763. HIV-Specific T Cells Can Be Expanded from Virus-Naive Donors to Target a Range of Viral Epitopes: Implications for a Cure Strategy After Allogeneic HSCT

Background: Adoptive T cell therapy has been successful in boosting viral-specific immunity post-hematopoietic stem cell transplant (HSCT), preventing viral rebound of CMV and EBV. However, the therapeutic use of T cells to boost HIV-specific T cell immunity in HIV+ patients has been met with limited success. Despite multiple attempts to eradicate HIV infection with allogeneic HSCT, the Berlin patient remains the only case of functional HIV cure. Previous infusions of HIV-specific T cells have resulted in immune escape from single epitope specificity and limited persistence of the T cell product. Our approach to address these limitations is to expand HIV-specific T cells derived from virus-naive donors including umbilical cord blood, employing a non-HLA restricted approach for HIV+ patients receiving allogeneic HSCT for HIV-associated hematologic malignancies. Design: We have developed a robust, reproducible platform that can expand HIV-specific T cells (HXTCs) from the naive pool in the allogeneic setting. Peripheral blood mononuclear cells isolated from virus-naive donors are used to generate dendritic cells and T cells. T cells are stimulated with antigen presenting cells pulsed with HIV-pepmix and a combination of cytokines that promote proliferation and differentiation. T cells were tested for: (1) specificity against HIV antigens and individual peptides, (2) pro-inflammatory cytokine secretion in response to stimulation with HIV peptides, and (3) ability to suppress HIV replication in vitro. Results: We successfully expanded (75.705 mean fold expansion) HXTCs recognizing HIV antigens from virus naive donors. IFNg ELISPOT showed HXTCs (n=8) were specific against Gag (mean=331.25 SFC/1e5 cells) and Nef (mean=242.63 SFC/1e5 cells) vs Irrelevant (mean=13 SFC/1e5 cells). HXTCs produced significantly pro-inflammatory responses (p less than 0.05) to stimulation by gag/nef, as determined by levels of TNF-alpha, IL-2, IL-6, IL-8, and perforin (n=3). Importantly, HXTCs (n=4) were able to suppress HIV replication more than non-specific CD8+ T cells when co-cultured with autologous CD4+ T cells infected with HIV SF162 (HXTC 78.62% viral suppression compared to CD8+ T cell 34.19% viral suppression). HXTCs showed both HLA Class I or II specificity for individual HIV epitopes, as determined by HLA blocking and IFNg ELISPOT. Conclusion: This is the first report demonstrating generation of functional, multi-HIV antigen specific T-cells from HIV-negative donors, which has implications for using allogeneic HSCT as a functional HIV cure. The low frequency of circulating HXTCs post-infusion suggests these HXTCs could have a significant effect on preventing viral rebound. The generation of HXTCs from cord blood could provide a further advantage to increase the donor pool.