SIV DNA vaccine co-administered with IL-12 expression plasmid enhances CD8 SIV cellular immune responses in cynomolgus macaques Background More than 20 million people have died of AIDS. The social and economic impact of human immunode- ficiency virus type 1 (HIV-1) infection in many countries is alarming. It appears that the only means of controlling this pandemic will be the development of a vaccine. It is believed that CD8 + T-cell responses targeted at HIV-1 are important for controlling infection. A correlation has been established be- tween long-term non-progression and HIV-1-speci- fic CD8 + T-cell responses [6, 24, 39, 42, 43, 41]. There are several vaccine approaches that induce cellular immunity [4, 10, 11, 23, 27, 29, 31, 34, 37, 54]. DNA vaccines are an appealing strategy because of their safety, ease of preparation, storage, and adminis- tration. However, initial DNA vaccine studies in humans and nonhuman primates have raised ques- tions regarding their immune potency. A first generation DNA vaccine was evaluated in a Phase 1 clinical trial. Subjects in the higher dose group demonstrated antigen-specific lymphoproliferation and production of interferon-c and b-chemokines from CD4 T cells [5]. However, the CD8 T cells response rate was below 30%. Mwau tested the immunogenicity of candidate DNA- and modified vaccinia virus Ankara vectored HIV vaccines in a prime boost combination. The vaccines induced low-level HIV-specific responses [33]. Researchers have experimented with engineering DNA vaccines for HIV-1 to include their own immune expansion signals as co-delivered plasmids [45, 3]. In mouse studies among the most potent drivers of CTL immunity were CD40L and interleukin (IL)-12 [19, 17, 18, 21, 20, 26, 47–49]. Each of these molecules plays a role in the induction of the cellular immune response. CD40L impacts a CD8 cellular immune response most likely J Med Primatol 2005: 34: 262–270 Boyer JD, Robinson TM, Kutzler MA, Parkinson R, Calarota SA, Sidhu MK, Muthumani K, Lewis M, Pavlakis G, Felber B, Weiner D. SIV DNA vaccine co-administered with IL-12 expression plasmid enhances CD8 SIV cellular immune responses in cynomolgus macaques. J Med Primatol 2005; 34:262–270. Ó Blackwell Munksgaard, 2005 Abstract: Current evidence suggests that a strong induced CD8 human immunodeficiency virus type 1 (HIV-1)-specific cell mediated immune response may be an important aspect of an HIV vaccine. The response rates and the magnitude of the CTL responses induced by current DNA vaccines in humans need to be improved and cellular immune responses to DNA vaccines can be enhanced in mice by co-delivering DNA plasmids expressing immune modulators. Two reported to work well in the mouse systems are interleukin (IL)-12 and CD40L. We sought to compare these molecular adjuvants in a primate model system. The cDNA for macaque IL-12 and CD40L were cloned into DNA vectors. Groups of cynomolgus macaques were immunized with 2 mg of plasmid expressing SIVgag alone or in combination with either IL-12 or CD40L. CD40L did not appear to enhance the cellular immune response to SIVgag antigen. However, more robust results were observed in animals co-injected with the IL-12 molecular adjuvant. The IL-12 expanded antigen-specific IFN-c positive effector cells as well as granzyme B production. The vaccine immune responses contained both a CD8 component as well a CD4 component. The adjuvanted DNA vaccines illustrate that IL-12 enhances a CD8 vaccine immune response, however, different cellular profiles. Jean D. Boyer 1 , Tara M. Robinson 1 , Michele A. Kutzler 1 , R. Parkinson 1 , Sandra A. Calarota 1 , Maninder K. Sidhu 2 , Karuppiah Muthumani 1 , Mark Lewis 3 , George Pavlakis 4 , Barbara Felber 4 , David Weiner 1 1 Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, 2 Vaccine Discovery, Wyeth, Pearl River, NY, 3 Bioqual, Frederick, MD, 4 National Cancer Institute, Bethesda, MD, USA Key words: vaccine – DNA – IL-12 – HIV – SIV Accepted April 14, 2005. David Weiner, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. Tel.: +1 215 3498365; fax: +1 215 5733496; e-mail: dbweiner@mail.med.upenn.edu Funding: This was funded in part by NIH IPCP and HVDDT grants 262