Successful development of a vaccine against HIV will likely require the induction of both antibody and/or cellular immune responses sufficient to prevent infection or disease respectively following infectious challenge. While the induction of antibody responses for a variety of other infectious pathogens is readily achieved by a variety of vaccine formulations, live attenuated, recombinant viral vaccines or plasmid DNA vaccines only induce the induction of long-lived cellular immune responses, particularly CD8+ T cell responses. Moreover, since live attenuated HIV vaccines might be precluded from use due to safety concerns and DNA vaccines at present only induce modest CD8+ T cell responses in humans, there is an urgent need to develop ways to enhance the generation and maintenance of CD8+ T cell responses in humans in following immunization. This study focuses on how to optimize the magnitude and duration of CD8+ T cell responses following vaccination in rodents and primates using a variety of vaccine formulations. The data obtained over this past year have shown the following; 1. A comparative analysis of single or combination TLR ligands was done in NHP using SIV Gag protein and an oil/water emulsion. Amongst the adjuvants used, Poly IC and a TLR 7/8 agonist were the most potent for inducing SIV Gag specific CD4 and CD8+ T cell responses. 2. A non-human primate study showed that a non-targeted and targeted HIV Gag protein to DEC-205, a receptor specific for dendritic cells induced potent and comparable Th1 immunity following a series of immunizations. However the protein vaccine elicited higher avidity antibody responses while the DEC-205 targeted vaccine had higher CD8+ T cell responses. These data show that delivery of protein with Poly ICLC as an adjuvant can influence the type of adaptive immunity generated. Animals have been boosted with a pox viral vector encoding HIV Gag and the immune responses will be assessed. 3. A comparative analysis of adjuvants and formulation was recently completed in NHP using HIV Env protein. This study focused on two clinically approved adjuvants ( alum and MF-59) with or without TLR 4 or TLR 7 ligands as additional immune stimulators. The data generated so far show that MF-59 induces more potent humoral and cellular immunity than alum when given with HIV Env protein. Combining alum with a TLR 7 ligand strongly enhanced immunity compared to alum alone. By contrast, adding TLR 4 or TLR 7 ligands to MF 59 did increase immunity compared to alum alone. In terms of T cell immunity, MF 59 induced a mixed Th1 and Th2 cytokine response. Additional analysis in terms of durability, avidity and ADCC is being performed. 4. A comparative analysis of adenoviral or pox viral vectors encoding SIV Gag was initiated this year. The data show that the amount and duration of antigen has a dramatic influence on the strong CD8+ T cell immunity with rAd5 compared to other Ad serotypes. By contrast, there is minimal innate immunity induced by Ad5.
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