ABSTRACT Immune checkpoint inhibitors (ICI) have revolutionized cancer therapy, but their use is limited by the development of autoimmunity in healthy tissues as a side effect of treatment. Such immune-related adverse events (IrAE) contribute to hospitalizations, cancer treatment interruption and even premature death. ICI-induced autoimmune diabetes mellitus (ICI-T1DM) is a life-threatening IrAE that presents with rapid pancreatic beta-islet cell destruction leading to hyperglycemia and life-long insulin dependence. While prior reports have focused on CD8 + T cells, the role for CD4 + T cells in ICI-T1DM is less understood. Here, we identify expansion CD4 + T follicular helper (Tfh) cells expressing interleukin 21 (IL-21) and interferon gamma (IFNγ) as a hallmark of ICI-T1DM. Furthermore, we show that both IL-21 and IFNγ are critical cytokines for autoimmune attack in ICI-T1DM. Because IL-21 and IFNγ both signal through JAK-STAT pathways, we reasoned that JAK inhibitors (JAKi) may protect against ICI-T1DM. Indeed, JAKi provide robust in vivo protection against ICI-T1DM in a mouse model that is associated with decreased islet-infiltrating Tfh cells. Moreover, JAKi therapy impaired Tfh cell differentiation in patients with ICI-T1DM. These studies highlight CD4 + Tfh cells as underrecognized but critical mediators of ICI-T1DM that may be targeted with JAKi to prevent this grave IrAE. VISUAL ABSTRACT

The genome organizer, special AT-rich binding protein-1 (SATB1), functions to globally regulate gene networks during primary T cell development and plays a pivotal role in lineage specification in CD4+ helper-, CD8+ cytotoxic-, and FOXP3+ regulatory-T cell subsets. However, it remains unclear how Satb1 gene expression is controlled, particularly in effector T cell function. Here, by using a novel reporter mouse strain expressing SATB1-Venus and genome editing, we have identified a cis-regulatory enhancer, essential for maintaining Satb1 expression specifically in TH2 cells. This enhancer is occupied by STAT6 and interacts with Satb1 promoters through chromatin looping in TH2 cells. Reduction of Satb1 expression, by the lack of this enhancer, resulted in elevated IL-5 expression in TH2 cells. In addition, we found that Satb1 is induced in activated group 2 innate lymphoid cells (ILC2s) through this enhancer. Collectively, these results provide novel insights into how Satb1 expression is regulated in TH2 cells and ILC2s during type 2 immune responses.
© 2023 Nomura et al.

The genome organizer, special AT-rich binding protein-1 (SATB1) functions to globally regulate gene networks during primary T cells development and plays a pivotal role in lineage-specification in CD4 + helper-, CD8 + cytotoxic- and FOXP3 + regulatory-T cell subsets. However, it remains unclear how Satb1 gene expression is controlled, particularly in effector T cell function. Here, by using a novel reporter mouse strain expressing SATB1-Venus and genome editing, we have identified a cis -regulatory enhancer, essential for maintaining Satb1 expression specifically in T H 2 cells. This enhancer is occupied by STAT6 and interacts with Satb1 promoters through chromatin looping in T H 2 cells. Reduction of Satb1 expression, by the lack of this enhancer, resulted in elevated IL-5 expression in T H 2 cells. In addition, we found that Satb1 is induced in activated group 2 innate lymphoid cells (ILC2s) through this enhancer. Collectively, these results provide novel insights into how Satb1 expression is regulated in T H 2 cells and ILC2s during type 2 immune responses.

T follicular helper (Tfh) cells are indispensable for the formation of germinal center (GC) reactions, whereas T follicular regulatory (Tfr) cells inhibit Tfh-mediated GC responses. Aberrant activation of Tfh cells contributes substantially to the pathogenesis of autoimmune diseases, such as systemic lupus erythematosus (SLE). Nonetheless, the molecular mechanisms mitigating excessive Tfh cell differentiation are not fully understood. Herein we demonstrate that the adenovirus E4 promoter-binding protein (E4BP4) mediates a feedback loop and acts as a transcriptional brake to inhibit Tfh cell differentiation. Furthermore, we show that such an immunological mechanism is compromised in patients with SLE. Establishing mice with either conditional knockout (cKO) or knockin (cKI) of the E4bp4 gene in T cells reveals that E4BP4 strongly inhibits Tfh cell differentiation. Mechanistically, E4BP4 regulates Bcl6 transcription by recruiting the repressive epigenetic modifiers HDAC1 and EZH2. E4BP4 phosphorylation site mutants have limited capability with regard to inhibiting Tfh cell differentiation. In SLE, we detected impaired phosphorylation of E4BP4, finding that this compromised transcription factor is positively correlated with disease activity. These findings unveiled molecular mechanisms by which E4BP4 restrains Tfh cell differentiation, whose compromised function is associated with uncontrolled autoimmune reactions in SLE.

Listeria monocytogenes (L. monocytogenes) has been developed as a cancer vaccine vector due to its ability to elicit strong innate and adaptive immune responses. For clinical application, it is necessary to exploit a Listeria platform strain that is safe and that also retains its immunogenicity to develop vaccine candidates against cancer. In this study, a highly attenuated strain with a deletion of actA/plcB was employed as a vector to deliver the human papillomavirus type 16 (HPV16) E7 antigen, which was stably inserted into the chromosome of L. monocytogenes. The prophylactic and therapeutic efficacy of the recombinant L. monocytogenes strain expressing E7 (LM1-2-E7) were evaluated in C57BL/6 mice. In prophylactic tumor challenge assays, immunization with the recombinant strain LM1-2-E7 was able to protect against tumor formation in 87.5% of the mice, even after a second challenge, suggesting that this prophylactic immunization can provide long-lasting immunity. In the therapeutic setting, immunization with LM1-2-E7 led to tumor regression in 50% of the mice and suppressed tumor growth in the remaining mice. The results showed that the recombinant strain was cleared by the immune system within 5 days after immunization and induced a Th1 immune response against E7 peptide and E7-specific cytotoxic T-lymphocyte (CTL) killing activity without severe inflammatory responses in the spleen and liver. Markedly, recombinant Listeria strain resulted in preferential accumulation within tumor tissues and induced higher numbers of CD8+ T cells that infiltrated into the tumor, which were associated with retardation of tumor growth. Collectively, these data indicate that LM1-2-E7 is a possible vaccine candidate against cervical cancer.