Evaluating the Safety and Efficacy of Anti-HIV Transgenic Cells in a Humanized Mouse Model (NOD/SCIDγ_c^−/−) for HIV Stem Cell Gene Therapy.

In vivo mouse models for safety and efficacy studies of anti-HIV gene therapeutics have been lacking in their ability to evaluate normal systemic hematopoiesis with the development of a functional immune system. These deficiencies in modeling these normal and essential physiologies can now be generated in the recently developed NOD/SCIDγ_c^−/− mouse model. Human CD34+ progenitor cells after intrahepatic injection will undergo multi-organ engraftment generating a functional thymus along with the production of T cells, B cells, and macrophages. Upon injection with various strains of HIV-1, engrafted mice display a disseminated infection due to viral replication in human T cells and macrophages. Infected mice acquire characteristics of increased viremia over time with human CD4+ T cell depletion. Anti-HIV immune responses can also be generated in mice with high viremia. Here we demonstrate the successful engraftment of NOD/SCIDγ_c^−/− mice after injection with human CD34+ progenitor cells isolated from umbilical cord blood. Human cell engraftment was observed in both primary and secondary lymphoid organs including the bone marrow (B cells and macrophages), thymus (T cells), spleen (T cells and B cells), lymph nodes (T cells and B cells), and peripheral blood (T cells and B cells). Human CD34+ cells were found in the liver concluding either organ retention from the initial injection or circulation in the peripheral blood. After displaying a high level of engraftment (>50%), we are now able to proceed with evaluating a number of anti- HIV gene therapeutic constructs for pre-clinical testing. These lentiviral vector constructs include a CCR5 shRNA which has been previously shown to knock down complete expression of CCR5, a human/rhesus macaque chimeric isoform of TRIM5α capable of potently inhibiting HIV-1 infection at the pre-integration step, and combination constructs containing multiple anti-HIV genes. The NOD/SCIDγ_c^−/− mouse model will allow us to evaluate both the safety of these various anti-HIV lentiviral constructs in generating normal functioning transgenic immune system cells and also the efficacy of these anti- HIV genes in inhibiting HIV-1 infection in vivo. With the ability to facilitate multilineage human cell engraftment with the susceptibility for HIV infection, this in vivo model allows for the evaluation of anti-HIV gene therapeutic constructs in a stem cell-based setting. Lentiviral vector transgenic cells can now be tested for their capacity for normal immune system reconstitution.