Severe acute respiratory syndrome (SARS) caused by a newly identified coronavirus (SARS-CoV) is a serious emerging human infectious disease. In this report, we immunized ferrets (Mustela putorius furo) with recombinant modified vaccinia virus Ankara (rMVA) expressing the SARS-CoV spike (S) protein. Immunized ferrets developed a more rapid and vigorous neutralizing antibody response than control animals after challenge with SARS-CoV; however, they also exhibited strong inflammatory responses in liver tissue. Inflammation in control animals exposed to SARS-CoV was relatively mild. Thus, our data suggest that vaccination with rMVA expressing SARS-CoV S protein is associated with enhanced hepatitis.

Severe acute respiratory syndrome (SARS) caused by a newly identified coronavirus (SARS-CoV) remains a threat to cause epidemics as evidenced by recent sporadic cases in China. In this communication, we evaluated the efficacy and safety of two SARS vaccine candidates based on the recombinant modified vaccinia Ankara (MVA) expressing SARS-CoV spike or nucleocapsid proteins in ferrets. No clinical signs were observed in all the ferrets challenged with SARS-CoV. On the other hand, vaccination did not prevent SARS-CoV infection in ferrets. In contrast, immunized ferrets (particularly those immunized with rMVA-spike) exhibited significantly stronger inflammatory responses and focal necrosis in liver tissue after SARS-CoV challenge than control animals. Thus, our data suggest that enhanced hepatitis is linked to vaccination with rMVA expressing SARS-CoV antigens.

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