EBI3 regulates the NK cell response to mouse cytomegalovirus infection

Malignant behaviors and immune response in melanoma: Epstein-Barr virus induced gene 3 as a therapeutic target based on an in-vitro exploration

Background

Epstein-Barr virus induced gene 3 (EBI3), a member of the IL-12 family, is known to be involved in malignant progression in a variety of cancers, but its role in melanoma is unclear. The aim of this study was to explore the effects of EBI3 on the malignant phenotype melanoma to reveal its potential as a therapeutic target.

Methods

In this study, we used bioinformatics to analyze the expression of EBI3 in pan-cancer and verified its expression level in melanoma cells by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Subsequently, the effects of EBI3 knockdown on cell proliferation, migration and invasion were detected using the Cell Counting Kit-8 (CCK-8) and Transwell assays. Changes in immune-related cytokines were detected by ELISA, and macrophage polarization was observed using immunofluorescence. Finally, the phosphorylation levels of signaling pathways such as Smad3, STAT6 and cGAS-STING were analyzed by Western blot.

Results

EBI3 was evidently highly-expressed in melanoma, and silencing of EBI3 could visibly suppress the survival and migration/invasion of melanoma cells, concurrent with the increased levels of BAX and CDH1 and the decreased expressions of BCL2 and CDH2. Meanwhile, EBI3 knockdown diminished the phosphorylation levels of both Smad3 and STAT6 and the levels of immune response-relevant cytokines in melanoma cells, while aggravating the macrophage M1 polarization and the expression of cGAS, p-STING and p-IRE1 α in THP-1 monocyte-derived macrophages co-cultured with EBI3-silenced melanoma cells.

Conclusion

This study filled the blank on the involvement of EBI3 in melanoma, hinting the possibility of controlling EBI3 as a therapeutic strategy in the management of melanoma.

IL-27 suppresses spring viremia of carp virus replication in zebrafish

Interleukin (IL) 27 is a member of the IL-12 family and is a heterodimeric cytokine composed of IL-27A and Epstein-Barr virus-induced 3 (EBI3). It plays an important role in regulating inflammation and cancer progression. IL-27A not only functions by dimerizing with EBI3 but also acts alone. Here, we report that IL-27A and EBI3 suppress spring viremia of carp virus (SVCV) replication in zebrafish. Expression analysis reveals that il-27a and ebi3 were significantly upregulated in the ZF4 cells by SVCV and poly(I:C), and in the zebrafish caudal fin (ZFIN) cells overexpressed with SVCV genes. Interestingly, il-27a and ebi3 were not modulated by IFNφ1, indicating that they are not IFN stimulated genes (ISGs). Furthermore, overexpression of IL-27A and EBI3 alone inhibited SVCV replication in the EPC cells, but less potent than co-expression of IL-27A and EBI3. Intriguingly, IL-27A could not induce the expression of irf3, ifn, isg15 and mx1. Taken together, our results demonstrate that IL-27A and EBI3 activate innate antiviral response in an IFN independent manner in zebrafish.

STING-induced regulatory B cells compromise NK function in cancer immunity

An immunosuppressive tumour microenvironment is a major obstacle in the control of pancreatic and other solid cancers1-3. Agonists of the stimulator of interferon genes (STING) protein trigger inflammatory innate immune responses to potentially overcome tumour immunosuppression4. Although these agonists hold promise as potential cancer therapies5, tumour resistance to STING monotherapy has emerged in clinical trials and the mechanism(s) is unclear5-7. Here we show that the administration of five distinct STING agonists, including cGAMP, results in an expansion of human and mouse interleukin (IL)-35+ regulatory B cells in pancreatic cancer. Mechanistically, cGAMP drives expression of IL-35 by B cells in an IRF3-dependent but type I interferon-independent manner. In several preclinical cancer models, the loss of STING signalling in B cells increases tumour control. Furthermore, anti-IL-35 blockade or genetic ablation of IL-35 in B cells also reduces tumour growth. Unexpectedly, the STING-IL-35 axis in B cells reduces proliferation of natural killer (NK) cells and attenuates the NK-driven anti-tumour response. These findings reveal an intrinsic barrier to systemic STING agonist monotherapy and provide a combinatorial strategy to overcome immunosuppression in tumours.

Novel Mouse Model of Murine Cytomegalovirus-Induced Adaptive NK Cells

NK cells are important mediators of viral control with the capacity to form adaptive immune features following infection. However, studies of infection-induced adaptive NK cells require adoptive cell transfer to lower the precursor frequency of "Ag-specific" NK cells, potentially limiting the diversity of the NK cell response. In seeking an unmanipulated model to probe the adaptive NK cells, we interrogated a wide range of Collaborative Cross (CC) inbred mice, inbred mouse strains that exhibit broad genetic diversity across strains. Our assessment identified and validated a putative "ideal" CC strain, CC006, which does not require manipulation to generate and maintain adaptive NK cells. Critically, CC006 mice, in contrast to C57BL/6 mice, are capable of developing enhanced NK cell-mediated protective responses to murine CMV infection following m157-mediated vaccination. This work both furthers our understanding of adaptive NK cells and demonstrates the utility of CC mice in the development and interrogation of immunologic models.

NK cell receptor and ligand composition influences the clearance of SARS-CoV-2

To explore how the immune system controls clearance of SARS-CoV-2, we used a single-cell, mass cytometry-based proteomics platform to profile the immune systems of 21 patients who had recovered from SARS-CoV-2 infection without need for admission to an intensive care unit or for mechanical ventilation. We focused on receptors involved in interactions between immune cells and virus-infected cells. We found that the diversity of receptor repertoires on natural killer (NK) cells was negatively correlated with the viral clearance rate. In addition, NK subsets expressing the receptor DNAM1 were increased in patients who more rapidly recovered from infection. Ex vivo functional studies revealed that NK subpopulations with high DNAM1 expression had cytolytic activities in response to target cell stimulation. We also found that SARS-CoV-2 infection induced the expression of CD155 and nectin-4, ligands of DNAM1 and its paired coinhibitory receptor TIGIT, which counterbalanced the cytolytic activities of NK cells. Collectively, our results link the cytolytic immune responses of NK cells to the clearance of SARS-CoV-2 and show that the DNAM1 pathway modulates host-pathogen interactions during SARS-CoV-2 infection.

The Effect of Unconventional Cytokine Combinations on NK-Cell Responses to Viral Infection

Cytokines are soluble and membrane-bound factors that dictate immune responses. Dogmatically, cytokines are divided into families that promote type 1 cell-mediated immune responses (e.g., IL-12) or type 2 humoral responses (e.g., IL-4), each capable of antagonizing the opposing family of cytokines. The discovery of additional families of cytokines (e.g., IL-17) has added complexity to this model, but it was the realization that immune responses frequently comprise mixtures of different types of cytokines that dismantled this black-and-white paradigm. In some cases, one type of response may dominate these mixed milieus in disease pathogenesis and thereby present a clear therapeutic target. Alternatively, synergistic or blended cytokine responses may obfuscate the origins of disease and perplex clinical decision making. Most immune cells express receptors for many types of cytokines and can mediate a myriad of functions important for tolerance, immunity, tissue damage, and repair. In this review, we will describe the unconventional effects of a variety of cytokines on the activity of a prototypical type 1 effector, the natural killer (NK) cell, and discuss how this may impact the contributions of these cells to health and disease.

KLF12 Regulates Mouse NK Cell Proliferation

NK cells are innate lymphocytes that play an integral role in tumor rejection and viral clearance. Unlike their other lymphocyte counterparts, NK cells have the unique ability to recognize and lyse target cells without prior exposure. However, there are no known NK cell-specific genes that are exclusively expressed by all NK cells. Therefore, identification of NK cell-specific genes would allow a better understanding of why NK cells are unique cytotoxic lymphocytes. From the Immunological Genome (ImmGen) Consortium studies, we identified kruppel-like factor 12 (Klf12), encoding a novel transcription factor, preferentially expressed in C57BL/6 mouse NK cells. KLF12 was dispensable for NK cell development, IFN-γ production, degranulation, and proliferation in Klf12 knockout mice. RNA-sequencing analysis revealed increased expression of Btg3, an antiproliferative gene, in KLF12-deficient NK cells compared with wild-type NK cells. Interestingly, competitive mixed bone marrow chimeric mice exhibited reduced development of KLF12-deficient NK cells, altered IFN-γ production and degranulation, and impairment of NK cell proliferation in vitro and in vivo in response to mouse CMV infection. KLF12-deficient NK cells from bone marrow chimeric mice also expressed higher levels of the IL-21R, which resulted in increased IL-21R signaling and correlated with greater inhibition of NK cell proliferation. Furthermore, IL-21 induced Btg3 expression, which correlated with arrested NK cell maturation and proliferation. In summary, we found that KLF12 regulates mouse NK cell proliferation potentially by regulating expression of Btg3 via IL-21.

Spatial and temporal coordination of antiviral responses by group 1 ILCs

Group 1 innate lymphocytes consist of a phenotypically, spatially, and functionally heterogeneous population of NK cells and ILC1s that are engaged during pathogen invasion. We are only beginning to understand the context-dependent roles that different subsets of group 1 innate lymphocytes play during homeostatic perturbations. With a focus on viral infection, this review highlights the organization and regulation of spatially and temporally distinct waves of NK cell and ILC1 responses that collectively serve to achieve optimal viral control.

Accumulation of EBI3 induced by virulent Mycobacterium tuberculosis inhibits apoptosis in murine macrophages

Macrophages are the primary host target cells of Mycobacterium tuberculosis (M. tb). As a subunit of immunoregulatory cytokines IL-27 and IL-35, Epstein–Barr virus-induced gene 3 (EBI3) has typically been explored as the secreted form and assessed in terms of its effects triggered by extracellular EBI3. However, little is known about intracellular EBI3 function. In the current study, we report that EBI3 production by macrophages is elevated in TB patients. We further demonstrate that increased EBI3 accumulates in virulent M. tb-treated murine macrophages. Eukaryotic translation elongation factor 1-alpha 1 (eEF1A1) binds to intracellular EBI3 to reduce Lys48 (K48)-linked ubiquitination of EBI3, leading to EBI3 accumulation. Moreover, the intracellular EBI3 inhibits caspase-3-mediated apoptosis in M. tb-treated macrophages. Herein, we propose a novel mechanism for accumulating intracellular EBI3 and its regulation of macrophage apoptosis in response to virulent M. tb.

Ebi3 promotes T- and B-cell division and differentiation via STAT3

Although sharing the same subunit Ebi3, IL-27 (p28/Ebi3) and IL-35 (p35/Ebi3) have different biological functions, suggesting that Ebi3 subunit may functions as a carrier. Our data demonstrated that activated T cells and B cells effectively up-regulated Ebi3 expression. In addition, Ebi3 effectively promoted T-cell activation and the differentiation of helper T 1 (Th1), Th17, and Foxp3⁺ regulatory T (Treg) cells induced by Th1, Th17, and Treg polarizing condition, respectively. Naturally, Ebi3 could promote B-cell activation and the production of CD138⁺ plasma cells (PC) induced by LPS. Conversely, neutralizing anti-Ebi3 antibody could significantly suppress T/B-cell activation and production of Th1, Th17, Tregs, and PC induced by Th1, Th17, Treg polarizing condition, and LPS, respectively. Furthermore, we found that Ebi3 time-dependently induced STAT3 activation in CD4⁺T cells and B cells. Conversely, STAT3^-/- effectively reduced Ebi3 expression and the production of Th1, Th17, Tregs, and plasma cells. Finally, we showed that gp130 but not IL-27Rα mediates Ebi3-induced STAT3 activation. These results suggest that Ebi3 promotes Th- and B-cell differentiation via gp130-STAT3 signaling pathway. Thus, autocrine Ebi3 may play an important role in the differentiation of Th and B cells and thus in infection, inflammation, and autoimmune disorders.

Tissue-specific control of latent CMV reactivation by regulatory T cells

Cytomegalovirus (CMV) causes a persistent, lifelong infection. CMV persists in a latent state and undergoes intermittent subclinical viral reactivation that is quelled by ongoing T cell responses. While T cells are critical to maintain control of infection, the immunological factors that promote CMV persistence remain unclear. Here, we investigated the role of regulatory T cells (Treg) in a mouse model of latent CMV infection using Foxp3-diphtheria toxin receptor (Foxp3-DTR) mice. Eight months after infection, MCMV had established latency in the spleen, salivary gland, lung, and pancreas, which was accompanied by an increased frequency of Treg. Administration of diphtheria toxin (DT) after establishment of latency efficiently depleted Treg and drove a significant increase in the numbers of functional MCMV-specific CD4+ and CD8+ T cells. Strikingly, Treg depletion decreased the number of animals with reactivatable latent MCMV in the spleen. Unexpectedly, in the same animals, ablation of Treg drove a significant increase in viral reactivation in the salivary gland that was accompanied with augmented local IL-10 production by Foxp3-CD4+T cells. Further, neutralization of IL-10 after Treg depletion significantly decreased viral load in the salivary gland. Combined, these data show that Treg have divergent control of MCMV infection depending upon the tissue. In the spleen, Treg antagonize CD8+ effector function and promote viral persistence while in the salivary gland Treg prevent IL-10 production and limit viral reactivation and replication. These data provide new insights into the organ-specific roles of Treg in controlling the reactivation of latent MCMV infection.