Potential Impact of HLA DQB1*05 on Identical Sibling Hematopoietic Stem Cell Transplantation Outcome

Background/Objectives: Human leukocyte antigens (HLAs) are major determinants of successful allogeneic hematopoietic stem cell transplantation (allo-HSCT). Their alleles are closely linked to outcomes, even in HLA-identical sibling donor (ISD) HSCT. This retrospective study analyzed the impact of HLA alleles on HLA-ISD HSCT outcomes in Omani patients. Methods: Data were collected for a heterogenous cohort of patients registered at the Sultan Qaboos University Hospital (SQUH), who underwent HLA-ISD HSCT from 2012 to 2022 (n = 153). HSCT outcomes, namely acute GVHD (aGVHD), chronic GVHD (cGVHD), chimerism status (complete or mixed) at 6 to 12 months after HSCT, neutrophil and platelet engraftment time, and patient five-year overall survival, were included. Low-resolution HLA-typing records were collected for five HLA loci: HLA-A, B, C, DRB1 and DQB1. GVHD and chimerism were analyzed by logistic regression analysis. Platelet and neutrophil engraftment times were assessed by Mann–Whitney tests. Patient overall survival was evaluated by the Kaplan–Meier model and Log-rank testing. At a 95% confidence interval, the p-value threshold was corrected using Bonferroni correction. Results: The incidence rates of aGVHD and cGVHD from all grades were 16% and 15%, respectively. Although no association between HLA alleles or any of the investigated outcomes was identified, survival curve analyses indicated a significant protective effect of HLA-DQB1*05 (p = 0.01). Patients carrying this allele had a better-estimated 5-year overall survival (90%) than did DQB1*05 negative patients (68%). Conclusions: This study suggests that HLA-DQB1*05 in the Omani population could have an impact on overall survival and might be a predictive biomarker. Further studies on a larger scale in other regional populations are needed to validate our findings and explore the underlying mechanism.