Anti-HLA antibodies do not recognize xenoantigens from DAF transgeneic pig kidneys

Abstract

81 We have investigated the behavior of transgeneic kidneys for the human DAF molecule perfused with plasmas of hyperimmunized patients against HLA molecules, in an ex vivo perfusion system. Indeed these latter patients could be potential candidates for renal xenograft since their constant high level of anti-HLA antibodies (Ab) renders then unlikely to be considered for an allograft. The use of transgeneic pig organs could be an attractive alternative solution, since they have been shown to be protected against hyperacute rejection, providing these alloantibodies do not cross-react with xenoantigens. We have selected 6 haemodialyzed patients of our waiting list and having anti-HLA Ab reaction on at least 80% of a panel of representative alloreactive cells and stable in time. All patients have accepted to undergo two plasmaphereses allowing us to obtain at least 4 liters of plasma per patient. DAF transgeneic kidneys were perfused for 2.5 hours, after a cold ischemia time of 6 hours, in a perfusion system with a separate cartridge oxygenator circuit and a constant monitoring of the perfusion pressure. Biopsies were performed before and at the end of the perfusion. Samples of plasma were sequentially harvested from the perfusion circuit during the procedure to measure the level of anti-Gal α 1-3 Gal and anti-HLA Ab. Finally, the organs were frozen in order to eluate and study the trapped Ab. Control organs were obtained from non transgeneic animals of the same genetic background and control plasmas were obtained from non immunized individuals. The histology at the end of perfusion, showed essentially a diffuse tubulopathy without any glomcrular or vascular abnormalities for transgenic as well as control organs. Electronic microscopy showed no abnormalities. Anti-Gal Ab decreased quickly to reach a plateau after 30 minutes of perfusion. On the contrary, the level of anti-HLA Ab remained stable, suggesting that these Ab did not cross-react with xeno epitopes and especially SLA molecules. Moreover, kidneys, once perfused, were processed to eluate the bound Ab (acid elution) which were identified as anti-Gal Ab; none of these were anti-HLA Ab. These results indicate that hyperimmunized patients would not be disadvantaged toward xenotransplantation as they are toward allotransplantation.