The viral envelope gene is involved in macrophage tropism of a human immunodeficiency virus type 1 strain isolated from brain tissue

Human immunodeficiency virus type 1 (HIV-1) strains isolated from the central nervous system (CNS) may represent a subgroup that displays a host cell tropism different from those isolated from peripheral blood and lymph nodes. One CNS-derived isolate, HIV-1(SF128A), which can be propagated efficiently in primary macrophage culture but not in any T-cell lines, was molecularly cloned and characterized. Recombinant viruses between HIV-1(SF128A) and the peripheral blood isolate HIV-1(SF2) were generated in order to map the viral gene(s) responsible for the macrophage tropism. The env gene sequences of the two isolates are about 91.1% homologous, with variations scattered mainly in the hypervariable regions of gp120. Recombinant viruses that have acquired the HIV-1(SF128A) env gene display HIV-1(SF128A) tropism for macrophages. Furthermore, the gp120 variable domains, V₁, V₂, V₄, and V₅, the CD4-binding domain, and the gp41 fusion domain are not directly involved in determining macrophage tropism.