CD4(81–92)-based peptide derivatives: Structural requirements for blockade of HIV infection, blockade of HIV-induced syncytium formation, and virostatic activity in vitro

Abstract

CD4(81–92) peptides block human immunodeficiency virus (HIV) infection, virus-induced cell fusion, and antigen production by HIV-1-infected cells when derivatized on specific amino acid residues. An extensive series of structural variants of 1,4,5-tribenzyl-10-acetyl-CD4(81–92) were tested as anti-viral agents in an attempt to define the sequence and derivatization requirements for antiviral activity, and to maximize potency and stability for use as potential therapeutic agents. Alteration of the primary amino acid sequence of the sterm compound 1,4,5-tribenzyl-CD4(81–92) diminished or abolished in parallel all three indices of anti-viral activity in a series of altered sequence compounds. Replacement of d- for l-amino acid residues at positions 1, 2, 3, 4, 5, or 6 but not position 10 decreased anti-viral potency, again with parallel effects on infection, synctium formation, and virostatic activity. Omission of the glutamine residue at position 9 did not affect anti-viral potency, while removal of the glutamic acids at positions 11 and 12 resulted in virtually complete loss of biological activity. Changes in the derivatization pattern of the CD4(81–92) peptide backbone also affected anti-viral potency and efficacy. Optimal activity was obtained with benzyl residues at positions 1, 4, and 5, whereas the 1,4,7-tribenzyl-CD4(81–92) compound was without activity in all assays tested. Replacement of one of the benzyl groups with an acetamidomethyl moiety resulted in complete loss of biological activity. The previously reported (Nara et al., Proc Natl Acad Sci USA 86: 7139–7143, 1989) virostatic activity of 1,4,5-tribenzyl-10-acetyl-CD4(81–92) (peptide #18) is apparently due to the acetylation, since the desacetyl stem compound shows much less virostatic activity while still possessing full anti-infective and anti-syncytial activity, and acetylation of the N-terminus rather than the lysine of 1,4,5-tribenzyl-CD4(81–92) yields a virostatic compound equipotent to peptide #18. Cyclization of the tribenzyl peptide to further conformatinally restrict the molecule resulted in a compound with anti-infection, anti-syncytial, and virostatic activity at submicromolar concentrations.