Changes in the host range and growth potential of an HIV-1 clone are conferred by the vpu gene

vpu, alone among the genes of human immunodeficiency virus type 1 (HIV-1), is unique to this virus, with no analogous reading frame evident in the genomes of either HIV-2 or the related SIVs. Effects of vpu upon levels of virus production from infected cells have been noted, but vpu is dispensable for HIV-1 replication in vitro and its significance in the natural viral life cycle is unclear. We have now identified and characterized a major influence of vpu upon the growth and host cell range of a cloned recombinant HIV-1. This effect required the presence of a second determinant mapping to the 3' end of the env gene, and was not detected in clones incorporating an env gene derived from a different strain of the virus. This indicates that important effects of vpu may have been lost in some experimental systems because of the particular viruses used, and further suggests the involvement of a determinant in the transmembrane glycoprotein of the virus in the action of vpu.