Abstract: To clarify which immunological factors were more effective in preventing influenza virus infection, we measured immunological parameters induced by vaccination and infection in vivo and in vitro. Healthy adult subjects (n = 128) were divided into vaccinated (n = 85) and untreated (n = 43) groups. Eighty-five were vaccinated intranasally with a trivalent cold-adapted recombinant influenza virus vaccine containing type A (H1N1 and H3N2) and B viruses. Subjects were mostly seropositive before vaccination. In 29 (80.6%) of the 36 examinees showing a prevaccination HI antibody titre of less than 1:128, the titre increased more than four times after vaccination. On the other hand, an increase of more than four times was found in four (8.2%) of the 49 individuals who had shown a prevaccination titre of more than 1:128. The IgA antibody was negligibly detected in the nasal wash specimens before vaccination, and was induced by vaccination in some cases. Lymphocyte proliferation and interleukin 2 (IL-2) production in cultured lymphocytes of the same subjects stimulated by H1N1 virus in vitro were correlated with the HI antibody titre. However, the interferon γ (IFN-γ) production was low before vaccination, regardless of the HI antibody titre, and showed a significant increase after vaccination. It was suggested that local IgA response and IFN-γ production play important roles in the prevention of influenza. Since there was the outbreak of influenza A (H1N1) in Kochi Prefecture after completion of blood samples 6–8 weeks after the second vaccination, we examined the above hypothesis. A significantly (p<0.01) lower morbidity rate in the vaccinated examinees was found. The HI antibody, lymphocyte DNA synthesis and IL-2 production, which had been increased by vaccination, showed little further increase in response to the epidemic. In contrast, local IgA response and IFN-γ production, which had been increased by vaccination, showed another increase because of the epidemc.

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   |wiki=    Sante
   |area=    H2N2V1
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   |clé=     ISTEX:A29E5FF5D88DFDA97C91FC301EC44CFA1A60B16E
   |texte=   Prevention of influenza by the intranasal administration of cold-recombinant, live-attenuated influenza virus vaccine: importance of interferon-γ production and local IgA response
}}