We show that infection of primary monocyte-derived macrophages (MDMs) and blood lymphocytes (PBLs) by human immunodeficiency virus type 1 (HIV-1) R5 strains, but not that of PBLs by X4 strain HIV-1LAI, is inhibited by beta-chemokines RANTES and MIP-1alpha. A biotinylated disulfide-bridged peptide mimicking the complete loop of clade B consensus V3 domain of gp120 (V3Cs), but not a biotinylated V3LAI peptide or a control beta-endorphin peptide of approximately the same molecular weight (MW), was found to bind specifically to MDM membrane proteins, in particular two proteins of 42 and 62 kDa migrating as sharp bands after electroblotting onto Immobilon, and this was specifically inhibited by anti-V3 antibodies. When biotinylated V3Cs was incubated with intact MDMs, which were then washed and lysed, and the resulting material was incubated with streptavidin-agarose beads and electroblotted onto Immobilon, fresh V3Cs also bound to proteins of the same molecular weight recovered in the V3Cs-interacting material. This binding was inhibited by anti-V3 antibodies, and no binding occurred with the control peptides. V3Cs also bound to soluble recombinant CD4, and CD4 monoclonal antibody Q4120 specifically recognized the V3Cs-interacting 62-kDa protein, which should thus correspond to CD4. Recombinant radiolabeled RANTES, MIP-1alpha, and MIP-1beta, but not IL-8, also bound to a 42-kDa protein on the membrane of MDMs as well as to the V3Cs-interacting 42-kDa protein, and excess unlabeled V3Cs inhibited such binding. This protein was also recognized by antibodies to CCR5, the RANTES/MIP-1alpha/MIP-1beta receptor. These data show that V3Cs binds to MDM membrane proteins that comprise CD4 and CCR5, and that multimolecular complexes involving at least gp120 V3, CD4, and CCR5 are formed on the surface of MDMs as part of V3-mediated postbinding events occurring during HIV-1 infection.