296. Pre-Selection of Anti-HIV Lentiviral Vector Gene Modified Hematopoietic Stem Cells Significantly Improves Protection from HIV Infection: The Basis for a Future Clinical Trial

The successful treatment and cure of HIV in the Berlin Patient has highlighted the utility of HIV-resistant hematopoietic stem cells (HSC) to offer a potential functional cure for HIV infected individuals. Stem cell gene therapy for HIV can mimic this result by genetically engineering a patientu0027s own HSC with lentiviral vectors encoding HIV resistance genes. Clinical trials of HIV stem cell gene therapy have been unsuccessful at demonstrating complete efficacy due to the transplantation of a low percentage of anti-HIV gene expressing cells.Therefore, to bridge the gap between these previous approaches and the Berlin patient, we have developed a pre-selection process which allows for the purification of vector transduced cells prior to transplantation into patients. This pre-selective lentiviral vector (1TAX) encodes a triple combination of anti-HIV genes (a human/rhesus macaque TRIM5alpha, a CCR5 shRNA, and a TAR decoy) in addition to a truncated/mutated form of human CD25 which is expressed on the cell surface of transduced HSC and is used to enrich for the HIV-resistant cell population.Purity levels of 1TAX transduced human HSC obtained after selection for CD25+ were u003e94% as determined by flow cytometry. Safety of the 1TAX vector transduced/purified human HSC was demonstrated in vivo in NOD-SCID-Rag-/-IL2rgamma-/-(NRG) mice with the detection of engraftment and multi-lineage hematopoiesis into human T cells, B cells, and macrophages in the peripheral blood and lymphoid organs. Upon infection of 1TAX mice with a CCR5-tropic BaL-1 or a CXCR4-tropic NL43 strain of HIV-1, maintenance of normal human CD4+ cell levels were observed in the peripheral blood. A significant decrease (u003e4 logs) in HIV-1 plasma viremia was also demonstrated in 1TAX mice as compared to mice transplanted with nontransduced human HSC. Together, this work has demonstrated the safety and efficacy of this 1TAX pre-selective lentiviral vector in HSC and is the basis for a future human clinical trial of HIV stem cell gene therapy.