TARGET-SENSITIVE IMMUNOERYTHROCYTES - INTERACTION OF BIOTINYLATED RED-BLOOD-CELLS WITH IMMOBILIZED AVIDIN INDUCES THEIR LYSIS BY COMPLEMENT

Red blood cells (RBC) coated with antibody (immunoerythrocytes) may be useful for drug targeting. Previously we have developed a methodology for avidin (streptavidin)-mediated attachment of biotinylated antibod ies (b-Ab) to biotinylated RBC (B-RBC). We have observed that binding of avidin to B-RBC in suspension leads to their complement-mediated ly sis by autologous serum. In the present work we have studied the inter action of B-RBC, which are not complement susceptible, with immobilize d avidin and their consequent susceptibility to lysis by complement. B -RBC adhered tightly to avidin-coated surfaces and were rendered susce ptible to lysis by autologous serum. A long biotin ester provided mon effective binding of the B-RBC to immobilized avidin and greater lysis by complement, than a short biotin ester. Based on these results, we have hypothesized that targeting of serum-stable drug-loaded B-RBC att ained by step-wise administration of b-Ab and streptavidin may provide target-sensitive lysis of B-RBC. To confirm this hypothesis, we have studied b-Ab and streptavidin mediated targeting of B-RBC to immobiliz ed antigen. Step-wise addition of biotinylated antibody, avidin or str eptavidin and b-RBC caused specific binding of B-RBC to immobilized an tigen and their subsequent lysis by autologous serum. Therefore, our r esults obtained in an in vitro model demonstrate that B-RBC might be u sed for targeting and local release of drug.