Comparison of experimental MERS-CoV infection acquired by three individual routes of infection in the common marmoset
Two strains of Middle East Respiratory Syndrome coronavirus (MERS-CoV), England -1 and EMC/2012, were used to challenge common marmosets ( Callithrix jacchus ) by three routes of infection, aerosol, oral and intra-nasal. Animals challenged by the intra-nasal and aerosol routes presented with a mild, transient disease, while those challenged by the oral route presented with a subclinical immunological response. Animals challenged with MERS-CoV strain EMC/2012 by the aerosol route responded with primary and/or secondary pyrexia. Marmosets had minimal to mild multifocal interstitial pneumonia, with the greatest relative severity observed in animals challenged by the aerosol route. Viable virus was isolated from the host in throat swabs and lung tissue. The transient disease described is consistent with a successful host response and was characterised by upregulation of macrophage and neutrophil function observed in all animals at the time of euthanasia. Importance Middle East Respiratory Syndrome is caused by a human Coronavirus, MERS-CoV, similar to SARS-CoV-2. Humans typically exhibit with a fever, cough, shortness of breath, gastrointestinal issues and breathing difficulties which can lead to pneumonia and/or renal complications. This emerging disease resulted in the first human lethal cases in 2012 and has a case fatality rate of approximately 36%. Consequently, there is a need for medical countermeasures and appropriate animal models for their assessment. This work has demonstrated the requirement for higher concentrations of virus to cause overt disease. Challenge by the aerosol, intra-nasal and oral route resulted in no or mild disease, but all animals had an immunological response. This shows that an appropriate early immunological response is able to control the disease.