Inhibitory effect of double transfection to xenoendothelial cells using both decay accelerating factor and homologous restriction factor 20 genes on complement dependent cytolysis.

Hyperacute rejection in discordant xenotransplantation occurs due to the complement activation via classical and/or alternative pathway. Regulator of complement activation (RCA) molecules inhibit species-specific complement dependent cytolysis. To confirm the effect of gene engineering using double RCA molecules on xenogeneic cells, the inhibitory effect on complement dependent cytolysis was compared between bovine aortic endothelial cells (BAEC) doubly transfected with both decay accelerating factor (DAF) and homologous restriction factor (HRF) 20 cDNA and BAEC singly transfected with DAF alone using retroviral vector. The positive percent expression of DAF and HRF20 antigen on double transfectant (BAEC/D+H) was 97.0% and 95.0%, respectively, whereas that of DAF antigen on single transfectant (BAEC/D) was 97.0%. After incubated with 25% human serum and anti-BAEC antibody, the viability of double transfectant (BAEC/ D+H) was significantly preserved, compared with that of single transfectant (BAEC/D). These findings demonstrated that xenoendothelial cells doubly transfected with both DAF and HRF20 cDNA could be protected from complement dependent cytolysis more effectively than those singly transfected with DAF alone in the presence of antixenoendothelial antibody.