CHANGES IN THE CYTOPATHIC EFFECTS OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ASSOCIATED WITH A SINGLE AMINO-ACID ALTERATION IN THE ECTODOMAIN OF THE GP41 TRANSMEMBRANE GLYCOPROTEIN

A human immunodeficiency virus type 1 mutant with a single amino acid change (designated 596 W/M) in the ectodomain of the gp41 transmembran e envelope glycoprotein replicated in T-cell lines and in CD4-positive peripheral blood mononuclear cells identically to the wild-type virus . However, the cytopathic effects associated with infection by the mut ant virus were altered, with a marked attenuation of syncytium formati on and a significant delay in single-cell lysis relative to those of t he wild-type virus-infected culture. The 596 W/M mutant is apparently defective in a function that is dispensable for virus entry but that c ontributes to the efficiency of induction of viral cytopathic effects.