Antibody Profiling by Proteome Microarray Reveals the Immunogenicity of the Attenuated Smallpox Vaccine, Modified Vaccinia Virus Ankara (MVA) is Comparable to Dryvax®

Division of Infectious Diseases, Department of Medicine, Hewitt Hall, University of California, Irvine, CA 92697; Laboratory of Viral Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892; Division of Infectious Diseases and Immunology, Saint Louis University School of Medicine, Saint Louis, MO, 63110; ImmPORT Therapeutics Inc., Irvine, CA 92618

^* To whom correspondence should be addressed. Email: ddavies{at}uci.edu.

	Abstract

Modified Vaccinia virus Ankara (MVA) is a highly attenuated vaccinia virus that is under consideration as an alternative to the conventional smallpox vaccine, Dryvax®. MVA was attenuated by extensive passage of vaccinia virus Ankara in chick embryo fibroblasts. Several immunomodulatory genes and genes that influence host range are deleted or mutated, and replication is aborted in the late stage of infection in most non-avian cells. The effect of these mutations on immunogenicity is not well understood. Since the structural genes appear to be intact in MVA, it is hypothesized that critical targets for antibody neutralization have been retained. To test this, we probed microarrays of the Western Reserve (WR) proteome with sera from humans and macaques after MVA and Dryvax vaccination. As most protein sequences of MVA are 97-99% identical to those of other vaccinia strains, extensive binding cross-reactivity is expected, except for those deleted or truncated. Despite different hosts and immunization regimens, the MVA and Dryvax antibody profiles were broadly similar, with antibodies against membrane and core proteins being the best conserved. The responses to non-structural proteins were less well conserved, although these are not expected to influence virus neutralization. The broadest antibody response was obtained in hyperimmune rabbits using WR, which is pathogenic in rabbits. These data indicate that, despite the mutations and deletions in MVA, its overall immunogenicity is broadly comparable to Dryvax, particularly at the level of antibodies to membrane proteins. The work supports other information suggesting that MVA may be a useful alternative to Dryvax.