Differential expression of alpha-gal epitopes (Gal alpha 1-3Gal beta 1-4GlcNac-R) on pig and mouse organs

Background. Expression of the alpha-gal epitope in mice can be completely e liminated by disruption of the alpha 1,3 galactosyltransferase gene. As an initial step for assessing the feasibility of this approach in the pig, it was of interest to compare the expression of alpha-gal epitopes in pig and mouse organs, Methods. Membranes from pig and mouse organ homogenates were analyzed for a lpha-gal epitope expression by Western blots, enzyme-linked immunosorbent a ssay (ELISA), immunostaining of tissues, and ELISA inhibition assay. Results. Immunostaining of Western blots with human anti-Gal detected alpha -gal epitopes on glycoproteins from pig organs but not on glycoproteins fro m the corresponding mouse organs, ELISA with membrane homogenates and immun ostaining of tissue sections demonstrated a much higher binding of human an ti-Gal to alpha-gal epitopes on pig membranes than on mouse membranes. ELIS A inhibition assay with monoclonal anti-Gal indicated that alpha-gal epitop e expression in pig organs is up to 500-fold higher than in mouse organs. Conclusion. Expression of alpha-gal epitopes in pig organs is many fold hig her than in mouse organs, The abundance of these epitopes in pigs raises th e question of whether pigs can properly develop without expression of alpha -gal epitopes.