TBC-3B

To evaluate the safety of administering Therion Recombinant Vaccinia-HIV-1 IIIB env/gag/pol Vaccine (TBC-3B) vaccinations to vaccinia-naive individuals. To evaluate the immunogenicity of priming with TBC-3B by the scarification, intradermal, and subcutaneous routes, followed by booster immunization of MN rgp120 HIV-1. To compare the immunogenicity of priming with TBC-3B in vaccinia-naive individuals to vaccinia-immune individuals.
In prior trials evaluating alternative methods of vaccine administration, scarification has been found to be an imprecise method of administration and allows only 1.0 - 2.5 microliters of immunogen to be given. Since it is not feasible to produce vaccine at concentrations higher than 10 to the 10th pfu/ml, this method limits the maximum deliverable dose. Intradermal and subcutaneous injection routes allow larger volumes of vaccinia to be given, i.e.: up to 200 microliters intradermally and up to 100 ml subcutaneously. In the present study, the initial priming dose will be the same administered by all 3 methods; however, the second priming dose administered at 2 months intradermally and subcutaneously will be 2 logs higher in order to achieve boosting of immune responses, particularly to gag and pol components of TBC-3B.

To evaluate, in healthy HIV-1 seronegative vaccinia-immune and vaccinia-naive volunteers, the safety and immunogenicity of an HIV-1 candidate vaccine (TBC-3B) consisting of a live recombinant vaccinia virus expressing the env, gag, and pol genes of HIV-1 IIIB strain. To evaluate the potential of boosting with one of a variety of HIV-1 recombinant subunit, peptide, or pseudovirion vaccines, if available, to augment the immune responses of the vaccinees.
Antigenic drift, defined as the genetic variation of the HIV-1 envelope gene that results in antigenic variation during natural infection, may confound attempts to achieve protective immunity using a vaccine based solely on HIV-1 envelope proteins. Inclusion of conserved core and polymerase proteins along with envelope protein in a candidate vaccine may address some of the problems with antigenic variability. A prime-boost immunization approach using a novel priming immunogen expressing env, gag, and pol genes of the HIV-1 IIIB strain will be attempted in this study.