A unique human immunodeficiency virus culture secreting soluble gp160.

A clone of the HUT78 cell line, chronically infected with the HIV-1 isolate HTLV-III451, has been demonstrated to secrete unprocessed HIV-1 envelope precursor protein gp160 as well as mature gp120. Further, when grown in serum-free defined medium these cells released approximately five times the amount of virus compared with cultures in normal medium. These proteins corresponded in their immunologic reactivities with the respective envelope proteins of the HTLV-IIIB isolate. They formed high-affinity soluble complexes with the CD4 antigen and inhibited the syncytium formation induced by HTLV-IIIB on CD4-positive cells. This is the first description of an HIV-1 culture system capable of shedding into the medium native gp160 that is soluble in the absence of detergents.