Inhibition of M-tropic HIV-1 infection by the fd phage-gene 3 protein with MIP-1α-binding activity

CCR5 is a chemokine receptor with seven transmembrane-domains. It is expressed on T cells and macrophages and functions as the principal co-receptor for macrophage (M)-tropic strains of HIV-1. The anti-CCR5 monoclonal antibody (mAb) 2D7 inhibits the binding and chemotaxis of the three natural β-chemokine ligands of CCR5, macrophage inflammatory protein (MIP)-1α, MIP-1β, and RANTES, to CCR5⁺ cells. The mAb also efficiently blocks the infectivity of several M-tropic and dual-tropic HIV-1 strains in vitro.In this study, we attempted to determine the peptide motif recognized with the 2D7 mAb. We isolated phage clones by panning a phage display library using 2D7 and identified three peptide motifs. One of these phage clones (M23) showed a marked inhibitory activity on HIV-1 infection. The unique sequence of 15 amino acids with an internal disulfide bond was inserted in the g3p of the M23 phage clone (M23-g3p). The M23-g3p was purified by fast-performance liquid chromatography (FPLC). We show here that (1) M23-g3p was specifically recognized with anti-CCR5 mAb; (2) M23-g3p showed inhibitory activity on the infectivity of M-tropic but not T-tropic HIV-1 strains; (3) M23-g3p bound to MIP-1α, MIP-1β, and RANTES but not MCP-1. These results suggested that the M23-g3p might mimic the CCR5-binding domain shared by β-chemokines, MIP-1α, MIP-1β, and RANTES as well as the HIV-1 infection.