Scientific Publications by FDA Staff

Clin Vaccine Immunol 2007 Aug;14(8):1032-44

Characterization and use of mammalian-expressed vaccinia virus extracellular membrane proteins for quantification of the humoral immune response to smallpox vaccines.

Garcia AD, Meseda CA, Mayer AE, Kumar A, Merchlinsky M, Weir JP

Garcia AD (reprint author), US FDA, Ctr Biol & Evaluat & Res, Div Viral Prod, 1401 Rockville Pike,HRM-457, Rockville, MD 20892 USA US FDA, Ctr Biol & Evaluat & Res, Div Viral Prod, Rockville, MD 20892 USA US FDA, Ctr Biol & Evaluat & Res, Div Viral Prod, Lab DNA Viruses, Bethesda, MD 20892 USA

The licensed smallpox vaccine Dryvax is used as the standard in comparative immunogenicity and protection studies of new smallpox vaccine candidates. Although the correlates of protection against smallpox are unknown, recent studies have shown that a humoral response against the intracellular mature virion (MV) and extracellular enveloped virion (EV) forms of vaccinia virus is crucial for protection. Using a recombinant Semliki Forest Virus (rSFV) vector system, we expressed a set of full-length EV proteins for the development of EV antigen-specific ELISAs and the production of mono-specific antisera. The EV-specific ELISAs were used to evaluate the EV humoral response elicited by Dryvax and the non-replicating modified vaccinia virus Ankara (MVA), in mouse vaccination experiments comparing doses and routes of vaccination. Quantitatively similar antibody titers against EV antigens A33R, A56R, and B5R were measured in mice vaccinated with Dryvax and MVA when MVA was administered at a dose of 10(8) pfu. Further, a substantial increase in the EV-specific antibody response was induced in mice inoculated with MVA using a prime-boost schedule. Finally, we investigated the ability of the EV-expressing rSFV vectors to elicit the production of polyclonal mono-specific antisera against the corresponding EV proteins in mice. The mono-specific sera antibody levels against A33R, A56R, and B5R were measurably higher than the antibody levels induced by Dryvax. The resulting polyclonal antisera were used in Western blot analysis and immunofluorescence assays, indicating that rSFV particles are useful vectors for generating mono-specific antisera.