Immunoproteomic Identification of Non-carbohydrate Antigens Eliciting Graft-Specific Adaptive Immune Responses in Patients with Bovine Pericardial Bioprosthetic Heart Valves.

PURPOSE: The purpose of this case-control retrospective discovery study is to identify antigenic bovine pericardium (BP) proteins that stimulate graft-specific humoral immune response in patients implanted with glutaraldehyde fixed bovine pericardial (GFBP) heart valves.

EXPERIMENTAL DESIGN: Banked serum was collected from age and sex matched patients who had received either a GFBP or mechanical heart valve replacement. Serum IgG was isolated and used to generate poly-polyclonal antibody affinity chromatography columns from each patient. Native and deglycosylated BP protein extracts were separately added to individual patient affinity chromatography columns, with unbound proteins washed through the column. Proteins captured in the affinity chromatography columns were submitted for LC-MS/MS. Differences between GFBP and mechanical heart valve replacement recipients were analyzed with Gaussian linearized modeling.

RESULTS: Carbohydrate antigens overwhelmed protein capture in the affinity chromatography column, requiring BP protein deglycosylation prior to affinity chromatography. Nineteen BP protein antigens, which stimulated graft-specific IgG production, were identified in patients who received GFBP valve replacements. Identified antigens were significantly over-represented for calcium binding proteins.

CONCLUSIONS AND CLINICAL RELEVANCE: Patients implanted with GFBP valves develop a graft-specific humoral immune response toward BP protein antigens, with 19 specific antigens identified in this work. The molecular functions of over-represented antigens, specifically calcium-binding proteins, may aid in understand the underlying factors that contribute to structural valve deterioration. This article is protected by copyright. All rights reserved.