S.L.Epstein1, T.M.Tumpey2, J.M.Misplon1, C.Y.Lo1, L.A.Cooper3, K.Subbarao3, M.Renshaw3, S.Sambhara3, J.M.Katz3, 1CBER, FDA, Rockville, MD, 2USDA, Athens, GA 30605, 3CDC, Atlanta, GA 30333
Current influenza vaccines are based on viral strains predicted to circulate during the coming season. If an unexpected strain or even a pandemic emerged, those vaccines could not be prepared quickly enough, so strategies based on conserved antigens should be explored. Viruses from the 1997 H5N1 Hong Kong outbreak provide a model of unexpected emerging strains. We immunized mice with DNA vaccines expressing conserved nucleoprotein (NP) and matrix (M) from A/H1N1, and challenged with A/H5N1 viruses. NP+M DNA vaccination reduced replication of A/Hong Kong/486/97, a nonlethal H5N1 strain, and protected against lethal challenge with A/Hong Kong/156/97. DNA vaccination protected only partially against extremely virulent A/Hong Kong/483/97. Mice given NP+M DNA and then exposed to HK/156 survived subsequent rechallenge with A/Hong Kong/483/97. In the absence of strain-matched vaccines, DNA vaccination to conserved influenza components may provide a useful first line of defense against a rapidly spreading pandemic virus. Immunity could be supplemented when strain-matched vaccines became available.