A central question to better understanding the pathogenesis of HIV infection is how memory CD4 T cells are infected and progressively depleted by HIV. Little is currently known about the impact of HIV infection on CD4 T cells of different pathogen or antigen specificities. Exploring this area is important for better understanding of the timing of different opportunistic infections in AIDS patients. In addition, identification of a functional population o vaccine-specific CD4 T cells that is resistant to HIV is critical for HIV vaccine design. We have established a novel system for studying the susceptibility of antigen-specific CD4 T cells to HIV, and have found that different antigen-specific CD4 T cells manifest marked differences in susceptibility to HIV infection. Our preliminary data show that compared to CD4 T cells specific to tetanus toxoid (TT) and Candida albicans (Candida), which are permissive to HIV, cytomegalovirus (CMV)-specific CD4 T cells are highly resistant to both R5 and X4 HIV with post-entry HIV restriction. Our microarray analysis identified a novel viral RNA sensor, IFIT1 that is highly upregulated in CMV-specific CD4 T cells. Of importance, in our ongoing experiments, we show that over-expression of IFIT1 inhibits HIV infection in A3R5 CD4 T cell line. Based on data already generated, we hypothesize that IFIT1 can inhibit HIV infection in human primary CD4 T cells and differential expression of IFIT1 regulates the permissiveness of antigen-specific CD4 T cells to HIV. We further propose to extend the novel system and observations to clinical HIV vaccine studies. Preferential infection of vaccine-induced CD4 T cells by HIV reduces the efficiency of vaccine-generated immunity. Our hypothesis is that a protective HIV vaccine should induce a type of vaccine-specific CD4 T cells that are not readily susceptible to HIV, and that different candidate HIV vaccines (e.g. different vectors) induce distinct phenotypes of vaccine- and/or vector-specific CD4 T cells that may impact their sensitivities to HIV. We will test peripheral blood mononuclear cell samples from three completed HIV vaccine trials: RV144 (ALVAC), RV158 (MVA) and IPCAVD 001(Ad26). Our hypotheses will be addressed in 2 Specific Aims: 1) To determine the role of IFIT1 in regulating the susceptibility of antigen-specific CD4 T cells to HIV and to further explore the mechanisms for inhibition of HIV by IFIT1; 2) To investigate the susceptibilities of different HIV vaccine-induced, antigen-specific CD4 T cells to HIV infection and the associated phenotypes in HIV vaccine trials. The proposed studies are exploratory, but expected to provide new insights to: 1) understand the mechanisms for the persistence of CMV-specific T cell immunity in AIDS patients; 2) identify a novel anti-HIV molecule with previously unidentified inhibitory mechanisms that could possibly lead to development of novel interventional strategies; 3) more thoroughly understand the quality of vaccine-generated CD4 T cell immunity and to provide proof of concept knowledge as to whether and how to induce functional, HIV-resistant CD4 T cells by an efficacious HIV vaccine.
HIV infection is global pandemic that affects millions of people. The exploratory studies proposed in this application are highly relevant to public health for these reasons. First, they may help us better understand HIV pathogenesis in terms of the timing of different opportunistic infections during HIV infection. Second, they may lead to identification of a novel anti-HIV molecule in human primary CD4 T cells that holds potential for developing novel interventional strategies. Third, they may aid HIV vaccine design by providing new insights into identification of the protective, HIV vaccine-generated CD4 T cell immunity.
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