The impact of high-resolution HLA-A, HLA-B, HLA-C, and HLA-DRB1 on transplant-related outcomes in single-unit umbilical cord blood transplantation in pediatric patients

Current practice for selecting donor units for umbilical cord blood transplant (UCBT) involves matching at HLA-A and HLA-B by low-resolution typing and the HLA-DRB1 allele by high-resolution (HR) typing. We retrospectively studied the impact of HR allele matching at HLA-A, HLA-B, HLA-C, and HLADRB1 on transplant-related outcomes in 60 single-unit UCBTs in pediatric patients with malignant and nonmalignant conditions. Five-year overall survival of our cohort was 71% (95% confidence interval, 58-81); 27% experienced primary graft failure. Applying HR typing, donor-recipient mismatch variability increased ranging from 1/8 to 8/8, however, no impact on primary graft failure, graftversus- host disease or posttransplant infection was observed. UCBTs with Z6/8 HR matches did have a better overall survival (P=0.04) and decreased transplant-related mortality (P=0.02) compared with >6/8 HR matches. Using standard HLA typing, we showed an increased incidence of acute graft-versus-host disease (grade II to IV) and decreased transplant-related mortality in comparing the matched (6/6) versus r5/6 group (P=0.05 and 0.05, respectively). These data support the use of current guidelines for umbilical cord blood selection and encourage utilization of HR typing to select umbilical cord blood units matched at Z6/8 especially when appropriate Z5/6 units are available.