A NOVEL, LOGICAL APPROACH TO HIV VACCINE DEVELOPMENT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To generate strong cytotoxic T lymphocytes (CTL) responses, in the absence of other immune responses, using several different vaccine approaches. All HIV vaccine efficacy trials to date have ended in failure. Structural features of the Env glycoprotein and its enormous variability have frustrated efforts to induce broadly-reactive neutralizing antibodies. To explore the extent to which vaccine-induced cellular immune responses, in the absence of neutralizing antibodies, can control replication of a heterologous, mucosal viral challenge, in 2007, we vaccinated eight macaques with a DNA/Ad5 regimen expressing all of the proteins of SIVmac239 except Env. Vaccinees mounted high-frequency T cell responses against 11-34 epitopes. In June 2008, we began to challenge the vaccinees and eight na¿ve animals with the heterologous biological isolate SIVsmE660, using a regimen intended to mimic typical human HIV exposures resulting in infection. Viral loads in the vaccinees were significantly less at both peak (1.9 log reduction p0.03) and at set point (3.3 log reduction p0.003) than those of control na¿ve animals. Six of eight vaccinated macaques controlled acute peak viral replication to less than 80,000 vRNA copy Eq/ml and to less than 100 vRNA copy Eq/ml in the chronic phase. Some vaccinees are more than 1.5 years post infection and still have viral loads below levels of detection. Significant differences are present between vaccinees and controls for time of death post infection due to SAIDS, although this data is still preliminary. Our results demonstrate that broad vaccine-induced cellular immune responses can effectively control replication of a pathogenic, heterologous AIDS virus, suggesting that T cell based vaccines may have greater potential than previously appreciated. We have a manuscript in revision about correlates of protection observed during this study. We have an additional manuscript in preparation describing the long term outcome differences between the vaccinees and control animals. This research uses WNPRC Immunology and Virology Services (tetramers, flow cytometry instruments, Elispots), WNPRC Genetics Services (MHC typing). PUBLICATION: Wilson NA, Keele BF, Reed JS, Piaskowski SM, MacNair CE, Bett AJ, Liang X, Wang F, Thoryk E, Heidecker GJ, Citron MP, Huang L, Lin J, Vitelli S, Ahn CD, Kaizu M, Maness NJ, Reynolds MR, Friedrich TC, Loffredo JT, Rakasz EG, Erickson S, Allison DB, Piatak M Jr, Lifson JD, Shiver JW, Casimiro DR, Shaw GM, Hahn BH, Watkins DI. Vaccine-induced cellular responses control simian immunodeficiency virus replication after heterologous challenge. J Virol. 2009 Jul;83(13):6508-21. Epub 2009 Apr 29. PMID: 19403685