Background: The recently emerged Middle East syndrome coronavirus (MERS-CoV) can cause severe and fatal respiratory diseases in humans. Antibodies against MESR-CoV can be found in camels in the Middle East but also outside this regionThe high prevalence of circulating MERS-CoV neutralizing antibodies in dromedary camels from different geographic regions may indicate wide circulation of MERS-CoV in camels. The ongoing MERS-CoV outbreak in the Middle East and the lack of treatment options or licensed vaccines is of great concern. Vaccination of camels could potentially prevent the spread of this virus.
Methods & Materials: We vaccinated 4 dromedary camels twice with a 4 week interval with108 PFU MVA-S via both nostrils and intramuscularly. Four control animals received non-recombinant MVA (n=2) or PBS (n=2). Three weeks post-boost, all animals were tested for presence specific antibody responses by MERS-CoV ELSA and virus neutralization assay (VNT). Next, all camels were challenged with a high dose of MERS-CoV and to study the pathological changes, two animals per groups were euthanized and necropsies were performed at day 4 and 14 pi. The antibody response, and pathology were analyses by MERS-CoV-S or MVA ELISAs, -VNTs, qRT-PCR, virus titration, immunohistochemistry (IHC) and in situ hybridization (ISH).
Results: All vaccinated animal developed detectable serum neutralizing MERS-CoV or MVA specific antibody titers 3 weeks post boost vaccination. No clinical signs were observed in MVA-S vaccinated animals but mild clinical sign and a runny nose were observed in control-vaccinated animals after virus challenge. Interestingly, significant reduction of infectious virus excreted and viral RNA transcripts in the vaccinated animals nose after MERS-CoV challenge was observed as compared with control animals, and these protection correlated with presence of neutralizing antibody to MERS-CoV. In addition, in the nose of MVA-S vaccinated animals at day 4 pi, a few MERS-CoV infected cells were detected by IHC and ISH as compared with control camels. Interestingly, sera from MVA-S vaccinated animals cross neutralized camelpox virus.
Conclusion: Our results demonstrate that vaccination of camels with MVA-S confers protects against MERS-CoV infection. In addition, induction of MVA specific antibody cross neutralize camelpox virus, suggesting that MVA-MERS-S can be used as a dual vaccine in dromedary camels.
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