CD4(81-92) peptide 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 stem 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 position 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 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 conformationally restrict the molecule resulted in a compound with anti-
infection, anti-syncytial, and virostatic activity at submicromolar concentrations.