Protective and disease-enhancing immune responses induced by recombinant modified vaccinia Ankara (MVA) expressing respiratory syncytial virus proteins.

Modified vaccinia Ankara (MVA) recombinants expressing single or multiple RSV surface proteins (F or G) are promising potential vaccines. We studied humoral and cellular responses induced by MVA-F and MVA-G in mice, comparing them to a formalin inactivated RSV preparation (FI-RSV) known to increase disease severity. MVA-F or MVA-G vaccination enhanced weight loss during RSV challenge, but did not show the lung eosinophilia seen after FI-RSV vaccination. FI-RSV induced a stronger total RSV IgG response than the MVA recombinants, but very little IgG2a. MVA recombinants induced cytokine responses biased towards IFNgamma and IL-12, while FI-RSV induced strong IL-4/5 responses in the lungs during RSV challenge. Thus, MVA vaccines induce a favourable immune profile in RSV disease but retain the potential to enhance disease.