Extracellular Vesicles as Biomarkers of chronic Graft-versus-Host Disease

Graft-versus-Host Disease (GVHD) remains a leading cause of non-relapse mortality after hematopoietic stem cell transplantation (HSCT). Thus, new diagnostic and therapeutic biomarkers are needed to optimize chronic GVHD (cGVHD) prevention and treatment. One potential attractive biomarker may be represented by Extracellular Vesicles (EVs): mainly exosomes (EXs) and shedding vesicles (SHds), in particular, those originating from T-Helper follicular or Dendritic/Monocytes cells (THDC), which are important players in cGVHD pathogenesis. In this pilot study we investigated the immunophenotype of different EVs subsets (total and CD4/CD185/PD1+ exosomes and shedding vesicles) in plasma samples from a cohort of 12 patients who underwent HSCT (6 of them developed cGVHD, whereas 6 did not). Correlation between membrane antigens on EVs and cGVHD onset was analyzed at a median of 63 days post HSCT (basal), before and after cGVHD onset (median 187 days and 243 days post HSCT, respectively) or at similar time points in patients without. We observe that the fluorescence levels of several EV biomarkers came out potentially associated to cGVHD developments, many of which are linked to dysregulation in both adaptive and innate immunity. Among those biomarkers the most predictive biomarkers (AUROC > 0.9) are: CD209 and CD326 (OR >100 p 0.004, OR 58.3 p 0.002, at basal time point, respectively), which suggest a major role of dendritic cells, M2 macrophages and thymic damage in cGVHD pathogenesis. Thus, our pilot study confirm the potential role of EVs as biomarkers for cGVHD, and a larger prospective study is ongoing to validate this findings.