Summary: (1) Goals of project: - To identify cellular genes required for optimal HIV-1 infection, or involved in HIV-1 pathogenesis. - To study the mechanism by which intrathymic HIV-1 infection affects the development of different T cell subsets. - To understand how HIV-1 infection leads to high levels of programmed cell cell in both CD4 and CD8 cells. - To apply the knowledge gained towards development of anti-viral therapy which target both viral and cellular genes. - To study in situ expression of chemokines and cytokines in normal and HIV-1-infected human thymic tissues. - Thymic regeneration and immune reconstitution: Development of animal models to study the role of cytokines and hormonal contributions (2) Experimental approach: - Scid/Hu mice were infeected intrathymically with primary isolate of HIV. Frozen sections were stained by immunohistochemistry with antibodies against HIV-1 p24, HIV-1 coreceptors, and against the CXCR4 ligand SDF1. - Develop imuunohistochemisry staining of thymic tissues to determine the sites and cellular origin of various chemokines and cytokines that may affect HIV infections and potential thymic regeneration in infected children on HAART. - Experiments were performed to evaluate the effects of estradiol-induced thymic atrophy on the population of peripheral lymphoid organs with naive T cells and to determine a role for IL-7 in restoration of thymic cellularity. 2. Specificity of anti-IL-7 antibodies was tested in immunohistochemistry. (3) Major Findings: - During the first year, the following assays and models have been established: immunohistochemistry with anti-IL-7 antibodies, TREC-PCR analysis, IL-7 RT-PCR, in vivo model of estradiol-induced thymic atrophy. The primary goal of the study was achieved that is we demonstrated that administration of a single dose of estrogens in mice induced transient thymic atrophy that correlated with transient reduction in the population of peripheral naive T cells. All the essential assays to evaluate generation of naive cells in vivo were established. - Preliminary data suggest that IL7 is produced by epithelial cells in the thymus. Apoptosis inducing regiments (i.e., in vivo treatment with corticosteroids) upregulate IL7 and re-start thymopoiesis.