Recent reports have identified the presence of HIV-1 gp160 specific IgA, but not IgG, responses in the female genital tract of highly exposed commercial sex workers as well as HIV-1 discordant couples. Similarly, a subset of rhesus macaques vaginally exposed to pathogenic SHIV-89.6PD, but who have remained SHIV PBMC virus co-culture negative with no clinical disease progression nor loss of CD4 T cells, developed a potent IgA response localized to the genital tract. Binding specificities of the vaginal IgA were unique and included a neutralizing epitope in gp41 as well as epitopes exposed uniquely on the gp120-CD4 complex. Furthermore, the macaque CVL IgA responses were capable of neutralizing SHIV-89.6PD infection of cultures of dendritic cells and T cells in vivo. Prime-boost immunization regimens using combinations of DNA and MVA vaccines have recently been demonstrated to be particularly potent at inducing both cellular and humoral immunity. We propose to mucosally administer DNA and MVA encoding HIV-1 env antigens and SIV gag/pol antigens in a prime-boost immunization regimen alone or in combination with boosting by a soluble oligomeric gp140 protein. The basic hypothesis of this proposal is that the induction of potent HIV envelope-specific vaginal IgA, together in combination with circulating as well as local lymph node T helper and CTL responses, will provide protection against vaginal pathogenic SHIV-89.6PD challenge.
The aims of this proposal are: (i) optimize adjuvant formulations of DNA vaccines encoding HIV-1 envelope and SIV gag/pol antigens for mucosal delivery; (ii) evaluate systemic and mucosal ummunogenicity of mucosally administered combinations of DNA, MVA and ogp140 in rhesus macaques and protection from vaginal challenge with pathogenic SHIV-89.6PD; (iii) determine whether co-administration of DNA encoding chemokine or cytokine molecular adjuvants enhances immunogenicity and degree of protection from vaginal pathogenic SHIV challenge; and (iv) correlate vaccine-induced immune responses with in-vivo protection from vaginal SHIV challenge and determine for the non-protected monkeys whether pre-existing immunity augments or modulates subsequent post challenge SHIV immunity. The ability of vaccination to influence vaginal transmission of pathogenic SHIV-89.6PD will be evaluated and correlated with mucosal and system immunogenicity parameters. By relating these results to challenge studies, insight may be gained into correlates of protection at mucosal surfaces.
