INHIBITION OF HIV-INFECTION BY PSEUDOPEPTIDES BLOCKING VIRAL ENVELOPEGLYCOPROTEIN-MEDIATED MEMBRANE-FUSION AND CELL-DEATH

The RP dipeptide motif is highly conserved in the third hypervariable region (V3 loop) of the extracellular envelope glycoprotein of differe nt types of HIV isolates. In view of this, we have designed and synthe sized a construction referred to as ''template assembled synthetic pep tide'' (TASP), in which a lysine-rich short polypeptide was used as a template to covalently anchor arrays of tripeptides, such as RPR, RPK, or KPR. The pentavalent presentation, 5(RPR)-, 5(RPK)-, or 5(KPR)-TAS P, molecules manifested maximum inhibitory activity on HIV infection w ith a 50% inhibitory concentration value of 1-5 mu M, respectively. St ructure and inhibitory-activity relationship studies using analogs of 5(KPR)-TASP indicated that the positively charged side chains of the K and R residues in the tripeptide molecules are critical for the optim al inhibitory activity of the pentavalent construct. Interestingly, re placement of L-amino acid residues by D-amino acids or reduction of th e peptide bond between the first two amino acids of the tripeptide gen erated peptide-TASP analogs active at sub-mu M, concentrations. The an ti-HIV action of the peptide-TASP constructs is specific, since they i nhibit infection of several types of CD4-expressing cells by HIV-1 Lai and HIV-2 EHO but not by the simian SIV-mac isolate. Our results sugg est that these inhibitors block three post-CD4 binding functions of th e HIV envelope glycoproteins, mediation of viral entry, syncytium form ation, and triggering cell death by apoptosis. As the peptide-TASP der ivatives with unnatural amino acid sequences in the tripeptide moiety retain full inhibitory activity, they should provide potent protease-r esistant peptide inhibitors as potential therapeutic agents for treatm ent of AIDS patients. (C) 1996 Academic Press, Inc.