Marked increase in anti-HIV activity, as well as inhibitory activity against HIV entry mediated by CXCR4, linked to enhancement of the binding ability of tachyplesin analogs to CXCR4

T22 ([Tyr(5,12), Lys(7)]-polyphemusin II) is a strong anti-HIV compound. Si x analogs of T22 and two natural forms were synthesized. Of them, all downs ized peptides (14 residues; TW70, T131, T134, and T140) showed a higher sel ectivity index than did other, 17- or 18-residue peptides, In particular, T 134 and T140 showed both loser cytotoxicity and higher antiviral activity t han did T22 against HIV infection of MT-4 cells, an HTLV-I-bearing T cell l ine. To clarify the inhibitory mode of T22 and its analogs, we used a singl e-round replication assay (luciferase assay), in which different envelope-b earing pseudotypes were used to infect CXCR4- or CCR5-bearing U87 cells via CD4. All of the analogs inhibited T cell line-tropic strain HXB-2 (X4) and dual-tropic strain 89.6 (R5X4) HIV infections mediated by CXCR4, but had n o effect on macrophagetropic strain ADA (R5) or 89.6 HN infections mediated by CCR5, The inhibition by T134 (IC50 Of 2.70 nM) and T140 (IC50 of 0.432 nM) was also stronger than that by T22 (IC50 of 5.05 nM). The binding of an ti-CXCR4 monoclonal antibody 12G5 to lymphoma-derived T cell line Sup-T1 wa s more efficiently blocked by T134 and T140 than by T22, Taken together, T2 2 and its analogs T134 and T140 exerted their inhibition by specific bindin g to CXCR4. The marked increase in the anti-HIV activity of T134 and T140 w as ascribed to an enhancement in their ability to bind to CXCR4.