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Session 97 Poster Session Neuropathogenesis Session Time: 4:30-6:30 pm Room 4E-F

735-W. Molecular Basis for Neurovirulence of CCR5 Tropic HIV-1 Isolates from Brain P. Gorry*1, J. Taylor2, G. Holm1, A. Mehle1, J. Moore3, T. Morgan3, M. Cayabyab1, M. Farzan1, J. Bell4, S. Wolinsky2, and D. Gabuzda1 1Dana-Farber Cancer Inst., Boston, MA; 2Northwestern Univ., Chicago, IL; 3Weill Med. Coll. of Cornell Univ., New York, NY; and 4Univ. of Edinburgh, UK Background: Most HIV-1 viruses in brain use CCR5 for entry. However, M-tropism rather than CCR5 usage predicts neurotropism. Neurotropic HIV-1 strains are not necessarily neurovirulent, and viral determinants that underlie pathogenic mechanisms in the brain are unknown. Methods: Viruses isolated from autopsy brain tissue samples from AIDS patients with dementia were characterized. Cytopathicity was determined by syncytium formation in MDM and quantitation of neuronal apoptosis in primary brain cultures. The gp160 regions of Env were cloned and sequenced. Fusion and infection assays were performed in cells expressing different amounts of each receptor. Binding assays using radiolabeled soluble Envs and cells expressing high or low levels of CCR5 were performed to determine relative Env-CCR5 affinity. Results: Neuronal apoptosis levels in primary brain cultures infected with the R5 virus UK1br increased by 160% compared to mock infected cultures (p<0.05), but were not significantly increased in cultures infected with the R5 isolate MACS2br. Two X4 viruses also induced apoptosis. The ability of HIV to induce neuronal apoptosis was closely associated with fusogenicity in MDM and was independent of replication capacity and coreceptor specificity. Fusion and single round infection assays using full-length Env clones demonstrated that a fusogenic and apoptosis-inducing phenotype was associated with reduced dependence of R5 viruses on levels of CCR5 and CD4. Binding assays demonstrated that these Envs have increased affinity for CCR5 compared to those from the MACS2br isolate. The UK1br isolate was more resistant to virus inhibition by TAK779 and other CCR5 inhibitors than was MACS2br. Examination of brain tissue sections revealed many MNGC in sections from patient UK1 but few in sections from patient MACS2. Conclusions: These results suggest that highly fusogenic R5 viruses in brain with reduced CCR5/CD4 dependence and increased CCR5 affinity are associated with cytopathicity and may contribute to neurodegenerative mechanisms in AIDS. High affinity Env-CCR5 interactions may facilitate resistance to virus inhibition by CCR5 inhibitors.

©2002 9th Conference on Retroviruses and Opportunistic Infections