Project Summary The presence of a long-lived reservoir of latently infected CD4 T cells in HIV infected individuals requires that they remain on antiretroviral drug regimens life-long. Rare elite controllers maintain virus loads below the level of detection by standard clinical assays without antiretroviral treatment. The ability of such individuals to suppress virus replication is associated with antiviral cytolytic T cells that are resistant to exhaustion as a result of continuous receptor stimulation and checkpoint activation. The project will develop a therapeutic lentiviral vector-based dendritic cell (DC) vaccine that enhances CD8 T cell responses and reverses exhaustion to achieve a functional cure in which virus replication is suppressed without antiviral therapy. The vaccine is based on lentiviral vectors delivered in virions that contain the SIV accessory protein Vpx for high efficiency DC transduction and that express HIV-1 antigen, an immunostimulatory cytokine and a checkpoint inhibitor. The antigen will be expressed as a fusion protein that allows for TAP-independent presentation on class I major histocompatibility proteins. The ability of the vectors to induce anti-viral T cell responses will be tested in vitro and in vivo. AIDS patient peripheral blood mononuclear cell-derived DCs will be transduced with the vectors and tested for their ability to activate and expand autologous HIV-specific T cells in a high throughput ELISPOT assay that determines the epitope specificity and frequency of responding CD8 T cells across the HIV genome. The ability of vector-transduced DCs to induce antigen specific T cells and to suppress virus load will be determined in a humanized mouse model. The ability of the vaccine to reverse T cell exhaustion and to stimulate protective responses will be evaluated in the lymphocytic choriomeningitis virus mouse model. In addition, Vpx-containing lentiviral vectors will be tested in an engineered immunity approach for the long-term in vivo expression of antiviral proteins in DCs.

Project Narrative The presence of a long-lived reservoir of latently infected CD4 T cells in HIV infected individuals requires that patients remain on antiretroviral drug regimens life-long. The project will develop a therapeutic vaccine that enhances the immune response against the virus such that patients can discontinue or reduce treatment and maintain low virus loads. The vaccine will use a viral vector to introduce genes into the dendritic cells of the patient that stimulate anti-viral T cells, preventing them from their natural tendency to become exhausted over time.