HLA Matching in Cardiac Transplantation - Impact on Cardiac Allograft Vasculopathy, Rejection and Donor Specific Antibodies

Introduction HLA matching is not current practice in heart transplant (HT) donor allocation due to scarcity of donor organs and ischemic time. However HLA mismatch might adversely affect transplant outcomes. Even if HLA matching is not possible the degree of HLA mismatch might help inform clinicians on a patients risk for long term transplant complications. Hypothesis We hypothesize that the degree of HLA mismatch affects long-term complications in a stable HT cohort. Methods 65 clinically stable HT recipients (no cellular (ACR) or antibody mediated rejection (AMR) in the preceding 6 months) ≥ 2 years post transplant were enrolled. Serologic HLA typing was obtained for donor and recipients (D/R) pairs and the number of matches was analyzed combined for HLA class I and HLA II. Study endpoints were donor specific antibody (DSA) formation and significant cardiac allograft vasculopathy (CAV). Results HLA-A,-B,-C, -DR and-DQ (ABCDRQ) typing were available for 37 D/R pairs and were analyzed for matches. Additionally, 53 D/R pairs had HLA-A,-B, -DR (ABDR) typing. Meantime post HT was 8.5±5.4 years. A total of 28 patients had CAV and 9 patients had DSA. Among the ABCDRDQ cohort the number of matches was 1.54 ± 1.17 and 1.00 (0.00-1.00) in the ABDR cohort. There were no differences in the number of HLA matches for both cohorts among those with and without DSA and those with and without CAV (Table).However among the ABCDRDQ cohort there was a trend towards higher number of HLA matches in those without DSA 1.63 ± 1.19 versus 1.14 ± 1.07 in the DSA group (p 0.32), this was likely limited by the small sample size.There was no significant relationship between total HLA matches and number of ACR episodes (p 0.89). The incidence of AMR was too low for analysis. Conclusion In this highly selected cohort of clinically stable long time transplant survivors the degree of serological HLA matching was not associated with the development of CAV or ACR. However, there was a trend towards less DSA formation in those with more D/R HLA matches. Future longitudinal studies should evaluate the development of long-term complications as a function of HLA matching and potentially incorporate HLA mismatch as an indicator for the need of enhanced clinical surveillance.