Abstract
HIV continues to be a global health problem due to the lack of an effective vaccine or curative treatment. HIV stem cell gene therapy is a promising strategy for the treatment of HIV as its effect is hypothesized to mimic the results observed in the Berlin patient. Previous attempts with HIV stem cell gene therapy were hindered due to low levels of transduction efficiency leading to a limited number of protected cells actually being transplanted into patients. In our current studies, we seek to improve the effectiveness of HIV stem cell gene therapy by evaluating the preclinical safety and efficacy of a preselective combination anti-HIV lentiviral vector, which allows for the purification of transduced cells prior to transplantation into patients. The combination vector contains a human/rhesus macaque TRIM5a isoform, a CCR5 short hairpin RNA (shRNA), a TAR decoy, and a truncated/mutated version of CD25, which is used as the pre-selective marker. In this project, both the safety and efficacy of CD34 human hematopoietic stem/progenitor cells (HSPCs) transduced with the pre-selective anti-HIV vector were evaluated by various in vitro assays as well as evaluated in vivo in the humanized murine NOD-SCID-RAG 1-IL2rg (NRG) model. We hypothesized that an increase in the level of transplanted HIV-resistant cells would allow for proper maintenance of human CD4+ cells, as seen in our previous studies, and subsequently offer a potential decrease of in vivo plasma viremia levels. Multilineage hematopoiesis from transduced human CD34+ HSPCs containing the pre-selective anti-HIV lentiviral vector was evaluated in the peripheral blood and various lymphoid organs, including the thymus, spleen, and bone marrow, of engrafted mice. Successfully engrafted mice were challenged with different tropic strains of HIV -1 and evaluated for levels of human CD4 + cells and for plasma viremia. Using gene therapy we have demonstrated that it is possible to genetically modify HSPCs to express anti-HIV genes. Through in vitro and in vivo experimentation, we were able to demonstrate on multiple levels the safety and efficacy of 1 TAX lentiviral vector transduced HSPCs. The results that have been obtained from this project hold tremendous promise for HIV gene therapy as a replacement to current HIV treatment, representing one more step toward a cure.