An Immunotherapeutic CD137 Agonist Releases Eomesodermin from ThPOK Repression in CD4 T Cells

Hypothesis of a CD137/Eomes activating axis for effector T cells in HPV oropharyngeal cancers

Chronic Human Papilloma Virus (HPV) infection is supplanting alcohol and tobacco intoxications as the leading cause of oropharyngeal cancer in developed countries. HPV-related squamous cell carcinomas of the oropharynx (HPV + OSC) present better survival and respond better to radiotherapy and chemotherapy. Regulatory T cells (TREG) are mainly described as immunosuppressive and protumoral in most solid cancers. However, TREG are paradoxically associated with a better prognosis in HPV + OSCs. The transcription factor FoxP3 is the basis for the identification of TREG. Among CD4 + FoxP3 + T cells, some have effector functions. A medical hypothesis is formulated here: the existence of a CD137 (4.1BB)-Eomesodermin (Eomes) activated pathway downstream of TCR-specific activation in a subpopulation of CD4 + FoxP3 + T cells may explain this effector function. Evidence suggest that this axis may exist either in CD4 + FoxP3 + T cells or CD8 + T cells. This pathway could lead T cells to strong antitumor cytotoxic activity in a tumor-specific manner. Furthermore, CD137 is one of the most expected targets for the development of agonist immunotherapies. The identification of CD137 + Eomes + FoxP3+/- T cells could be a key element in the selective activation of the most anti-tumor cells in the HPV + OSC microenvironment.

VEGF-A enhances the cytotoxic function of CD4+ cytotoxic T cells via the VEGF-receptor 1/VEGF-receptor 2/AKT/mTOR pathway

BACKGROUND

CD4⁺ cytotoxic T cells (CD4 CTLs) are CD4⁺ T cells with major histocompatibility complex-II-restricted cytotoxic function. Under pathologic conditions, CD4 CTLs hasten the development of autoimmune disease or viral infection by enhancing cytotoxicity. However, the regulators of the cytotoxicity of CD4 CTLs are not fully understood.

METHODS

To explore the potential regulators of the cytotoxicity of CD4 CTLs, bulk RNA and single-cell RNA sequencing (scRNA-seq), enzyme-linked immunosorbent assay, flow cytometry, quantitative PCR, and in-vitro stimulation and inhibition assays were performed.

RESULTS

In this study, we found that VEGF-A promoted the cytotoxicity of CD4 CTLs through scRNA-seq and flow cytometry. Regarding the specific VEGF receptor (R) involved, VEGF-R1/R2 signaling was activated in CD4 CTLs with increased cytotoxicity, and the VEGF-A effects were inhibited when anti-VEGF-R1/R2 neutralizing antibodies were applied. Mechanistically, VEGF-A treatment activated the AKT/mTOR pathway in CD4 CTLs, and the increases of cytotoxic molecules induced by VEGF-A were significantly reduced when the AKT/mTOR pathway was inhibited.

CONCLUSION

In conclusion, VEGF-A enhances the cytotoxicity of CD4 CTLs through the VEGF-R1/VEGF-R2/AKT/mTOR pathway, providing insights for the development of novel treatments for disorders associated with CD4 CTLs.

Regulation of CD4 T Cell Responses by the Transcription Factor Eomesodermin

Central to the impacts of CD4 T cells, both positive in settings of infectious disease and cancer and negative in the settings of autoimmunity and allergy, is their ability to differentiate into distinct effector subsets with specialized functions. The programming required to support such responses is largely dictated by lineage-specifying transcription factors, often called ‘master regulators’. However, it is increasingly clear that many aspects of CD4 T cell immunobiology that can determine the outcomes of disease states involve a broader transcriptional network. Eomesodermin (Eomes) is emerging as an important member of this class of transcription factors. While best studied in CD8 T cells and NK cells, an increasing body of work has focused on impacts of Eomes expression in CD4 T cell responses in an array of different settings. Here, we focus on the varied impacts reported in these studies that, together, indicate the potential of targeting Eomes expression in CD4 T cells as a strategy to improve a variety of clinical outcomes.

Cytotoxic CD4+ T cells driven by T-cell intrinsic IL-18R/MyD88 signaling predominantly infiltrate Trypanosoma cruzi-infected hearts

Increasing attention has been directed to cytotoxic CD4+ T cells (CD4CTLs) in different pathologies, both in humans and mice. The impact of CD4CTLs in immunity and the mechanisms controlling their generation, however, remain poorly understood. Here, we show that CD4CTLs abundantly differentiate during mouse infection with the intracellular parasite Trypanosoma cruzi. CD4CTLs display parallel kinetics to Th1 cells in the spleen, mediate specific cytotoxicity against cells presenting pathogen-derived antigens and express immunoregulatory and/or exhaustion markers. We demonstrate that CD4CTL absolute numbers and activity are severely reduced in both Myd88-/- and Il18ra-/- mice. Of note, the infection of mixed-bone marrow chimeras revealed that WT but not Myd88-/- cells transcribe the CD4CTL gene signature and that Il18ra-/- and Myd88-/- CD4+ T cells phenocopy each other. Moreover, adoptive transfer of WT CD4+GzB+ T cells to infected Il18ra-/- mice extended their survival. Importantly, cells expressing the CD4CTL phenotype predominate among CD4+ T cells infiltrating the infected mouse cardiac tissue and are increased in the blood of Chagas patients, in which the frequency of CD4CTLs correlates with the severity of cardiomyopathy. Our findings describe CD4CTLs as a major player in immunity to a relevant human pathogen and disclose T-cell intrinsic IL-18R/MyD88 signaling as a key pathway controlling the magnitude of the CD4CTL response.

Bona Fide Th17 Cells without Th1 Functional Plasticity Protect against Influenza

Optimal transcriptional programming needed for CD4 T cells to protect against influenza A virus (IAV) is unclear. Most IAV-primed CD4 T cells fit Th1 criteria. However, cells deficient for the Th1 "master regulator," T-bet, although marked by reduced Th1 identity, retain robust protective capacity. In this study, we show that T-bet's paralog, Eomesodermin (Eomes), is largely redundant in the presence of T-bet but is essential for the residual Th1 attributes of T-bet-deficient cells. Cells lacking both T-bet and Eomes instead develop concurrent Th17 and Th2 responses driven by specific inflammatory signals in the infected lung. Furthermore, the transfer of T-bet- and Eomes-deficient Th17, but not Th2, effector cells protects mice from lethal IAV infection. Importantly, these polyfunctional Th17 effectors do not display functional plasticity in vivo promoting gain of Th1 attributes seen in wild-type Th17 cells, which has clouded evaluation of the protective nature of Th17 programming in many studies. Finally, we show that primary and heterosubtypic IAV challenge is efficiently cleared in T-bet- and Eomes double-deficient mice without enhanced morbidity despite a strongly Th17-biased inflammatory response. Our studies thus demonstrate unexpectedly potent antiviral capacity of unadulterated Th17 responses against IAV, with important implications for vaccine design.

A novel CD4+ CTL subtype characterized by chemotaxis and inflammation is involved in the pathogenesis of Graves' orbitopathy

Graves' orbitopathy (GO), the most severe manifestation of Graves' hyperthyroidism (GH), is an autoimmune-mediated inflammatory disorder, and treatments often exhibit a low efficacy. CD4+ T cells have been reported to play vital roles in GO progression. To explore the pathogenic CD4+ T cell types that drive GO progression, we applied single-cell RNA sequencing (scRNA-Seq), T cell receptor sequencing (TCR-Seq), flow cytometry, immunofluorescence and mixed lymphocyte reaction (MLR) assays to evaluate CD4+ T cells from GO and GH patients. scRNA-Seq revealed the novel GO-specific cell type CD4+ cytotoxic T lymphocytes (CTLs), which are characterized by chemotactic and inflammatory features. The clonal expansion of this CD4+ CTL population, as demonstrated by TCR-Seq, along with their strong cytotoxic response to autoantigens, localization in orbital sites, and potential relationship with disease relapse provide strong evidence for the pathogenic roles of GZMB and IFN-γ-secreting CD4+ CTLs in GO. Therefore, cytotoxic pathways may become potential therapeutic targets for GO.

Costimulation Induces CD4 T Cell Antitumor Immunity via an Innate-like Mechanism

Chronic exposure to tumor-associated antigens inactivates cognate T cells, restricting the repertoire of tumor-specific effector T cells. This problem was studied here by transferring TCR transgenic CD4 T cells into recipient mice that constitutively express a cognate self-antigen linked to MHC II on CD11c-bearing cells. Immunotherapeutic agonists to CD134 plus CD137, "dual costimulation," induces specific CD4 T cell expansion and expression of the receptor for the Th2-associated IL-1 family cytokine IL-33. Rather than producing IL-4, however, they express the tumoricidal Th1 cytokine IFNγ when stimulated with IL-33 or IL-36 (a related IL-1 family member) plus IL-12 or IL-2. IL-36, which is induced within B16-F10 melanomas by dual costimulation, reduces tumor growth when injected intratumorally as a monotherapy and boosts the efficacy of tumor-nonspecific dual costimulated CD4 T cells. Dual costimulation thus enables chronic antigen-exposed CD4 T cells, regardless of tumor specificity, to elaborate tumoricidal function in response to tumor-associated cytokines.

The transcription factors Runx3 and ThPOK cross-regulate acquisition of cytotoxic function by human Th1 lymphocytes

Cytotoxic CD4 (CD4_CTX) T cells are emerging as an important component of antiviral and antitumor immunity, but the molecular basis of their development remains poorly understood. In the context of human cytomegalovirus infection, a significant proportion of CD4 T cells displays cytotoxic functions. We observed that the transcriptional program of these cells was enriched in CD8 T cell lineage genes despite the absence of ThPOK downregulation. We further show that establishment of CD4_CTX-specific transcriptional and epigenetic programs occurred in a stepwise fashion along the Th1-differentiation pathway. In vitro, prolonged activation of naive CD4 T cells in presence of Th1 polarizing cytokines led to the acquisition of perforin-dependent cytotoxic activity. This process was dependent on the Th1 transcription factor Runx3 and was limited by the sustained expression of ThPOK. This work elucidates the molecular program of human CD4_CTX T cells and identifies potential targets for immunotherapy against viral infections and cancer.