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Variability or stability might have an impact on treatment success and toxicity of CD19 CAR T-cells. We conducted a prospective observational study of 12 patients treated with Tisagenlecleucel for CD19+ B-cell malignancies. Using a 31-color spectral flow cytometry panel, we analyzed differentiation stages and exhaustion markers of CAR T-cell subsets prior to CAR T-cell infusion and longitudinally during 6 months of follow-up. The majority of activation markers on CAR T-cells showed stable expression patterns over time and were not associated with response to therapy or toxicity. Unsupervised cluster analysis revealed an immune signature of CAR T-cell products associated with the development of immune cell-associated neurotoxicity syndrome. Warranting validation in an independent patient cohort, in-depth phenotyping of CAR T-cell products as well as longitudinal monitoring post cell transfer might become a valuable tool to increase efficacy and safety of CAR T-cell therapy. [ABSTRACT FROM AUTHOR]

We investigated ≥ grade 3 (CTC-AE) organ toxicities for commercial CD19 chimeric antigen receptor T cell (CAR-T cell) products in 492 patients (Axi-Cel; n = 315; Tisa-Cel; n = 177) with Large B-cell Lymphoma in the European Society for Blood and Marrow Transplantation (EBMT) CAR-T registry. The incidence of ≥ grade 3 organ toxicities during the first 100 days after CAR-T was low and the most frequent were: renal (3.0%), cardiac (2.3%), gastro-intestinal (2.3%) and hepatic (1.8%). The majority occurred within three weeks after CAR-T cell therapy. Overall survival was 83.1% [79.8-86.5; 95% CI] at 3 months and 53.5% [49-58.4; 95% CI] at one year after CAR-T. The most frequent cause of death was tumour progression (85.1%). Non-relapse mortality was 3.1% [2.3-4.1; 95% CI] at 3 months and 5.2% [4.1-6.5; 95% CI] at one year after CAR-T. The most frequent causes of non-relapse mortality were cell-therapy-related toxicities including organ toxicities (6.4% of total deaths) and infections (4.4% of total deaths). Our data demonstrates good safety in the European real-world setting. [ABSTRACT FROM AUTHOR]

Identification of immune phenotypes linked to durable graft-versus-leukemia (GVL) response following donor lymphocyte infusions (DLI) is of high clinical relevance. In this prospective observational study of 13 AML relapse patients receiving therapeutic DLI, we longitudinally investigated changes in differentiation stages and exhaustion markers of T cell subsets using cluster analysis of 30-color spectral flow cytometry during 24 months follow-up. DLI cell products and patient samples after DLI were analyzed and correlated to the clinical outcome. Analysis of DLI cell products revealed heterogeneity in the proportions of naïve and antigen experienced T cells. Cell products containing lower levels of effector memory (eff/m) cells and higher amounts of naïve CD4+ and CD8+ T cells were associated with long-term remission. Furthermore, investigation of patient blood samples early after DLI showed that patients relapsing during the study period, had higher levels of CD4+ eff/m T cells and expressed a mosaic of surface molecules implying an exhausted functional state. Of note, this observation preceded the clinical diagnosis of relapse by five months. On the other hand, patients with continuous remission retained lower levels of exhausted CD4+ eff/m T cells more than four months post DLI. Moreover, lower frequencies of exhausted CD8+ eff/m T cells as well as higher amounts of CD4+temra CD45RO+ T cells were present in this group. These results imply the formation of functional long-term memory pool of T cells. Finally, unbiased sample analysis showed that DLI cell products with low levels of eff/m cells both in CD4+ and CD8+ T cell subpopulations associate with a lower relapse incidence. Additionally, competing risk analysis of patient samples taken early after DLI revealed that patients with high amounts of exhausted CD4+ eff/m T cells in their blood exhibited significantly higher rates of relapse. In conclusion, differentially activated T cell clusters, both in the DLI product and in patients post infusion, were associated with AML relapse after DLI. Our study suggests that differences in DLI cell product composition might influence GVL. In-depth monitoring of T cell dynamics post DLI might increase safety and efficacy of this immunotherapy, while further studies are needed to assess the functionality of T cells found in the DLI. [ABSTRACT FROM AUTHOR]

Nonalcoholic steatohepatitis (NASH) is induced by steatosis and metabolic inflammation. While involvement of the innate immune response has been shown, the role of the adaptive immune response in NASH remains controversial. Likewise, the role of regulatory T cells (Treg) in NASH remains unclear although initial clinical trials aim to target these regulatory responses. High‐fat high‐carbohydrate (HF‐HC) diet feeding of NASH‐resistant BALB/c mice as well as the corresponding recombination activating 1 (Rag)‐deficient strain was used to induce NASH and to study the role of the adaptive immune response. HF‐HC diet feeding induced strong activation of intrahepatic T cells in BALB/c mice, suggesting an antigen‐driven effect. In contrast, the effects of the absence of the adaptive immune response was notable. NASH in BALB/c Rag1−/− mice was substantially worsened and accompanied by a sharp increase of M1‐like macrophage numbers. Furthermore, we found an increase in intrahepatic Treg numbers in NASH, but either adoptive Treg transfer or anti‐cluster of differentiation (CD)3 therapy unexpectedly increased steatosis and the alanine aminotransferase level without otherwise affecting NASH. Conclusion: Although intrahepatic T cells were activated and marginally clonally expanded in NASH, these effects were counterbalanced by increased Treg numbers. The ablation of adaptive immunity in murine NASH led to marked aggravation of NASH, suggesting that Tregs are not regulators of metabolic inflammation but rather enhance it. [ABSTRACT FROM AUTHOR]

Introduction: Treatment with CD19 chimeric antigen receptor (CAR) T cells is an innovative therapeutic approach for patients with relapsed/refractory diffuse large B cell lymphoma (r/rDLBCL) and B-lineage acute lymphoblastic leukemia (r/rALL). However, convincing therapeutic response rates can be accompanied by cytokine release syndrome (CRS) and severe neurotoxicity termed immune effector cell-associated neurotoxicity syndrome (ICANS). Methods: Single center, prospective observational study of fifteen consecutive r/r DLBCL patients treated with Tisagenlecleucel within 1 year at Hannover Medical School. Extensive neurological work-up prior to CAR T cell infusion included clinical examination, cognitive testing (Montreal-Cognitive-Assessment), brain MRI, electroencephalogram, electroneurography, and analysis of cerebrospinal fluid. After CAR T cell infusion, patients were neurologically examined for 10 consecutive days. Afterwards, all patients were assessed at least once a week. Results: ICANS occurred in 4/15 patients (27%) within 6 days (4-6 days) after CAR T cell infusion. Patients with ICANS grade 2 (n = 3) exhibited similar neurological symptoms including apraxia, expressive aphasia, disorientation, and hallucinations, while brain MRI was inconspicuous in either case. Treatment with dexamethasone rapidly resolved the clinical symptoms in all three patients. Regarding baseline parameters prior to CAR T cell treatment, patients with and without ICANS did not differ. Conclusions: In our cohort, ICANS occurred in only every fourth patient and rather low grade neurotoxicity was found during daily examination. Our results demonstrate that a structured neurological baseline examination and close monitoring are helpful to detect CAR T cell related neurotoxicity already at an early stage and to potentially prevent higher grade neurotoxicity. [ABSTRACT FROM AUTHOR]

Here, we described the case of a B cell-deficient patient after CD19 CAR-T cell therapy for refractory B cell Non-Hodgkin Lymphoma with protracted coronavirus disease 2019 (COVID-19). For weeks, this patient only inefficiently contained the virus while convalescent plasma transfusion correlated with virus clearance. Interestingly, following convalescent plasma therapy natural killer cells matured and virus-specific T cells expanded, presumably allowing virus clearance and recovery from the disease. Our findings, thus, suggest that convalescent plasma therapy can activate cellular immune responses to clear SARS-CoV-2 infections. If confirmed in larger clinical studies, these data could be of general importance for the treatment of COVID-19 patients. [ABSTRACT FROM AUTHOR]

IL-17A and IL-17F cytokines are important regulators of acute graft-versus-host-disease (GVHD). However, contrary effects of these cytokines in inflammatory diseases have been reported. To investigate the effects of donor-derived IL-17A and IL-17F on GVHD, we made use of single (Il17a-/- or Il17f-/-) and double deficient (Il17af-/-) allogeneic donor CD4+ T cells. We could demonstrate that transplantation of Il17af-/- CD4+ donor T cells led to aggravated GVHD. However, this phenotype was not observed after transplantation of single, Il17a-/- or Il17f-/-, deficient CD4+ T cells, suggesting redundant effects of IL-17A and IL-17F. Moreover, Il17af-/- cell recipients showed an increase of systemic IFNγ, indicating a heightened pro-inflammatory state, as well as infiltration of IFNγ-secreting CD4+ T cells in the recipients' intestinal tract. These recipients exhibited significant gut leakage, and markedly macrophage infiltration in the gastrointestinal epithelial layer. Moreover, we saw evidence of impaired recovery of gut epithelial cells in recipients of Il17af-/- CD4+ T cells. In this study, we show that IL-17A/F double deficiency of donor CD4+ T cells leads to accelerated GVHD and therefore highlight the importance of these cytokines. Together, IL-17 cytokines might serve as a brake to an intensified Th1 response, leading to the exacerbated gut damage in acute GVHD. [ABSTRACT FROM AUTHOR]

γδ T cells support the immunological control of viral infections, in particular during cytomegalovirus (CMV) reactivation in immunocompromised patients after allogeneic hematopoietic stem cell transplantation. It is unclear how γδ T cells sense CMV-infection and whether this involves specific T cell receptor (TCR)-ligand interaction. Here we summarize recent findings that revealed an adaptive-like anti-CMV immune response of γδ T cells, characterized by acquisition of effector functions and long-lasting clonal expansion. We propose that rather CMV-induced self-antigen than viral antigens trigger γδ TCRs during CMV reactivation. Given that the TCRs of CMV-activated γδ T cells are often cross-reactive to tumor cells, these findings pinpoint γδ T cells and their γδ TCRs as attractive multipurpose tools for antiviral and antitumor therapy. [ABSTRACT FROM AUTHOR]

Epstein–Barr virus (EBV)-associated posttransplant lymphoproliferative disease (PTLD) with central nervous system (CNS) involvement is a severe complication after solid organ transplantation. Standard treatment with reduction of immunosuppression and anti-CD20 antibody application often fails leading to poor outcome. Here, we report the case of an 11-year-old boy with multilocular EBV-positive CNS PTLD 10 years after liver transplantation. Complete remission was achieved by repeated intravenous and intrathecal anti-CD20 antibody rituximab administration combined with intrathecal chemotherapy (methotrexate, cytarabine, prednisone) over a time period of 3 months. Due to the poor prognosis of CNS PTLD and lack of EBV-specific T-cells (EBV-CTLs) in patient’s blood, we decided to perform EBV-directed T-cell immunotherapy as a consolidating treatment. The patient received five infusions of allogeneic EBV-CTLs from a 5/10 HLA-matched unrelated third-party donor. No relevant acute toxicity was observed. EBV-CTLs became detectable after first injection and increased during the treatment course. Next-generation sequencing (NGS) TCR-profiling verified the persistence and expansion of donor-derived EBV-specific clones. After two transfers, epitope spreading to unrelated EBV antigens occurred suggesting onset of endogenous T-cell production, which was supported by detection of recipient-derived clones in NGS TCR-profiling. Continuous complete remission was confirmed 27 months after initial diagnosis. [ABSTRACT FROM AUTHOR]

Upon antigen-specific or allogeneic activation, T cells sharply increase their metabolic activity to cope with augmented needs for proliferation and effector functions. Therefore, enzymes involved in energy metabolism constitute attractive targets to modulate the activity of pathogenic effector T cells in the setting of graft-versus-host-disease (GVHD). Here, we show that T cells deficient for acetyl-CoA carboxylase 1 (TACC1) are dramatically less pathogenic than wild-type (WT) T cells in a lethal C57BL/6 into BALB/c model of acute GVHD and permitted sustained survival of recipient mice. In line with this clinical observation, higher frequencies of GVHD-suppressing Foxp3+ regulatory T (Treg) cells were detected in the colon of TACC T-cell recipients. In vitro, T-cell stimulation with allogeneic DCs induced higher proportions of Treg cells but also led to diminished proliferation of TACC1 T cells compared to WT T cells. Furthermore, TACC1 T cells activated by allogeneic DCs showed impaired glycolysis and lipid synthesis. Thus, targeting de novo fatty acid synthesis via acetyl-CoA carboxylase inhibition may be a promising new strategy to prevent GVHD. [ABSTRACT FROM AUTHOR]

It is emerging that CD4+Foxp3+ regulatory T (Treg) cells can produce the proinflammatory cytokine IFN-&ggr; when stimulated in a Thl cytokine environment. In this study, we report that Foxp3+ Treg cells readily produced IFN-&ggr; in vivo in a highly inflammatory model of graft-versus-host disease (GVHD) and during a Thl-dominated immune response to intracellular bacteria. Moreover, stimulation in vitro via TCR in the presence of IL-12 alone was sufficient to induce IFN-&ggr; production by Treg cells in a dose-dependent manner. Transfer of donor Treg cells can prevent lethal GVHD; therefore, we used this model as a robust readout for in vivo Treg function. Interestingly, >50% of allogeneic donor, but not residual recipient Foxp3+ Treg cells produced IFN-&ggr; after transplantation, suggesting that this cytokine production was alloantigen specific. These IFN-&ggr; producers were stable Foxp3+ Treg cells because methylation analysis of the Foxp3 gene locus of transferred and reisolated Treg cells during GVHD showed a fully demethylated Treg-specific-demethylated region. Next, we addressed whether IFN-&ggr; production was supporting or rather impairing the immunosuppressive function of Treg cells during GVHD. Blocking of IFN-&ggr; with specific mAb completely abolished the beneficial effect of donor Treg cells. We could further show that only wild-type Treg cells, but not Treg cells from IFN-&ggr;-deficient donor mice, prevented GVHD. This indicated that Treg cell-intrinsic IFN-&ggr; production was required for their protective function. In conclusion, our data show that IFN-&ggr; produced by Foxp3+ Treg cells has essential immune-regulatory functions that are required for prevention of expérimentai GVHD. [ABSTRACT FROM AUTHOR]

Gut-homing of donor T cells is causative for the development of intestinal GvHD in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). Expression of the gut-specific homing receptors integrin-α4β7 and chemokine receptor CCR9 on T cells is imprinted in gut-associated lymphoid tissues (GALT) under the influence of the vitamin A metabolite retinoic acid. Here we addressed the role of vitamin A deficiency in HSCT-recipients for donor T cell migration in the course of experimental GvHD. Vitamin A-deficient (VAD) mice were prepared by feeding them a vitamin A-depleted diet. Experiments were performed in a C57BL/6 into BALB/c model of acute GvHD. We found that expression of integrin-α4β7 and CCR9 in GALT was reduced in VAD recipients after HSCT. Competitive in vivo homing assays showed that allogeneic T cells primed in VAD mice did not home as efficiently to the intestine as T cells primed in mice fed with standard diet (STD). The course of GvHD was ameliorated in VAD HSCT-recipients and, consequently, their survival was prolonged compared to recipients receiving STD. However, VAD-recipients were not protected and died of clinical GvHD. We found reduced numbers of donor T cells in the intestine but increased cell counts and tissue damage in other organs of VAD-recipients. Furthermore, we observed high IFN-γ+CD4+ and low FoxP3+CD4+ frequencies of total donor CD4+ T cells in VAD as compared to STD recipients. Taken together, these results indicate that dietary vitamin A deficiency in HSCT-recipients changed target organ tropism in GvHD but also resulted in fatal inflammation after HSCT. [ABSTRACT FROM AUTHOR]

Simple Summary: CD19+ Chimeric antigen receptor (CAR) T-cells are used against CD19+ hematologic malignancies, such as high-grade B-cell lymphoma and acute lymphoblastic leukemia. Since this is a relatively new treatment approach, not all potential side effects are well described, and the underlying pathobiology is often not well defined. Here, we summarize current data on the incidence and the current management of CD19+ CAR T-cell complications. We discuss frequently occurring toxicities and we highlight evidence for the occurrence of rarer side effects affecting different organ systems. In addition, we highlight new findings that shed light on the pathophysiology of CAR T-cell-related complications. Clinical trials demonstrated that CD19+ chimeric antigen receptor (CAR) T-cells can be highly effective against a number of malignancies. However, the complete risk profile of CAR T-cells could not be defined in the initial trials. Currently, there is emerging evidence derived from post approval studies in CD19+ CAR T-cells demonstrating both short-term and medium-term effects, which were unknown at the time of regulatory approval. Here, we review the incidence and the current management of CD19+ CAR T-cell complications. We highlight frequently occurring events, such as cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, cardiotoxicity, pulmonary toxicity, metabolic complications, secondary macrophage-activation syndrome, and prolonged cytopenia. Furthermore, we present evidence supporting the hypothesis that CAR T-cell-mediated toxicities can involve any other organ system and we discuss the potential risk of long-term complications. Finally, we discuss recent pre-clinical and clinical data shedding new light on the pathophysiology of CAR T-cell-related complications. [ABSTRACT FROM AUTHOR]

CMV reactivation is a major complication after allogeneic stem cell transplantation (SCT). Immune reconstitution of CMV-specific CTLs (CMV-CTLs) is essential for virus control. During CMV-CTL monitoring using mutated HLA/CMV tetramers selectively detecting high-avidity T cells, we observed coappearance of CMV-CTLs with low (CMV tetlow CTLs) and high tetramer binding (CMV tethigh CTLs) in 53/115 CMV IgG+ patients stem cell transplanted from CMV IgG+ donors. However, the relevance of these coappearing differentially tetramer binding ("dual") CMV-CTLs was unclear. In this study, we investigated the kinetics, properties, and clinical impact of coappearing CMV tetlow and tethigh CTLs after allogeneic SCT. Patients with dual CMV-CTLs had more CMV tethigh than tetlow CTLs. Chimerism analysis of isolated CMV tetlow and tethigh CTLs revealed their exclusive donor origin. CMV tetlow and tethigh CTLs had an identical effector memory CD45RA-CCR7- and CD45RA+CCR7- T cell distribution, equal differentiation, senescence, and exhaustion marker expression and were negative for regulatory CD8+ T cell markers. Isolated CMV tetlow and tethigh CTLs were equally sensitive to CMV peptides in IFN-γ release and cytotoxicity assays. However, CMV tethigh CTLs proliferated more in response to low CMV peptide concentrations than tetlow CTLs. TCR repertoire analysis revealed that CMV tetlow and tethigh CTLs use different TCRs. Finally, dual CMV-CTLs were not associated with CMV antigenemia. In conclusion, these data show for the first time, to our knowledge, that both CMV tetlow and tethigh CTLs are functional effector T cells differing by proliferation, numbers in peripheral blood, and probably by their precursors without increasing the CMV reactivation risk after allogeneic SCT. [ABSTRACT FROM AUTHOR]

Because miR-181a has been described to alter T cell activation, we hypothesized that manipulation of miR-181a expression in donor T cells may alter acute graft-versus-host disease (aGvHD) after allogeneic bone marrow transplantation (BMT). We therefore analyzed the impact of enhanced and reduced miR-181a expression in donor T cells on aGvHD induction by lentiviral gene transfer into primary T cells and using miR-181a/b-1-/- T cells, respectively. BMT-recipient mice receiving donor T cells with enhanced miR-181a expression showed no signs of aGvHD and survived for the time of follow-up, whereas T cells lacking miR-181a/b-1 accelerated aGvHD. In line with these data, analysis of donor T cells in blood, secondary lymphoid organs, and target organs of aGvHD after BMT showed significantly reduced numbers of miR-181a-transduced T cells, as compared with controls. In addition, expansion of activated T cells with enhanced miR-181a expression was reduced in vitro and in vivo. We further show that anti-apoptotic BCL-2 protein expression is reduced in murine and human T cells upon overexpression of miR-181a, suggesting that regulation of BCL-2-expression by miR-181a may contribute to altered alloreactivity of T cells in aGvHD. These data indicate that proteins regulated by miR-181a may be therapeutic targets for aGvHD prevention. [ABSTRACT FROM AUTHOR]

Homing of allogeneic donor T cells to recipient tissue is imperative for the development of acute graft-versus-host disease (GVHD) after bone marrow transplantation (BMT). In this study we show that alteration of T cell homing due to integrin-β7 deficiency on T cells or its ligand MAdCAM-1 in BMT recipients contributes to the pathophysiology of experimental GVHD. In contrast, lack of CC chemokine receptor 9 on donor T cells alters tissue homing but does not impact GVHD survival. We further demonstrate that MAdCAM-1 is aberrantly expressed in hepatic murine GVHD as well as in patients with active liver GVHD. However, infiltration of donor T cells in gut but not liver was dependent of MAdCAM-1 expression, indicating, that homing and/or retention of donor T cells rests on divergent molecular pathways depending on the GVHD target tissue. [ABSTRACT FROM AUTHOR]