Preferential coreceptor utilization and cytopathicity by dual-tropic HIV-1in human lymphoid tissue ex vivo

Many HIV-1 isolates at the late stage of disease are capable of using both CXCR4 and CCR5 in transfected cell lines, and are thus termed dual-tropic. Here we asked whether these dual-tropic variants also use both coreceptors for productive infection in a natural human lymphoid tissue microenvironmen t, and whether use of a particular coreceptor is associated with viral cyto pathicity. We used 3 cloned dual-tropic HIV-1 variants, 89.6 and its chimer as 89-v345.SF and 89-v345.FL, which use both CCR5 and CXCR4 in transfected cell lines. In human lymphoid tissue ex vivo, one variant preferentially us ed CCR5, another preferentially used CXCR4, and a third appeared to be a tr ue dual-tropic variant. The 2 latter variants severely depleted CD4(+)T cel ls, whereas cytopathicity of the virus that used CCR5 only in lymphoid tiss ue was mild and confined to CCR5(+)/CD4(+) T cells. Thus, (a) HIV-1 corecep tor usage in vitro cannot be unconditionally extrapolated to natural microe nvironment of human lymphoid tissue; (b) dual-tropic viruses are not homoge neous in their coreceptor usage in lymphoid tissue, but probably comprise a continuum between the 2 polar variants that use CXCR4 or CCR5 exclusively; and (c) cytopathicity toward the general CD4(+) T cell population in lymph oid tissue is associated with the use of CXCR4.