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Comprehensive Characterization of Co-receptor Utilization by HIV-1 Subtype C Primary Isolates E Sepako*, T Ndung’u, S Gaseitsiwe, K Bedi, T Peter, Charles Kasipo, M Modukanele, and M Essex Botswana-Harvard Partnership for HIV Research and Education Private Bag BO320, Gaborone, Botswana Background: Human immunodeficiency virus type 1 subtype C accounts for nearly 50% of all HIV/AIDS cases in the pandemic and is the predominant subtype in the heavily burdened region of southern Africa. Although the reasons for the rapid spread of HIV-1 subtype C remain largely unclear, the HIV-1 subtype C env gene possesses unique genetic features that have suggested important biological differences from other subtypes. In this study, we sought to investigate the frequency and efficiency of usage of different chemokine receptors by HIV-1 subtype C isolates for entry into cells. Isolates were obtained from individuals at different stages of infection. We also investigated whether as the epidemic ages, is there a discernable evolution of the virus, as assesses by changes in coreceptor usage profile. Methods: HIV-1 subtype C isolates were obtained from individuals at different stages of infection by co-cultivation of peripheral blood mononuclear cells (PBMCs) with donor PBMCs. We attempted viral isolations from 43 individuals, whose CD4 cell count ranged from 10 cells/µl to 1047 cells/µl. 28 isolates were successfully generated. Isolates were then propagated in cells lines that express CCR1, CCR2(b), CCR3, CXCR4 and CCR5 chemokine receptors. Results: We have determined co-receptor usage of 19 isolates. 14 isolates utilized the chemokine receptor CCR5 as the only co-receptor for entry into cells. The rest, whose CD4 cell count ranged from 10 cells/µl to 351 cells/µl used both CXCR4 and CCR5 as the coreceptors for cell entry. No isolates used any of the minor coreceptors, and importantly, no isolate was found to use CXCR4 chmokine receptor exclusively. Conclusions/Summary: We have demonstrated that the use of coreceptors other than CCR5 is very rare among HIV-1 subtype C isolates. There appears however to be an evolution towards dultropism of HIV-1 s subtype C isolates in individuals at advanced stages of disease. These results have important implications for the design and use of HIV entry inhibitors as a therapeutic approach in regions where HIV-1 subtype C is the predominant virus. |