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Graft versus host disease (GVHD) is a major complication of allogeneic hematopoietic stem cell transplantation (HSCT). Rabbit anti-T lymphocyte globulin (ATLG) in addition to calcineurin inhibitors and antimetabolites is a suitable strategy to prevent GVHD in several transplant settings. Randomized studies already demonstrated its efficacy in terms of GVHD prevention, although the effect on relapse remains the major concern for a wider use. Tailoring of ATLG dose on host characteristics is expected to minimize its side effects (immunological reconstitution, relapse, and infections). Here, day -6 to day +15 pharmacokinetics of active ATLG serum level was first assayed in an explorative cohort of 23 patients by testing the ability of the polyclonal serum to bind antigens on human leukocytes. Significantly lower levels of serum active ATLG were found in the patients who developed GVHD (ATLG_AUCCD45: 241.52 ± 152.16 vs. 766.63 +/- 283.52 (μg*day)/ml, p = 1.46e-5). Consistent results were obtained when the ATLG binding capacity was assessed on CD3+ and CD3+/CD4+ T lymphocytes (ATLG_AUCCD3: 335.83 ± 208.15 vs. 903.54 ± 378.78 (μg*day)/ml, p = 1.92e-4; ATLG_AUCCD4: 317.75 ± 170.70 vs. 910.54 ± 353.35 (μg*day)/ml, p = 3.78e-5. Concomitantly, at pre-infusion time points, increased concentrations of CD69+ extracellular vesicles (EVs) were found in patients who developed GVHD (mean fold 9.01 ± 1.33; p = 2.12e-5). Consistent results were obtained in a validation cohort of 12 additional ATLG-treated HSCT patients. Serum CD69+ EVs were mainly represented in the nano (i.e. 100 nm in diameter) EV compartment and expressed the leukocyte marker CD45, the EV markers CD9 and CD63, and CD103, a marker of tissue-resident memory T cells. The latter are expected to set up a host pro-inflammatory cell compartment that can survive in the recipient for years after conditioning regimen and contribute to GVHD pathogenesis. In summary, high levels of CD69+ EVs are significantly correlated with an increased risk of GVHD, and they may be proposed as a tool to tailor ATLG dose for personalized GVHD prevention.

BackgroundInfusion of second generation autologous CD19-targeted chimeric antigen receptor (CAR) T cells in patients with R/R relapsed/refractory B-cell lymphoma (BCL) is affected by inflammatory complications, such as Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS). Current literature suggests that the immune profile prior to CAR-T infusion modifies the chance to develop ICANS.MethodsThis is a monocenter prospective study on 53 patients receiving approved CAR T-cell products (29 axi-cel, 24 tisa-cel) for R/R-BCL. Clinical, biochemical, and hematological variables were analyzed at the time of pre-lymphodepletion (pre-LD). In a subset of 21 patients whose fresh peripheral blood sample was available, we performed cytofluorimetric analysis of leukocytes and extracellular vesicles (EVs). Moreover, we assessed a panel of soluble plasma biomarkers (IL-6/IL-10/GDF-15/IL-15/CXCL9/NfL) and microRNAs (miR-146a-5p, miR-21-5p, miR-126-3p, miR-150-5p) which are associated with senescence and inflammation.ResultsMultivariate analysis at the pre-LD time-point in the entire cohort (n=53) showed that a lower percentage of CD3+CD8+ lymphocytes (38.6% vs 46.8%, OR=0.937 [95% CI: 0.882-0.996], p=0.035) and higher levels of serum C-reactive protein (CRP, 4.52 mg/dl vs 1.00 mg/dl, OR=7.133 [95% CI: 1.796-28], p=0.005) are associated with ICANS. In the pre-LD samples of 21 patients, a significant increase in the percentage of CD8+CD45RA+CD57+ senescent cells (median % value: 16.50% vs 9.10%, p=0.009) and monocytic-myeloid derived suppressor cells (M-MDSC, median % value: 4.4 vs 1.8, p=0.020) was found in ICANS patients. These latter also showed increased levels of EVs carrying CD14+ and CD45+ myeloid markers, of the myeloid chemokine CXCL-9, as well of the MDSC-secreted cytokine IL-10. Notably, the serum levels of circulating neurofilament light chain, a marker of neuroaxonal injury, were positively correlated with the levels of senescent CD8+ T cells, M-MDSC, IL-10 and CXCL-9. No variation in the levels of the selected miRNAs was observed between ICANS and no-ICANS patients.DiscussionOur data support the notion that pre-CAR-T systemic inflammation is associated with ICANS. Higher proportion of senescence CD8+ T cells and M-MDSC correlate with early signs of neuroaxonal injury at pre-LD time-point, suggesting that ICANS may be the final event of a process that begins before CAR-T infusion, consequence to patient clinical history.

BackgroundT cells engineered to target CD19 antigen on neoplastic B cells represent the most striking example of CAR-T cell therapy. The success rate of this therapy is affected by several limitations: target antigen loss, and/or acquisition of a senescent/exhausted phenotype by CAR and non-CAR T cells.Case presentationWe report on a patient affected by refractory Diffuse Large B-cell Lymphoma who was resistant to CAR T-cell therapy and to two cycles post CAR-T of pembrolizumab (PBZ) due to the evolution into a B-cell Hodgkin-like lymphoma. Owing to the CD30 expression and the Hodgkin-like phenotype, the patient was ultimately treated with Brentuximab-Vedotin and finally underwent remission. Upon PBZ treatment, 100% of circulating CAR-T+ cells showed a persistent CD8+ senescent/exhausted phenotype, while an increase in the percentage of senescent cells was found in the non-CAR CD8+ T cells compartment.ConclusionsPBZ is not able to reinvigorate exhausted CAR+ T cells and to confer durable clinical response. We hypothesize that the phenomenon is due to the senescent phenotype of CAR+ T cells, which did not allow PBZ-induced reactivation and proliferative rescue. The phenomenon, together with the loss of CAR-T target CD19 and the shift of non-CAR CD8+ T cells towards a senescent phenotype likely contributed to set up an immune landscape with poor antitumor capacity.