FUSOGENICITY OF MUTANT AND CHIMERIC PROVIRUSES DERIVED FROM MOLECULARCLONES OF CYTOPATHIC AND NONCYTOPATHIC HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-2

Analysis of the phenotype of the molecular clones of cytopathic and fu sogenic, noncytopathic and nonfusogenic, and chimeric proviruses of hu man immunodeficiency virus type 2 (HIV-2) suggests that the major dete rminant of the attenuated fusogenicity and cytopathicity of HIV-2 was located in the 3'-half of the genome, with envelope playing the more d ominant role. However, no single linear domain within the envelope, in cluding the major CD4 binding domain and fusogenic domain, was suffici ent by itself for syncytia induction and cytopathic effects. Truncatio n of the transmembrane envelope glycoprotein downstream of the transme mbrane region was not a major factor in this regard. However, truncati on within the transmembrane region rendered the provirus replication i ncompetent. The regulatory genes (tat, rev) and auxiliary gene (nef) d id not seem to play a critical role in determining HIV-2 fusogenicity in vitro. The results suggest the importance of the overall conformati on of the envelope in the divergent phenotypes of HIV-2.