The immune repertoire of HIV-infected individuals is characterized by the presence of progressively dysfunctional viral-specific CD4+ and CD8+ T cells, also referred to as "anergic" or "exhausted" T cells. The anergic T cells fail to control viremia and prevent the induction of vaccine-induced protective immunity. The hypotheses underlying this project are: (a) Reversing T cell dysfunction in HIV-infected patients will significantly enhance the effectiveness of therapeutic vaccination strategies. (b) Multiple mechanisms contribute to T cell dysfunction, the relative importance of which has not been fully determined (c) Re- activation of a potent and therapeutically useful antiviral immune response will require the simultaneous engagement of multiple costimulatory and coinhibitory receptors in the HIV-infected patient. (d) Development of increasingly accessible and less immunogenic reagents targeting immune modulatory receptors will significantly facilitate and expedite their combined exploration and use. The specific goal of this 2-year project is to develop a novel and clinically useful reagent to block the function of the coinhibitory receptor PD-1 expressed by the anergic T cells of HIV infected patients, The PD-1 inhibitor will consist of an oligonucleotide (ODN)-based aptamer. Aptamers are high-affinity nucleic acid ligands which like antibodies exhibit exquisite specificity and high affinity to their targets. Unlike antibodies, aptamers can be synthesized in a simple chemical process and hence offer a more straightforward, cost effective, and vastly simpler regulatory approval process for clinical use. In addition, ODN-based aptamers are expected to be significantly less immunogenic than antibodies. The specific aims of this project are: (1). To isolate cross-species PD-1 aptamers which bind to both murine and human PD-1 expressed on T cells. (2). To demonstrate that PD-1 binding aptamers can rescue dysfunctional T cells obtained from HIV-infected patients (3). To demonstrate that the PD-1 binding aptamers can reverse T cell anergy in an LCMV infection model in mice. Accumulating evidence suggest that PD-1 signaling is not the sole mechanism for T cell anergy in HIV-infected patients. The development of PD-1 aptamers in this 2 year project will guide the development of cross-species aptamers against other immune receptors implicated in T cell anergy, such as blocking CTLA-4 aptamers or agonistic 4-1BB and CD27 aptamers. The ODN-based aptamers represent a novel platform technology enabling the combined evaluation and clinical exploration of immune receptor-targeted aptamers to modulate antiviral immunity in the vaccinated HIV-infected patients. PUBLIC HEALTH RELEVANCE: Immune defects in HIV infected patients are manifested in various dysfunctions of the immune system. This dysfunction, referred to as "anergy", is largely responsible why patients don't control the virus and progress to AIDS and also limits the effectiveness of immune-based treatments. The goal of this research proposal is to reverse anergy in HIV infected patients. We propose to develop a new platform technology which will provide effective and clinically useful, namely cost-effective and user-friendly, drugs to convert the dysfunctional immune cells of HIV-infected patients into active cells capable of targeting and eliminating HIV. These drugs will be particularly useful when used in combination with treatments designed to stimulate HIV specific immunity in the infected patients, known also as "therapeutic vaccination".