Development of a single-shot subunit vaccine for HIV-1. 2. Defining optimal autoboost characteristics to maximize the humoral immune response.

The design of a single-shot subunit vaccine for HIV-1 with polylactic-coglycolic acid (PLGA) sustained-release technology to effect an autoboost of antigen (MN gp120) at a given time after the primary immunization requires in-depth knowledge about the timing, the duration, and the need for coadjuvant in the autoboost. These questions cannot be answered unambiguously with PLGA microspheres, so we have conducted studies using Alzet minipumps to release antigen at prescribed times to mimic a PLGA autoboost. The results show that a discrete autoboost is preferred over continuous release of antigen, that the time profile of the autoboost (whether pulsatile or a 2-week continuous release) does not affect the booster immune response, and that only antigen is required in the booster immunization (a coadjuvant in the boost does not give higher titers).