Disclosed herein are isolated nucleic acids encoding a first polypeptide comprising a heavy chain of an anti-CCR5 antibody or a portion thereof containing three CDR regions, wherein the three CDR regions comprise consecutive amino acids, the sequences of such consecutive amino acids being identical to the sequences of CDR regions present in a heavy chain of a monoclonal antibody selected from the group: PA14, PA8, PA9, PA10, PA11, and PA12; and wherein the first polypeptide in combination with a second polypeptide comprising a light chain of an anti-CCR5 antibody binds to an epitope of CCR5 comprising amino acid residues in (1) an N-terminus of CCR5, (2) one of three extracellular loop regions of CCR5, or (3) a combination of (1) and (2).