Potential Impact of HLA DQB1*05 on Identical Sibling Hemato-Poietic Stem Cell Transplantation Outcome

Background/Objectives: Human leukocyte antigens (HLA) are major determinants of successful allogeneic hem-atopoietic stem cell transplantation (allo-HSCT). Their alleles are closely linked to outcomes, even in HLA-identical sibling donors (ISD) HSCT. This retrospective study analyzed the impact of HLA alleles on HLA-ISD HSCT outcome in Omani patients. Methods: Data was collected for a heterogenous cohort of patients registered at Sultan Qaboos University Hospital (SQUH) system, who underwent HLA-ISD HSCT from 2012 to 2022 (n=153). HSCT outcomes, namely acute GVHD (aGVHD), chronic GVHD (cGVHD), chimerism status (com-plete 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 en-graftment times were assessed by Mann-Whitney test. Patient overall survival was evaluated by Kaplan-Meier model and Log-rank testing. At 95% confidence interval, P-value threshold was corrected using Bonferroni correc-tion. Results: The incidence rates of aGVHD and cGVHD from all grades were 16% and 15%, respectively. Alt-hough no association between HLA alleles and 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 bet-ter-estimated 5-year overall survival (90%) than did DQB1*05 negative patients (68%). Conclusion: This study suggests that HLA-DQB1*05 in the Omani population could have an impact on overall survival and be used as a predictive biomarker. Further studies on a larger scale in other regional populations are needed to validate our findings and explore the underlying mechanism.