INCREASED INCORPORATION OF CHIMERIC HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 GP120 PROTEINS INTO PR55(GAG) VIRUS-LIKE PARTICLES BY AN EPSTEIN-BARR-VIRUS GP220 350-DERIVED TRANSMEMBRANE DOMAIN/

Noninfectious Pr55(gag) virus-like particles containing high quantitie s of oligomeric human immunodeficiency virus type-1 (HIV-1) envelope ( Env) proteins represent potential candidate immunogens for a vaccine a gainst HIV-1 infection. Thus, chimeric env genes were constructed enco ding the HIV-1 exterior glycoprotein gp120 which was covalently linked at different C-terminal positions to a transmembrane domain (TM) from the Epstein-Barr virus (EBV) major Env glycoprotein gp220/ 350. All c himeric Env-TM polypeptides as well as the wild-type HIV Env proteins were equally produced and incorporated the outer surface of insect cel ls using the baculovirus expression system. In the presence of coexpre ssed HIV pr55(gag) polyproteins significantly decreased amounts of wil d-type Env proteins were presented al the cell surface, whereas the me mbrane incorporation of the Env-TM chimeras was not affected. Biochemi cal and immunoelectron microscopical analysis particles that were effi ciently released from these cells displayed the incorporation of both wild-type Env and chimeric Env-TM proteins on the surface of VLPs. How ever, the quantities of particle-associated chimeric Env-TM proteins e xceeded those of incorporated wild-type Env proteins by a factor of 5- 10. Chemical cross-linking and subsequent polyacrylamide gel electroph oresis of VLP-entrapped Env proteins revealed that the chimeric Env-TM proteins form homodimers and a higher-order oligomer, similar to that observed for wild-type Env proteins. Thus, the results of this study clearly demonstrate that the replacement of the gp41 transmembrane pro tein of gp160 by a heterologous, EBV gp220/350-derived membrane anchor provides an effective strategy to incorporate high quantities of olig omeric HIV gp120 proteins on the surface of Pr55(gag) virus-like parti cles. (C) 1997 Academic Press.