Neural xenotransplantation: Pretreatment of porcine embryonic nigral tissue with anti-gal antibodies and complement is not toxic for the dopaminergicneurons

The immunogenicity of porcine tissue is a major obstacle to its use as dono r material in xenotransplantation for neurodegenerative diseases. We are cu rrently evaluating a novel strategy for reducing the immunogenicity, in whi ch the alpha -galactosyl epitope (Gal alpha1,3Gal beta1,4GlcNAc-R) is used as a target for antibody- and complement-mediated removal of microglia. In the present study, our aim was to determine whether a pretreatment with ant ibodies against the alpha -galactosyl epitope (anti-Gal) and complement wou ld lyse or otherwise damage dopaminergic neurons in porcine embryonic ventr al mesencephalon (VM), the donor tissue for treatment of Parkinson's diseas e by xenotransplantation. Cell suspensions prepared from VM tissue from 27- day-old pig embryos were incubated with anti-Gal, purified from normal huma n serum by affinity chromatography. or medium only (control), and subsequen tly with rabbit complement. After these pretreatments. the cell suspensions were transplanted into the right striatum of 14 adult rats (two groups of 7 animals). The animals were sacrificed 20 days after transplantation, the brains were processed for histology. and the sections were stained for Niss l substance, porcine neurofilament. tyrosine hydroxylase, and rat CD45 to d eter mine graft volume, presence of porcine neurons, content of dopaminergi c cells, and leukocyte infiltration, respectively. The VM tissue pretreated with anti-Gal and complement gave rise to dopaminergic grafts that were in distinguishable from those derived from VM tissue given the control pretrea tment. In 5 of the 14 animals, the grafts were infiltrated by host leukocyt es, but in two of these recipients, the infiltration was only minimal. We c onclude that anti-Gal and complement can be applied to porcine embryonic VM tissue without damaging the dopaminergic neurons and their precursors.