Phd in IINNOVATION IN IMMUNO-MEDIATED AND HEMATOLOGICAL DISORDERS

Thesis title: Cytokine release syndrome post haploidentical hematopoietic stem cell transplantation is associated with an early enhanced T-cell and dendritic cell reconstitution.

Introduction Cytokine release syndrome (CRS) was originally defined in the context of CAR-T therapy, viral infections, and immunotherapy. As the number of haploidentical hematopoietic cell transplantion (haplo-HCT) conducted has increased over the last several years, CRS has also been recognized as a common phenomenon occurring after haplo-HCT. However, the implications of its development post-HCT remain unclear in terms of outcome and immune-reconstitution. Aims 1) To evaluate the risk factors associated with CRS development. 2) To evaluate immune-reconstitution in T cells, B cells, NK cells and dendritic cells post haplo-HCT in patients developing CRS vs those who did not. 3) To evaluate the effect of CRS on patients’ outcome. Methods We included in the study patients that received haplo-HCT during the period of 2011-2020 at the Dana-Farber Cancer Institute. CRS was diagnosed based on the presence of fever in the first 7 days post haplo-HCT without any evidence of infection or infusion reaction. Immune reconstitution was assessed using whole blood or post-Ficoll cryopreserved samples collected at specific timepoints post-HCT (namely 1, 2, 3, 6 and 12 months). Four twelve-color panels of directly conjugated monoclonal antibodies were used to define functionally distinct immune cell subsets and homeostatic characteristics of each subset. After staining, cells were acquired on a Fortessa LSR flow cytometer and analyzed using FlowJo software. Results A total of 169 patients met study inclusion criteria, 98/169 (57.9%) had a CRS. Comparing patients who did and did not develop CRS, there were no significant differences with respect to age, gender, diagnosis at transplant, conditioning intensity, and CMV serostatus of both patient and donor. There was a significant association between development of CRS and use of a PBSC product (p < 0.0001). Regarding immune reconstitution, no difference was found in B cells and NK cells reconstitution in the two groups. The reconstitution of CD4+ and CD8+ T-cells was increased, with Tregs showing the most significant increase in patients who developed CRS (p < 0.001), although this did not persist beyond the first month. In the CRS group, also dendritic cells were found to be increased at 1 month after haplo-HCT (p < 0.004) and this difference was maintained also at subsequent timepoints but became less significant. Among all patients, there was no difference in overall survival (61% vs 67%, p = 0.93), progression-free survival (56% vs 48%, p=0.13), or cumulative incidence non-relapse mortality (17% vs 11%, p = 0.59) between patients who developed CRS and those who did not. There was a significantly greater cumulative incidence of post-transplant relapse in patients who did not develop CRS compared to those who did (41% vs 27%, p = 0.04). The development of CRS was associated with an increase in the incidence of moderate-severe chronic GVHD (18% vs 4%, p = 0.01). Conclusions These findings suggest that post-HCT CRS may be associated may be associated with immune effector populations transplanted directly in the graft. In fact, in the CRS group, we found a transient effect on the immune reconstitution of T cells and their subsets. Also dendritic cells were found to be increased in this group. CRS, in fact, is sustained and enhanced by T cell interactions with bystander cells, such as dendritic cells. These data supports the association of the development of CRS with a reduced incidence of post-HCT relapse and increased incidence of moderate-severe chronic GVHD.