Natural protection from zoonosis by alpha-gal epitopes on virus particles in xenotransmission

Clinical transplantation has become one of the preferred treatments for end-stage organ failure, and one of the novel approaches being pursued to overcome the limited supply of human organs involves the use of organs from other species. The pig appears to be a near ideal animal due to proximity to humans, domestication, and ability to procreate. The presence of Gal-α1,3-Gal residues on the surfaces of pig cells is a major immunological obstacle to xenotransplantation. Alpha1,3galactosyltransferase (α1,3GT) catalyzes the synthesis of Galα1-3Galβ1-4GlcNAc-R (α-gal epitope) on the glycoproteins and glycolipids of non-primate mammals, but this does not occur in humans. Moreover, the α-gal epitope causes hyperacute rejection of pig organs in humans, and thus, the elimination of this antigen from pig tissues is highly desirable. Recently, concerns have been raised that the risk of virus transmission from such pigs may be increased due to the absence of α-gal on their viral particles. In this study, transgenic cells expressing α1,3GT were selected using 1.25 mg/ml neomycin. The development of HeLa cells expressing α1,3GT now allows accurate studies to be conducted on the function of the α-gal epitope in xenotransmission. The expressions of α-gal epitopes on HeLa/α-gal cells were demonstrated by flow cytometry and confocal microscopy using cells stained with IB4-fluorescein isothiocyanate lectin. Vaccinia viruses propagated in HeLa/α-gal cells also expressed α-gal on their viral envelopes and were more sensitive to inactivation by human sera than vaccinia virus propagated in HeLa cells. Moreover, neutralization of vaccinia virus was inhibited in human serum by 10 mm ethylene glycol bis(β-aminoethylether) tetraacetic acid (EDTA) treatment. Our data indicated that α-gal epitopes are one of the major barriers to zoonosis via xenotransmission.