Small amino acid changes in the V3 loop of human immunodeficiency virus type 2 determines the coreceptor usage for CXCR4 and CCr5

Abstract

HIV-2 GH-1 is a molecular clone derived from an AIDS patient from Ghana. In contrast to the prototypic molecular clone ROD, GH-1 exhibits a narrow range of target cell specificity. By an infectious assay using HeLa-CD4 cells stably transfected with an HIV-1 LTR-β-galactosidase reporter gene and transiently expressing various cloned chemokine receptors, we have examined the coreceptor usage of GH-1. In contrast to ROD, which uses principally CXCR4, GH-1 was found to use mainly if not exclusively CCR5 but not CXCR4. The distinct coreceptor usage of these two molecular clones allowed us to further map the region of gp120 that is important for the coreceptor specificity. By constructing a series of chimeric viruses between GH-1 and ROD, we have demonstrated that the C-terminal half of the V3 loop region of gp120 determines the differential coreceptor usage between GH-1 and ROD, and only a few amino acid differences in this region appear to be able to shift the specificity between CCR5 and CXCR4. Notably, the shift in the coreceptor usage from CCR5 to CXCR4 is associated with an increase in the net positive charge in the V3 region.