (NP) bands were quantified using a laser-excited gel scanner</p>
<p>
<bold>
<italic>Immunoelectron microscopy (IEM)</italic>
</bold>IEM was performed, as described elsewhere [<xref ref-type="bibr" rid="ref25">25</xref>], using a mixture of monoclonal antibodies against 7 different N2 NAs representing the range of NAs studied. Anti-NA monoclonal antibodies 152/6 (A/Japan/1/57), 25/4 (A/Tokyo/3/67), 5/2 (A/Aichi/2/68), 1/1 (A/Udorn/307/72), and E12-8 (A/Memphis/12/85) were provided by Dr. Robert Webster (St. Jude Children’s Research Hospital) [<xref ref-type="bibr" rid="ref26">26</xref>, <xref ref-type="bibr" rid="ref27">27</xref>], and Mem4 and Mem5 (A/Memphis/31/98) were provided by Dr. Gillian Air (University of Oklahoma Health Sciences Center) [<xref ref-type="bibr" rid="ref28">28</xref>]. Negative staining was performed with 2% phosphotungstic acid, and positive staining was performed with ethanolic uranyl acetate. Gold particles representing the amount of NA per virion were counted in positively stained samples</p>
<p>
<bold>
<italic>Adherence assay</italic>
</bold>Adherence assays were performed using standard methods, as described elsewhere [<xref ref-type="bibr" rid="ref13">13</xref>], using <italic>S. pneumoniae</italic> strain R6T after a 30-min incubation with influenza virus at 37°C. Controls were treated identically, except that influenza virus was not added. For inhibition of viral NA, 30 min before incubation with monolayers, the oseltamivir prodrug Ro 64-0796 (Roche Products) was added to the viral suspension at a concentration of 10 μmol/L (the concentration of the active metabolite oseltamivir carboxylate was not determined)</p>
<p>
<bold>
<italic>Mice and infection model</italic>
</bold>Experimental procedures were performed after the mice (8–10-week-old female BALB/c; Jackson Laboratory) were anesthetized with inhaled 2.5% isoflurane (Baxter Healthcare). Infectious agents were administered intranasally in a volume of 100 μL of PBS. For synergism between influenza virus and <italic>S. pneumoniae</italic> mice were infected first with influenza virus and then 7 days later with <italic>S. pneumoniae</italic> and were monitored at least daily for illness and mortality. Groups of 9–10 mice were infected with 0.01 MLD<sub>50</sub> of influenza virus and 100 cfu of <italic>S. pneumoniae</italic> and were imaged daily. Instead of using a fixed number of infectious particles, we calculated doses of influenza virus in relation to the MLD<sub>50</sub>, so that weight loss, viral lung titers, and damage to the respiratory tract before bacterial challenge were the same between groups. Mice found to be moribund were euthanized and were considered to have died that day. All animal experiments were approved by the St. Jude Children’s Research Hospital Animal Care and Use Committee and were performed under biosafety level 2 conditions</p>
<p>
<bold>
<italic>Imaging of live mice</italic>
</bold>Anesthetized mice were imaged for 20 s by an IVIS CCD camera (Xenogen Corp.). The total emission of photons from selected and defined areas within the images of each mouse was quantified by LivingImage software (version 2.20; Xenogen Corp.), as described elsewhere [<xref ref-type="bibr" rid="ref29">29</xref>], and was expressed as relative light units (rlu). Pneumonia was defined as detection of >20,000 rlu/min from the thorax</p>
<p>
<bold>
<italic>Statistical analysis</italic>
</bold>Comparison of survival rates in the groups of mice was performed using the Mantel-Cox χ<sup>2</sup> test on Kaplan-Meier survival data, and comparisons of bacterial adherence were made using 1-way analysis of variance followed by Dunn’s test. P<.05 was considered to be statistically significant</p>
</sec>
<sec id="S2">
<title>Results</title>
<p>
<bold>
<italic>Recombinant influenza viruses differing only in NA</italic>
</bold> Influenza viruses with an N2 NA have been circulating in the human population since 1957. Representative NA genes were selected from 6 human pandemic and interpandemic H2N2 and H3N2 influenza viruses isolated between 1957 and 2004. Recombinant influenza viruses that differed only in their NAs were rescued on the common background of 7 gene segments (6 internal gene segments from PR8 and the HK68 HA gene). For comparison with these human influenza viruses, an influenza virus that had an NA gene from a 1999 chicken H9N2 influenza virus was also rescued. All the recombinant viruses grew to high titers in embryonated eggs (<xref ref-type="table" rid="tb1">table 1</xref>). They caused morbidity and mortality in mice and thus were suitable for further study of viral-bacterial synergism in a mouse model. The MLD<sub>50</sub> of the influenza viruses that had a human NA gene were similar, whereas the MLD<sub>50</sub>s of the influenza virus that had the chicken virus NA gene and of the mouse-adapted parental strain PR8 were 3–4 logs lower. An influenza virus that had the Fuj02 NA gene could not be rescued when the Fuj02 NA gene was paired with the HK68 HA gene, and it was therefore excluded from comparison with other isogenic influenza viruses. However, it was rescued when it had its own HA gene (Fuj02 HA), and a comparison influenza virus containing the Fuj02 HA gene and the Mem72 NA gene was also rescued. Because mutations may be generated during rescue of influenza viruses when the 8-plasmid system is used and during passage of influenza viruses in eggs, NA gene sequences of the recombinant influenza viruses were compared with published NA gene sequences of the parental viruses. Site-directed mutagenesis was used to ensure that the NA gene of all influenza viruses matched the GenBank sequence of the NA gene of the target influenza viruses</p>
<p>
<bold>
<italic>NA activity in recombinant influenza viruses</italic>
</bold>To characterize this set of viral tools, the level of NA activity in concentrated influenza viruses was measured using Mu-NANA as the substrate [<xref ref-type="bibr" rid="ref23">23</xref>] and was expressed as a function of the amount of NA protein (<xref ref-type="fig" rid="Fig1">figure 1</xref>). The level of NA activity was highest in the pandemic strain containing the Sing57 NA. The level of NA activity decreased and was lowest in the influenza virus containing the HK68 NA. From 1968 to 1997, a general increase in the level of NA activity was seen, such that the influenza virus containing the Syd97 NA had the second-highest level of NA activity. Although a direct comparison with the isogenic set of influenza viruses was not possible, both the wild-type Fuj02 influenza virus and the recombinant influenza virus that had the Fuj02 NA had NA activity levels that were similar to that of the influenza virus containing the Syd97 NA (data not shown). WF2 NA from a recent chicken strain of the H9N2 subtype had a very low level of NA activity—only 2% of that of the influenza virus containing the Sing57 NA. A similar pattern of NA activity was seen when values were expressed relative to the amount of the most abundant viral proteins, HA and NP, or when fetuin was used as a substrate: a decline in NA activity in the influenza viruses isolated from 1957 to 1968, then a gradual increase in those isolated from 1968 to 2002 (data not shown)</p>
<p>Changes in the amino acid sequences of the NAs of influenza viruses isolated between 1957 and 1962 have been associated with a decrease in the level of NA activity, which suggests that these structural changes are responsible for the observed differences [<xref ref-type="bibr" rid="ref30">30</xref>]. To determine whether these differences might reflect different preferences for α(2–3)– or α(2–6)–linked substrates, we performed additional experiments. IEM was used to quantify the amount of NA protein per virion (<xref ref-type="fig" rid="Fig2">figure 2<italic>A</italic>
</xref> and <xref ref-type="fig" rid="Fig2">2<italic>B</italic>
</xref>). The differences in the amount of NA protein were minor (<xref ref-type="fig" rid="Fig2">figure 2<italic>B</italic>
</xref>) and did not correlate with the differences in the level of NA activity. Thus, it seems unlikely that changes in expression over time contributed significantly to changes in the level of NA activity. In addition to demonstrating the relatively stable amount of NA protein per virion, IEM studies confirmed the earlier finding of a clustered distribution of NA protein on virions [<xref ref-type="bibr" rid="ref25">25</xref>]</p>
<p>Next, the substrate preference of the recombinant influenza viruses was examined. The ability of viral NA to liberate sialic acid from α(2–3)sialyllactose and α(2–6)sialyllactose as substrate was determined. All influenza viruses had the majority of NA activity against α(2–3) linkage of sialic acid. As expected, the influenza virus containing the Sing57 NA, as well as the chicken influenza virus WF2 NA, had activity almost solely (98%) against substrate with an α(2–3) linkage, which is the primary linkage of sialic acid in the gastrointestinal tract of aquatic birds [<xref ref-type="bibr" rid="ref31">31</xref>]. As is consistent with previous findings [<xref ref-type="bibr" rid="ref30">30</xref>, <xref ref-type="bibr" rid="ref32">32</xref>], the ratio of α(2–6) activity:α(2–3) activity increased in the influenza viruses isolated from 1957 to 1986. Even for NAs from influenza viruses circulating in 1986 or 1997, however, only ∼11% of their activity was against the α(2–6) linkage. Thus, it seems unlikely that substrate preference is responsible for differences in the level of N2 NA activity. It is noteworthy that passaging influenza viruses in eggs causes selective pressure in favor of α(2–3) NA activity, because only α(2–3)–linked sialic acid is found in chicken egg allantoic cells [<xref ref-type="bibr" rid="ref33">33</xref>]</p>
<p>
<bold>
<italic>Adherence of</italic>
</bold>
<bold>S. pneumoniae</bold>
<bold>
<italic> to human respiratory cells and NA activity</italic>
</bold>We next tested the effect that the level of NA activity has on adherence of <italic>S. pneumoniae</italic> strain R6T. Before incubation on A549 cell cultures, the recombinant influenza viruses were diluted until they had the same amount of viral protein. At a viral protein concentration of 1 μg/mL, all influenza viruses clearly increased the adherence of <italic>S. pneumoniae</italic> strain R6T to cells, but incubation with the influenza virus containing the HK68 NA, which has a relatively low level of NA activity, increased the adherence of <italic>S. pneumoniae</italic> strain R6T by only 2.1-fold, compared with a 3.8-fold increase after incubation with the influenza virus containing the Sing57 NA and a 2.9-fold increase after incubation with the influenza virus containing the Syd97 NA. At a lower viral protein concentration of 0.2 μg/mL, the influenza virus with the most active NA, the one containing the Sing57 NA, still increased the adherence of <italic>S. pneumoniae</italic> strain R6T by 3.6-fold, whereas, at this concentration, the other influenza viruses caused only 1.3–1.7-fold increases in adherence (<xref ref-type="fig" rid="Fig3">figure 3</xref>). The effect of all influenza viruses on the adherence of <italic>S. pneumoniae</italic> strain R6T was reversed when oseltamivir was added to the incubation mixture (only data related to the higher concentration of influenza virus are shown). Oseltamivir carboxylate is a specific inhibitor of influenza virus NA and has no effect on bacterial NAs [<xref ref-type="bibr" rid="ref13">13</xref>]. This reversal by oseltamivir in the effect of all influenza viruses on the adherence of <italic>S. pneumoniae</italic> strain R6T, together with a 30-min incubation time that is too short for the completion of mechanisms involved in viral replication, suggest that differences between influenza viruses in their effects on the adherence of <italic>S. pneumoniae</italic> are due to their intrinsic level of NA activity</p>
<p>
<bold>
<italic>Higher levels of NA activity and higher mortality from secondary bacterial pneumonia in mice</italic>
</bold>Infection with influenza virus primes mice for subsequent lethal pneumonia caused by <italic>S. pneumoniae</italic> [<xref ref-type="bibr" rid="ref11">11</xref>, <xref ref-type="bibr" rid="ref12">12</xref>]. We infected mice with influenza virus and, 7 days later, infected them with a strain of <italic>S. pneumoniae</italic> that had been transformed with the luciferase-expressing <italic>lux</italic> operon that permits bioluminescent imaging of pneumonia in live anesthetized mice [<xref ref-type="bibr" rid="ref13">13</xref>]. We compared pairs of recombinant influenza viruses that differed ∼2-fold in their level of NA activity (pair 1, the influenza virus containing the Sing57 NA and the influenza virus containing the Syd97 NA matched with the HK68 HA; pair 2, the influenza virus containing the Fuj02 NA and the influenza virus containing the Mem72 NA matched with the Fuj02 HA). The mean weight loss at the time of infection with <italic>S. pneumoniae</italic> was similar in paired groups of mice—7.9% in mice infected with the influenza virus containing the Sing57 NA versus 8.9% in mice infected with the influenza virus containing the Syd97 NA and 0.1% in mice infected with the influenza virus containing the Fuj02 NA versus 1.3% in mice infected with the influenza virus containing the Mem72 NA—which indicated that morbidity relating to infection with the 2 different influenza viruses was similar. However, a significant difference in survival after infection with <italic>S. pneumoniae</italic> was observed: 8 (42%) of 19 mice infected with the influenza virus containing the Sing57 NA versus 15 (79%) of 19 mice infected with the influenza virus containing the Syd97 NA (P<.05) lived (<xref ref-type="fig" rid="Fig4">figure 4<italic>A</italic>
</xref>), and 3 (33%) of 9 mice infected with the influenza virus containing the Fuj02 NA versus 8 (89%) of 9 mice infected with the influenza virus containing the Mem72 NA (P<.05) lived (<xref ref-type="fig" rid="Fig4">figure 4<italic>D</italic>
</xref>). Daily imaging showed the development of pneumococcal pneumonia 2–3 days before death (<xref ref-type="fig" rid="Fig4">figure 4<italic>A</italic>
</xref>
<xref ref-type="fig" rid="Fig4">4<italic>C</italic>
</xref> and <xref ref-type="fig" rid="Fig4">4<italic>E;</italic>
</xref> 2 representative mice are shown). Results of studies using several other recombinant influenza viruses indicated that there were similar differences when influenza viruses with high and low levels of NA activity were compared (data not shown). These data establish that even small differences in the level of NA activity are reflected in differences in the ability of influenza viruses to permit the development of secondary bacterial pneumonia in a mouse model. Data for the influenza virus containing the Syd97 NA (<xref ref-type="fig" rid="Fig4">figure 4<italic>A</italic>
</xref> and <xref ref-type="fig" rid="Fig4">4<italic>B</italic>
</xref>) and the influenza virus containing the Fuj02 NA (<xref ref-type="fig" rid="Fig4">figure 4<italic>C</italic>
</xref> and <xref ref-type="fig" rid="Fig4">4<italic>D</italic>
</xref>) are not directly comparable, despite the similarities in measured levels of NA activity, because the HA differs between the 2 pairs of viruses and could independently contribute to secondary bacterial pneumonia</p>
<p>The experiment using the influenza viruses containing the Sing57 and Syd97 NAs was repeated, and lung viral titers were measured 3 and 7 days after infection to make certain that the kinetics of viral infection in the 2 groups of mice were comparable. On day 3 after infection, groups of 4 mice infected with the influenza virus containing the Sing57 NA had mean ± SD viral titers of 6.5±0.4 log<sub>10</sub> TCID<sub>50</sub>/mL, compared with 6.3±0.3 log<sub>10</sub> TCID<sub>50</sub>/mL in mice infected with the influenza virus containing the Syd97 NA. On day 7, the mean ± SD viral titers were 2.4±0.7 log<sub>10</sub> TCID<sub>50</sub>/mL and 2.5±0.4 log<sub>10</sub> TCID<sub>50</sub>/mL, respectively, and there was no detectable influenza virus in the lungs of 1 mouse from each group of 4 mice</p>
</sec>
<sec id="S3">
<title>Discussion</title>
<p>Results of a previous study using a panel of reassortant duck influenza viruses containing human N2 NAs suggested that the level of NA activity in influenza viruses decreased markedly between 1957 and 1968 [<xref ref-type="bibr" rid="ref30">30</xref>]. We have confirmed and extended this observation by use of human influenza viruses that were generated by reverse genetics to contain N2 NAs representative of influenza viruses isolated between 1957 and 2004. The level of NA activity decreased in influenza viruses isolated from 1957 to 1968 and increased again in those isolated from 1968 to 1997. This trend in NA activity correlates with the observed historic mortality caused by H3N2 influenza viruses, which was highest in 1957, decreased during the next decade, but increased again during the 1990s (<xref ref-type="table" rid="tb2">table 2</xref>). Low levels of NA activity in the influenza viruses circulating in 1968 is consistent with lower mortality from this pandemic, compared with that in the 1957 pandemic or during the epidemics caused by H3N2 influenza viruses during the 1990s. It has been suggested that conservation of the N2 NA in the influenza viruses circulating in 1968 resulted in relatively low mortality during this pandemic, but this does not explain why influenza viruses circulating later that had no antigenic shift in HA or NA caused higher mortality. The N2 NA in the influenza virus circulating in 1997 had the second highest level of NA activity, and this influenza virus caused the highest mortality during an epidemic since the 1957 pandemic [<xref ref-type="bibr" rid="ref2">2</xref>, <xref ref-type="bibr" rid="ref34">34</xref>, <xref ref-type="bibr" rid="ref36">36</xref>]</p>
<p>Although the correlation between historical excess mortality in humans and the NA activity and secondary bacterial pneumonia found in our model is intriguing, other factors must be involved. A large proportion of excess deaths related to influenza are coded as cardiovascular disease, cerebrovascular disease, or diabetes [<xref ref-type="bibr" rid="ref37">37</xref>], and most of these conditions are presumably not related to bacterial superinfection. Virus-specific factors contribute to excess morbidity and mortality, and differences in these virulence factors account for differences in morbidity and mortality from season to season. Our data suggest that NA activity is such a factor and that its impact can be seen in deaths from secondary bacterial pneumonia. Other virulence factors—such as the antigenic novelty of the HA, the modulation of interferon [<xref ref-type="bibr" rid="ref38">38</xref>] or cytokine expression by nonstructural protein–1 [<xref ref-type="bibr" rid="ref39">39</xref>], or interactions between several genes—may be involved, and NA may have effects on the host unrelated to cleavage of sialic acid, as is suggested by its ability to activate tumor growth factor–β [<xref ref-type="bibr" rid="ref40">40</xref>]</p>
<p>Results of our previous studies indicated that pharmacological inhibition of viral NA improves survival in secondary pneumococcal pneumonia after influenza [<xref ref-type="bibr" rid="ref13">13</xref>, <xref ref-type="bibr" rid="ref14">14</xref>]. However, these studies were performed using a single influenza virus and could not establish whether a dose effect based on the activities of different influenza viruses might exist. In the present study, we created a set of recombinant influenza viruses that differed from each other only in their level of NA activity. A hierarchy of support for bacterial adherence and secondary bacterial pneumonia could be seen when recombinant influenza viruses were compared in cell culture and animal models of viral-bacterial interactions. The NA that had the highest level of activity (from Sing57, the strain that caused the 1957 pandemic) was capable of inducing more adherence by <italic>S. pneumoniae</italic> to cultured respiratory epithelial cells and higher mortality from secondary bacterial pneumonia in mice than an NA with 2-fold less activity (from Syd97). Similar weight loss and lung viral titers during the influenza phase of the infections indicated that differences in viral kinetics were not interfering in the comparisons. An influenza virus containing the NA of the Fuj02 strain, which has a level of NA activity comparable to that of an influenza virus containing the Syd97 NA, more effectively supported secondary bacterial pneumonia than did an influenza virus that had another 2-fold decrease in relative activity (Mem72) when tested on the same background (paired with the Fuj02 HA). An H3N2 virus (Fuj02) caused high mortality during the 2003–2004 influenza season and contributed to a number of well-publicized deaths from methicillin-resistant <italic>Staphylococcus aureus</italic> [<xref ref-type="bibr" rid="ref41">41</xref>]. The activity of the NA from the influenza virus that caused the 1918 pandemic has not been reported, and activities of N1 NAs from influenza viruses circulating before 1957 have not been studied in a comprehensive fashion. Our data provide direct evidence that NA activity in influenza viruses is a predictor of mortality from secondary bacterial pneumonia</p>
<p>These results, together with our previous data showing that oseltamivir treatment prevents secondary bacterial pneumonia in mice even when it is administered late during the course of the viral infection [<xref ref-type="bibr" rid="ref13">13</xref>], warrant clinical studies of the prevention and treatment of secondary bacterial infections after influenza with NA inhibitors. Effectiveness studies of these drugs in the treatment of influenza have already shown that they decrease the number of complications, although the populations studied have most often not included those individuals who are most vulnerable, because of underlying illnesses or extremities of age, to secondary bacterial infections [<xref ref-type="bibr" rid="ref42">42</xref>
<xref ref-type="bibr" rid="ref43"></xref>–<xref ref-type="bibr" rid="ref44">44</xref>]. Preparations for the next influenza pandemic must take into account the possibility that many deaths will be caused by secondary bacterial pneumonia, and an increased focus on viral NA—including stockpiling of NA inhibitors—is therefore essential</p>
</sec>
</body>
<back>
<ack>
<title>Acknowledgments</title>
<p>We thank G. Air, for providing us with Mem4 and Mem5 monoclonal antibodies; E. Hoffmann, D. R. Perez, L. Widjaja, and R. G. Webster, for providing us with A/Puerto Rico/8/34, A/Hong Kong/1/68 hemagglutinin, and A/Fujian/411/02 hemagglutinin and neuraminidase plasmids; R. McKeon, for technical support; and R. G. Webster and E. I. Tuomanen, for critical reading of the manuscript</p>
</ack>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Simonsen</surname>
<given-names>L</given-names>
</name>
<name>
<surname>Clarke</surname>
<given-names>MJ</given-names>
</name>
<name>
<surname>Williamson</surname>
<given-names>GD</given-names>
</name>
<name>
<surname>Stroup</surname>
<given-names>DF</given-names>
</name>
<name>
<surname>Arden</surname>
<given-names>NH</given-names>
</name>
<name>
<surname>Schonberger</surname>
<given-names>LB</given-names>
</name>
</person-group>
<article-title>The impact of influenza epidemics on mortality: introducing a severity index</article-title>
<source>Am J Public Health</source>
<year>1997</year>
<volume>87</volume>
<fpage>1944</fpage>
<lpage>50</lpage>
</nlm-citation>
</ref>
<ref id="ref2">
<label>2.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Thompson</surname>
<given-names>WW</given-names>
</name>
<name>
<surname>Shay</surname>
<given-names>DK</given-names>
</name>
<name>
<surname>Weintraub</surname>
<given-names>E</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Mortality associated with influenza and respiratory syncytial virus in the United States</article-title>
<source>JAMA</source>
<year>2003</year>
<volume>289</volume>
<fpage>179</fpage>
<lpage>86</lpage>
</nlm-citation>
</ref>
<ref id="ref3">
<label>3.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Hers</surname>
<given-names>JFP</given-names>
</name>
<name>
<surname>Masurel</surname>
<given-names>N</given-names>
</name>
<name>
<surname>Mulder</surname>
<given-names>J</given-names>
</name>
</person-group>
<article-title>Bacteriology and histopathology of the respiratory tract and lungs of fatal Asian influenza</article-title>
<source>Lancet</source>
<year>1958</year>
<volume>2</volume>
<fpage>1141</fpage>
<lpage>3</lpage>
</nlm-citation>
</ref>
<ref id="ref4">
<label>4.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Lindsay</surname>
<given-names>MI</given-names>
<suffix>Jr</suffix>
</name>
<name>
<surname>Herrmann</surname>
<given-names>EC</given-names>
<suffix>Jr</suffix>
</name>
<name>
<surname>Morrow</surname>
<given-names>GW</given-names>
<suffix>Jr</suffix>
</name>
<name>
<surname>Brown</surname>
<given-names>AL</given-names>
<suffix>Jr</suffix>
</name>
</person-group>
<article-title>Hong Kong influenza: clinical, microbiologic, and pathologic features in 127 cases</article-title>
<source>JAMA</source>
<year>1970</year>
<volume>214</volume>
<fpage>1825</fpage>
<lpage>32</lpage>
</nlm-citation>
</ref>
<ref id="ref5">
<label>5.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Scadding</surname>
<given-names>JG</given-names>
</name>
</person-group>
<article-title>Lung changes in influenza</article-title>
<source>Quart J Med</source>
<year>1937</year>
<volume>6</volume>
<fpage>425</fpage>
<lpage>65</lpage>
</nlm-citation>
</ref>
<ref id="ref6">
<label>6.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Stuart‐Harris</surname>
<given-names>CH</given-names>
</name>
<name>
<surname>Laird</surname>
<given-names>J</given-names>
</name>
<name>
<surname>Tyrrell</surname>
<given-names>DA</given-names>
</name>
<name>
<surname>Kelsall</surname>
<given-names>MH</given-names>
</name>
<name>
<surname>Franks</surname>
<given-names>ZC</given-names>
</name>
</person-group>
<article-title>The relationship between influenza and pneumonia</article-title>
<source>J Hyg (Lond)</source>
<year>1949</year>
<volume>47</volume>
<fpage>434</fpage>
<lpage>48</lpage>
</nlm-citation>
</ref>
<ref id="ref7">
<label>7.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Tyrrell</surname>
<given-names>DAJ</given-names>
</name>
</person-group>
<article-title>The pulmonary complications of influenza as seen in Sheffield in 1949</article-title>
<source>Quart J Med</source>
<year>1952</year>
<volume>21</volume>
<fpage>291</fpage>
<lpage>306</lpage>
</nlm-citation>
</ref>
<ref id="ref8">
<label>8.</label>
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname>Nicholson</surname>
<given-names>KG</given-names>
</name>
</person-group>
<person-group person-group-type="editor">
<name>
<surname>Nicholson</surname>
<given-names>KG</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
<name>
<surname>Hay</surname>
<given-names>AJ</given-names>
</name>
</person-group>
<article-title>Human influenza</article-title>
<source>Textbook of influenza</source>
<year>1998</year>
<publisher-loc>London</publisher-loc>
<publisher-name>Blackwell Science</publisher-name>
<fpage>222</fpage>
<lpage>3</lpage>
</nlm-citation>
</ref>
<ref id="ref9">
<label>9.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Simonsen</surname>
<given-names>L</given-names>
</name>
</person-group>
<article-title>The global impact of influenza on morbidity and mortality</article-title>
<source>Vaccine</source>
<year>1999</year>
<volume>17</volume>
<supplement>Suppl 1</supplement>
<fpage>S3</fpage>
<lpage>10</lpage>
</nlm-citation>
</ref>
<ref id="ref10">
<label>10.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Bartlett</surname>
<given-names>JG</given-names>
</name>
<name>
<surname>Mundy</surname>
<given-names>LM</given-names>
</name>
</person-group>
<article-title>Community‐acquired pneumonia</article-title>
<source>N Engl J Med</source>
<year>1995</year>
<volume>333</volume>
<fpage>1618</fpage>
<lpage>24</lpage>
</nlm-citation>
</ref>
<ref id="ref11">
<label>11.</label>
<nlm-citation citation-type="book">
<person-group person-group-type="author">
<name>
<surname>McCullers</surname>
<given-names>JA</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
</person-group>
<person-group person-group-type="editor">
<name>
<surname>Osterhaus</surname>
<given-names>ADME</given-names>
</name>
<name>
<surname>Cox</surname>
<given-names>N</given-names>
</name>
<name>
<surname>Hampson</surname>
<given-names>AW</given-names>
</name>
</person-group>
<article-title>A mouse model of dual infection with influenza virus and <italic>Streptococcus pneumoniae</italic>
</article-title>
<source>Options for the control of influenza IV</source>
<year>2001</year>
<publisher-loc>Amsterdam</publisher-loc>
<publisher-name>Elsevier Science</publisher-name>
<fpage>601</fpage>
<lpage>7</lpage>
</nlm-citation>
</ref>
<ref id="ref12">
<label>12.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>McCullers</surname>
<given-names>JA</given-names>
</name>
<name>
<surname>Rehg</surname>
<given-names>JE</given-names>
</name>
</person-group>
<article-title>Lethal synergism between influenza virus and <italic>Streptococcus pneumoniae:</italic> characterization of a mouse model and the role of platelet‐activating factor receptor</article-title>
<source>J Infect Dis</source>
<year>2002</year>
<volume>186</volume>
<fpage>341</fpage>
<lpage>50</lpage>
</nlm-citation>
</ref>
<ref id="ref13">
<label>13.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>McCullers</surname>
<given-names>JA</given-names>
</name>
<name>
<surname>Bartmess</surname>
<given-names>KC</given-names>
</name>
</person-group>
<article-title>Role of neuraminidase in lethal synergism between influenza virus and <italic>Streptococcus pneumoniae</italic>
</article-title>
<source>J Infect Dis</source>
<year>2003</year>
<volume>187</volume>
<fpage>1000</fpage>
<lpage>9</lpage>
</nlm-citation>
</ref>
<ref id="ref14">
<label>14.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>McCullers</surname>
<given-names>JA</given-names>
</name>
</person-group>
<article-title>Effect of antiviral treatment on the outcome of secondary bacterial pneumonia after influenza</article-title>
<source>J Infect Dis</source>
<year>2004</year>
<volume>190</volume>
<fpage>519</fpage>
<lpage>26</lpage>
</nlm-citation>
</ref>
<ref id="ref15">
<label>15.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Tong</surname>
<given-names>HH</given-names>
</name>
<name>
<surname>McIver</surname>
<given-names>MA</given-names>
</name>
<name>
<surname>Fisher</surname>
<given-names>LM</given-names>
</name>
<name>
<surname>DeMaria</surname>
<given-names>TF</given-names>
</name>
</person-group>
<article-title>Effect of lacto‐N‐neotetraose, asialoganglioside‐GM1 and neuraminidase on adherence of otitis media‐associated serotypes of <italic>Streptococcus pneumoniae</italic> to chinchilla tracheal epithelium</article-title>
<source>Microb Pathog</source>
<year>1999</year>
<volume>26</volume>
<fpage>111</fpage>
<lpage>9</lpage>
</nlm-citation>
</ref>
<ref id="ref16">
<label>16.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>LaMarco</surname>
<given-names>KL</given-names>
</name>
<name>
<surname>Diven</surname>
<given-names>WF</given-names>
</name>
<name>
<surname>Glew</surname>
<given-names>RH</given-names>
</name>
</person-group>
<article-title>Experimental alteration of chinchilla middle ear mucosae by bacterial neuraminidase</article-title>
<source>Ann Otol Rhinol Laryngol</source>
<year>1986</year>
<volume>95</volume>
<fpage>304</fpage>
<lpage>8</lpage>
</nlm-citation>
</ref>
<ref id="ref17">
<label>17.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Linder</surname>
<given-names>TE</given-names>
</name>
<name>
<surname>Lim</surname>
<given-names>DJ</given-names>
</name>
<name>
<surname>DeMaria</surname>
<given-names>TF</given-names>
</name>
</person-group>
<article-title>Changes in the structure of the cell surface carbohydrates of the chinchilla tubotympanum following <italic>Streptococcus pneumoniae</italic>‐induced otitis media</article-title>
<source>Microb Pathog</source>
<year>1992</year>
<volume>13</volume>
<fpage>293</fpage>
<lpage>303</lpage>
</nlm-citation>
</ref>
<ref id="ref18">
<label>18.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Tong</surname>
<given-names>HH</given-names>
</name>
<name>
<surname>Grants</surname>
<given-names>I</given-names>
</name>
<name>
<surname>Liu</surname>
<given-names>X</given-names>
</name>
<name>
<surname>DeMaria</surname>
<given-names>TF</given-names>
</name>
</person-group>
<article-title>Comparison of alteration of cell surface carbohydrates of the chinchilla tubotympanum and colonial opacity phenotype of <italic>Streptococcus pneumoniae</italic> during experimental pneumococcal otitis media with or without an antecedent influenza A virus infection</article-title>
<source>Infect Immun</source>
<year>2002</year>
<volume>70</volume>
<fpage>4292</fpage>
<lpage>301</lpage>
</nlm-citation>
</ref>
<ref id="ref19">
<label>19.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Wagner</surname>
<given-names>R</given-names>
</name>
<name>
<surname>Wolff</surname>
<given-names>T</given-names>
</name>
<name>
<surname>Herwig</surname>
<given-names>A</given-names>
</name>
<name>
<surname>Pleschka</surname>
<given-names>S</given-names>
</name>
<name>
<surname>Klenk</surname>
<given-names>HD</given-names>
</name>
</person-group>
<article-title>Interdependence of hemagglutinin glycosylation and neuraminidase as regulators of influenza virus growth: a study by reverse genetics</article-title>
<source>J Virol</source>
<year>2000</year>
<volume>74</volume>
<fpage>6316</fpage>
<lpage>23</lpage>
</nlm-citation>
</ref>
<ref id="ref20">
<label>20.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Hoffmann</surname>
<given-names>E</given-names>
</name>
<name>
<surname>Neumann</surname>
<given-names>G</given-names>
</name>
<name>
<surname>Kawaoka</surname>
<given-names>Y</given-names>
</name>
<name>
<surname>Hobom</surname>
<given-names>G</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
</person-group>
<article-title>A DNA transfection system for generation of influenza A virus from eight plasmids</article-title>
<source>Proc Natl Acad Sci USA</source>
<year>2000</year>
<volume>97</volume>
<fpage>6108</fpage>
<lpage>13</lpage>
</nlm-citation>
</ref>
<ref id="ref21">
<label>21.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Hoffmann</surname>
<given-names>E</given-names>
</name>
<name>
<surname>Krauss</surname>
<given-names>S</given-names>
</name>
<name>
<surname>Perez</surname>
<given-names>D</given-names>
</name>
<name>
<surname>Webby</surname>
<given-names>R</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
</person-group>
<article-title>Eight‐plasmid system for rapid generation of influenza virus vaccines</article-title>
<source>Vaccine</source>
<year>2002</year>
<volume>20</volume>
<fpage>3165</fpage>
<lpage>70</lpage>
</nlm-citation>
</ref>
<ref id="ref22">
<label>22.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Reed</surname>
<given-names>LJ</given-names>
</name>
<name>
<surname>Muench</surname>
<given-names>H</given-names>
</name>
</person-group>
<article-title>A simple method for estimating fifty percent endpoints</article-title>
<source>Am J Hyg</source>
<year>1938</year>
<volume>27</volume>
<fpage>493</fpage>
<lpage>7</lpage>
</nlm-citation>
</ref>
<ref id="ref23">
<label>23.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Warner</surname>
<given-names>TG</given-names>
</name>
<name>
<surname>O’Brien</surname>
<given-names>JS</given-names>
</name>
</person-group>
<article-title>Synthesis of 2′‐(4‐methylumbelliferyl)‐alpha‐D‐N‐acetylneuraminic acid and detection of skin fibroblast neuraminidase in normal humans and in sialidosis</article-title>
<source>Biochemistry</source>
<year>1979</year>
<volume>18</volume>
<fpage>2783</fpage>
<lpage>7</lpage>
</nlm-citation>
</ref>
<ref id="ref24">
<label>24.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Warren</surname>
<given-names>L</given-names>
</name>
</person-group>
<article-title>The thiobarbituric acid assay of sialic acids</article-title>
<source>J Biol Chem</source>
<year>1959</year>
<volume>234</volume>
<fpage>1971</fpage>
<lpage>5</lpage>
</nlm-citation>
</ref>
<ref id="ref25">
<label>25.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Murti</surname>
<given-names>KG</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
</person-group>
<article-title>Distribution of hemagglutinin and neuraminidase on influenza virions as revealed by immunoelectron microscopy</article-title>
<source>Virology</source>
<year>1986</year>
<volume>149</volume>
<fpage>36</fpage>
<lpage>43</lpage>
</nlm-citation>
</ref>
<ref id="ref26">
<label>26.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
<name>
<surname>Brown</surname>
<given-names>LE</given-names>
</name>
<name>
<surname>Laver</surname>
<given-names>WG</given-names>
</name>
</person-group>
<article-title>Antigenic and biological characterization of influenza virus neuraminidase (N2) with monoclonal antibodies</article-title>
<source>Virology</source>
<year>1984</year>
<volume>135</volume>
<fpage>30</fpage>
<lpage>42</lpage>
</nlm-citation>
</ref>
<ref id="ref27">
<label>27.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Air</surname>
<given-names>GM</given-names>
</name>
<name>
<surname>Els</surname>
<given-names>MC</given-names>
</name>
<name>
<surname>Brown</surname>
<given-names>LE</given-names>
</name>
<name>
<surname>Laver</surname>
<given-names>WG</given-names>
</name>
<name>
<surname>Webster</surname>
<given-names>RG</given-names>
</name>
</person-group>
<article-title>Location of antigenic sites on the three‐dimensional structure of the influenza N2 virus neuraminidase</article-title>
<source>Virology</source>
<year>1985</year>
<volume>145</volume>
<fpage>237</fpage>
<lpage>48</lpage>
</nlm-citation>
</ref>
<ref id="ref28">
<label>28.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Gulati</surname>
<given-names>U</given-names>
</name>
<name>
<surname>Hwang</surname>
<given-names>CC</given-names>
</name>
<name>
<surname>Venkatramani</surname>
<given-names>L</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Antibody epitopes on the neuraminidase of a recent H3N2 influenza virus (A/Memphis/31/98)</article-title>
<source>J Virol</source>
<year>2002</year>
<volume>76</volume>
<fpage>12274</fpage>
<lpage>80</lpage>
</nlm-citation>
</ref>
<ref id="ref29">
<label>29.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Francis</surname>
<given-names>KP</given-names>
</name>
<name>
<surname>Yu</surname>
<given-names>J</given-names>
</name>
<name>
<surname>Bellinger‐Kawahara</surname>
<given-names>C</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Visualizing pneumococcal infections in the lungs of live mice using bioluminescent <italic>Streptococcus pneumoniae</italic> transformed with a novel gram‐ positive <italic>lux</italic> transposon</article-title>
<source>Infect Immun</source>
<year>2001</year>
<volume>69</volume>
<fpage>3350</fpage>
<lpage>8</lpage>
</nlm-citation>
</ref>
<ref id="ref30">
<label>30.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Kobasa</surname>
<given-names>D</given-names>
</name>
<name>
<surname>Wells</surname>
<given-names>K</given-names>
</name>
<name>
<surname>Kawaoka</surname>
<given-names>Y</given-names>
</name>
</person-group>
<article-title>Amino acids responsible for the absolute sialidase activity of the influenza A virus neuraminidase: relationship to growth in the duck intestine</article-title>
<source>J Virol</source>
<year>2001</year>
<volume>75</volume>
<fpage>11773</fpage>
<lpage>80</lpage>
</nlm-citation>
</ref>
<ref id="ref31">
<label>31.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Ito</surname>
<given-names>T</given-names>
</name>
<name>
<surname>Couceiro</surname>
<given-names>JN</given-names>
</name>
<name>
<surname>Kelm</surname>
<given-names>S</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Molecular basis for the generation in pigs of influenza A viruses with pandemic potential</article-title>
<source>J Virol</source>
<year>1998</year>
<volume>72</volume>
<fpage>7367</fpage>
<lpage>73</lpage>
</nlm-citation>
</ref>
<ref id="ref32">
<label>32.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Baum</surname>
<given-names>LG</given-names>
</name>
<name>
<surname>Paulson</surname>
<given-names>JC</given-names>
</name>
</person-group>
<article-title>The N2 neuraminidase of human influenza virus has acquired a substrate specificity complementary to the hemagglutinin receptor specificity</article-title>
<source>Virology</source>
<year>1991</year>
<volume>180</volume>
<fpage>10</fpage>
<lpage>5</lpage>
</nlm-citation>
</ref>
<ref id="ref33">
<label>33.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Ito</surname>
<given-names>T</given-names>
</name>
<name>
<surname>Suzuki</surname>
<given-names>Y</given-names>
</name>
<name>
<surname>Takada</surname>
<given-names>A</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Differences in sialic acid‐galactose linkages in the chicken egg amnion and allantois influence human influenza virus receptor specificity and variant selection</article-title>
<source>J Virol</source>
<year>1997</year>
<volume>71</volume>
<fpage>3357</fpage>
<lpage>62</lpage>
</nlm-citation>
</ref>
<ref id="ref34">
<label>34.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Housworth</surname>
<given-names>WJ</given-names>
</name>
<name>
<surname>Spoon</surname>
<given-names>MM</given-names>
</name>
</person-group>
<article-title>The age distribution of excess mortality during A2 Hong Kong influenza epidemics compared with earlier A2 outbreaks</article-title>
<source>Am J Epidemiol</source>
<year>1971</year>
<volume>94</volume>
<fpage>348</fpage>
<lpage>50</lpage>
</nlm-citation>
</ref>
<ref id="ref35">
<label>35.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Lui</surname>
<given-names>KJ</given-names>
</name>
<name>
<surname>Kendal</surname>
<given-names>AP</given-names>
</name>
</person-group>
<article-title>Impact of influenza epidemics on mortality in the United States from October 1972 to May 1985</article-title>
<source>Am J Public Health</source>
<year>1987</year>
<volume>77</volume>
<fpage>712</fpage>
<lpage>6</lpage>
</nlm-citation>
</ref>
<ref id="ref36">
<label>36.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Simonsen</surname>
<given-names>L</given-names>
</name>
<name>
<surname>Clarke</surname>
<given-names>MJ</given-names>
</name>
<name>
<surname>Schonberger</surname>
<given-names>LB</given-names>
</name>
<name>
<surname>Arden</surname>
<given-names>NH</given-names>
</name>
<name>
<surname>Cox</surname>
<given-names>NJ</given-names>
</name>
<name>
<surname>Fukuda</surname>
<given-names>K</given-names>
</name>
</person-group>
<article-title>Pandemic versus epidemic influenza mortality: a pattern of changing age distribution</article-title>
<source>J Infect Dis</source>
<year>1998</year>
<volume>178</volume>
<fpage>53</fpage>
<lpage>60</lpage>
</nlm-citation>
</ref>
<ref id="ref37">
<label>37.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Reichert</surname>
<given-names>TA</given-names>
</name>
<name>
<surname>Simonsen</surname>
<given-names>L</given-names>
</name>
<name>
<surname>Sharma</surname>
<given-names>A</given-names>
</name>
<name>
<surname>Pardo</surname>
<given-names>SA</given-names>
</name>
<name>
<surname>Fedson</surname>
<given-names>DS</given-names>
</name>
<name>
<surname>Miller</surname>
<given-names>MA</given-names>
</name>
</person-group>
<article-title>Influenza and the winter increase in mortality in the United States, 1959–1999</article-title>
<source>Am J Epidemiol</source>
<year>2004</year>
<volume>160</volume>
<fpage>492</fpage>
<lpage>502</lpage>
</nlm-citation>
</ref>
<ref id="ref38">
<label>38.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Garcia‐Sastre</surname>
<given-names>A</given-names>
</name>
<name>
<surname>Egorov</surname>
<given-names>A</given-names>
</name>
<name>
<surname>Matassov</surname>
<given-names>D</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Influenza A virus lacking the NS1 gene replicates in interferon‐deficient systems</article-title>
<source>Virology</source>
<year>1998</year>
<volume>252</volume>
<fpage>324</fpage>
<lpage>30</lpage>
</nlm-citation>
</ref>
<ref id="ref39">
<label>39.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Guan</surname>
<given-names>Y</given-names>
</name>
<name>
<surname>Poon</surname>
<given-names>LL</given-names>
</name>
<name>
<surname>Cheung</surname>
<given-names>CY</given-names>
</name>
<etal></etal>
</person-group>
<article-title>H5N1 influenza: a protean pandemic threat</article-title>
<source>Proc Natl Acad Sci USA</source>
<year>2004</year>
<volume>101</volume>
<fpage>8156</fpage>
<lpage>61</lpage>
</nlm-citation>
</ref>
<ref id="ref40">
<label>40.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Schultz‐Cherry</surname>
<given-names>S</given-names>
</name>
<name>
<surname>Hinshaw</surname>
<given-names>VS</given-names>
</name>
</person-group>
<article-title>Influenza virus neuraminidase activates latent transforming growth factor beta</article-title>
<source>J Virol</source>
<year>1996</year>
<volume>70</volume>
<fpage>8624</fpage>
<lpage>9</lpage>
</nlm-citation>
</ref>
<ref id="ref41">
<label>41.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<collab>Centers for Disease Control and Prevention</collab>
</person-group>
<article-title>Update: influenza‐associated deaths reported among children aged <18 years—United States, 2003–04 influenza season</article-title>
<source>MMWR Morb Mortal Wkly Rep</source>
<year>2004</year>
<volume>52</volume>
<fpage>1254</fpage>
<lpage>5</lpage>
</nlm-citation>
</ref>
<ref id="ref42">
<label>42.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Treanor</surname>
<given-names>JJ</given-names>
</name>
<name>
<surname>Hayden</surname>
<given-names>FG</given-names>
</name>
<name>
<surname>Vrooman</surname>
<given-names>PS</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. US Oral Neuraminidase Study Group</article-title>
<source>JAMA</source>
<year>2000</year>
<volume>283</volume>
<fpage>1016</fpage>
<lpage>24</lpage>
</nlm-citation>
</ref>
<ref id="ref43">
<label>43.</label>
<nlm-citation citation-type="journal">
<person-group person-group-type="author">
<name>
<surname>Whitley</surname>
<given-names>RJ</given-names>
</name>
<name>
<surname>Hayden</surname>
<given-names>FG</given-names>
</name>
<name>
<surname>Reisinger</surname>
<given-names>KS</given-names>
</name>
<etal></etal>
</person-group>
<article-title>Oral oseltamivir treatment of influenza in children</article-title>
<source>Pediatr Infect Dis J</source>
<year>2001</year>
<volume>20</volume>
<fpage>127</fpage>
<lpage>33</lpage>
</nlm-citation>
</ref>
<ref id="ref44">
<label>44.</label>
<nlm-citation citation-type="journal">
<article-title>Randomised trial of efficacy and safety of inhaled zanamivir in treatment of influenza A and B virus infections. The MIST (Management of Influenza in the Southern Hemisphere Trialists) Study Group</article-title>
<source>Lancet</source>
<year>1998</year>
<volume>352</volume>
<fpage>1877</fpage>
<lpage>81</lpage>
</nlm-citation>
</ref>
</ref-list>
<sec sec-type="display-objects">
<title>Figures and Tables</title>
<fig id="Fig1" position="float">
<label>Figure 1</label>
<caption>
<p>Neuraminidase (NA) activity in influenza viruses. The level of NA activity in influenza viruses differing from each other only in NA were measured using 2′-(4-methylumbelliferyl)-<italic>N-</italic>acetylneuraminic acid as the substrate. Activity is expressed per amount of viral protein. The mean ± SD percentages from 3–5 independent measurements are shown as the percentage of the NA activity in the influenza virus containing the Sing57 NA. *P<.001, compared with all other influenza viruses (analysis of variance); **P<.05, compared with all other influenza viruses containing a human NA</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-fig001.tif"></graphic>
</fig>
<fig id="Fig2" position="float">
<label>Figure 2</label>
<caption>
<p>Amount of neuraminidase (NA) per virion. NA protein was detected by immunoelectron microscopy (IEM) using a mixture of monoclonal NA antibodies to bind gold particles to NA. <italic>A</italic> Negatively stained IEM sample in which the viral structure is visualized more clearly than in positive staining, but the resolution of the gold particles (seen as black dots) is not as good. A clustered distribution of the NA can be seen. <italic>B</italic> The relative amount of NA per virion, shown as the mean±SD number of gold particles per virion. Gold particles from 31–49 virions of each influenza virus were counted. <italic>C</italic> The amount of NA per virion, estimated by counting the gold particles from positively stained samples. Examples of 4 representative influenza viruses are shown. *P<.001, compared with influenza viruses containing the Sing57, Eng62, HK68, or Mem72 NAs (analysis of variance); **P<.05, compared with influenza viruses containing the Eng62 or Mem72 NAs</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-fig002.tif"></graphic>
</fig>
<fig id="Fig3" position="float">
<label>Figure 3</label>
<caption>
<p>Effect of influenza viruses on adherence of <italic>Streptococcus pneumoniae</italic> to A549 cells. Cells were incubated for 30 min with 1 μg/mL or 0.2 μg/mL influenza virus, with or without the neuraminidase (NA) inhibitor oseltamivir, before the adherence of <italic>S. pneumoniae</italic> strain R6T to A549 cells was measured. A comparison between the influenza virus containing the Sing57 NA, which has a high level of NA activity, and 3 representative influenza viruses containing NAs with lower levels of activity is shown. Data are mean±SD of 3–6 consecutive, independent experiments. *P<.05, compared with different treatments with the same influenza virus (analysis of variance); **P<.05, compared with the influenza virus containing the Sing57 NA and the other influenza viruses (0.2 μg/mL) without oseltamivir treatment (analysis of variance)</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-fig003.tif"></graphic>
</fig>
<fig id="Fig4" position="float">
<label>Figure 4</label>
<caption>
<p>Lethal pneumococcal pneumonia in mice after infection with pairs of recombinant influenza viruses differing ∼2-fold in the level of neuraminidase (NA) activity. Mice were challenged intranasally with 100 cfu of <italic>Streptococcus pneumoniae</italic> transformed with the <italic>lux</italic> operon 7 days after intranasal infection with influenza virus. <italic>A</italic> Detection of pneumococcal pneumonia in mice infected with the influenza virus containing the Sing57 or Syd97 NA (9 mice/group). Pneumonia was defined as the detection of >20,000 relative light units (rlu) from the thorax by use of a live imaging system. <italic>B</italic> Survival curves of mice infected with the influenza virus containing the Sing57 or Syd97 NA (19 mice/group). <italic>C</italic> Detection of pneumococcal pneumonia in mice infected with the influenza virus containing the Mem72 or Fuj02 NA (9 mice/group). <italic>D</italic> Survival curves of mice infected with the influenza virus containing the Mem72 or Fuj02 NA (9 mice/group). <italic>E</italic> Daily live imaging of 2 representative mice. The mouse infected with the influenza virus containing the Sing57 NA died of pneumonia on day 6 after infection with <italic>S. pneumoniae</italic>. The mouse infected with the influenza virus containing the Syd97 NA survived and did not contract pneumonia. One mouse infected with the influenza virus containing the Syd97 NA and 1 mouse infected with the influenza virus containing the Fuj02 NA recovered from pneumonia; all other mice that developed pneumonia died. *P<.05, for comparisons of the development of pneumonia or survival between groups (Mantel-Cox χ<sup>2</sup> test on Kaplan-Meier survival data)</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-fig004.tif"></graphic>
</fig>
<fig id="tb1" position="float">
<label>Table 1</label>
<caption>
<p>Lung titers of influenza viruses and their virulence in mice</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-tab001.tif"></graphic>
</fig>
<fig id="tb2" position="float">
<label>Table 2</label>
<caption>
<p>Comparison of neuraminidase (NA) activity with excess mortality from influenza</p>
</caption>
<graphic mimetype="image" xlink:href="192-2-249-tab002.tif"></graphic>
</fig>
</sec>
<fn-group>
<fn id="fn1">
<p>Financial support: National Institutes of Health (grants AI-49178 and AI-54802); American Lebanese Syrian Associated Charities; Academy of Finland (grant to V.T.P.); Leiras Research Foundation (grant to V.T.P.); Pediatric Research Foundation of Finland (grant to V.T.P.)</p>
</fn>
<fn id="fn2">
<p>Present affiliation: Department of Pediatrics, Turku University Hospital, Turku, Finland</p>
</fn>
</fn-group>
</back>
</article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo><title>Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia</title></titleInfo><titleInfo type="alternative" contentType="CDATA"><title>Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia</title></titleInfo><name type="personal"><namePart type="given">Ville T.</namePart><namePart type="family">Peltola</namePart><affiliation>Infectious Diseases and</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">K. Gopal</namePart><namePart type="family">Murti</namePart><affiliation>Molecular Biotechnology, St. Jude Children’s Research Hospital, Memphis, Tennessee</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal" displayLabel="corresp"><namePart type="given">Jonathan A.</namePart><namePart type="family">McCullers</namePart><affiliation>Infectious Diseases and</affiliation><affiliation>E-mail: jon.mccullers@stjude.org</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="research-article" authority="ISTEX" authorityURI="https://content-type.data.istex.fr" valueURI="https://content-type.data.istex.fr/ark:/67375/XTP-1JC4F85T-7">research-article</genre><originInfo><publisher>The University of Chicago Press</publisher><dateIssued encoding="w3cdtf">2005-07-15</dateIssued><dateCreated encoding="w3cdtf">2005-02-24</dateCreated><copyrightDate encoding="w3cdtf">2005</copyrightDate></originInfo><abstract>Secondary bacterial pneumonia is a common cause of death during influenza epidemics. We hypothesized that virus-specific factors could contribute to differences in annual excess mortality. Recombinant influenza viruses with neuraminidases from representative strains from the past 50 years were created and characterized. The specific level of their neuraminidase activity correlated with their ability to support secondary bacterial pneumonia. Recombinant viruses with neuraminidases from 1957 and 1997 influenza strains had the highest level of activity, whereas a virus with the neuraminidase from a 1968 strain had the lowest level of activity. The high level of activity of the neuraminidase from the 1957 strain, compared with that of other neuraminidases, more strongly supported the adherence of Streptococcus pneumoniae and the development of secondary bacterial pneumonia in a mouse model. These data lend support to our hypothesis that the influenza virus neuraminidase contributes to secondary bacterial pneumonia and subsequent excess mortality</abstract><relatedItem type="host"><titleInfo><title>The Journal of Infectious Diseases</title></titleInfo><titleInfo type="abbreviated"><title>The Journal of Infectious Diseases</title></titleInfo><genre type="journal" authority="ISTEX" authorityURI="https://publication-type.data.istex.fr" valueURI="https://publication-type.data.istex.fr/ark:/67375/JMC-0GLKJH51-B">journal</genre><identifier type="ISSN">0022-1899</identifier><identifier type="eISSN">1537-6613</identifier><identifier type="PublisherID">jid</identifier><identifier type="PublisherID-hwp">jinfdis</identifier><part><date>2005</date><detail type="volume"><caption>vol.</caption><number>192</number></detail><detail type="issue"><caption>no.</caption><number>2</number></detail><extent unit="pages"><start>249</start><end>257</end></extent></part></relatedItem><relatedItem type="references" displayLabel="b1"><titleInfo><title>The impact of influenza epidemics on mortality: introducing a severity index</title></titleInfo><name type="personal"><namePart type="given">L</namePart><namePart type="family">Simonsen</namePart></name><name type="personal"><namePart type="given">MJ</namePart><namePart type="family">Clarke</namePart></name><name type="personal"><namePart type="given">GD</namePart><namePart type="family">Williamson</namePart></name><name type="personal"><namePart type="given">DF</namePart><namePart type="family">Stroup</namePart></name><name type="personal"><namePart type="given">NH</namePart><namePart type="family">Arden</namePart></name><name type="personal"><namePart type="given">LB</namePart><namePart type="family">Schonberger</namePart></name><genre>journal</genre><note>Simonsen L Clarke MJ Williamson GD Stroup DF Arden NH Schonberger LB The impact of influenza epidemics on mortality: introducing a severity index Am J Public Health 1997 87 1944 50</note><relatedItem type="host"><titleInfo><title>Am J Public Health</title></titleInfo><part><date>1997</date><detail type="volume"><caption>vol.</caption><number>87</number></detail><extent unit="pages"><start>1944</start><end>50</end><list>1944-50</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b2"><titleInfo><title>Mortality associated with influenza and respiratory syncytial virus in the United States</title></titleInfo><name type="personal"><namePart type="given">WW</namePart><namePart type="family">Thompson</namePart></name><name type="personal"><namePart type="given">DK</namePart><namePart type="family">Shay</namePart></name><name type="personal"><namePart type="given">E</namePart><namePart type="family">Weintraub</namePart></name><genre>journal</genre><note>Thompson WW Shay DK Weintraub E Mortality associated with influenza and respiratory syncytial virus in the United States JAMA 2003 289 179 86</note><relatedItem type="host"><titleInfo><title>JAMA</title></titleInfo><part><date>2003</date><detail type="volume"><caption>vol.</caption><number>289</number></detail><extent unit="pages"><start>179</start><end>86</end><list>179-86</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b3"><titleInfo><title>Bacteriology and histopathology of the respiratory tract and lungs of fatal Asian influenza</title></titleInfo><name type="personal"><namePart type="given">JFP</namePart><namePart type="family">Hers</namePart></name><name type="personal"><namePart type="given">N</namePart><namePart type="family">Masurel</namePart></name><name type="personal"><namePart type="given">J</namePart><namePart type="family">Mulder</namePart></name><genre>journal</genre><note>Hers JFP Masurel N Mulder J Bacteriology and histopathology of the respiratory tract and lungs of fatal Asian influenza Lancet 1958 2 1141 3</note><relatedItem type="host"><titleInfo><title>Lancet</title></titleInfo><part><date>1958</date><detail type="volume"><caption>vol.</caption><number>2</number></detail><extent unit="pages"><start>1141</start><end>3</end><list>1141-3</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b4"><titleInfo><title>Hong Kong influenza: clinical, microbiologic, and pathologic features in 127 cases</title></titleInfo><name type="personal"><namePart type="given">MI</namePart><namePart type="family">Lindsay Jr</namePart></name><name type="personal"><namePart type="given">EC</namePart><namePart type="family">Herrmann Jr</namePart></name><name type="personal"><namePart type="given">GW</namePart><namePart type="family">Morrow Jr</namePart></name><name type="personal"><namePart type="given">AL</namePart><namePart type="family">Brown Jr</namePart></name><genre>journal</genre><note>Lindsay MI Jr Herrmann EC Jr Morrow GW Jr Brown AL Jr Hong Kong influenza: clinical, microbiologic, and pathologic features in 127 cases JAMA 1970 214 1825 32</note><relatedItem type="host"><titleInfo><title>JAMA</title></titleInfo><part><date>1970</date><detail type="volume"><caption>vol.</caption><number>214</number></detail><extent unit="pages"><start>1825</start><end>32</end><list>1825-32</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b5"><titleInfo><title>Lung changes in influenza</title></titleInfo><name type="personal"><namePart type="given">JG</namePart><namePart type="family">Scadding</namePart></name><genre>journal</genre><note>Scadding JG Lung changes in influenza Quart J Med 1937 6 425 65</note><relatedItem type="host"><titleInfo><title>Quart J Med</title></titleInfo><part><date>1937</date><detail type="volume"><caption>vol.</caption><number>6</number></detail><extent unit="pages"><start>425</start><end>65</end><list>425-65</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b6"><titleInfo><title>The relationship between influenza and pneumonia</title></titleInfo><name type="personal"><namePart type="given">CH</namePart><namePart type="family">Stuart‐Harris</namePart></name><name type="personal"><namePart type="given">J</namePart><namePart type="family">Laird</namePart></name><name type="personal"><namePart type="given">DA</namePart><namePart type="family">Tyrrell</namePart></name><name type="personal"><namePart type="given">MH</namePart><namePart type="family">Kelsall</namePart></name><name type="personal"><namePart type="given">ZC</namePart><namePart type="family">Franks</namePart></name><genre>journal</genre><note>Stuart‐Harris CH Laird J Tyrrell DA Kelsall MH Franks ZC The relationship between influenza and pneumonia J Hyg (Lond) 1949 47 434 48</note><relatedItem type="host"><titleInfo><title>J Hyg (Lond)</title></titleInfo><part><date>1949</date><detail type="volume"><caption>vol.</caption><number>47</number></detail><extent unit="pages"><start>434</start><end>48</end><list>434-48</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b7"><titleInfo><title>The pulmonary complications of influenza as seen in Sheffield in 1949</title></titleInfo><name type="personal"><namePart type="given">DAJ</namePart><namePart type="family">Tyrrell</namePart></name><genre>journal</genre><note>Tyrrell DAJ The pulmonary complications of influenza as seen in Sheffield in 1949 Quart J Med 1952 21 291 306</note><relatedItem type="host"><titleInfo><title>Quart J Med</title></titleInfo><part><date>1952</date><detail type="volume"><caption>vol.</caption><number>21</number></detail><extent unit="pages"><start>291</start><end>306</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b8"><titleInfo><title>Human influenza</title></titleInfo><name type="personal"><namePart type="given">KG</namePart><namePart type="family">Nicholson</namePart></name><name type="personal"><namePart type="given">KG</namePart><namePart type="family">Nicholson</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><name type="personal"><namePart type="given">AJ</namePart><namePart type="family">Hay</namePart></name><genre>book</genre><note>Nicholson KG Nicholson KG Webster RG Hay AJ Human influenza Textbook of influenza 1998 London Blackwell Science 222 3</note><relatedItem type="host"><titleInfo><title>Textbook of influenza</title></titleInfo><originInfo><publisher>Blackwell Science. </publisher><place><placeTerm type="text">London</placeTerm></place></originInfo><part><date>1998</date><extent unit="pages"><start>222</start><end>3</end><list>222-3</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b9"><titleInfo><title>The global impact of influenza on morbidity and mortality</title></titleInfo><name type="personal"><namePart type="given">L</namePart><namePart type="family">Simonsen</namePart></name><genre>journal</genre><note>Simonsen L The global impact of influenza on morbidity and mortality Vaccine 1999 17 Suppl 1 S3 10</note><relatedItem type="host"><titleInfo><title>Vaccine</title></titleInfo><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>17</number></detail><extent unit="pages"><start>S3</start><end>10</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b10"><titleInfo><title>Community‐acquired pneumonia</title></titleInfo><name type="personal"><namePart type="given">JG</namePart><namePart type="family">Bartlett</namePart></name><name type="personal"><namePart type="given">LM</namePart><namePart type="family">Mundy</namePart></name><genre>journal</genre><note>Bartlett JG Mundy LM Community‐acquired pneumonia N Engl J Med 1995 333 1618 24</note><relatedItem type="host"><titleInfo><title>N Engl J Med</title></titleInfo><part><date>1995</date><detail type="volume"><caption>vol.</caption><number>333</number></detail><extent unit="pages"><start>1618</start><end>24</end><list>1618-24</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b11"><titleInfo><title>A mouse model of dual infection with influenza virus and Streptococcus pneumoniae</title></titleInfo><name type="personal"><namePart type="given">JA</namePart><namePart type="family">McCullers</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><name type="personal"><namePart type="given">ADME</namePart><namePart type="family">Osterhaus</namePart></name><name type="personal"><namePart type="given">N</namePart><namePart type="family">Cox</namePart></name><name type="personal"><namePart type="given">AW</namePart><namePart type="family">Hampson</namePart></name><genre>book</genre><note>McCullers JA Webster RG Osterhaus ADME Cox N Hampson AW A mouse model of dual infection with influenza virus and Streptococcus pneumoniae Options for the control of influenza IV 2001 Amsterdam Elsevier Science 601 7</note><relatedItem type="host"><titleInfo><title>Options for the control of influenza IV</title></titleInfo><originInfo><publisher>Elsevier Science. </publisher><place><placeTerm type="text">Amsterdam</placeTerm></place></originInfo><part><date>2001</date><extent unit="pages"><start>601</start><end>7</end><list>601-7</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b12"><titleInfo><title>Lethal synergism between influenza virus and Streptococcus pneumoniae: characterization of a mouse model and the role of platelet‐activating factor receptor</title></titleInfo><name type="personal"><namePart type="given">JA</namePart><namePart type="family">McCullers</namePart></name><name type="personal"><namePart type="given">JE</namePart><namePart type="family">Rehg</namePart></name><genre>journal</genre><note>McCullers JA Rehg JE Lethal synergism between influenza virus and Streptococcus pneumoniae: characterization of a mouse model and the role of platelet‐activating factor receptor J Infect Dis 2002 186 341 50</note><relatedItem type="host"><titleInfo><title>J Infect Dis</title></titleInfo><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>186</number></detail><extent unit="pages"><start>341</start><end>50</end><list>341-50</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b13"><titleInfo><title>Role of neuraminidase in lethal synergism between influenza virus and Streptococcus pneumoniae</title></titleInfo><name type="personal"><namePart type="given">JA</namePart><namePart type="family">McCullers</namePart></name><name type="personal"><namePart type="given">KC</namePart><namePart type="family">Bartmess</namePart></name><genre>journal</genre><note>McCullers JA Bartmess KC Role of neuraminidase in lethal synergism between influenza virus and Streptococcus pneumoniae J Infect Dis 2003 187 1000 9</note><relatedItem type="host"><titleInfo><title>J Infect Dis</title></titleInfo><part><date>2003</date><detail type="volume"><caption>vol.</caption><number>187</number></detail><extent unit="pages"><start>1000</start><end>9</end><list>1000-9</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b14"><titleInfo><title>Effect of antiviral treatment on the outcome of secondary bacterial pneumonia after influenza</title></titleInfo><name type="personal"><namePart type="given">JA</namePart><namePart type="family">McCullers</namePart></name><genre>journal</genre><note>McCullers JA Effect of antiviral treatment on the outcome of secondary bacterial pneumonia after influenza J Infect Dis 2004 190 519 26</note><relatedItem type="host"><titleInfo><title>J Infect Dis</title></titleInfo><part><date>2004</date><detail type="volume"><caption>vol.</caption><number>190</number></detail><extent unit="pages"><start>519</start><end>26</end><list>519-26</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b15"><titleInfo><title>Effect of lacto‐N‐neotetraose, asialoganglioside‐GM1 and neuraminidase on adherence of otitis media‐associated serotypes of Streptococcus pneumoniae to chinchilla tracheal epithelium</title></titleInfo><name type="personal"><namePart type="given">HH</namePart><namePart type="family">Tong</namePart></name><name type="personal"><namePart type="given">MA</namePart><namePart type="family">McIver</namePart></name><name type="personal"><namePart type="given">LM</namePart><namePart type="family">Fisher</namePart></name><name type="personal"><namePart type="given">TF</namePart><namePart type="family">DeMaria</namePart></name><genre>journal</genre><note>Tong HH McIver MA Fisher LM DeMaria TF Effect of lacto‐N‐neotetraose, asialoganglioside‐GM1 and neuraminidase on adherence of otitis media‐associated serotypes of Streptococcus pneumoniae to chinchilla tracheal epithelium Microb Pathog 1999 26 111 9</note><relatedItem type="host"><titleInfo><title>Microb Pathog</title></titleInfo><part><date>1999</date><detail type="volume"><caption>vol.</caption><number>26</number></detail><extent unit="pages"><start>111</start><end>9</end><list>111-9</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b16"><titleInfo><title>Experimental alteration of chinchilla middle ear mucosae by bacterial neuraminidase</title></titleInfo><name type="personal"><namePart type="given">KL</namePart><namePart type="family">LaMarco</namePart></name><name type="personal"><namePart type="given">WF</namePart><namePart type="family">Diven</namePart></name><name type="personal"><namePart type="given">RH</namePart><namePart type="family">Glew</namePart></name><genre>journal</genre><note>LaMarco KL Diven WF Glew RH Experimental alteration of chinchilla middle ear mucosae by bacterial neuraminidase Ann Otol Rhinol Laryngol 1986 95 304 8</note><relatedItem type="host"><titleInfo><title>Ann Otol Rhinol Laryngol</title></titleInfo><part><date>1986</date><detail type="volume"><caption>vol.</caption><number>95</number></detail><extent unit="pages"><start>304</start><end>8</end><list>304-8</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b17"><titleInfo><title>Changes in the structure of the cell surface carbohydrates of the chinchilla tubotympanum following Streptococcus pneumoniae‐induced otitis media</title></titleInfo><name type="personal"><namePart type="given">TE</namePart><namePart type="family">Linder</namePart></name><name type="personal"><namePart type="given">DJ</namePart><namePart type="family">Lim</namePart></name><name type="personal"><namePart type="given">TF</namePart><namePart type="family">DeMaria</namePart></name><genre>journal</genre><note>Linder TE Lim DJ DeMaria TF Changes in the structure of the cell surface carbohydrates of the chinchilla tubotympanum following Streptococcus pneumoniae‐induced otitis media Microb Pathog 1992 13 293 303</note><relatedItem type="host"><titleInfo><title>Microb Pathog</title></titleInfo><part><date>1992</date><detail type="volume"><caption>vol.</caption><number>13</number></detail><extent unit="pages"><start>293</start><end>303</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b18"><titleInfo><title>Comparison of alteration of cell surface carbohydrates of the chinchilla tubotympanum and colonial opacity phenotype of Streptococcus pneumoniae during experimental pneumococcal otitis media with or without an antecedent influenza A virus infection</title></titleInfo><name type="personal"><namePart type="given">HH</namePart><namePart type="family">Tong</namePart></name><name type="personal"><namePart type="given">I</namePart><namePart type="family">Grants</namePart></name><name type="personal"><namePart type="given">X</namePart><namePart type="family">Liu</namePart></name><name type="personal"><namePart type="given">TF</namePart><namePart type="family">DeMaria</namePart></name><genre>journal</genre><note>Tong HH Grants I Liu X DeMaria TF Comparison of alteration of cell surface carbohydrates of the chinchilla tubotympanum and colonial opacity phenotype of Streptococcus pneumoniae during experimental pneumococcal otitis media with or without an antecedent influenza A virus infection Infect Immun 2002 70 4292 301</note><relatedItem type="host"><titleInfo><title>Infect Immun</title></titleInfo><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>70</number></detail><extent unit="pages"><start>4292</start><end>301</end><list>4292-301</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b19"><titleInfo><title>Interdependence of hemagglutinin glycosylation and neuraminidase as regulators of influenza virus growth: a study by reverse genetics</title></titleInfo><name type="personal"><namePart type="given">R</namePart><namePart type="family">Wagner</namePart></name><name type="personal"><namePart type="given">T</namePart><namePart type="family">Wolff</namePart></name><name type="personal"><namePart type="given">A</namePart><namePart type="family">Herwig</namePart></name><name type="personal"><namePart type="given">S</namePart><namePart type="family">Pleschka</namePart></name><name type="personal"><namePart type="given">HD</namePart><namePart type="family">Klenk</namePart></name><genre>journal</genre><note>Wagner R Wolff T Herwig A Pleschka S Klenk HD Interdependence of hemagglutinin glycosylation and neuraminidase as regulators of influenza virus growth: a study by reverse genetics J Virol 2000 74 6316 23</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>74</number></detail><extent unit="pages"><start>6316</start><end>23</end><list>6316-23</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b20"><titleInfo><title>A DNA transfection system for generation of influenza A virus from eight plasmids</title></titleInfo><name type="personal"><namePart type="given">E</namePart><namePart type="family">Hoffmann</namePart></name><name type="personal"><namePart type="given">G</namePart><namePart type="family">Neumann</namePart></name><name type="personal"><namePart type="given">Y</namePart><namePart type="family">Kawaoka</namePart></name><name type="personal"><namePart type="given">G</namePart><namePart type="family">Hobom</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><genre>journal</genre><note>Hoffmann E Neumann G Kawaoka Y Hobom G Webster RG A DNA transfection system for generation of influenza A virus from eight plasmids Proc Natl Acad Sci USA 2000 97 6108 13</note><relatedItem type="host"><titleInfo><title>Proc Natl Acad Sci USA</title></titleInfo><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>97</number></detail><extent unit="pages"><start>6108</start><end>13</end><list>6108-13</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b21"><titleInfo><title>Eight‐plasmid system for rapid generation of influenza virus vaccines</title></titleInfo><name type="personal"><namePart type="given">E</namePart><namePart type="family">Hoffmann</namePart></name><name type="personal"><namePart type="given">S</namePart><namePart type="family">Krauss</namePart></name><name type="personal"><namePart type="given">D</namePart><namePart type="family">Perez</namePart></name><name type="personal"><namePart type="given">R</namePart><namePart type="family">Webby</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><genre>journal</genre><note>Hoffmann E Krauss S Perez D Webby R Webster RG Eight‐plasmid system for rapid generation of influenza virus vaccines Vaccine 2002 20 3165 70</note><relatedItem type="host"><titleInfo><title>Vaccine</title></titleInfo><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>20</number></detail><extent unit="pages"><start>3165</start><end>70</end><list>3165-70</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b22"><titleInfo><title>A simple method for estimating fifty percent endpoints</title></titleInfo><name type="personal"><namePart type="given">LJ</namePart><namePart type="family">Reed</namePart></name><name type="personal"><namePart type="given">H</namePart><namePart type="family">Muench</namePart></name><genre>journal</genre><note>Reed LJ Muench H A simple method for estimating fifty percent endpoints Am J Hyg 1938 27 493 7</note><relatedItem type="host"><titleInfo><title>Am J Hyg</title></titleInfo><part><date>1938</date><detail type="volume"><caption>vol.</caption><number>27</number></detail><extent unit="pages"><start>493</start><end>7</end><list>493-7</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b23"><titleInfo><title>Synthesis of 2′‐(4‐methylumbelliferyl)‐alpha‐D‐N‐acetylneuraminic acid and detection of skin fibroblast neuraminidase in normal humans and in sialidosis</title></titleInfo><name type="personal"><namePart type="given">TG</namePart><namePart type="family">Warner</namePart></name><name type="personal"><namePart type="given">JS</namePart><namePart type="family">O’Brien</namePart></name><genre>journal</genre><note>Warner TG O’Brien JS Synthesis of 2′‐(4‐methylumbelliferyl)‐alpha‐D‐N‐acetylneuraminic acid and detection of skin fibroblast neuraminidase in normal humans and in sialidosis Biochemistry 1979 18 2783 7</note><relatedItem type="host"><titleInfo><title>Biochemistry</title></titleInfo><part><date>1979</date><detail type="volume"><caption>vol.</caption><number>18</number></detail><extent unit="pages"><start>2783</start><end>7</end><list>2783-7</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b24"><titleInfo><title>The thiobarbituric acid assay of sialic acids</title></titleInfo><name type="personal"><namePart type="given">L</namePart><namePart type="family">Warren</namePart></name><genre>journal</genre><note>Warren L The thiobarbituric acid assay of sialic acids J Biol Chem 1959 234 1971 5</note><relatedItem type="host"><titleInfo><title>J Biol Chem</title></titleInfo><part><date>1959</date><detail type="volume"><caption>vol.</caption><number>234</number></detail><extent unit="pages"><start>1971</start><end>5</end><list>1971-5</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b25"><titleInfo><title>Distribution of hemagglutinin and neuraminidase on influenza virions as revealed by immunoelectron microscopy</title></titleInfo><name type="personal"><namePart type="given">KG</namePart><namePart type="family">Murti</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><genre>journal</genre><note>Murti KG Webster RG Distribution of hemagglutinin and neuraminidase on influenza virions as revealed by immunoelectron microscopy Virology 1986 149 36 43</note><relatedItem type="host"><titleInfo><title>Virology</title></titleInfo><part><date>1986</date><detail type="volume"><caption>vol.</caption><number>149</number></detail><extent unit="pages"><start>36</start><end>43</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b26"><titleInfo><title>Antigenic and biological characterization of influenza virus neuraminidase (N2) with monoclonal antibodies</title></titleInfo><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><name type="personal"><namePart type="given">LE</namePart><namePart type="family">Brown</namePart></name><name type="personal"><namePart type="given">WG</namePart><namePart type="family">Laver</namePart></name><genre>journal</genre><note>Webster RG Brown LE Laver WG Antigenic and biological characterization of influenza virus neuraminidase (N2) with monoclonal antibodies Virology 1984 135 30 42</note><relatedItem type="host"><titleInfo><title>Virology</title></titleInfo><part><date>1984</date><detail type="volume"><caption>vol.</caption><number>135</number></detail><extent unit="pages"><start>30</start><end>42</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b27"><titleInfo><title>Location of antigenic sites on the three‐dimensional structure of the influenza N2 virus neuraminidase</title></titleInfo><name type="personal"><namePart type="given">GM</namePart><namePart type="family">Air</namePart></name><name type="personal"><namePart type="given">MC</namePart><namePart type="family">Els</namePart></name><name type="personal"><namePart type="given">LE</namePart><namePart type="family">Brown</namePart></name><name type="personal"><namePart type="given">WG</namePart><namePart type="family">Laver</namePart></name><name type="personal"><namePart type="given">RG</namePart><namePart type="family">Webster</namePart></name><genre>journal</genre><note>Air GM Els MC Brown LE Laver WG Webster RG Location of antigenic sites on the three‐dimensional structure of the influenza N2 virus neuraminidase Virology 1985 145 237 48</note><relatedItem type="host"><titleInfo><title>Virology</title></titleInfo><part><date>1985</date><detail type="volume"><caption>vol.</caption><number>145</number></detail><extent unit="pages"><start>237</start><end>48</end><list>237-48</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b28"><titleInfo><title>Antibody epitopes on the neuraminidase of a recent H3N2 influenza virus (A/Memphis/31/98)</title></titleInfo><name type="personal"><namePart type="given">U</namePart><namePart type="family">Gulati</namePart></name><name type="personal"><namePart type="given">CC</namePart><namePart type="family">Hwang</namePart></name><name type="personal"><namePart type="given">L</namePart><namePart type="family">Venkatramani</namePart></name><genre>journal</genre><note>Gulati U Hwang CC Venkatramani L Antibody epitopes on the neuraminidase of a recent H3N2 influenza virus (A/Memphis/31/98) J Virol 2002 76 12274 80</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>2002</date><detail type="volume"><caption>vol.</caption><number>76</number></detail><extent unit="pages"><start>12274</start><end>80</end><list>12274-80</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b29"><titleInfo><title>Visualizing pneumococcal infections in the lungs of live mice using bioluminescent Streptococcus pneumoniae transformed with a novel gram‐ positive lux transposon</title></titleInfo><name type="personal"><namePart type="given">KP</namePart><namePart type="family">Francis</namePart></name><name type="personal"><namePart type="given">J</namePart><namePart type="family">Yu</namePart></name><name type="personal"><namePart type="given">C</namePart><namePart type="family">Bellinger‐Kawahara</namePart></name><genre>journal</genre><note>Francis KP Yu J Bellinger‐Kawahara C Visualizing pneumococcal infections in the lungs of live mice using bioluminescent Streptococcus pneumoniae transformed with a novel gram‐ positive lux transposon Infect Immun 2001 69 3350 8</note><relatedItem type="host"><titleInfo><title>Infect Immun</title></titleInfo><part><date>2001</date><detail type="volume"><caption>vol.</caption><number>69</number></detail><extent unit="pages"><start>3350</start><end>8</end><list>3350-8</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b30"><titleInfo><title>Amino acids responsible for the absolute sialidase activity of the influenza A virus neuraminidase: relationship to growth in the duck intestine</title></titleInfo><name type="personal"><namePart type="given">D</namePart><namePart type="family">Kobasa</namePart></name><name type="personal"><namePart type="given">K</namePart><namePart type="family">Wells</namePart></name><name type="personal"><namePart type="given">Y</namePart><namePart type="family">Kawaoka</namePart></name><genre>journal</genre><note>Kobasa D Wells K Kawaoka Y Amino acids responsible for the absolute sialidase activity of the influenza A virus neuraminidase: relationship to growth in the duck intestine J Virol 2001 75 11773 80</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>2001</date><detail type="volume"><caption>vol.</caption><number>75</number></detail><extent unit="pages"><start>11773</start><end>80</end><list>11773-80</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b31"><titleInfo><title>Molecular basis for the generation in pigs of influenza A viruses with pandemic potential</title></titleInfo><name type="personal"><namePart type="given">T</namePart><namePart type="family">Ito</namePart></name><name type="personal"><namePart type="given">JN</namePart><namePart type="family">Couceiro</namePart></name><name type="personal"><namePart type="given">S</namePart><namePart type="family">Kelm</namePart></name><genre>journal</genre><note>Ito T Couceiro JN Kelm S Molecular basis for the generation in pigs of influenza A viruses with pandemic potential J Virol 1998 72 7367 73</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>72</number></detail><extent unit="pages"><start>7367</start><end>73</end><list>7367-73</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b32"><titleInfo><title>The N2 neuraminidase of human influenza virus has acquired a substrate specificity complementary to the hemagglutinin receptor specificity</title></titleInfo><name type="personal"><namePart type="given">LG</namePart><namePart type="family">Baum</namePart></name><name type="personal"><namePart type="given">JC</namePart><namePart type="family">Paulson</namePart></name><genre>journal</genre><note>Baum LG Paulson JC The N2 neuraminidase of human influenza virus has acquired a substrate specificity complementary to the hemagglutinin receptor specificity Virology 1991 180 10 5</note><relatedItem type="host"><titleInfo><title>Virology</title></titleInfo><part><date>1991</date><detail type="volume"><caption>vol.</caption><number>180</number></detail><extent unit="pages"><start>10</start><end>5</end><list>10-5</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b33"><titleInfo><title>Differences in sialic acid‐galactose linkages in the chicken egg amnion and allantois influence human influenza virus receptor specificity and variant selection</title></titleInfo><name type="personal"><namePart type="given">T</namePart><namePart type="family">Ito</namePart></name><name type="personal"><namePart type="given">Y</namePart><namePart type="family">Suzuki</namePart></name><name type="personal"><namePart type="given">A</namePart><namePart type="family">Takada</namePart></name><genre>journal</genre><note>Ito T Suzuki Y Takada A Differences in sialic acid‐galactose linkages in the chicken egg amnion and allantois influence human influenza virus receptor specificity and variant selection J Virol 1997 71 3357 62</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>1997</date><detail type="volume"><caption>vol.</caption><number>71</number></detail><extent unit="pages"><start>3357</start><end>62</end><list>3357-62</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b34"><titleInfo><title>The age distribution of excess mortality during A2 Hong Kong influenza epidemics compared with earlier A2 outbreaks</title></titleInfo><name type="personal"><namePart type="given">WJ</namePart><namePart type="family">Housworth</namePart></name><name type="personal"><namePart type="given">MM</namePart><namePart type="family">Spoon</namePart></name><genre>journal</genre><note>Housworth WJ Spoon MM The age distribution of excess mortality during A2 Hong Kong influenza epidemics compared with earlier A2 outbreaks Am J Epidemiol 1971 94 348 50</note><relatedItem type="host"><titleInfo><title>Am J Epidemiol</title></titleInfo><part><date>1971</date><detail type="volume"><caption>vol.</caption><number>94</number></detail><extent unit="pages"><start>348</start><end>50</end><list>348-50</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b35"><titleInfo><title>Impact of influenza epidemics on mortality in the United States from October 1972 to May 1985</title></titleInfo><name type="personal"><namePart type="given">KJ</namePart><namePart type="family">Lui</namePart></name><name type="personal"><namePart type="given">AP</namePart><namePart type="family">Kendal</namePart></name><genre>journal</genre><note>Lui KJ Kendal AP Impact of influenza epidemics on mortality in the United States from October 1972 to May 1985 Am J Public Health 1987 77 712 6</note><relatedItem type="host"><titleInfo><title>Am J Public Health</title></titleInfo><part><date>1987</date><detail type="volume"><caption>vol.</caption><number>77</number></detail><extent unit="pages"><start>712</start><end>6</end><list>712-6</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b36"><titleInfo><title>Pandemic versus epidemic influenza mortality: a pattern of changing age distribution</title></titleInfo><name type="personal"><namePart type="given">L</namePart><namePart type="family">Simonsen</namePart></name><name type="personal"><namePart type="given">MJ</namePart><namePart type="family">Clarke</namePart></name><name type="personal"><namePart type="given">LB</namePart><namePart type="family">Schonberger</namePart></name><name type="personal"><namePart type="given">NH</namePart><namePart type="family">Arden</namePart></name><name type="personal"><namePart type="given">NJ</namePart><namePart type="family">Cox</namePart></name><name type="personal"><namePart type="given">K</namePart><namePart type="family">Fukuda</namePart></name><genre>journal</genre><note>Simonsen L Clarke MJ Schonberger LB Arden NH Cox NJ Fukuda K Pandemic versus epidemic influenza mortality: a pattern of changing age distribution J Infect Dis 1998 178 53 60</note><relatedItem type="host"><titleInfo><title>J Infect Dis</title></titleInfo><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>178</number></detail><extent unit="pages"><start>53</start><end>60</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b37"><titleInfo><title>Influenza and the winter increase in mortality in the United States, 1959–1999</title></titleInfo><name type="personal"><namePart type="given">TA</namePart><namePart type="family">Reichert</namePart></name><name type="personal"><namePart type="given">L</namePart><namePart type="family">Simonsen</namePart></name><name type="personal"><namePart type="given">A</namePart><namePart type="family">Sharma</namePart></name><name type="personal"><namePart type="given">SA</namePart><namePart type="family">Pardo</namePart></name><name type="personal"><namePart type="given">DS</namePart><namePart type="family">Fedson</namePart></name><name type="personal"><namePart type="given">MA</namePart><namePart type="family">Miller</namePart></name><genre>journal</genre><note>Reichert TA Simonsen L Sharma A Pardo SA Fedson DS Miller MA Influenza and the winter increase in mortality in the United States, 1959–1999 Am J Epidemiol 2004 160 492 502</note><relatedItem type="host"><titleInfo><title>Am J Epidemiol</title></titleInfo><part><date>2004</date><detail type="volume"><caption>vol.</caption><number>160</number></detail><extent unit="pages"><start>492</start><end>502</end></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b38"><titleInfo><title>Influenza A virus lacking the NS1 gene replicates in interferon‐deficient systems</title></titleInfo><name type="personal"><namePart type="given">A</namePart><namePart type="family">Garcia‐Sastre</namePart></name><name type="personal"><namePart type="given">A</namePart><namePart type="family">Egorov</namePart></name><name type="personal"><namePart type="given">D</namePart><namePart type="family">Matassov</namePart></name><genre>journal</genre><note>Garcia‐Sastre A Egorov A Matassov D Influenza A virus lacking the NS1 gene replicates in interferon‐deficient systems Virology 1998 252 324 30</note><relatedItem type="host"><titleInfo><title>Virology</title></titleInfo><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>252</number></detail><extent unit="pages"><start>324</start><end>30</end><list>324-30</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b39"><titleInfo><title>H5N1 influenza: a protean pandemic threat</title></titleInfo><name type="personal"><namePart type="given">Y</namePart><namePart type="family">Guan</namePart></name><name type="personal"><namePart type="given">LL</namePart><namePart type="family">Poon</namePart></name><name type="personal"><namePart type="given">CY</namePart><namePart type="family">Cheung</namePart></name><genre>journal</genre><note>Guan Y Poon LL Cheung CY H5N1 influenza: a protean pandemic threat Proc Natl Acad Sci USA 2004 101 8156 61</note><relatedItem type="host"><titleInfo><title>Proc Natl Acad Sci USA</title></titleInfo><part><date>2004</date><detail type="volume"><caption>vol.</caption><number>101</number></detail><extent unit="pages"><start>8156</start><end>61</end><list>8156-61</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b40"><titleInfo><title>Influenza virus neuraminidase activates latent transforming growth factor beta</title></titleInfo><name type="personal"><namePart type="given">S</namePart><namePart type="family">Schultz‐Cherry</namePart></name><name type="personal"><namePart type="given">VS</namePart><namePart type="family">Hinshaw</namePart></name><genre>journal</genre><note>Schultz‐Cherry S Hinshaw VS Influenza virus neuraminidase activates latent transforming growth factor beta J Virol 1996 70 8624 9</note><relatedItem type="host"><titleInfo><title>J Virol</title></titleInfo><part><date>1996</date><detail type="volume"><caption>vol.</caption><number>70</number></detail><extent unit="pages"><start>8624</start><end>9</end><list>8624-9</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b41"><titleInfo><title>Update: influenza‐associated deaths reported among children aged <18 years—United States, 2003–04 influenza season</title></titleInfo><genre>journal</genre><note>Centers for Disease Control and Prevention Update: influenza‐associated deaths reported among children aged <18 years—United States, 2003–04 influenza season MMWR Morb Mortal Wkly Rep 2004 52 1254 5</note><relatedItem type="host"><titleInfo><title>MMWR Morb Mortal Wkly Rep</title></titleInfo><part><date>2004</date><detail type="volume"><caption>vol.</caption><number>52</number></detail><extent unit="pages"><start>1254</start><end>5</end><list>1254-5</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b42"><titleInfo><title>Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. US Oral Neuraminidase Study Group</title></titleInfo><name type="personal"><namePart type="given">JJ</namePart><namePart type="family">Treanor</namePart></name><name type="personal"><namePart type="given">FG</namePart><namePart type="family">Hayden</namePart></name><name type="personal"><namePart type="given">PS</namePart><namePart type="family">Vrooman</namePart></name><genre>journal</genre><note>Treanor JJ Hayden FG Vrooman PS Efficacy and safety of the oral neuraminidase inhibitor oseltamivir in treating acute influenza: a randomized controlled trial. US Oral Neuraminidase Study Group JAMA 2000 283 1016 24</note><relatedItem type="host"><titleInfo><title>JAMA</title></titleInfo><part><date>2000</date><detail type="volume"><caption>vol.</caption><number>283</number></detail><extent unit="pages"><start>1016</start><end>24</end><list>1016-24</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b43"><titleInfo><title>Oral oseltamivir treatment of influenza in children</title></titleInfo><name type="personal"><namePart type="given">RJ</namePart><namePart type="family">Whitley</namePart></name><name type="personal"><namePart type="given">FG</namePart><namePart type="family">Hayden</namePart></name><name type="personal"><namePart type="given">KS</namePart><namePart type="family">Reisinger</namePart></name><genre>journal</genre><note>Whitley RJ Hayden FG Reisinger KS Oral oseltamivir treatment of influenza in children Pediatr Infect Dis J 2001 20 127 33</note><relatedItem type="host"><titleInfo><title>Pediatr Infect Dis J</title></titleInfo><part><date>2001</date><detail type="volume"><caption>vol.</caption><number>20</number></detail><extent unit="pages"><start>127</start><end>33</end><list>127-33</list></extent></part></relatedItem></relatedItem><relatedItem type="references" displayLabel="b44"><titleInfo><title>Randomised trial of efficacy and safety of inhaled zanamivir in treatment of influenza A and B virus infections. The MIST (Management of Influenza in the Southern Hemisphere Trialists) Study Group</title></titleInfo><genre>journal</genre><note>Randomised trial of efficacy and safety of inhaled zanamivir in treatment of influenza A and B virus infections. The MIST (Management of Influenza in the Southern Hemisphere Trialists) Study Group Lancet 1998 352 1877 81</note><relatedItem type="host"><titleInfo><title>Lancet</title></titleInfo><part><date>1998</date><detail type="volume"><caption>vol.</caption><number>352</number></detail><extent unit="pages"><start>1877</start><end>81</end><list>1877-81</list></extent></part></relatedItem></relatedItem><identifier type="istex">D587CC152DC4685067505883F679482ED1939AE2</identifier><identifier type="ark">ark:/67375/HXZ-XXR113JR-N</identifier><identifier type="DOI">10.1086/430954</identifier><accessCondition type="use and reproduction" contentType="copyright">© 2005 by the Infectious Diseases Society of America</accessCondition><recordInfo><recordContentSource authority="ISTEX" authorityURI="https://loaded-corpus.data.istex.fr" valueURI="https://loaded-corpus.data.istex.fr/ark:/67375/XBH-GTWS0RDP-M">oup</recordContentSource><recordOrigin>Converted from (version 1.2.0) to MODS version 3.6.</recordOrigin><recordCreationDate encoding="w3cdtf">2019-12-09</recordCreationDate></recordInfo></mods><json:item><extension>json</extension><original>false</original><mimetype>application/json</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/record.json</uri></json:item></metadata><covers><json:item><extension>tiff</extension><original>true</original><mimetype>image/tiff</mimetype><uri>https://api.istex.fr/document/D587CC152DC4685067505883F679482ED1939AE2/covers/tiff</uri></json:item></covers><annexes><json:item><extension>gif</extension><original>true</original><mimetype>image/gif</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/annexes.gif</uri></json:item><json:item><extension>jpeg</extension><original>true</original><mimetype>image/jpeg</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/annexes.jpeg</uri></json:item><json:item><extension>pdf</extension><original>true</original><mimetype>application/pdf</mimetype><uri>https://api.istex.fr/ark:/67375/HXZ-XXR113JR-N/annexes.pdf</uri></json:item></annexes><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
EXPLOR_STEP=$WICRI_ROOT/Sante/explor/H2N2V1/Data/Istex/Corpus
HfdSelect -h $EXPLOR_STEP/biblio.hfd -nk 001246 | SxmlIndent | more
Ou
HfdSelect -h $EXPLOR_AREA/Data/Istex/Corpus/biblio.hfd -nk 001246 | SxmlIndent | more
Pour mettre un lien sur cette page dans le réseau Wicri
{{Explor lien
|wiki= Sante
|area= H2N2V1
|flux= Istex
|étape= Corpus
|type= RBID
|clé= ISTEX:D587CC152DC4685067505883F679482ED1939AE2
|texte= Influenza Virus Neuraminidase Contributes to Secondary Bacterial Pneumonia
}}
| This area was generated with Dilib version V0.6.33. |  |