DESCRIPTION (provided by applicant): DNA vaccines have shown promise as a means to develop meaningful CTL responses in HIV and in other settings, but antibody responses are often poor. The goal of this proposal is to employ a series of improvements that are designed to overcome the poor neutralizing antibody responses to HIV envelope (Env) DNA vaccine. The key hypotheses to be explored are as follows: i) Coexpression of the extremely potent B cell stimulatory molecules BAFF or CD40L will promote enhanced antibody responses, and physical linkage between Env and these TNF family ligands will provide an even more potent stimulus, ii) HIV gp120 or gp140 variants that mask irrelevant portions of the surface with N-linked glycans will focus the antibody response to relevant epitopes, iii) Expressing HIV gp120/gp140 genes as fusion proteins with molecules that have a strong propensity to trimerize can facilitate the expression of the most relevant form of HIV Env. iv) Oral delivery of the DNA vaccine using an attenuated Salmonella typhimurium vector will promote a strong immune response in mucosal immune tissue, v) A combination of these features will yield a more effective vaccine candidate. These goals will be approached through the following Specific Aims: 1) To determine if selected HIV gp120 variants stimulate a better antibody response to DNA vaccination when introduced along with BAFF expressed either as a fusion gene or in the unlinked form. 2) To test the ability of linked or unlinked expression of BAFF or CD40L to improve the antibody responses to DNA vaccine delivered orally by attenuated Salmonella typhimurium. While the long-term goal is to generate an effective HIV vaccine, important achievable intermediate goals will be i) to assess the adjuvanticity of BAFF and other TNF family members, ii) to determine if gp120/BAFF or gp140/BAFF fusion molecules enforce envelope protein trimerization, and iii) to determine if these bioengineering steps facilitate the production of a broadly neutralizing antibody.