IDENTIFICATION OF THE ENVELOPE V3 LOOP AS THE PRIMARY DETERMINANT OF CELL TROPISM IN HIV-1

Cells of the monocyte-macrophage lineage are targets for human immunodeficiency virus-1 (HIV-1) infection in vivo. However, many laboratory strains of HIV-l that efficiently infect transformed T cell lines replicate poorly in macrophages. A 20-amino acid sequence from the macrophage-tropic BaL isolate of HIV-1 was sufficient to confer macrophage tropism on HTLV-IIIB, a T cell line-tropic isolate. This small sequence element is in the V3 loop, the envelope domain that is the principal neutralizing determinant of HIV-1. Thus, the V3 loop not only serves as a target of the host immune response but is also pivotal in determining HIV-l tissue tropism.