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175 Preclinical Immunogenicity Studies on Pilot Lots of a Prototype VEE Replicon Vector HIV-1 Subtype C Vaccine for South Africa
E. Reap*1, R. Reid1, A. West2, M. Maughan1, S. Dryga1, I. Caley1, P. Norberg1, K. Dinka1, B. Pancorbo1, E. Raaf1, P. Keith1, and R. Olmsted1
1AlphaVax, Inc., Res. Triangle Park, NC, USA and 2Univ. of North Carolina, Chapel Hill, USA
Background: Through an international collaborative effort supported by the International AIDS Vaccine Initiative, a prototype Venezuelan equine encephalitis virus (VEE) replicon vaccine expressing gag from a South African HIV-1 subtype C isolate is in GMP production, and it is scheduled to begin phase I testing within the HVTN in early 2002. During the development of the manufacturing process prior to off-site GMP production, 3 pilot-lot VEE replicon particle (HIVgagVRP) vaccine preparations were produced in-house. The immunogenicity of each lot has been tested and compared with provide lot-to-lot consistency data necessary for regulatory filings.
Methods: Following each pilot-lot production run, 1 ( 105 infectious units (IU) of HIVgagVRP were administered to BALB/c mice on days 0 and 21. Post-prime and -boost humoral responses to Gag were measured by subtype C Gag-specific ELISA. To evaluate T-cell responses, splenocytes were harvested at least 8 days after boost and analyzed for Gag-specific CTLs by standard chromium release assays.
Results: Inter-assay comparisons of data showed Gag-specific serum antibody levels induced by HIVgagVRP pilot lots 1, 2, and 3 were similar. A 100% seroconversion rate was observed for all animals following prime-boost. Importantly, Gag antigen-stimulated splenocytes showed a robust Gag-specific CTL response, and when evaluated in one study, a strong response was observed 7 weeks post-boost. The isotypic pattern of serum IgG from mice immunized with pilot lot 1 showed a Th1 bias, providing further evidence that a strong cellular response is induced after just 2 doses.
Conclusions: The results of the immunogenicity studies with HIVgagVRP pilot lots 1, 2, and 3 revealed that the present manufacturing process yields vaccine that stimulates the desired humoral and cellular immune responses. Importantly, these studies provide the lot-to-lot consistency data necessary for regulatory documents.
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