Identification of a T-bet hi Quiescent Exhausted CD8 T Cell Subpopulation That Can Differentiate into TIM3 + CX3CR1 + Effectors and Memory-like Cells
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ABSTRACT: Identification of a T-bet hi Quiescent Exhausted CD8 T Cell Subpopulation That Can Differentiate into TIM3 + CX3CR1 + Effectors and Memory-like Cells
Project description:Persistent Ag induces a dysfunctional CD8 T cell state known as "exhaustion" characterized by PD-1 expression. Nevertheless, exhausted CD8 T cells retain functionality through continued differentiation of progenitor into effector cells. However, it remains ill-defined how CD8 T cell effector responses are sustained in situ. In this study, we show using the mouse chronic lymphocytic choriomeningitis virus infection model that CX3CR1+ CD8 T cells contain a T-bet-dependent TIM3-PD-1lo subpopulation that is distinct from the TIM3+CX3CR1+PD-1+ proliferative effector subset. The TIM3-CX3CR1+ cells are quiescent and express a low but significant level of the transcription factor TCF-1, demonstrating similarity to TCF-1hi progenitor CD8 T cells. Furthermore, following the resolution of lymphocytic choriomeningitis virus viremia, a substantial proportion of TCF-1+ memory-like CD8 T cells show evidence of CX3CR1 expression during the chronic phase of the infection. Our results suggest a subset of the CX3CR1+ exhausted population demonstrates progenitor-like features that support the generation of the CX3CR1+ effector pool from the TCF-1hi progenitors and contribute to the memory-like pool following the resolution of viremia.
Project description:Persistent Ag induces a dysfunctional CD8 T cell state known as "exhaustion" characterized by PD-1 expression. Nevertheless, exhausted CD8 T cells retain functionality through continued differentiation of progenitor into effector cells. However, it remains ill-defined how CD8 T cell effector responses are sustained in situ. In this study, we show using the mouse chronic lymphocytic choriomeningitis virus infection model that CX3CR1+ CD8 T cells contain a T-bet-dependent TIM3-PD-1lo subpopulation that is distinct from the TIM3+CX3CR1+PD-1+ proliferative effector subset. The TIM3-CX3CR1+ cells are quiescent and express a low but significant level of the transcription factor TCF-1, demonstrating similarity to TCF-1hi progenitor CD8 T cells. Furthermore, following the resolution of lymphocytic choriomeningitis virus viremia, a substantial proportion of TCF-1+ memory-like CD8 T cells show evidence of CX3CR1 expression during the chronic phase of the infection. Our results suggest a subset of the CX3CR1+ exhausted population demonstrates progenitor-like features that support the generation of the CX3CR1+ effector pool from the TCF-1hi progenitors and contribute to the memory-like pool following the resolution of viremia.
Project description:TIM3, a T-cell inhibitory receptor, is expressed on exhausted T cells in tumor microenvironment (TME). Anti-TIM3 antibody therapy could alleviate the suppression of tumor-infiltrating lymphocytes (TILs) in IL-2 dependent fashion. We hypothesize that high expression of TIM3 and limited IL-2 in TME facilitate immune evasion. To test that, we engineered anti-TIM3-pro-IL2 to selectively deliver IL-2 to TIM3high TILs by TIM3 antibody and reduce its toxicity with a cis delivery mechanism. Since IL-2 could reduce its activity at acidic pH inside TME, we also screened a low pH-selective IL-2 mutein (IL2V2) with enhanced affinity for IL-2Rβ. We then integrated pro-IL-2 into the anti-TIM3 antibodies in two different forms: TIM3-Rα-MMPs-IL2V2 (TIM3-ProIL2V2) as IL-2 release-form vs TIM3-IL2V2-MMPs-Rα as cis-form after binding to TIM3high T cells, ensuring the need of targeted delivery to TIM3-expressing TILs. Surprisingly, released IL2V2 from TIM3-Rα-MMPs-IL2V2 proved superior in anti-tumor immunity, but not cis delivery form TIM3-IL2V2-MMPs-Rα. Mechanistically, TIM3-ProIL2V2 not only reactivated TIM3+ TILs but also facilitated the activation and expansion of TIM3- T cells which in turn supported a sustained source of TIM3+ effector. TIM3-ProIL2V2 could control multiple tumor models including human tumor in humanized mice, confirming the hypothesis. TIM3-ProIL2V2 activates and expands TIM3-CD8+ T cells to overcome current major unmet medical need: anti-PD-1/L1 resistance. This strategy illustrates the potential of a tailored, low pH-resistant IL2 variant in invigorating both TIM3-negative and positive CD8+ T cells, offering a promising avenue for treating resistant tumors with reduced toxicity.
Project description:The aging brain shows changes in microglial function, morphology, and phenotype, indicating chronic microglial activation. CX3CR1 is crucial for microglial chemotaxis, phagocytosis, and activation. However, its exact role in the aging brain is not well understood. In this study, we examined the expression of CX3CR1 in the brains of middle-aged mice (10 months old) and explored its functional implications by conducting proteomic profiling in CX3CR1-deficient mouse cerebrum. Proteomic analysis revealed an enrichment of differentially expressed proteins (DE-proteins) in the cerebrum of middle-aged mice in GO pathways such as “synapse”, “translation”, and “ribosome”. CX3CR1 deficiency affected protein levels in GO pathways such as “glutamatergic synapse” and “RNA splicing.” We also detected the proteomics in age-matched 5xFAD mice for comparison, since this mouse strain featured aberrant microglial activation and CX3CR1 upregulation in the hippocampus and frontal cortex. Our findings demonstrated that CX3CR1 was upregulated to maintain synaptic homeostasis probably through regulating microglial activation and phagocytosis in the brains of middle-aged mice. CX3CR1 may represent a promising therapeutic target for alleviating the effects of aging and preventing neurodegeneration.
Project description:In metastasis, the existence tumor cells overcoming the immune system during early organ seeding is crucial, yet the dynamics of tumor-immune interactions during micrometastasis remain unclear. Examining the immune selective pressure in breast cancer (BC) mouse models, we unexpectedly found TIM3 among the most upregulated genes in metastatic surviving BC cells. The selection of TIM3+ tumor cells, was specifically occurring during early seeding of micrometastasis, escaping the immune attack and acquiring stemness. Also clinical data confirmed increased TIM3+ tumor cells in BC metastasis. The aim of the study was to understand the mechanistic insgihts of Tim3 in breast cancer cells in vivo to decipher pivotal pathways of Tim3-mediated immun-evasion.
Project description:CX3CR1, one of the highest expressed genes in microglia in mice and humans, is implicated in numerous microglial functions. However, the molecular mechanisms underlying Cx3cr1 signaling are not well understood. Here, we analyzed transcriptomes of Cx3cr1-deficient microglia under varying conditions by RNA-Seq. In 2 mos mice, Cx3cr1 deletion resulted in the downregulation of a subset of immune-related genes, without substantial epigenetic changes in markers of active chromatin. Surprisingly, Cx3cr1-deficient microglia from young mice exhibited a transcriptome consistent with that of aged Cx3cr1-sufficient animals, suggesting a premature aging transcriptomic signature. Immunohistochemical analysis of microglia in young and aged mice revealed that loss of Cx3cr1 modulates microglial morphology in a compatible fashion. Our results suggest that CX3CR1 may regulate microglial function in part by modulating the expression levels of a subset of inflammatory genes during chronological aging, making Cx3cr1-deficient mice useful for studying aged microglia.
Project description:CX3CR1, one of the highest expressed genes in microglia in mice and humans, is implicated in numerous microglial functions. However, the molecular mechanisms underlying Cx3cr1 signaling are not well understood. Here, we analyzed transcriptomes of Cx3cr1-deficient microglia under varying conditions by RNA sequencing (RNA-Seq). In 2 mos mice, Cx3cr1 deletion resulted in the downregulation of a subset of immune-related genes, without substantial epigenetic changes in markers of active chromatin. Surprisingly, Cx3cr1-deficient microglia from young mice exhibited a transcriptome consistent with that of aged Cx3cr1-sufficient animals, suggesting a premature aging transcriptomic signature.
Project description:Memory T cells are important for protective immunity against infectious microorganisms. Such protection is achieved by cooperative action of memory T cell populations that differ in their tissue localization and functionality. We report on the identification of the fractalkine receptor CX3CR1 as marker for stratification of memory T cells with cytotoxic effector function from those with proliferative function in both, mice and man. Based on CX3CR1 and CD62L expression levels four distinct memory T cell populations can be distinguished based on their functional properties. Transcriptome and proteome profiling revealed that CX3CR1 expression was superior to CD62L to resolve memory T cell functionality and allowed determination of a core signature of memory T cells with cytotoxic effector function. This identifies a CD62Lhi CX3CR1+ memory T cell population with an identical gene signature to CD62LlowCX3CR1+ effector memory T cells. In lymph nodes, this so far unrecognized CD62LhiCX3CR1+ T cell population shows a distinct migration pattern and anatomic positioning compared to CD62LhiCX3CR1neg TCM. Furthermore, CX3CR1+ memory T cells were scarce or absent during chronic HBV, HCV and HIV infection in man and chronic LCMV infection in mice confirming the value of CX3CR1+ in understanding principles of protective immune memory. CD8+ T cells were isolated and directly assessed or incubated with DC or LSEC. After harvesting, cells were immediately lysed in Trizol (Invitrogen) before storage at -80°C for RNA isolation.
Project description:Muscle injury triggers inflammation in which infiltrating mononuclear phagocytes are crucial for tissue regeneration. The interaction of the CCL2/CCR2 and CX3CL1/CX3CR1 chemokine axis that guides phagocyte infiltration is incompletely understood. Here, we show that CX3CR1 deficiency promotes muscle repair and rescues Ccl2-/- mice from impaired muscle regeneration as a result of altered macrophage function, not infiltration. Transcriptomic analysis of muscle mononuclear phagocytes reveals that Apolipoprotein E (ApoE) is up-regulated in mice with efficient regeneration. ApoE treatment enhances phagocytosis by mononuclear phagocytes in vitro, and restores phagocytic activity and muscle regeneration in Ccl2-/- mice. Because CX3CR1 deficiency may compensate for defective CCL2-dependant monocyte recruitment by modulating ApoE-dependent macrophage phagocytic activity, targeting CX3CR1 expressed by macrophages might be a powerful therapeutic approach to improve muscle regeneration.