A novel betacoronavirus, Middle East respiratory syndrome coronavirus (MERS-CoV), emerged on the Arabian Peninsula in 2012. MERS-CoV was found to produce severe respiratory illness with case-fatality rates near 50%, and may be transmitted person-to-person in instances of close physical contact, such as among family members and to health care workers. As mice, hamsters, ferrets, and cynomolgus macaques are either not susceptible to MERS-CoV infection or do not develop observable clinical disease, we sought to determine whether rhesus macaques (Macaca mulatta) can be used as a model of MERS-CoV infection and disease. Animals challenged with MERS-CoV via multiple combined infection routes rapidly developed pneumonia, and we observed other clinical signs of illness, virus shedding, and virus replication in respiratory tissues. Using microarrays to compare transcripts associated with histopathologic lesions removed from the lungs of infected animals, we identified 173 significant differentially expressed genes (DEG) associated with lung lesions on day 3 post-infection concurrent with peak clinical signs. Functional analysis indicated that these genes were predominantly associated with proinflammatory processes, recruitment and chemotaxis of inflammatory cells, and antiviral immunity. Using singular value decomposition coupled multidimensional scaling (SVD-MDS), we also identified changes in similar inflammatory genes in peripheral blood mononuclear cells, suggesting a rapid activation of innate immune and inflammatory processes in leukocytes after infection. These data were consistent with cytokine and chemokine profiles in the blood of animals.

Due to the urgent need for an effective therapeutic means of treating MERS-CoV patients, we used this rhesus macaque model to evaluate post-exposure treatment with combination interferon (IFN)-a2b and ribavirin (RBV), and identified key transcriptional signatures associated with disease severity and treatment efficacy. Animals treated with IFN-a2b/RBV beginning 8 h post-infection did not develop significant clinical or severe histopathologic signs of disease, breathing abnormalities, or radiographic evidence of pneumonia, and showed reduced viral loads and lower levels of serum proinflammatory cytokines. Microarray analysis of treated animals showed significant induction of interferon-stimulated genes (ISGs) and fewer upregulated transcripts associated with inflammatory processes. Additionally, we identified a subset of statistically significant DEGs associated with signaling pathways such as hedgehog, which has been linked to airway function and protection against pulmonary injury. Together, these data indicate that treatment of MERS-CoV-infected rhesus macaques with IFN-a2b and ribavirin reduces virus replication and improves clinical outcome, and suggests a transcriptomic basis for therapeutic efficacy. As these two drugs are already used together in the clinic, IFN-a2b and ribavirin may be useful for therapeutic intervention and patient management of new human MERS-CoV cases.