THE DOMAIN ON THE DUFFY BLOOD-GROUP ANTIGEN FOR BINDING PLASMODIUM-VIVAX AND P-KNOWLESI MALARIAL PARASITES TO ERYTHROCYTES

Plasmodium vivax and the related simian malarial parasite P. krowlesi use the Duffy blood group antigen as a receptor to invade human erythr ocytes and region II of the parasite ligands for binding to this eryth rocyte receptor. Here, we identify the peptide within the Duffy blood group antigen of human and rhesus erythrocytes to which the P. vivax a nd P. knowlesi ligands bind. Peptides from the NH2-terminal extracellu lar region of the Duffy antigen were tested for their ability to block the binding of erythrocytes to transfected Cos cells expressing on th eir surface region II of the Duffy-binding ligands. The binding site o n the human Duffy antigen used by both the P. vivax and P. knowlesi li gands maps to a 35-amino acid region. A 34-amino acid peptide from the equivalent region of the rhesus Duffy antigen blocked the binding of P. vivax to human erythrocytes, although the P. vivax ligand expressed on Cos cells does not bind rhesus erythrocytes. The binding of the rh esus peptide, but not the rhesus erythrocyte, to the P. vivax ligand w as explained by interference of carbohydrate with the binding process. Rhesus erythrocytes, treated with N-glycanase, bound specifically to P. vivax region II. Thus, the interaction of P. vivax ligand with huma n and rhesus erythrocytes appears to be mediated by a peptide-peptide interaction. Glycosylation of the rhesus Duffy antigen appears to bloc k binding of the P. vivax ligand to rhesus erythrocytes.