Chronic Antigen Exposure Research Articles

Rapidly Progressive Primary Cutaneous Gamma Delta T-Cell Lymphoma With FYN Gene Alteration.

Primary cutaneous gamma delta T-cell lymphoma (PCGDTCL) is a rare type of non-Hodgkin lymphoma accounting for <1% of primary cutaneous T-cell lymphomas. The exact cause of PCGDTCL is not known, however, it is thought that chronic antigen exposure in the skin may lead to immune dysregulation at the site, resulting in abnormal proliferation of mature, post-thymic cytotoxic gamma delta T cells. Mutations are the most common genetic alteration seen in PCGDTCL, while structural abnormalities such as gene fusions are not common. We report a case of PCGDTCL with atypical immunophenotypic features, including expression of CD5 with lack of cytotoxic marker expression, and a structural alteration leading to FYN deletion at exon 8. Recently, it was described that a deletion of the area between FYN exon 8 and TRAF3IP2 intron 2 results in a novel FYN::TRAF3IP2 fusion in peripheral T-cell lymphoma, not otherwise specified. We describe our patient's clinical course, differential diagnosis, and potential implications of FYN deletion on disease pathogenesis. To our knowledge, this is the first report of an FYN structural alteration to be described in PCGDTCL.

Epigenetic regulators of clonal hematopoiesis control CD8 T cell stemness during immunotherapy.

Epigenetic reinforcement of T cell exhaustion is known to be a major barrier limiting T cell responses during immunotherapy. However, the core epigenetic regulators restricting antitumor immunity during prolonged antigen exposure are not clear. We investigated three commonly mutated epigenetic regulators that promote clonal hematopoiesis to determine whether they affect T cell stemness and response to checkpoint blockade immunotherapy. CD8 T cells lacking Dnmt3a, Tet2, or Asxl1 preserved a progenitor-exhausted (Tpex) population for more than 1 year during chronic antigen exposure without undergoing malignant transformation. Asxl1 controlled the self-renewal capacity of T cells and reduced CD8 T cell differentiation through H2AK119 ubiquitination and epigenetic modification of the polycomb group-repressive deubiquitinase pathway. Asxl1-deficient T cells synergized with anti-PD-L1 immunotherapy to improve tumor control in experimental models and conferred a survival advantage to mutated T cells from treated patients.

Autoimmune CD4+ T cells fine-tune TCF1 expression to maintain function and survive persistent antigen exposure during diabetes

Self-reactive Tcells experience chronic antigen exposure but do not exhibit signs of exhaustion. Here, we investigated the mechanisms for sustained, functioning autoimmune CD4+ Tcells despite chronic stimulation. Examination of Tcell priming showed that CD4+ Tcells activated in the absence of infectious signals retained TCF1 expression. At later time points and during blockade of new Tcell recruitment, most islet-infiltrating autoimmune CD4+ Tcells were TCF1+, although expression was reduced on a per Tcell basis. The Tcf7 locus was epigenetically modified in circulating autoimmune CD4+ Tcells, suggesting a pre-programmed de novo methylation of the locus in early stages of autoimmune CD4+ Tcell differentiation. This mirrored the epigenetic profile of recently recruited CD4+CD62L+ Tcells in the pancreas. Collectively, these data reveal a unique environment during autoimmune CD4+ Tcell priming that allows Tcells to fine-tune TCF1 expression and maintain long-term survival and function.

ICOS limits memory-like properties and function of exhausted PD-1 + CD8 T cells.

During persistent antigen stimulation, PD-1 + CD8 T cells are maintained by progenitor exhausted PD-1 + TCF-1 + CD8 T cells (Tpex). Tpex respond to PD-1 blockade, and regulation of Tpex differentiation into more functional Tex is of major interest for cancer immunotherapies. Tpex express high levels of Inducible Costimulator (ICOS), but the role of ICOS for PD-1 + CD8 T cell responses has not been addressed. In chronic infection, ICOS-deficiency increased both number and quality of virus-specific CD8 T cells, with accumulation of effector-like Tex due to enhanced survival. Mechanistically, loss of ICOS signaling potentiated FoxO1 activity and memory-like features of Tpex. In mice with established chronic infection, ICOS-Ligand blockade resulted in expansion of effector-like Tex and reduction in viral load. In a mouse model of hepatocellular carcinoma, ICOS inhibition improved cytokine production by tumor-specific PD-1 + CD8 T cells and delayed tumor growth. Overall, we show that ICOS limits CD8 T cell responses during chronic antigen exposure.

The peculiar features, diversity and impact of citrulline-reactive autoantibodies.

Since entering the stage 25 years ago as a highly specific serological biomarker for rheumatoid arthritis, anti-citrullinatedprotein antibodies (ACPAs) have been a topic of extensive research. This hallmark B cell response arises years before disease onset, displays interpatient autoantigen variability, and is associated with poor clinical outcomes. Technological and scientific advances have revealed broad clonal diversity and intriguing features including high levels of somatic hypermutation, variable-domain N-linked glycosylation, hapten-like peptide interactions, and clone-specific multireactivity to citrullinated, carbamylated and acetylated epitopes. ACPAs have been found in different isotypes and subclasses, in both circulation and tissue, and are secreted by both plasmablasts and long-lived plasma cells. Notably, although some disease-promoting features have been reported, results now demonstrate that certain monoclonal ACPAs therapeutically block arthritis and inflammation in mouse models. A wealth of functional studies using patient-derived polyclonal and monoclonal antibodies have provided evidence for pathogenic and protective effects of ACPAs in the context of arthritis. To understand the roles of ACPAs, one needs to consider their immunological properties by incorporating different facets such as rheumatoid arthritis B cell biology, environmental triggers and chronic antigen exposure. The emerging picture points to a complex role of citrulline-reactive autoantibodies, in which the diversity and dynamics of antibody clones could determine clinical progression and manifestations.

Overexpression of an Engineered SERPINB9 Enhances Allogeneic T-cell Persistence and Efficacy.

Allogeneic chimeric antigen receptor (CAR)-expressing T cells offer many advantages over autologous therapies, but their benefits are curtailed by graft-versus-host disease and elimination by recipient immune cells. Moreover, just as with autologous therapies, allogeneic CAR T cells are susceptible to activation-induced cell death (AICD) caused by chronic antigen exposure (CAE). Granzyme B- and Fas/Fas ligand-initiated caspase-mediated apoptoses are key mechanisms of T-cell death caused by T/NK cell-mediated allorejection or CAE. We explored a protective strategy of engineering CAR T cells to overexpress variants of the Granzyme B-specific serine protease inhibitor SERPINB9 (SB9) to improve allogeneic T-cell persistence and antitumor efficacy. We showed that the overexpression of an SB9 variant with broadened caspase specificity, SB9(CAS), not only significantly reduced rejection of allogeneic CAR T cells but also increased their resistance to AICD and enabled them to thrive better under CAE, thus improving allogeneic T-cell persistence and antitumor activity in vitro and in vivo. In addition, although SB9(CAS) overexpression improved the efficacy of allogeneic CAR T-cell therapy by conferring protection to cell death, we did not observe any autonomous growth, and the engineered CAR T cells were still susceptible to an inducible suicide switch. Hence, SB9(CAS) overexpression is a promising strategy that can strengthen current development of cell therapies, broadening their applications to address unmet medical needs.

Abstract LB070: In vitro modeling of antigen-driven exhaustion in human CAR T cells

Abstract A major hurdle for chimeric antigen receptor (CAR) T cells to function in solid tumors is chronic antigen exposure leading to terminal lymphocyte exhaustion and impaired anti-tumor activity. Therefore, it is necessary to establish improved in vitro models of antigen-driven CAR T cell exhaustion to evaluate new CAR design candidates prior to validation with costly in vivo studies. Using the human tumor antigen mesothelin (MSLN) and MSLN-targeting CAR T cells as a model, we developed two in vitro assays that drive an exhausted phenotype in human CAR T cells and can be used to predict anti-tumor responses in vivo: 1) a chronic stimulation assay with plate-bound recombinant antigen (MSLN), ICAM-1, and CD58 and 2) a high antigen-expressing 3D tumor spheroid co-culture assay. In the chronic antigen stimulation assay, repetitive exposure to plate-bound MSLN (alongside co-stimulation signals provided by recombinant ICAM-1 and CD58) reprogrammed the transcriptomic profile of MSLN CAR T cells leading to increased surface expression of inhibitory checkpoint molecules and reduced cytokine production. Moreover, chronically stimulated MSLN CAR T cells demonstrated a drastically impaired ability to kill MSLN+ tumor cells compared to their unstimulated or acutely stimulated counterparts. A similar exhausted phenotype was observed in the high-antigen tumor spheroid model: when MSLN CAR T cells were co-cultured with MSLN-high human NCI-H226 spheroids for 7 days in a 96-well plate, expression of inhibitory checkpoint molecules markedly increased on the surface of CAR T cells. This increased expression of exhaustion markers coincided with impairment of NCI-H226 spheroid clearance. By contrast, other tumor spheroid models expressing low to intermediate levels of MSLN (NCI-H1650, NCI-H2052, NCI-H292, and SKOV-3 tumor cells) did not substantially induce expression of inhibitory checkpoint molecules and the spheroids were successfully cleared by MSLN CAR T cells. Importantly, the ability (or inability) of a CAR construct to clear NCI-H226 high-antigen tumor spheroids in vitro accurately predicted CAR T cell performance in in vivo solid tumor studies: the CAR construct that showed effective killing in the in vitro spheroid model was the only condition to provide durable regression of NCI-H1650 tumors in a NSG xenograft mouse model. Additionally, the rank order of CAR efficacy for a series of MSLN CAR binders obtained using the tumor spheroid model mirrored in vivo efficacy. As the CAR T cell field develops novel strategies to combat antigen-driven exhaustion for use in solid tumors, these new antigen-dependent in vitro models of exhaustion can enable more cost-efficient and effective evaluation of those strategies than using in vivo models alone. Citation Format: Maria Steele, Tina Tan, Jason Yokoyama, Allan Wang, Ty Crowl, Jared Hammer, Jerry Chen, Kevin Haworth, Howell Moffett, Aaron Foster, Marc Lajoie, Scott Boyken, Rupesh Amin. In vitro modeling of antigen-driven exhaustion in human CAR T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB070.

Abstract 4063: SAR445877, an anti-PD-1 antibody-IL-15 mutein fusion protein restores function to exhausted T cells

Abstract During persistent viral infections and cancer, antigen-specific T cells become exhausted, express elevated levels of inhibitory receptors and gradually lose their functional potential. Immune checkpoint blockade can restore function of exhausted T cells to result in tumor clearance, however, only a minority of cancer patients see durable tumor control. Immune-stimulatory cytokines can augment the antitumor efficacy of checkpoint blockade, but their clinical use is marred by substantial toxicity. SAR445877 (SAR’877, formerly KD050), is a novel antibody-cytokine fusion protein consisting of Fc silenced human anti-PD-1 IgG1 fused to a mutated interleukin-15 (IL-15)/IL-15 receptor alpha sushi domain fusion, which can cis-activate direct cytokine stimulation to effector T cells and alleviate off target binding and the resultant toxicity. Here, we leveraged existing models of chronic antigen exposure to characterize the potential of SAR’877 to restore activity of exhausted T cells.C57BL/6 mice exposed to lymphocytic choriomeningitis virus (LCMV) Clone 13 develop persistent viral infection that results in development of dysfunctional, exhausted T cells. We tested the SAR’877 murine surrogate molecule (mKD050) using the LCMV Clone-13 (CL13) infection model for its ability to promote T cell function in vitro, in vivo, and to control viral infection. Treatment of exhausted T cells with mKD050 in vitro was able to increase expansion and cytokine production of antigen-specific CD8 T cells which was superior to anti-PD-1 antibody or non-targeting antibody-IL15/IL-15Ra fusion protein (mntKD050). Moreover, in vivo treatment of CL13 infected mice with mKD050 increased the numbers and functional output of antigen-specific CD4 and CD8 T cells compared to anti-PD-1 or mntKD050 treatments. Further, mKD050 increased the frequency of antigen-specific TCF1+TIM-3- stem-like CD8 T cells, which are critical to maintaining the T cell pool during chronic viral infection and cancer. The enhanced T cell function observed following treatment with mKD050 translated to hastened clearance of CL13. Finally, the hastened CL13 clearance observed following mKD050 treatment required an intact CD4 T cell compartment. Given the robust activity of mKD050 in reinvigorating dysfunctional T cells in a mouse model of chronic viral infection, we utilized the MIMIC CD8 T cell exhaustion model to explore whether SAR’877 could rescue the function of exhausted human T cells. SAR’877 stimulated proliferation and functional activity of exhausted human CD8 T cells in vitro. SAR’877 more potently induced proliferation and IFNγ and granzyme B production compared to anti-PD-1 and non-targeted IL15 mutein alone. Together, these results demonstrate that the PD-1 targeted IL15 mutein SAR’877 rescues the functional activity of chronically stimulated, exhausted T cells. Citation Format: Isaraphorn Pratumchai, Marie Bernardo, Kristi Lynn Marquardt, Chen Zhu, Fatima Menas, Roberto Carrio, Tony Byers, Donald Shaffer, Xiangming Li, John Ross Teijaro. SAR445877, an anti-PD-1 antibody-IL-15 mutein fusion protein restores function to exhausted T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4063.

Stat5 opposes the transcription factor Tox and rewires exhausted CD8+ T cells toward durable effector-like states during chronic antigen exposure

Rewiring exhausted CD8+ T (Tex) cells toward functional states remains a therapeutic challenge. Tex cells are epigenetically programmed by the transcription factor Tox. However, epigenetic remodeling occurs as Tex cells transition from progenitor (Texprog) to intermediate (Texint) and terminal (Texterm) subsets, suggesting development flexibility. We examined epigenetic transitions between Tex cell subsets and revealed a reciprocally antagonistic circuit between Stat5a and Tox. Stat5 directed Texint cell formation and re-instigated partial effector biology during this Texprog-to-Texint cell transition. Constitutive Stat5a activity antagonized Tox and rewired CD8+ Tcells from exhaustion to a durable effector and/or natural killer (NK)-like state with superior anti-tumor potential. Temporal induction of Stat5 activity in Tex cells using an orthogonal IL-2:IL2Rβ-pair fostered Texint cell accumulation, particularly upon PD-L1 blockade. Re-engaging Stat5 also partially reprogrammed the epigenetic landscape of exhaustion and restored polyfunctionality. These data highlight therapeutic opportunities of manipulating the IL-2-Stat5 axis to rewire Tex cells toward more durably protective states.

Modular chimeric cytokine receptors with leucine zippers enhance the antitumour activity of CAR T cells via JAK/STAT signalling.

The limited availability of cytokines in solid tumours hinders maintenance of the antitumour activity of chimeric antigen receptor (CAR) T cells. Cytokine receptor signalling pathways in CAR T cells can be activated by transgenic expression or injection of cytokines in the tumour, or by engineering the activation of cognate cytokine receptors. However, these strategies are constrained by toxicity arising from the activation of bystander cells, by the suboptimal biodistribution of the cytokines and by downregulation of the cognate receptor. Here we show that replacement of the extracellular domains of heterodimeric cytokine receptors in T cells with two leucine zipper motifs provides optimal Janus kinase/signal transducer and activator of transcription signalling. Such chimeric cytokine receptors, which can be generated for common γ-chain receptors, interleukin-10 and -12 receptors, enabled T cells to survive cytokine starvation without induction of autonomous cell growth, and augmented the effector function of CAR T cells in vitro in the setting of chronic antigen exposure and in human tumour xenografts in mice. As a modular design, leucine zippers can be used to generate constitutively active cytokine receptors in effector immune cells.

The DNA Sensor AIM2 Determines B Cell Fate after BCR Activation in Chronic Graft-Vs-Host Disease

Prevention and treatment of chronic graft-vs-host disease (cGVHD), a debilitating late immune toxicity in patients after allogeneic hematopoietic stem cell transplantation (allo-HCT), who are otherwise cured of hematological malignancies, remains a major challenge. T cells incite and promote cGVHD through coordinated T-B cell responses. Alloantibody production ( Srinivasan et al, Blood 2012, Jin et al, Blood 2016) and aberrant B Cell Receptor (BCR) signaling ( Allen et al, Blood 2014, Flynn et al, Blood 2015) play fundamental roles in the pathology of cGVHD. B cell-intrinsic pathways in cGVHD remain incompletely understood, limiting our therapeutic capacity for patients. In a single cell RNA sequencing study, we found that transcript levels of the DNA sensor Absent in Melanoma 2 (AIM2) were significantly increased in CD27+ BCR-activated B cell clusters in circulating as well as in tissue-resident cGVHD B cells ( Poe et al, JCI Insight 2023). After confirming AIM2 expression is restricted to the nucleus, we also previously showed that AIM2-expressing B cells were augmented after BCR and interferon-gamma (IFNγ) and/or Toll-like receptor (TLR)-7 or 9 stimulation ( Visentin J, Blood 2022;140 Supp 1), suggesting a context-dependent role for AIM2 after allo-HCT. Our new findings now afford the hypothesis that an AIM2-BCR signaling axis determines B cell fate after allo-HCT. To address this hypothesis, we first examined whether AIM2 modulates the promotion of antibody-secreting cells (ASCs) after BCR activation using a hapten-carrier immunization model. We compared numbers of hapten-specific ASCs from immunized WT and AIM2-KO mouse splenocytes using enzyme-linked immunosorbent spot (ELISPOT). We compared numbers of ASCs on day 3 post-immunization, when early germinal center (GC) formation is known to occur. We found that hapten-specific IgM ASCs were significantly increased in WT splenocytes compared to AIM2-KO (p=0.002). By contrast, when we looked at day 8, when mature GC formation and rapid ASC proliferation is known to occur, we found that AIM2-KO immunized mice had significantly lower numbers of hapten-specific IgM (p=0.005) and IgG (p=0.004) ASCs in AIM2-expressing mice (Figure 1a). Our results suggest a role for AIM2 in regulating the survival of short-lived plasmablast-like ASCs after high affinity antigen encounter and maturation of germinal centers. To further investigate whether AIM2 affects expansion of GC-derived (GL7+CD95+) ASCs, we stimulated B cells purified from wildtype (WT) or global AIM2-deficient (AIM2-KO) mice in vitro with lipopolysaccharide (LPS) and IL-4 +/- BCR stimulation. We found that AIM2-deficient B cells, especially GC-like cell populations, expanded significantly in an anti-IgM concentration-dependent manner up to 12-fold (p=0.03) after 72 hr (Figure 1b). By contrast, B cell expansion was constrained in AIM2-sufficient B cells. This expansion was unlikely to be due to differences in proliferation alone, as we did not detect differential Ki67 expression in stimulated B cells with or without AIM2. Together, these data suggest a role for AIM2 in modulating BCR signaling. Finally, we examined the role of AIM2 in BCR-mediated cell death after chronic antigen exposure using our previously described bone marrow transplant (BMT) model, where recipients of bone marrow and splenocytes (BM+Spl) exhibit cGVHD manifestations ( Poe et al, JCI Insight 2018, Jia et al, Blood 2021). We have previously generated C57BL/6J mice with conditional deficiency of AIM2 only in B cells (AIM2 fl/flMb1 Cre/+, CKO), and used these in our BMT model as donors. At day 58 post BMT, we performed ex vivo stimulation of splenic B cells from BMT recipients. While B cells from CKO BM+Spl recipients expanded ex vivo in an anti-IgM concentration-dependent manner, B cells from AIM2-sufficient BM+Spl recipients demonstrated limited responsiveness ex vivo to BCR stimulation. This extends our in vitro observations by suggesting a role for AIM2 in B cell tolerance after chronic antigen exposure. Ongoing experiments will determine if B cell-intrinsic AIM2 contributes to cGVHD pathogenesis. Thus far, our data reveal a novel role for AIM2 as a B cell survival checkpoint after BCR activation. Further delineation of context-dependent and synergistic AIM2-BCR signaling after allo-HCT will lead to strategies that block the development of cGVHD without adversely affecting anti-tumor activity.

Development of a Regulated, Optimized Mesothelin Chimeric Antigen Receptor (CAR) for the Treatment of Mesothelin Positive Cancers

Introduction: Mesothelin (MSLN) is an attractive target for chimeric antigen receptor T cell (CAR-T) immunotherapy as it is highly expressed on mesothelioma, ovarian, lung cancer, and some forms of leukemia, including approximately 30% of acute myeloid leukemia (AML); however, MSLN directed CAR-T cells are prone to exhaustion, and soluble proteins, such as shed MSLN and MUC16 can inhibit anti-tumor efficacy. To address these deficiencies, we developed a novel, fully-human MSLN-specific CAR using our OutSpacer™ technology to optimize the immune synapse geometry. Further, this MSLN CAR is expressed using a novel regulatory response element to dynamically express the CAR molecule to enhance CAR-T potency and durability. Methods: A set of fully-human single domain binders (VHH) were produced and screened against a spacer library to identify high-performing CARs. The spacer library is composed of human extracellular polypeptides selected for optimal biophysical properties (e.g., flexibility), enabling systematic sampling to identify CAR constructs with optimal immune synapse geometry. More than 300 MSLN-directed CAR candidates were evaluated in vitro using 2D or 3D (spheroid) culture assays to measure tumor killing and cytokine production against several MSLN + cell lines that express different levels of the target protein. These functional assays were also performed in the presence of recombinant MSLN (10ug/mL) or MUC16 (1ug/mL) to assess potential inhibition by shed target or ligand. Top performing MSLN CARs were subsequently tested in NSG mice (2e6, 4e6 and 8e6 cells/animal; 2 donors) subcutaneously engrafted with MSLN + H1650 tumor cells to identify the best CAR candidate. To further improve the durability of T cell response, the MSLN CAR was expressed under the control of an engineered promoter (OP1) to dynamically regulate expression, and compared to CARs expressed constitutively using the MND promoter. CAR-T cells were repetitively stimulated (4x) by plate-bound antigen in combination with CD58 and ICAM1, and subsequently tested in a tumor spheroid assay for killing, cytokine production, CAR expression and T cell activation/ exhaustion markers (i.e., PD-1, TIGIT, CD39 and TIM3). Results: Anti-MSLN VHH domains targeting region 1 or 3 (RI and RIII) of the MLSN extracellular domain were paired with a defined spacer library to define the optimal immune synapse. Contrary to the conclusions of prior studies, RI (membrane-distal) binders outperformed RIII (membrane-proximal) binders when paired with their optimal spacer. Based on tumor killing and cytokine production, RI targeted CARs preferred a spacer length of approximately 75 Å, consistent with our previously-reported optimal CAR synapse of ~200 Å. All spacer optimized MSLN-specific CARs resisted inhibition by soluble MSLN and MUC16. In vivo studies with two donors in NSG mice engrafted with MSLN + tumors showed that one CAR (B8S8) eliminated tumors at a dose of 2e6 and 4e6 CAR-T cells per animal, where other CAR constructs, including a clinically-used MSLN-specific CAR, failed to control tumors even at 8e6 cells per animal. Secondly, we assessed whether a novel “stim-on” promoter (OP1) could enhance CAR-T activity by preserving T cell function. Here, B8S8 CAR was expressed via OP1 or the constitutive MND promoter (n=3 donors). Following chronic antigen exposure by plate-bound antigen, OP1 regulated MSLN CAR T cells retained the capacity to eliminate MSLN + H226 tumor spheroids compared to MND-driven CAR T constructs. OP1-regulated CAR T cells also continued to produce high levels of cytokines (IFN-γ and IL-2) whereas MND CAR-T cells lost cytokine production ability. Further, phenotypic analyses showed that MND CAR-T cells expressed elevated levels of PD-1 and TIGIT compared to OP1 CAR-T cells. Conclusions: Contrary to the conclusions of prior studies with MSLN-targeted CARs, membrane distal epitopes were superior to membrane proximal epitopes when binders were paired with the correct spacer, and shed MSLN and MUC16 were not inhibitory for the best-performing CARs, regardless of target epitope. Furthermore, regulated expression enhanced the potency and durability of response compared to constitutive expression. This approach may improve CAR activity in patients with MSLN + solid tumors or leukemia.

Ablation of Cullin-5 in Primary Human T Cells Improves Tumor Killing and Persistence in BCMA-Targeting CAR-T Cells in a Multiple Myeloma Model

While adoptive T cell therapies have led to remarkable clinical responses in certain subsets of B cell leukemia and lymphoma, many challenges remain that are limiting the efficacy in other hematological malignancies. Compromised T cell function and exhaustion due to chronic antigen exposure can impair the persistence of chimeric antigen receptor (CAR)-T and T-cell-receptor (TCR)-T cells. Gene editing strategies have the potential to circumvent some of these challenges and enhance T cell function. To identify key genes that are involved in regulating T cell dysfunction, we performed a genome-wide CRISPR loss-of-function screen in primary human T cells in conditions that mimic chronic antigen exposure. Primary T cells from two donors were transduced with lentivirus containing a NY-ESO-1 TCR as well as a genome-wide sgRNA library and subsequently CRISPR edited using Cas9-RNP electroporation. These antigen specific TCR-T cells were then co-cultured with the NY-ESO-1+ melanoma cell line A375 at an effector-to-target (E:T) ratio of 1:1 for 48 hours and challenged under the pressure of chronic tumor stimulation for 9 rounds in total. The resulting next-generation sequencing data was then analyzed utilizing the MAGeCK pipeline to identify top scoring hits for validation regarding their role in T cell fitness and persistence. Among the hits with the highest positive fold changes, we found seven genes which are part of the Cullin-RING ligase 5 multi-protein complex (Fig. 1). These hits were then validated in a CAR-T cell context. We first edited primary human T cells by knocking out CUL5 as well as the endogenous TCR. The template for the B Cell Maturation Antigen (BCMA)-specific CAR bb2121 was then delivered to the TRAC locus via CRISPR/Cas9-RNP and adeno-associated virus (AAV). Here, we tested a panel with four CAR modifications, including two different co-stimulatory domains (CD28ζ, 4-1BB), a CAR with mutated immunoreceptor tyrosine-based activation motifs (ITAM) (1XX CAR), and a CAR containing an alternative BCMA-targeting single-chain variable fragment. This panel of CUL5 ablated CAR-T cells were then repeatedly co-cultured with BCMA-expressing tumor cells. After 6 rounds of tumor exposures, CUL5 ablated T cells showed a striking tumor killing advantage compared to control edited cells in a functional tumor killing assay (Fig. 2). Notably, we also observed vastly increased production of the cytotoxic cytokines INF-γand TNF-α in CUL5 ablated cells. Furthermore, the distinct tumor killing advantage of CUL5 KO cells in vitro was reproduced in the context of a CD19-specific CAR, which will be relevant in other clinical settings. Finally, we evaluated the striking tumor killing capacity of CUL5 ablated BCMA-specific CAR-T cells in vivo. For this, NOD.Cg- PrkdcscidIl2rgtm1Wjl/SzJ mice engrafted with luciferase-expressing BCMA+ multiple myeloma cell line OPM2 were treated with this panel of CUL5 ablated and control CAR-T cells and tumor burden was measured via Bioluminescent Imaging (BLI) over time. Mice treated with CUL5 KO BCMA-specific CAR-T cells showed lower median radiance measured by BLI, except for the 1XX CAR condition where both cohorts completely cleared the disease. In addition to the complete tumor clearance in both the control and CUL5 edited cohorts, we observed that the BLI levels in the 1XX CAR treated animals remained stable even after the mice were subjected to five tumor rechallenges. After 90 days, the mice were sacrificed and CAR+ human T cells were isolated from the bone marrow and spleens and phenotypically assessed. Analysis of these samples revealed a significantly higher frequency of CAR+ cells in the mouse bone marrow in the CUL5 KO group compared to control, while there were equivalent numbers in the spleens, suggesting an antigen-specific expansion advantage for the CUL5 KO CAR-T cells. We then co-cultured the isolated BCMA CAR-T cells from the spleens of these mice with OMP2 tumor cells in different E:T ratios and assessed tumor killing. We found a significant advantage in tumor killing of CUL5 ablated T cells compared to control cells in this ex vivo setting, suggesting an improved functional persistence. In summary, our findings identify the CUL5 complex as a novel potential therapeutic target to improve T cell persistence and counteract T cell exhaustion in order to improve the efficacy of adaptive cell immunotherapies for the treatment of BCMA+ hematological malignancies.

Pathogenicity of functionally activated PD-1+CD8+ cells and counterattacks by muscular PD-L1 through IFNγ in myositis

Programmed-cell-death 1 (PD-1) expression is associated not only with T-cell activation but with exhaustion. Specifically, PD-1+ T cells present an exhausted phenotype in conditions of chronic antigen exposure, such as tumor microenvironments and chronic viral infection. However, the immune status regarding exhaustion of PD-1+CD8+ T cells in chronic autoimmune diseases including idiopathic inflammatory myopathies (IIMs) remains unclear. We aimed to clarify the role of PD-1+CD8+ T cells and PD-1 ligand (PD-L1) in IIMs. We showed that PD-1+ cells infiltrated into PD-L1-expressing muscles in patients with IIMs and immune checkpoint inhibitor-related myopathy. According to the peripheral blood immunophenotyping, the PD-1+CD8+ cell proportions were comparable between the active and inactive patients. Of note, PD-1+CD8+ cells in the active patients highly expressed cytolytic molecules, indicating their activation, while PD-1−CD8+ cells expressed low levels of cytolytic molecules in the active and inactive patients. A part of PD-1+CD8+ cells expressed the HMG-box transcription factor TOX highly and presented the exhausted phenotype in the active patients. Among PD-1+CD4+ T cells, PD-1highCXCR5−CD45RO+CD4+ peripheral helper T cells were increased in the active patients. PD-L1-deficient mice developed severer C-protein-induced myositis (CIM), a model of polymyositis, with abundant infiltration of PD-1+CD8+ cells expressing cytolytic molecules than wild-type mice, indicating pathogenicity of the PD-1+CD8+ cells and the protective role of PD-L1. The deficiency of IFNγ, a general PD-L1-inducer, impaired muscular PD-L1 expression and exacerbated CIM, indicating IFNγ-dependent muscular PD-L1 regulation. IFNγ-induced PD-L1 on myotubes was protective in an established muscle injury model. In conclusion, PD-1+CD8+ T cells rather than PD-1−CD8+ T cells were a pathogenic subset of IIMs. Muscular PD-L1 was regulated by IFNγ and exerted protective properties in IIMs.

Disease activity in chronic inflammatory demyelinating polyneuropathy: association between circulating B-cell subsets, cytokine levels, and clinical outcomes.

Chronic inflammatory demyelinating polyneuropathy (CIDP), a common and treatable autoimmune neuropathy, is frequently misdiagnosed. The aim of this study is to evaluate the relationship between immunological markers and clinical outcome measures in a mixed cohort of patients with typical CIDP and CIDP variants at different disease stages. Twenty-three typical, 16 multifocal and five distal CIDP patients were included. Twenty-five sex and age-matched healthy controls and 12 patients with Charcot-Marie-Tooth type 1A (CMT1A) disease served as controls. Peripheral B-cell populations were analyzed by flow cytometry. IL6, IL10, TNFA mRNA and mir-21, mir-146a, and mir-155-5p expression levels were evaluated by real-time polymerase chain reaction in peripheral blood mononuclear cells (PBMC) and/or skin biopsy specimens. Results were then assessed for a possible association with clinical disability scores and intraepidermal nerve fiber densities (IENFD) in the distal leg. We detected a significant reduction in naive B cells (P ≤ 0.001), plasma cells (P ≤ 0.001) and regulatory B cells (P < 0.05), and an elevation in switched memory B cells (P ≤ 0.001) in CIDP compared to healthy controls. CMT1A and CIDP patients had comparable B-cell subset distribution. CIDP cases had significantly higher TNFA and IL10 gene expression levels in PBMC compared to healthy controls (P < 0.05 and P ≤ 0.01, respectively). IENFDs in the distal leg showed a moderate negative correlation with switched memory B-cell ratios (r = -0.51, P < 0.05) and a moderate positive correlation with plasma cell ratios (r = 0.46, P < 0.05). INCAT sum scores showed a moderate positive correlation with IL6 gene expression levels in PBMC (r = 0.54, P < 0.05). Altered B-cell homeostasis and IL10 and TNFA gene expression levels imply chronic antigen exposure and overactivity in the humoral immune system, and seem to be a common pathological pathway in both typical CIDP and CIDP variants.

Exploiting the CD200-CD200R immune checkpoint axis in multiple myeloma to enhance CAR T-cell therapy

AbstractPatients with multiple myeloma (MM) treated with B-cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR) T cells usually relapse with BCMA+ disease, indicative of CAR T-cell suppression. CD200 is an immune checkpoint that is overexpressed on aberrant plasma cells (aPCs) in MM and is an independent negative prognostic factor for survival. However, CD200 is not present on MM cell lines, a potential limitation of current preclinical models. We engineered MM cell lines to express CD200 at levels equivalent to those found on aPCs in MM and show that these are sufficient to suppress clinical-stage CAR T-cells targeting BCMA or the Tn glycoform of mucin 1 (TnMUC1), costimulated by 4-1BB and CD2, respectively. To prevent CD200-mediated suppression of CAR T cells, we compared CRISPR-Cas9–mediated knockout of the CD200 receptor (CD200RKO), to coexpression of versions of the CD200 receptor that were nonsignaling, that is, dominant negative (CD200RDN), or that leveraged the CD200 signal to provide CD28 costimulation (CD200R-CD28 switch). We found that the CD200R-CD28 switch potently enhanced the polyfunctionality of CAR T cells, and improved cytotoxicity, proliferative capacity, CAR T-cell metabolism, and performance in a chronic antigen exposure assay. CD200RDN provided modest benefits, but surprisingly, the CD200RKO was detrimental to CAR T-cell activity, adversely affecting CAR T-cell metabolism. These patterns held up in murine xenograft models of plasmacytoma, and disseminated bone marrow predominant disease. Our findings underscore the importance of CD200-mediated immune suppression in CAR T-cell therapy of MM, and highlight a promising approach to enhance such therapies by leveraging CD200 expression on aPCs to provide costimulation via a CD200R-CD28 switch.

Coengineering specificity, safety, and function into T cells for cancer immunotherapy.

Adoptive T-cell transfer (ACT) therapies, including of tumor infiltrating lymphocytes (TILs) and T cells gene-modified to express either a T cell receptor (TCR) or a chimeric antigen receptor (CAR), have demonstrated clinical efficacy for a proportion of patients and cancer-types. The field of ACT has been driven forward by the clinical success of CD19-CAR therapy against various advanced B-cell malignancies, including curative responses for some leukemia patients. However, relapse remains problematic, in particular for lymphoma. Moreover, for a variety of reasons, relative limited efficacy has been demonstrated for ACT of non-hematological solid tumors. Indeed, in addition to pre-infusion challenges including lymphocyte collection and manufacturing, ACT failure can be attributed to several biological processes post-transfer including, (i) inefficient tumor trafficking, infiltration, expansion and retention, (ii) chronic antigen exposure coupled with insufficient costimulation resulting in T-cell exhaustion, (iii) a range of barriers in the tumor microenvironment (TME) mediated by both tumor cells and suppressive immune infiltrate, (iv) tumor antigen heterogeneity and loss, or down-regulation of antigen presentation machinery, (v) gain of tumor intrinsic mechanisms of resistance such as to apoptosis, and (vi) various forms of toxicity and other adverse events in patients. Affinity-optimized TCRs can improve T-cell function and innovative CAR designs as well as gene-modification strategies can be used to coengineer specificity, safety, and function into T cells. Coengineering strategies can be designed not only to directly support the transferred T cells, but also to block suppressive barriers in the TME and harness endogenous innate and adaptive immunity. Here, we review a selection of the remarkable T-cell coengineering strategies, including of tools, receptors, and gene-cargo, that have been developed in recent years to augment tumor control by ACT, more and more of which are advancing to the clinic.

Distinct phenotypes of rare autoreactive and virus-reactive CD8+ T cells revealed through novel clustering algorithm

Abstract Antigen-specific cells are implicated in the development and progression of disease in autoimmunity, infectious disease, and cancer, and are an attractive target for therapies. While robust detection of antigen-specific cells is possible with tetramer and activation-induced marker assays, extensive characterization of these cells remains challenging due to their rarity. Here we present a novel computational tool, DISCOV-R, that enables deep phenotyping of rare antigen-specific cells through unbiased clustering of a parent population into subsets defined by expression of phenotyping markers and overlaying the antigen-specific population. Using this tool with 35-parameter mass cytometry (CyTOF) along with class I MHC-tetramer assays, we identified phenotypes enriched among rare islet autoantigen-reactive and chronic virus-reactive CD8+ T cells when compared to total CD8+ T cells from 46 type 1 diabetics. CD8+ T cells were clustered based on expression of 24 phenotypic markers, revealing 12 CD8+ T cell phenotypes shared across subjects. Overlaying antigen-specific tetramer-positive cells on this phenotypic landscape revealed that both islet- and virus-reactive cells were enriched for an exhausted-like memory phenotype (p=1.7E-07 and 1.6E-05, respectively) consistent with chronic antigen exposure, while islet-reactive cells were enriched for two transitional memory phenotypes (p=0.01 and 0.03). The characterization of these rare antigen-specific cells using DISCOV-R reveals unique phenotypes associated with their specificity that may indicate different function, and enables comparison over time and between individuals to identify biomarkers and potential pathways to disease development and progression.

Early Generation and Anatomical Commitment of Stem-like CD8 T cells

Abstract Stem-like CD8 T cells sustain the CD8 T cell response during chronic viral infection and cancer, and residency in lymphoid tissues is a key aspect of their biology. We used the chronic LCMV strain, clone 13, to determine when these cells first emerge and commit to positioning in lymphoid sites. Phenotypical and transcriptional profiling of virus-specific CD8 T cells indicated that stem-like and effector fates diverge as early as day 5 after infection. PD-1+ stem-like CD8 T cells sorted from the early (day 5) and established phases (&amp;gt;day 45) of clone 13 infection showed substantial transcriptional overlap indicating that the canonical gene signature of these cells manifests early and is maintained throughout infection. Intravascular labeling and imaging showed that the spatial commitment of these cells to the splenic white pulp also began on day 5. These observations were striking as stem-like CD8 T cells are considered an adaptation to prolonged antigen exposure, yet their fate and anatomical commitments are made before the trajectory of infection is clearly acute or chronic. There were important time-related changes to these cells as well. Early stem-like cells were proliferating and expressed genes involved in the cell cycle, mTOR signaling, and anabolic metabolism. As infection progressed, they upregulated multiple inhibitory molecules and eventually became quiescent. Thus, the stem-like transcriptional and anatomical commitment occurs very early after infection. These data indicate that the CD8 T cell response is equipped for chronic antigen exposure before the trajectory of infection is clearly acute or chronic and further highlight the importance of location for stem-like CD8 T cells. Supported by grants from NIH (5R01AI030048-29)

Adrenergic receptors regulate T cell differentiation in viral infection and cancer

Abstract CD8 +T cells are critical components of the immune reaction against viral infections and cancer and have the potential to eliminate infected or malignant cells. However, when the antigen persists, CD8 +T cells enter an exhausted state. Chronic disease can lead to increased systemic noradrenaline (NA) levels, but it is currently still unclear how NA impacts the differentiation and function of exhausted CD8 +T cells. We here set out to characterize the effects of β adrenergic signaling on CD8 +T cells in chronic viral infection with LCMV-clone 13 and in murine cancer models. We observed that chronically infected mice had elevated systemic NA levels and CD8 +T cells expressed higher levels of the β-1 adrenergic NA receptor, Adrb1. NA impaired T cell receptor signaling of ADRB1-expressing CD8 +T cells, and reduced T cell proliferation and function. Conversely, genetic ablation of ADRB1 prevented terminal CD8 +T cell differentiation in chronic viral infection and ADRB1-blockade enhanced T cell functionality in combination with immune checkpoint blockade (ICB) in an ICB-sensitive melanoma model. Expanding these observations to an ICB-resistant model of pancreatic cancer, we found that pharmacological blockade of adrenergic receptors synergized with ICB to genetically reprogram CD8 +T cells towards a tissue resident memory T cell-like state and improved T cell functionality, resulting in decreased tumor size. In summary, our data suggest that β adrenergic receptors represent a novel immune checkpoint that modulates CD8 +T cell differentiation and function in the context of chronic antigen exposure and that targeting adrenergic receptors may synergize with ICB in cancer patients. AMG was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, GL 991/1-1). SZ was supported by K00CA222741. This work was supported by grants from the NIH 5 R01 CA240909 (SMK) and 5 R01 CA216101 (SMK).