Low levels of CD26 on certain cellular subtypes of donor harvest is associated with better clinical outcomes post allogeneic stem cell transplantation through regulation of NF-κB pathway and pro-inflammatory cytokines.

BACKGROUND: We had previously reported significant association of immunoectoenzyme CD26 expression on donor harvest with acute Graft-versus-Host-Disease (aGVHD) in allogeneic stem cell transplantation (ASCT) patients. The current study was aimed at analysing CD26 signaling pathway molecules and understanding their impact on immune reconstitution and clinical outcomes post-ASCT. SUBJECTS AND METHODOLOGY: The study cohort included 26 transplant donors/patients who underwent reduced intensity (n = 21), myeloablative (n = 4) and non-myeloablative (n = 1) ASCT for hematological malignancies. Donors were matched related donors (n = 19) and haploidentical donors (n = 7). Surface expression of CD26, CD73 and ADA, and various immune cell subtypes were assessed by multicolour-flow cytometry. Soluble CD26 (sCD26) and cytokine levels were measured in plasma samples by ELISA and Multiplex Luminex assay, respectively. Immune cells from healthy individuals were stimulated with phytohemagglutinin (PHA) in the presence or absence of CD26 inhibitor. Effect of CD26 inhibition on NF-κB localization in PHA stimulated cells was analysed by immunofluorescence and confocal microscopy. Pro-inflammatory cytokines from the culture supernatants were detected with Cytometric bead array flow cytometry. Association of all measured markers with clinical outcomes was evaluated using appropriate statistical tests. RESULTS: CD26 surface expression on PBSC donor harvest cells showed increased risk of chronic GVHD (cGVHD, p = 0.055). Amongst the various immune cell subtypes, decreased B cells in harvest showed significant association with aGVHD (p = 0.022) whereas increased myeloid dendritic cells and CD3+T cells at Day100 in peripheral blood of transplant recipients correlated with cGVHD (p = 0.046) and aGVHD (p = 0.035), respectively. Further, high sCD26 in transplant recipients at Day100 exhibited association with reduced event-free survival (EFS) (p = 0.011). Higher CD26 expression on more & less mature NK cells, naïve & post-switched memory B cells and Treg cells in the donor harvest (p < 0.05) led to lower EFS in transplant recipients. Mechanistically, CD26 inhibitor caused dose-dependent reduction in CD26 enzyme activity and in pro-inflammatory cytokine production in post mitogen-stimulated T cell cultures. CONCLUSION: Our study has implicated that lower CD26 expression on immune cell subtypes of the donor stem cell harvest is associated with reduced risk of GVHD and better survival. The underlying mechanism was found to be through NF-κB pathway and pro-inflammatory cytokines. Based on these observations, chemically designed or natural resources-based CD26 inhibitors can be explored further in clinical trials for improving ASCT outcomes.

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.