CD26 expression on donor harvest as a risk predictive biomarker for developing graft-versus-host disease post-allogeneic hematopoietic stem cell transplantation: A ten-year follow-up study

BACKGROUND: Allogeneic hematopoietic stem cell transplantation (ASCT) is the preferred treatment option for patients with several hematologic disorders and immunodeficiency syndromes. Graft-versus-host disease (GVHD) is an immune mediated post-transplant complication which has a major impact on long-term transplant outcomes. OBJECTIVE: Current efforts are focused on identification of new markers that serve as potential predictors of GVHD and other post-transplant clinical outcomes. METHODS: This study includes donor harvests collected from twenty-three allogeneic donors during period 2008-2009 and respective transplant recipients followed for clinical outcomes till March 2019. Percent CD26+ and CD34+ cells in donor harvest were analyzed using flow cytometry. Percent expression and infused dose of CD26+ and CD34+ cells were evaluated for association with various clinical outcomes. RESULTS: Total 23 healthy donors with median age of 28 years (13 males), and transplant recipients with median age of 24 years (17 males) formed the study cohort. The diagnosis included malignant (n = 13) and non-malignant (n = 10) hematological disorders. Median CD34brCD45lo HSC expression was 0.57% (IQR 0.24-1.03) while median CD26 expression was 19.64% (IQR 8.96-33.56) of all nucleated cells. CD26 expression was associated with donor age (P = 0.037). CD26 percent expression correlated with WBC engraftment (P = 0.015) and with acute GVHD (P = 0.023) whereas infused CD26 cell dose correlated with WBC engraftment (P = 0.004) and risk of CMV reactivation (P = 0.020). There was no statistically significant correlation of either CD26 expression or cell dose with chronic GVHD, EFS or OS. CONCLUSIONS: Our findings suggest a role of CD26 expression on human donor harvest as a potential predictor of acute GVHD. This association warrants further exploration.