Concordant utilization of macrophage entry coreceptors by related variantswithin an HIV type 1 primary isolate viral swarm

There is considerable diversity among HIV-1 strains in terms of their abili ty to use entry coreceptors on macrophages, especially CXCR4, but it is not known whether virus-specific differences exist among related members of a viral swarm. Defining how entry coreceptors on primary target cells are uti lized by the spectrum of HIV-1 variants that emerge in vivo is important fo r understanding the relationship between coreceptor selectivity and pathoge nesis. HIV-1 89.6(PI) is a dual-tropic primary isolate, and the prototype 8 9.6-cloned R5X4 Env uses both CXCR4 and CCR5 on macrophages. We generated a panel of env clones from the 89.6(PI) quasispecies and found a mixture of R5, R5X4, and X4 variants on the basis of fusion and infection of corecepto r-transfected cell lines. Here we address the use of macrophage coreceptors by these related Envs by analyzing fusion and infection of primary monocyt e-derived macrophages mediated specifically through each coreceptor. All R5 X4 Envs utilized both CXCR4 and CCR5 on macrophages, while R5 variants used CCR5 only. One variant characterized in cell lines as X4 used both CXCR4 a nd CCR5 on macrophages. No Env variant fused with macrophages through alter native coreceptor pathways. Thus, there was heterogeneity in coreceptor use among the related Env variants, but use of each coreceptor specifically in macrophages was consistent among members of the viral swarm. Coreceptor us e in transfected cells generally predicted use in primary macrophages, alth ough for some Envs macrophages may be a more sensitive indicator of CCR5 us e than transfected cell lines.