A new humanized mouse model for studying HIV infection and antiretroviral therapeutics and human hematopoietic stem cell-delivered gene therapy to generate anti-HIV cytotoxic T cells
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In recent years, humanized Rag2-/-gammac -/- mice have emerged as a potential model for studying HIV infection and immune responses in vivo. These mice support the in vivo maturation of human hematopoietic stem cells into functional T, B, monocytic and dendritic cells following transplantation with human CD34+ hematopoietic stem cells (HSCs). In the first project, we tested the ability of these reconstituted mice to mount anti-HIV-1 humoral responses, using an intrasplenic route of injection, and to evaluate the in vivo efficacy of antiretroviral therapy. The intrasplenic injection resulted in high levels of HIV infection, with a subsequent depletion of the CD4+ T cell population. This paralleled a significant increase in the levels of CD8+ T cells as seen in human patients. More importantly, HIV infection increased serum levels of human IgG and IgM including human IgG specific for HIV gp120 and Gag, and IgM against gp120 and Gag. We also demonstrated here that humanized Rag2-/-gammac-/- mice were able to control the infection and prevent CD4+ depletion when receiving antiretroviral therapy.;HIV specific cytotoxic T cells play a critical role in controlling HIV infection. Since antigenic specificity of T lymphocytes is determined by the unique sequence of T cell receptor (TCR), an effective anti-HIV CTL response is more likely to rely on antigen specific TCR created by TCR rearrangement during T cell development. Thus, HIV specific immunity may be enhanced by gene transfer of the TCR sequences specific to HIV epitopes. In the second project, to generate potent anti-HIV CTLs, human HSCs were genetically engineered with HIV specific TCR and the cell differentiation was induced using a novel in vitro system. As a result, HSCs were successfully transduced with lentiviral vectors, and when co-cultured with Delta-like 1-expressing murine stromal cells, the engineered cells matured into T lymphocytes with a phenotypic expression of transferred TCRs with antigen specificity, in an athymic environment. These results demonstrate that HSCs can be reprogrammed to acquire and express transferred anti-HIV TCR, and Delta-like 1 expressing in vitro culturing system can drive HCSs into a T cell lineage.