Indiscernible benefit of high-resolution HLA typing in improving long-term clinical outcome of unrelated umbilical cord blood transplant

The success of allogeneic hematopoietic stem cell transplantation depends in part on the accuracy of human leukocyte antigen (HLA) matching between the donor recipient pair. The higher the number of matching HLA alleles, the smaller the chance that the transplant recipient will develop complications. Umbilical cord blood (UCB) transplantation was noted to result in a remarkably low frequency and severity of graft-versus-host disease (GvHD) and graft rejection compared to that in unrelated bone marrow transplant recipients. At present most banks match UCB donors for respective recipients by HLA-A, -B low-resolution typing and -DRB1 high-resolution typing. We retrospectively conducted high-resolution sequence-based HLA typing on DNA samples available from 65 Chinese UCB-recipient pairs typed previously by using low-resolution sequence-specific oligonucleotide probes and sequence-specific primers, and evaluated the clinical outcome. High-resolution typing revealed imperceptible HLA alleles that were hardly identified in low-resolution typing. Univariate analyses demonstrated no significant correlation between the extents of high-resolution HLA disparity with engraftment, graft failure, acute GvHD, transplant-related mortality and long-term 6-year overall survival. Data from the study suggest that high-resolution typing for HLA-A, -B and -DRB1 contributed no substantial improvement to UCB transplant outcome. Low-resolution typing appears to be amenable to matching UCB-recipient pairs without compromising the quality of transplant.