An anti-human immunodeficiency virus multiple antigen peptide encompassing the cleavage region of the Env precursor interferes with membrane fusion at a Post-CD4 binding step

Abstract

CLIV is a multiple antigen peptide ([PTKAKRRVVQREKR]4-K2-K-βA) that encompasses the cleavage region of the human immunodeficiency virus type 1 (HIV-1) envelope precursor. It displays an antiviral activity against HIV-1 and HIV-2 and inhibits HIV-1 Env-mediated cell-to-cell fusion. This effect has previously been attributed to interference with Env processing, resulting in the expression of a nonfusogenic envelope [Virology (1998) 247, 137]. However, we show here that CLIV does not alter the status of Env cleavage at steady state. Using various aggregation/syncytium assays that allow us to discriminate between gp120/CD4 binding and binding followed by gp41-mediated fusion, we demonstrate that CLIV inhibits a step of the cell-to-cell fusion process after CD4 binding. We demonstrate also that CLIV binds at 37°C to a single class of protein present at the CD4+ cell surface (Scatchard analysis: K(d) = 8 nM; B(max) = 104 sites/cell) and that the fusion inhibition activity seems to correlate with binding to this proteic component. In contrast, CLIV interacts with neither membrane-inserted nor CD4-associated Env. We therefore propose that CLIV interferes after Env/CD4 binding with a step of the membrane fusion process that may involve the C-terminal domain of gp120. (C) 2000 Academic Press.