CCR5 and HIV infectious disease: Since Peptide 3 powerfully inhibited CCR5-dependent HIV infection of THP-1 cells under conditions where gp120 binding to CCR5 was unaffected but chemotaixs in response to RANTES was profoundly blocked, it is likely that at least some of the signals elicted by CCR5 occupation that result in chemotaxis are required for successful infection of the cell by HIV.