Chemokine receptor-5 (CCR5) is a receptor for the HIV entry inhibitor peptide T (DAPTA)

The chemokine receptor CCR5 plays a crucial role in transmission of HIV isolates, which predominate in the early and middle stages of infection, as well as those, which populate the brain and cause neuro-AIDS. CCR5 is therefore an attractive therapeutic target for design of entry inhibitors. Specific rapid filtration binding assays have been useful for almost 30 years both for drug discovery and understanding molecular mechanisms of drug action. Reported in 1986, prior to discovery of chemokine co-receptors and so thought to act at CD4, peptide T (DAPTA) appears to greatly reduce cellular viral reservoirs in both HAART experienced and treatment naïve patients, without toxicities. We here report that DAPTA potently inhibits specific CD4-dependent binding of gp120 Bal (IC50 = 0.06 nM) and CM235 (IC50 = 0.32 nM) to CCR5. In co-immunoprecipitation studies, DAPTA (1 nM) blocks formation of the gp120/sCD4 complex with CCR5. Confocal microscopic studies of direct FITC-DAPTA binding to CCR5+, but not CCR5−, cells show that CCR5 is a DAPTA receptor. The capability of DAPTA to potently block gp120-CD4 binding to the major co-receptor CCR5 explains its molecular and therapeutic mechanism of action as a selective antiviral entry inhibitor for R5 tropic HIV-1 isolates.