RECEPTOR INTERFERENCE MEDIATED BY THE ENVELOPE GLYCOPROTEINS OF VARIOUS HIV-1 AND HIV-2 ISOLATES

The envelope glycoprotein of human immunodeficiency virus type 1 (HIV- 1) plays a major role in the down-regulation of its receptor, CD4. Thi s down-regulation, at least in part, is caused by the formation of gp1 60-CD4 intracellular complexes which fail to transport out of the endo plasmic reticulum (ER). In this report, we have evaluated the ability of envelope glycoproteins from various isolates to block CD4 transport within the endoplasmic reticulum. Using a recombinant vaccinia virus expression system in HeLa cells, we expressed different HIV-1 and HIV- 2 envelope glycoproteins with CD4. Pulse-chase labeling followed by im munoprecipitation demonstrated that envelope glycoproteins from primar y and lab-adapted isolates were capable of forming intracellular compl exes with CD4, resulting in the partial inhibition of CD4 transport to the Golgi. Although the efficiency of CD4 modulation was variable, th ese differences did not correlate with the type of isolate from which the HIV-1 glycoprotein was derived. However, we did find that the HIV- 2 ST envelope glycoprotein (gp150) was not as efficient at blocking CD 4 as the glycoprotein (gp140) derived from HIV-2 ROD. The decreased ab ility of ST gp150 to block CD4 within the ER was associated with an in creased efficiency of ST gp150 transport and cleavage. Thus, differenc es in the ability of HIV envelope glycoproteins to block CD4 transport do exist, and these differences may be determined by envelope glycopr otein transport kinetics.