Modification of xenoantigens on porcine erythrocytes for xenotransfusion.

BACKGROUND

Problems of supply and disease transmission with blood transfusion may be controlled by the use of an isolated animal donor pool. However, porcine erythrocytes (PRBCs) usually are destroyed rapidly by preformed antibodies in human serum. We examined the impact on PRBC antigenicity by the removal of cell membrane alpha-gal(1-3)beta-galGlcNac epitopes (called alpha-gal) and chemical masking of other xenoantigens.

METHODS

From porcine "low expressors" of alpha-gal, PRBCs were subjected to (1) enzymatic removal of membrane alpha-gal with alpha-galactosidase, (2) covalent attachment of cyanuric acid-linked methoxypolyethylene glycol, or (3) both processes. PRBC integrity was assessed by light microscopy, scanning electron microscopy, osmotic fragility, and determination of oximetric p50. The effects of treatment were measured by hemagglutination, complement fixation, flow cytometric assay of immunoglobulin G/M binding, and clinical cross-match testing to human sera.

RESULTS

Cyanuric acid-linked methoxypolyethylene glycol reduced hemagglutination titers moderately, although alpha-galactosidase treatment reduced hemagglutination titers to levels similar to negative controls. The combination of the treatments was most effective, by the reduction of binding of human immunoglobulin M by 61% compared with controls. RBC morphologic condition, stability, and p50 values were maintained. Clinically used cross-match tests between PRBCs and human sera demonstrated increased compatibility.

CONCLUSIONS

These data suggest that strategies to remove or mask xenoantigens on PRBCs reduce antigenicity sufficiently to allow in vitro cross-match compatibility to human sera.