This proposal is designed to extend our previous studies where we achieved significant systemic and mucosal cellular responses after oral cavity and intestinal immunizations with a SIV DNA-rMVA approach. These immunizations had two important impacts on SIV exposure and infection: 1. the intestinal immunization provided significant protection from infection but no protection from disease progression; 2. the oral cavity immunization provided significant protection from disease with no AIDS development observed during the post-challenge follow up and with more than 50% of the animals controlling virus replication to undetectable blood levels after experiencing a peak of viremia, and apparently clearing the infection, as no rebound was observed after CD8+ T-cell depletion. Here we propose to investigate in Cynomolgus macaques anti-SIV and SHIV oral immunization approaches aimed at stimulating cellular immune responses, previously achieved via oral immunization, and persistent anti-Env IgG and IgA titers, previously sporadic or missing, systemically and at mucosal sites where HIV exposure occurs in humans. The goal sof the proposal are the following: I. To evaluate how oral immunization regimens composed of 1. pSIVvaxE543 DNA, boosted with gp140(smE543) Env and rMVA, 2. pSIVvaxE543 DNA + SIVgag239 and SIVenvsmE543 recombinant OPVs (collectively called SIV-OPV), and 3. SIV-OPV alone compare in their stimulation of cell mediated and humoral immunity systemically and at mucosal sites where HIV transmission occurs in humans, and whether they provide protection from heterologous SIVmac251 infection and disease in Cynomolgus macaques (CM). II. To evaluate stimulation of systemic and mucosal cell-mediated immunity and humoral immunity by three regimes that include SHIVBG505 DNA + SIVgag239-OPV and HIV Env-OPV, where Env in this last component is linear HIVBG505 gp140 in Group 1, a SOSIP-gp140 BG505 in Group 2, and a V1-V2 BG505 scaffold in Group 3, and whether these responses provide protection from heterologous SHIVAD8 infection and disease in CM; III. To evaluate the extent of anti-HIV Env antibody affinity maturation observed with repeated SHIV-OPV immunization. During these experiments we will evaluate mechanistic characteristics of the anti-SIV or SHIV immune response and correlates of protection from infection and disease, with focus on the analysis of intestinal mucosa responses and viral loads, viral reservoirs, and possibly eradication post infection.
This proposal is designed to investigate immunization approaches aimed at improving the oral vaccination regimen that we previously explored and showed promising partial protection from infection and significant disease delay in the infected animals. The experiments described in this proposal are critical to investigate the immunogenicity of a new vaccine platform made of recombinant DNA and purified Env protein or recombinant oral polio vaccines, engineered to induce immunity for SIV and HIV and not yet explored in preclinical vaccination studies. Our oral SIV DNA/rMVA vaccine approach, which includes vaccines similar to those of the human RV144 trial that showed partial protection of infection, has already achieved better results than those observed in macaques with the corresponding RV144 vaccine. These modified approaches have the potential to provide a cheap, safe and efficacious vaccine for protection from HIV and AIDS.
