EXPRESSION AND CHARACTERIZATION OF A FUNCTIONAL HUMAN-IMMUNODEFICIENCY-VIRUS ENVELOPE GLYCOPROTEIN IN INSECT CELLS

Recombinant baculoviruses were used to express the gpl60 envelope glycoprotein of the human immunodeficiency virus type 1 (HIV-1) and a truncated variant designated gp160(t) which lacks a transmembrane domain. Glycosylation, proteolytic cleavage, secretion, and biological activities of gpl60 and gpl60(t) were studied in Spodoptera frugiperda cells. Both proteins were rapidly glycosylated and initially were found to be totally endo-β-N-acetyl-d-glucosaminidase H (endo-H) sensitive. However, partial resistance to endo-H was gradually acquired by both molecules. gp160 was found to remain cell-associated, whereas gpl60(t) was secreted into the culture medium in large amounts. A fraction of gpl60 and gp160(t) appeared to be proteolytically cleaved, and a cleavage product corresponding in size to gpi 20 was identified in the culture medium. gpl 60(t) was found to interact specifically with CD4 receptors without any requirement for proteolytic cleavage. The gpl60 protein was shown to be expressed on the surface of S. frugiperda cells by direct immunofluorescence. These surface molecules were biologically active, as demonstrated by their ability to induce syncytium formation when cocultivated with HeLa T4 cells. © 1990.