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Session 52 Poster Session Pathogenesis Studies in Animal Models Session Time: 4:30-6:30 pm Room 4E-F

334-W. Development of a Murine Model for HIV Infection T. Soos*1, N. Bitton1, V. Kewal-Ramani2, D. R. Littman1, and 3 1Skirball Inst. for Biomolecular Med., New York Univ. Med. Ctr., NY; 2NCI, NIH, Frederick, MD; and 3Howard Hughes Med. Inst., New York, NY Background: The development of a murine model to study HIV pathogenesis would significantly advance our understanding of HIV replication in vivo, the immune response to infection as well as aid in new approaches to treat or prevent HIV infection. However, mice are resistant to HIV infection, as species-specific blocks occur in viral entry, viral gene expression, and virion assembly. In murine cell lines, the expression of human CD4, the co-receptors CXCR4 or CCR5, and human cyclin T1 rescues some of the blocks in HIV replication by permitting viral entry and gene transcription. In an effort to develop a mouse model susceptible to HIV infection, we have created transgenic mice expressing human CD4, CCR5, and cyclin T1. Methods:We created mice that express human CD4, CCR5, and cyclin T1 using a transgenic construct containing the murine CD4 enhancer and promoter as well as a monocyte/macrophage enhancer from the human CD4 gene. This construct directs expression of the transgene in CD4+ T cells, macrophages and dendritic cells. We infected activated CD4+ T cells or macrophages from the spleen, lymph nodes, and thymus in vitro with replication competent R5 tropic virus, or pseudo-typed HIV containing a GFP reporter gene. Results: We observed expression of human CD4 and CCR5 in CD4+ T cells in the spleen and lymph nodes and thymus as well as in splenic macrophages and dendritic cells. Expression of human CD4 and CCR5 permitted pseudotyped HIV entry in activated CD4+ T cells and macrophages, but not viral transcription. HIV viral transcription was enhanced 20- to 80-fold in transgenic mice expressing human cyclin T1. However, preliminary results suggest that CD4+ T cells do not support HIV replication in vitro as determined by p24 ELISA analysis and the infection of GHOST reporter cells. Interestingly, Western blot analysis of infected transgenic T cells demonstrates that gag protein is processed to p24/p17. We are currently characterizing the block in replication in infected T cells as well as analyzing HIV replication in macrophages. Conclusions: Mice transgenic for human CD4, CCR5, and cyclin T1 partially rescue a block in HIV replication in primary murine lymphoid cell types, suggesting that the block to HIV replication occurs post-translationally, perhaps at viral budding. Furthermore, this model may be a useful tool for the analysis of species-specific requirements for HIV replication and pathogenesis.

©2002 9th Conference on Retroviruses and Opportunistic Infections