Multiple determinants for growth of human immunodeficiency virus type 1 in monocyte-macrophages

Attempts to define the genetic determinants required for efficient growth of human immunodeficiency virus type 1 (HIV-1) in monocyte-macrophages were made by constructing chimeras between two infectious clones of HIV-1 (HXB2 and LW/C), which despite only minor differences in their DNA sequence have striking differences in cell tropism. Although both of them replicate efficiently in peripheral blood mononuclear cells, HXB2 replicates extensively in permanent T cell lines but poorly in primary monocyte macrophages (T cell line tropic); the reverse is true for LW/C (macrophage tropic). The envelope proved to contain the major determinants of macrophage tropism. However, tropism determinants appeared to be scattered along the envelope. In particular, the V3 loop alone appeared to be neither necessary nor sufficient for growth in macrophages. Both vpr and nef genes appeared to play a less significant role to improve viral replication in macrophages, but only in the presence of the proper envelope sequences. HIV-1 macrophage tropism thus appears to result from the contribution of several different determinants.