Elimination of α-Gal Xenoreactive Epitope: α-Galactosidase Treatment of Porcine Heart Valves

Background and aim of the study: Porcine heart valves are among the most widely used tissue valves in clinical heart valve implantation. However, immunologic responses have been implicated as potential causes of the limited durability of xenograft heart valves. The study aim was to determine the effectiveness of α-galactosidase treatment used to degrade the major xenoreactive antigens found in xenograft heart valves.
Methods: Fresh porcine heart valves and pericardium treated with α-galactosidase were studied to evaluate the xenoreactive galactose (α1,3) galactose (α-gal) antigen. Removal of the α-gal epitope from the porcine heart valve was monitored via 3,3’-diaminobenzidine staining intensity, while the removal of α-gal from N-glycans on porcine heart valves treated with recombinant α-galactosidase was determined either qualitatively or quantitatively by mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The porcine pericardium was used for monitoring the change in mechanical properties after α-galactosidase treatment. In addition, the biomechanical modification property of collagen fiber rearrangement on tissue was assessed using transmission electron microscopy (TEM).

Results: Following a 24-h incubation at pH 7.2, 4°C, employing 0.1 U/ml of Bacteroides thetaiotaomicron-derived recombinant α-galactosidase, the enzyme effectively removed the α-gal epitopes expressed on porcine heart valves. The identification type of α-gal N-glycan on fresh aortic valve, aortic wall, pulmonary valve, and pulmonary wall was 7.1%, 10.3%, 6% and 8%, respectively. In the presence of α-galactosidase treatment, α-gal-containing N-glycans were converted into α-gal-negative N-glycans. Likewise, α-gal-containing N-glycans were not detected when MALDI-TOF MS quantitative analysis was used. Furthermore, no significant difference was observed in the mechanical properties and findings from TEM in α-galactosidase-treated porcine pericardial tissue when compared to fresh porcine pericardium.
Conclusion: α-galactosidase can effectively remove the α-gal epitope from porcine heart valves and pericardium. This may possibly alleviate harmful xenoreactive immunologic responses by α-gal, without adversely affecting the biomechanical properties of the α-galactosidase-processed tissue.



The Journal of Heart Valve Disease 2012;21:387-397