COFACTOR REQUIREMENT FOR HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENTRY INTO A CD4-EXPRESSING HUMAN CELL-LINE

Expression of the human immunodeficiency virus type 1 (HIV-1) receptor CD4 on many nonhuman and some human cell lines is not sufficient to p ermit HIV-1 infection. We describe a human glioblastoma cell line (U37 3-MG) which remains resistant to HIV-1 despite the added expression of an authentic CD4 molecule. The block to HIV-1 infection of these cell s is strain independent and appears to be at viral entry. Heterokaryon s of CD4-expressing U373-MG (U373-CD4) cells fused to HeLa cells allow HIV-1 entry. A U373-CD4/HeLa hybrid clone allows efficient HIV-1 repl ication. These results suggest that HeLa cells express a factor(s) tha t can complement the viral entry defect of U373-CD4 cells and is neces sary for efficient CD4-mediated HIV-1 infection.