BIOLOGIC AND THERAPEUTIC ADVANCES IN HEART TRANSPLANTATION I

D. Chen¹, N.L. Reinsmoen², B.O. Burgess³, G.F. Egnaczyk1³, C.B. Patel1³, C.A. Milano³, J.G. Rogers^3
1Clinical Transplantation Immunology Laboratory, Duke University Health System, Durham/NC/UNITED STATES OF AMERICA, ²Hla Laboratory, Cedars-Sinai Health Systems, Los Angelos/CA/UNITED STATES OF AMERICA, ³, Duke University Health System, Durham/UNITED STATES OF AMERICA

Body: Introduction: Solid phase immunoassays allow identification of unacceptable HLA antigens (Ag) for compatible donor selection for sensitized transplant recipients. This process is referred to as virtual crossmatch (vXM). Since 2001, we have used solid phase immunoassays to define the specificity of HLA antibodies (Ab) for our sensitized patients on the kidney, heart, or lung transplant waitlists. The aim of the study was to evaluate the characterization of unacceptable Ags and the success of utilizing vXM to select donors for sensitized heart transplant recipients.
Methods: Solid phase immunoassays were used to screen HLA Abs and to define unacceptable HLA Ags for each sensitized recipient. Utilizing the principle of vXM, only donors without unacceptable HLA Ags were used for non-emergent sensitized patients. For sensitized recipients needing emergent transplant, anti-HLA Abs not detected at a dilution of 1:16 were considered “low titer” and were not considered in donor selection. All final XMs were performed by flow cytometry since mid-2005. Results: In this study, 222 patients who received heart transplants between 2005 and 2009 were included. Sensitization was defined by presence of positive flow PRA and defined specificity of HLA Abs. Using these criteria, 62 (28%) were pre-transplant sensitized. All non-sensitized patients (n=162) had a negative HLA specific final XM. Among the 62 sensitized patients, 12 had positive final XMs (21%). Of these 12 positive XMs, 7 were expected due to the presence of weak Abs detected in evaluation sera collected prior to time of listing. The other 5 positive XMs were unexpected and 3 of them appeared to be caused by the presence of HLA Abs only detected in sera obtained immediate prior to the transplant and the specificities were not available at the time for listing. Furthermore, 8 sensitized patients had a negative donor-specific XM despite transplantation with a donor with known low titer unacceptable Ags. Among the 62 sensitized recipients, 48 had an at least one-year follow-up. The one-year survival rate for these 48 sensitized recipients was 94%.

Conclusion: Based on these data, we conclude that the vXM used for heart donor selection in sensitized patients had a 95% (5 with unexpected pos XM among 62 sensitized) predictive validity. This outcome could be further improved by close HLA Ab monitoring after every sensitization event.

Disclosure: All authors have declared no conflicts of interest.