Differential immunogenicity of vaccinia and HIV-1 components of a human recombinant vaccine in mucosal and blood compartments

Mucosal immune responses induced by HIV-1 vaccines are likely critical for prevention. We report a Phase 1 safety and immunogenicity trial in eight participants using the vaccinia-based TBC-3B vaccine given subcutaneously to determine the relationship between HIV-1 specific systemic and gastrointestinal mucosal responses. Across all subjects, detectable levels of blood vaccinia- and HIV-1-specific antibodies were elicited but none were seen mucosally. While the vaccinia component was immunogenic for CD8+ T lymphocyte (CTL) responses in both blood and mucosa, it was greater in blood. The HIV-1 component of the vaccine was poorly immunogenic in both blood and mucosa. Although only eight volunteers were studied intensively, the discordance between mucosal and blood responses may highlight mechanisms contributing to recent vaccine failures.