ATTACHMENT OF ANTIBODY TO BIOTINYLATED RED-BLOOD-CELLS - IMMUNO-RED BLOOD-CELLS DISPLAY HIGH-AFFINITY TO IMMOBILIZED ANTIGEN AND NORMAL BIODISTRIBUTION IN RATS

Streptavidin-mediated attachment of biotinylated antibodies (b-Ab) to biotinylated red blood cells (b-RBC) is useful for preparation of immu no-red blood cells, a prospective vehicle for drug targeting. However, streptavidin (SA) induces lysis of extensively biotinylated RBC by co mplement due to cross-linking and inactivation of RBC complement regul ators. To reduce cross-linking of RBC membrane proteins, we utilized m ild biotinylation of RBC with 20 mu M biotin ester (b(20)-RBC). SA eff ectively binds to rat b(20)-RBC (10(5) SA molecules/cell) and provides for following attachment of 5x10(4) molecules of b-IgG/SA per b(20)-R BC. By in vitro assay, b-Ab/SA/b(20)-RBC were stable in fresh rat seru m. Serum-stable immuno-red blood cells (b-Ab/SA/b(20)-RBC) specificall y bound to antigen-coated surfaces, but not to BSA-coated surfaces. Bi odistribution of Cr-51-labelled b-Ab/SA/b(20)-RBC in rats was similar to that of control RBC, with no indication of lysis in vivo. These res ults suggest b-Ab/SA/b(20)-RBC may be explored as a vehicle for drug t argeting.