IDENTIFICATION OF A PUTATIVE CELLULAR RECEPTOR FOR FELINE IMMUNODEFICIENCY VIRUS AS THE FELINE HOMOLOG OF CD9

A monoclonal antibody vpg15 has been identified which recognizes a put ative cellular receptor for feline immunodeficiency virus (FIV). The a ntibody immunoprecipitates a single 24,000 MW species from feline cell s. The molecular size and pattern of expression of the ligand for the vpg15 antibody displayed similarities to that of the human leucocyte d ifferentiation antigen CD9. The reactivity of the vpg15 antibody was t herefore compared with that of the anti-human CD9 antibody FMC56, an a ntibody which cross-reacts with feline cells. Expression of the vpg15 ligand correlated well with the reactivity of the FMC56 antibody on pe ripheral blood leucocytes and a panel of feline cell lines. Furthermor e, the anti-human CD9 antibody reacted with murine fibroblast cells wh ich had been transfected with high molecular weight feline DNA and imm unoselected with the vpg15 antibody. FMC56 and vpg15 immunoprecipitate d a similar 24,000 MW species from surface-iodinated feline cells and depletion of the vpg15 ligand from cell lysates resulted in a correspo nding depletion of the FMC56 ligand. The data demonstrate that the vpg 15 antibody recognizes the feline homologue of human CD9 and implicate feline CD9 as a cellular receptor for FIV.