Analisi delle microvescicole circolanti in pazienti sottoposti a trapianto allogenico di midollo e correlazione con l’insorgenza di GVHD

Acute and chronic Graft Versus Host Disease (GVHD) are the major complications of allogeneic hematopoietic stem cell transplantation (HSCT). Predictors of GVHD are rearly routinely implemented and the majority refers to the interaction between donor immune system and the recipient immune/inflammatory make-up in the post-transplant phase. With the aim to investigate the role of the recipient's immune/inflammatory status before stem cell transplantation, we analyzed the circulating extracellular vehicles (EVs) in plasma and serum of HSCT patients. In an explorative cohort of 39 patients, we observed high levels of CD69+EVs in GVHD patients at pre-HSCT infusion time point up to day +90. Recent studies have highlighted the role of recipient-derived, tissue-resident memory T (TRM-T) cells, a long-lived, pro-inflammatory population known to persist despite conditioning regimens, in the initiation and propagation of GVHD. To support the hypothesis that CD69+EVs originate from TRM-T cells, we assessed the presence of CD103 protein, a hallmark of TRM-T cells, on the CD69+ EVs. The results showed that double-positive CD69+CD103+ EVs were present at higher levels in GVHD patients' serum. Furthermore, the study found a strong negative correlation between serum Sphingosine 1-Phosphate Receptor (S1PR) and CD69+EVs levels, a finding consistent with literature data showing that CD69 expression impairs the S1P and S1PR axis function, which halts the egress of TRM-T cells from tissues. In a validation cohort of 100 patients, multi flow cytometry and multicolor diffractometric analysis, found that day -6 and day -1 before HSCT serum level of CD69+ EVs were predictive of acute and chronic GVHD. Our data show that pre-transplant CD69+EVs are likely to be the telltale of pre-transplant TRM burden and are strong predictors of GVHD in HSCT patients.