Expression of the human alpha 1,2-fucosyltransferase in transgenic pigs modifies the cell surface carbohydrate phenotype and confers resistance to human serum-mediated cytolysis

Hyperacute rejection (HAR) is the first critical immunological hurdle that must be addressed in order to develop xenogeneic organs for human transplan tation. In the area of cell-based xenotransplant therapies, natural antibod ies (XNA) and complement have also been considered barriers to successful e ngraftment. Transgenic expression of human complement inhibitors in donor c ells and organs has significantly prolonged the survival of xenografts. How ever, expression of complement inhibitors without eliminating xenogeneic na tural antibody (XNA) reactivity may provide insufficient protection for cli nical application. An approach designed to prevent XNA reactivity during HA R is the expression of human alpha 1,2-fucosyltransferase (H-transferase, H T). H-transferase expression modifies the cell surface carbohydrate phenoty pe of the xenogeneic cell, resulting in the expression of the universal don or O antigen and a concomitant reduction in the expression of the antigenic Gal alpha 1,3-Gal epitope. We have engineered various transgenic pig lines that express HI in different cells and tissues, including the vascular end othelium. We demonstrate that in two different HT transgenic lines containi ng two different HT promoter constructs, expression can be differentially r egulated in a constitutive and cytokine-inducible manner. The transgenic ex pression of HT results in a significant reduction in the expression of the Gal alpha 1,3-Gal epitope, reduced XNA reactivity, and an increased resista nce to human serum-mediated cytolysis. Transgenic pigs that express H-trans ferase promise to become key components for the development of xenogeneic c ells and organs for human traosplantation.-Costa, C., Zhao, L., Burton, W. V., Bondioli, K. R., Williams, B. L., Hoagland, T. A, DiTullio, P. A., Eber t, K. M., Fodor, W. L. Expression of the human alpha 1,2-fucosyltransferase in transgenic pigs modifies the cell surface carbohydrate phenotype human serum-mediated cytolysis.