Blocking of human anti-pig xenoantibodies by soluble GAL alpha 1-3Gal and Gal alpha 1-2Gal disaccharides; studies in a pig kidney in vitro perfusion model.

Abstract

Depletion of anti-pig xenoantibodies reduces cell cytotoxicity of human serum to pig endothelial cells and lymphocytes. The aim of this study was to test, in a pig kidney xenoperfusion model, the ability of soluble alpha Gal terminated disaccharides to prevent the hyperacute rejection process in an organ. Porcine kidneys were perfused with whole human blood lacking saccharide and blood supplemented with Gal alpha 1-3GAL, Gal alpha 1-2Gal and lactose. Parameters evaluated were, urine production, renal blood flow, vascular resistance, renal clearance, blood cell counts, xenoantibody titers, complement activation and histopathology. The blood flow was higher in the Gal alpha 1-3Gal (155 +/- 31 ml/min x 100 g-1 kidney tissue) group compared to Gal alpha 1-2Gal (138 +/- 16), lactose (92 +/- 78) and controls (69 +/- 16), When calculated as percent of the blood flow value at 1 min, the blood flow at 30 min was 157% for the Gal alpha 1-3Gal and for 187% the Gal alpha 1-2Gal. The corresponding values for the lactose and control groups were 102% and 74%, respectively. Urine production in the lactose/control groups was lower (0.7 ml/min x 100 g-1 kidney tissue) compared to Gal alpha 1-3Gal (3.0) and Gal alpha 1-2Gal (3.7). Urine sodium excretion was reduced in the lactose/control groups, compared to the Gal alpha alpha 1-groups during the perfusions. An increase in urine potassium excretion was found in the Gal alpha alpha 1-groups while a reduction occurred in the lactose/control experiments. An initial 40-50% reduction in platelet count was observed in all groups while the leukocyte count showed a continuous decrease. Immunohistochemistry revealed less deposition of IgM, IgG, C3 and C1 q in the Gal alpha alpha 1-saccharide groups compared to the lactose/control groups. Soluble Gal alpha a1-disaccharides improved both functional and histological parameters. However, significant pathological changes were still present indicating that this approach to inhibit HAR must be used in combination with additional therapeutic approaches such as solid phase xenoantibody immunoadsorption and blocking of complement activation.