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Obesity is a well-established risk factor for human cancer, yet the underlying mechanisms remain elusive. Immune dysfunction is commonly associated with obesity but whether compromised immune surveillance contributes to cancer susceptibility in individuals with obesity is unclear. Here we use a mouse model of diet-induced obesity to investigate tumor-infiltrating CD8 + T cell responses in lean, obese, and previously obese hosts that lost weight through either dietary restriction or treatment with semaglutide. While both strategies reduce body mass, only dietary intervention restores T cell function and improves responses to immunotherapy. In mice exposed to a chemical carcinogen, obesity-related immune dysfunction leads to higher incidence of sarcoma development. However, impaired immunoediting in the obese environment enhances tumor immunogenicity, making the malignancies highly sensitive to immunotherapy. These findings offer insight into the complex interplay between obesity, immunity and cancer, and provide explanation for the obesity paradox observed in clinical immunotherapy settings. Obesity represents a risk factor for cancer and compromises immune function, however the mechanisms linking the two together are not fully known. Here authors show in a mouse sarcoma model that obesity increases tumour incidence, impairs intra-tumoral T cell immunity but paradoxically increases sensitivity to immune therapy via impairing immunoediting. [ABSTRACT FROM AUTHOR]

Checkpoint blockade immunotherapy has become a first-line treatment option for cancer patients, with success in increasingly diverse cancer types. Still, many patients do not experience durable responses and the reasons for clinical success versus failure remain largely undefined. Investigation of immune responses within the tumor microenvironment can be highly informative but access to tumor tissue is not always available, highlighting the need to identify biomarkers in the blood that correlate with clinical success. Here, we used single-cell RNA sequencing coupled with T cell receptor sequencing to define CD8+ T cell responses in peripheral blood of two patients with melanoma before and after immunotherapy with either anti-PD-1 (nivolumab) alone or the combination of anti-PD-1 and CTLA-4 (ipilimumab). Both treatment regimens increased transcripts associated with cytolytic effector function and decreased transcripts associated with naive T cells. These responses were further evaluated at the protein level and extended to a total of 53 patients with various cancer types. Unexpectedly, the induction of CD8+ T cell responses associated with cytolytic function was variable and did not predict therapeutic success in this larger patient cohort. Rather, a decrease in the frequency of T cells with a naive-like phenotype was consistently observed after immunotherapy and correlated with prolonged patient survival. In contrast, a more detailed clonotypic analysis of emerging and expanding CD8+ T cells in the blood revealed that a majority of individual T cell clones responding to immunotherapy acquired a transcriptional profile consistent with cytolytic effector function. These results suggest that responses to checkpoint blockade immunotherapy are evident and traceable in patients' blood, with outcomes predicted by the simultaneous loss of naive-like CD8+ T cells and the expansion of mostly rare and diverse cytotoxic CD8+ T cell clones. [ABSTRACT FROM AUTHOR]

Checkpoint blockade immunotherapy is now a first-line treatment option for patients with melanoma. Despite achieving objective responses in about half of patients, the exact immune mechanisms elicited and those required for therapeutic success have not been clearly identified. Insight into these mechanisms is key for improving outcomes in a broader range of cancer patients. We used a murine melanoma model to track responses by different subsets of tumor-infiltrating lymphocytes (TIL) during checkpoint blockade immunotherapy. Tumors from treated mice had increased frequencies of both CD4+ and CD8+ T cells, which also showed evidence of functional reinvigoration and elevated effector cytokine production after immunotherapy. We predicted that increased T cell numbers and function within tumors reflected either infiltration by new T cells or clonal expansion by a few high-affinity tumor-reactive T cells. To address this, we compared TIL diversity before and after immunotherapy by sequencing the complementarity determining region 3 (CDR3) of all T cell receptor beta (TCRβ) genes. While checkpoint blockade effectively slowed tumor progression and increased T cell frequencies, the diversity of intratumoral T cells remained stable. This was true when analyzing total T cells and when focusing on smaller subsets of effector CD4+ and CD8+ TIL as well as regulatory T cells. Our study suggests that checkpoint blockade immunotherapy does not broaden the T cell repertoire within murine melanoma tumors, but rather expands existing T cell populations and enhances effector capabilities. [ABSTRACT FROM AUTHOR]

Discussion on low integrin expression on T cells from geriatric donors as a barrier for CAR expression, and a potential target for improved CAR‐T cell therapy. [ABSTRACT FROM AUTHOR]

Establishing peripheral CD8+ T cell tolerance is vital to avoid immune mediated destruction of healthy self-tissues. However, it also poses a major impediment to tumor immunity since tumors are derived from self-tissue and often induce T cell tolerance and dysfunction. Thus, understanding the mechanisms that regulate T cell tolerance versus immunity has important implications for human health. Signals received from the tissue environment largely dictate whether responding T cells become activated or tolerant. For example, induced expression and subsequent ligation of negative regulatory receptors on the surface of self-reactive CD8+ T cells are integral in the induction of tolerance. We utilized a murine model of T cell tolerance to more completely define the molecules involved in this process. We discovered that, in addition to other known regulatory receptors, tolerant self-reactive CD8+ T cells distinctly expressed the surface receptor neuropilin-1 (Nrp1). Nrp1 was highly induced in response to self-antigen, but only modestly when the same antigen was encountered under immune conditions, suggesting a possible mechanistic link to T cell tolerance. We also observed a similar Nrp1 expression profile on human tumor infiltrating CD4+ and CD8+ T cells. Despite high expression on tolerant CD8+ T cells, our studies revealed that Nrp1 had no detectable role in the tolerant phenotype. Specifically, Nrp1-deficient T cells displayed the same functional defects as wild-type self-reactive T cells, lacking in vivo cytolytic potential, IFNγ production, and antitumor responses. While reporting mostly negative data, our findings have therapeutic implications, as Nrp1 is now being targeted for human cancer therapy in clinical trials, but the precise molecular pathways and immune cells being engaged during treatment remain incompletely defined. [ABSTRACT FROM AUTHOR]

Strategies to boost the numbers and functions of regulatory T cells (Tregs) are currently being tested as means to treat autoimmunity. While Tregs have been shown to be effective in this role, strategies to manipulate Tregs to effectively suppress later stages of ongoing diseases need to be established. In this study, we evaluated the ability of TGF-β-induced Tregs (iTregs) specific for the major self-antigen in autoimmune gastritis to suppress established autoimmune gastritis in mice. When transferred into mice during later stages of disease, iTregs demethylated the Foxp3 promoter, maintained Foxp3 expression, and suppressed effector T cell proliferation. More importantly, these iTregs were effective at stopping disease progression. Untreated mice had high numbers of endogenous Tregs (enTregs) but these were unable to stop disease progression. In contrast, iTregs, were found in relatively low numbers in treated mice, yet were effective at stopping disease progression, suggesting qualitative differences in suppressor functions. We identified several inhibitory receptors (LAG-3, PD-1, GARP, and TNFR2), cytokines (TGF-β1 and IL12p35), and transcription factors (IRF4 and Tbet) expressed at higher levels by iTregs compared to enTregs isolated form mice with ongoing disease, which likely accounts for superior suppressor ability in this disease model. These data support efforts to use iTregs in therapies to treat establish autoimmunity, and show that iTregs are more effective than enTregs at suppressing inflammation in this disease model. [ABSTRACT FROM AUTHOR]

The ubiquitin ligase Cbl-b is an established regulator of T cell immune response thresholds. We recently showed that adoptive cell transfer (ACT) of cblb-/- CD8+ T cells enhances dendritic cell (DC) immunization-mediated anti-tumor effects in immune-competent recipients. However, translation of cblb targeting to clinically applicable concepts requires that inhibition of cblb activity be transient and reversible. Here we provide experimental evidence that inhibition of cblb using chemically synthesized siRNA has such potential. Silencing cblb expression by ex vivo siRNA transfection of polyclonal CD8+ T cells prior to ACT increased T cell tumor infiltration, significantly delayed tumor outgrowth, and increased survival rates of tumor-bearing mice. As shown by ex vivo recall assays, cblb silencing resulted in significant augmentation of intratumoral T cell cytokine response. ACT of cblb-silenced polyclonal CD8+ T cells combined with DC-based tumor vaccines predominantly mediated anti-tumor immune responses, whereas no signs of autoimmunity could be detected. Importantly, CBLB silencing in human CD8+ T cells mirrored the effects observed for cblb-silenced and cblb-deficient murine T cells. Our data validate the concept of enhanced anti-tumor immunity by repetitive ACT of ex vivo cblb siRNA-silenced hyper-reactive CD8+ T cells as add-on adjuvant therapy to augment the efficacy of existing cancer immunotherapy regimens in clinical practice. [ABSTRACT FROM AUTHOR]

Adoptive T-cell immunotherapy has shown promise in the treatment of human malignancies, but the challenge of isolating T cells with high avidity for tumor antigens in each patient has limited application of this approach. The transfer into T cells of T-cell receptor (TCR) genes encoding high-affinity TCRs recognizing defined tumor-associated antigens can potentially circumvent this obstacle. Using a well-characterized murine model of adoptive T-cell immunotherapy for widely disseminated leukemia, we demonstrate that TCR gene–modified T cells can cure mice of disseminated tumor. One goal of such adoptive therapy is to establish a persistent memory response to prevent recurrence; however, long-term function of transferred TCR-transduced T cells is limited due to reduced expression of the introduced TCR in vivo in quiescent resting T cells. However, by introducing the TCR into a cell with a known endogenous specificity, activation of these T cells by stimulation through the endogenous TCR can be used to increase expression of the introduced TCR, potentially providing a strategy to increase the total number of tumor-reactive T cells in the host and restore more potent antitumor activity.Molecular Therapy (2009) 17 4, 742–749 doi:10.1038/mt.2008.300 [ABSTRACT FROM AUTHOR]

Summary Dendritic cells (DCs) initiate immunity and also antigen-specific tolerance mediated by extrathymic regulatory T (Treg) cells, yet it remains unclear how DCs regulate induction of such tolerance. Here, we report that efficient induction of Treg cells was instructed by BTLA + DEC205 + CD8 + CD11c + DCs and the immunomodulatory functions of BTLA. In contrast, T cell activation in steady state by total CD11c + DCs that include a majority of DCs that do not express BTLA did not induce Treg cells and had no lasting impact on subsequent immune responses. Engagement of HVEM, a receptor of BTLA, promoted Foxp3 expression in T cells through upregulation of CD5. In contrast, T cells activated in the absence of BTLA and HVEM-mediated functions remained CD5 lo and therefore failed to resist the inhibition of Foxp3 expression in response to effector cell-differentiating cytokines. Thus, DCs require BTLA and CD5-dependent mechanisms to actively adjust tolerizing T cell responses under steady-state conditions. [ABSTRACT FROM AUTHOR]

Spontaneous antigen-specific T cell responses can be generated in hosts harboring a variety of solid malignancies, but are subverted by immune evasion mechanisms active within the tumor microenvironment. In contrast to solid tumors, the mechanisms that regulate T cell activation versus tolerance to hematological malignancies have been underexplored. A murine acute myeloid leukemia (AML) model was used to investigate antigenspecific T cell responses against AML cells inoculated i.v. versus s.c. Robust antigen-specific T cell responses were generated against AML cells after s.c., but not i.v., inoculation. In fact, i.v. AML cell inoculation prevented functional T cell activation in response to subsequent s.c. AML cell challenge. T cell dysfunction was antigen specific and did not depend on Tregs or myeloid-derived suppressor cells (MDSCs). Antigen-specific TCRTg CD8+ T cells proliferated, but failed to accumulate, and expressed low levels of effector cytokines in hosts after i.v. AML induction, consistent with abortive T cell activation and peripheral tolerance. Administration of agonistic anti-CD40 Ab to activate host APCs enhanced accumulation of functional T cells and prolonged survival. Our results suggest that antigen-specific T cell tolerance is a potent immune evasion mechanism in hosts with AML that can be reversed in vivo after CD40 engagement. [ABSTRACT FROM AUTHOR]

Tolerizing mechanisms within the host and tumor microenvironment inhibit T-cell effector functions that can control cancer. These mechanisms blunt adoptive immunotherapy with infused T-cells due to a complex array of signals that determine T-cell tolerance, survival, or deletion. Ligation of the negative regulatory receptors CTLA4, PD-1(PDCD1), or LAG3 on T-cells normally hinders their response to antigen through nonredundant biochemical processes that interfere with stimulatory pathways. In this study, we used an established mouse model of T-cell tolerance to define the roles of these inhibitory receptors in regulating CD8+ T-cell tolerance during adoptive immunotherapy to treat leukemia. Blocking CTLA4 and PD-1 in vivo combined to promote survival of transferred T-cells despite powerful deletional signals that mediate Bim (BCL2L11)-dependent apoptosis. However, this dual blockade was not optimal for stimulating effector function by responding T-cells, which required the additional blockade of LAG3 to induce full expansion and allow the acquisition of robust cytolytic activity. Thus, the cooperation of multiple distinct regulatory pathways was needed for the survival and effector differentiation of adoptively transferred tumor-reactive CD8+ T-cells. Our work defines the immune escape pathways in which simultaneous blockade could yield durable immunotherapeutic responses that can eradicate disseminated leukemia. [ABSTRACT FROM AUTHOR]

The ability to regulate ongoing inflammation using regulatory T cells (Tregs) is under intense investigation. Strategies to induce and expand Ag-specific Tregs are being developed, and whether various types of Tregs are suppressive in the inflammatory conditions associated with ongoing disease needs to be determined. In this study, we report that TGF-β-induced Tregs (iTregs) and expanded Tregs specific for a major self-Ag in autoimmune gastritis suppress inflammation and associated pathology when administered late in the process of ongoing disease. Transferred iTregs localized to the stomach, maintained Foxp3 and suppressor functions, and engaged several distinct mechanisms to alleviate disease progression. In addition to suppressing the production of inflammatory cytokines in the stomach and preventing the destruction of parietal cells, we show that iTregs secrete numerous chemokines and regulate both iTreg and effector T cell trafficking into the stomach. These data support efforts to use iTregs in therapies to treat autoimmunity and inflammatory diseases and provide novel insight into the biological mechanisms of iTreg-mediated immune suppression. [ABSTRACT FROM AUTHOR]