Characterization of immunogenic Neu5Gc in bioprosthetic heart valves.
The two common sialic acids (Sias) in mammals are N-acetylneuraminic acid (Neu5Ac) and its hydroxylated form N-glycolylneuraminic acid (Neu5Gc). Unlike most mammals, humans cannot synthesize Neu5Gc that is considered foreign and recognized by circulating antibodies. Thus, Neu5Gc is a potential xenogenic carbohydrate antigen in bioprosthetic heart valves (BHV) that tend to deteriorate in time within human patients.



We investigated Neu5Gc expression in non-engineered animal-derived cardiac tissues and in clinically used commercial BHV, and evaluated Neu5Gc immunogenicity on BHV through recognition by human anti-Neu5Gc IgG.



Neu5Gc was detected by immunohistochemistry in porcine aortic valves and in porcine and bovine pericardium. Qualitative analysis of Sia linkages revealed Siaα2-3>Siaα2-6 on porcine/bovine pericardium while the opposite in porcine aortic/pulmonary valve cusps. Similarly, six commercial BHV containing either porcine aortic valve or porcine/bovine/equine pericardium revealed Siaα2-3>Siaα2-6 expression. Quantitative analysis of Sia by HPLC showed porcine/bovine pericardium express 4-fold higher Neu5Gc levels compared to the porcine aortic/pulmonary valves, with Neu5Ac at 6-fold over Neu5Gc. Likewise, Neu5Gc was expressed on commercial BHV (186.3±16.9 pmol Sia/μg protein), with Neu5Ac at 8-fold over Neu5Gc. Affinity-purified human anti-Neu5Gc IgG showing high specificity toward Neu5Gc-glycans (with no binding to Neu5Ac-glycans) on a glycan microarray, strongly bound to all tested commercial BHV, demonstrating Neu5Gc immune recognition in cardiac xenografts.



We conclusively demonstrated Neu5Gc expression in native cardiac tissues, as well as in six commercial BHV. These Neu5Gc xeno-antigens were recognized by human anti-Neu5Gc IgG, supporting their immunogenicity. Altogether, these findings suggest BHV-Neu5Gc/anti-Neu5Gc may play a role in valve deterioration warranting further investigation.
Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel.
Eliran Moshe
EM
Reuven
Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel.
Shani
S
Leviatan Ben-Arye
Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel.
Tal
T
Marshanski
Department of Surgery, Institute of Clinical Sciences, Sahlgrenska Academy at University of Gothenburg, Gothenburg, Sweden.
Michael E
ME
Breimer
Department of Chemistry, University of California-Davis, Davis, CA, USA.
Hai
H
Yu
Department of Thoracic and Cardiovascular Surgery, Institut du Thorax, University Hospital, Nantes, France.
Imen
I
Fellah-Hebia
Department of Thoracic and Cardiovascular Surgery, Institut du Thorax, University Hospital, Nantes, France.
Jean-Christian
JC
Roussel
Infectious Diseases and Transplantation Division, Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Spain.
Cristina
C
Costa
Department of Cardiac Surgery, Reparative Therapy of the Heart, Hospital Universitari Vall d'Hebron and Vall d'Hebron Research Institute, Barcelona, Spain.
Manuel
M
Galiñanes
Infectious Diseases and Transplantation Division, Bellvitge Biomedical Research Institute (IDIBELL), L'Hospitalet de Llobregat, Barcelona, Spain.
Rafael
R
Mañez
Department of Cardiology, Institut du Thorax, University Hospital, Nantes, France.
Thierry
T
Le Tourneau
Institut de Transplantation-Urologie-Néphrologie, INSERM Unité Mixte de Recherche 1064, Centre Hospitalo Universitaire de Nantes, Nantes, France.
Jean-Paul
JP
Soulillou
Transplant Immunology Unit, Department of Transfusion Medicine, Padua University Hospital, Padua, Italy.
Emanuele
E
Cozzi
Department of Chemistry, University of California-Davis, Davis, CA, USA.
Xi
X
Chen
Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, Israel. vkaravani@post.tau.ac.il.
Vered
V
Padler-Karavani
D000818:Animals; D000906:Antibodies / Q000276:immunology*; D001705:Bioprosthesis; D002417:Cattle; D006351:Heart Valves / Q000276:immunology*; D009438:Neuraminic Acids / Q000276:immunology*; D010496:Pericardium / Q000276:immunology*; D013552:Swine; D014183:Transplantation, Heterologous / Q000379:methods
D000906:Antibodies; D009438:Neuraminic Acids; C032592:N-glycolylneuraminic acid
Neu5Gc; immunology; transplantation; valvular heart disease; xeno-antigens