In Acute Dengue Infection, High TIM-3 Expression May Contribute to the Impairment of IFNγ Production by Circulating Vδ2 T Cells

γδ T cells are innate cells able to quickly eliminate pathogens or infected/tumoral cells by their antiviral and adjuvancy activities. The role of γδ T cells during Dengue Viral Infection (DENV) infection is not fully elucidated. Nevertheless, human primary γδ T cells have been shown to kill in vitro DENV-infected cells, thus highlighting their possible antiviral function. The aim of this work was to characterize the phenotype and function of Vδ2 T cells in DENV patients. Fifteen DENV patients were enrolled for this study and peripheral blood mononuclear cells (PBMC) were used to analyze Vδ2-T-cell frequency, differentiation profile, activation/exhaustion status, and functionality by multiparametric flow cytometry. Our data demonstrated that DENV infection was able to significantly reduce Vδ2-T-cell frequency and to increase their activation (CD38 and HLA-DR) and exhaustion markers (PD-1 and TIM-3). Furthermore, Vδ2 T cells showed a reduced capability to produce IFN-γ after phosphoantigenic stimulation that can be associated to TIM-3 expression. Several studies are needed to depict the possible clinical impact of γδ-T-cell impairment on disease severity and to define the antiviral and immunoregulatory activities of γδ T cells in the first phases of infection.

Cancer cell-expressed BTNL2 facilitates tumour immune escape via engagement with IL-17A-producing γδ T cells

Therapeutic blockade of the immune checkpoint proteins programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA4) has transformed cancer treatment. However, the overall response rate to these treatments is low, suggesting that immune checkpoint activation is not the only mechanism leading to dysfunctional anti-tumour immunity. Here we show that butyrophilin-like protein 2 (BTNL2) is a potent suppressor of the anti-tumour immune response. Antibody-mediated blockade of BTNL2 attenuates tumour progression in multiple in vivo murine tumour models, resulting in prolonged survival of tumour-bearing mice. Mechanistically, BTNL2 interacts with local γδ T cell populations to promote IL-17A production in the tumour microenvironment. Inhibition of BTNL2 reduces the number of tumour-infiltrating IL-17A-producing γδ T cells and myeloid-derived suppressor cells, while facilitating cytotoxic CD8+ T cell accumulation. Furthermore, we find high BTNL2 expression in several human tumour samples from highly prevalent cancer types, which negatively correlates with overall patient survival. Thus, our results suggest that BTNL2 is a negative regulator of anti-tumour immunity and a potential target for cancer immunotherapy.

The Role of γδ T Cells as a Line of Defense in Viral Infections after Allogeneic Stem Cell Transplantation: Opportunities and Challenges

In the complex interplay between inflammation and graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (allo-HSCT), viral reactivations are often observed and cause substantial morbidity and mortality. As toxicity after allo-HSCT within the context of viral reactivations is mainly driven by αβ T cells, we describe that by delaying αβ T cell reconstitution through defined transplantation techniques, we can harvest the full potential of early reconstituting γδ T cells to control viral reactivations. We summarize evidence of how the γδ T cell repertoire is shaped by CMV and EBV reactivations after allo-HSCT, and their potential role in controlling the most important, but not all, viral reactivations. As most γδ T cells recognize their targets in an MHC-independent manner, γδ T cells not only have the potential to control viral reactivations but also to impact the underlying hematological malignancies. We also highlight the recently re-discovered ability to recognize classical HLA-molecules through a γδ T cell receptor, which also surprisingly do not associate with GVHD. Finally, we discuss the therapeutic potential of γδ T cells and their receptors within and outside the context of allo-HSCT, as well as the opportunities and challenges for developers and for payers.

Effect of Salivary Exosomal miR-25-3p on Periodontitis With Insulin Resistance

Periodontitis is caused by an oral microbial dysbiosis-mediated imbalance of the local immune microenvironment, which is promoted by insulin resistance and obesity. The prevalence and severity of periodontitis is higher in patients with type 2 diabetes than in healthy individuals, possibly because of differences in immune responses. The level of glycemic control also affects the saliva profile, which may further promote periodontal disease in diabetes patients. Therefore, we compared the salivary exosomal miRNA profiles of patients with type 2 diabetes with those of healthy individuals, and we found that exosomal miR-25-3p in saliva is significantly enriched (by approximately 2-fold, p < 0.01) in obese patients with type 2 diabetes. We also identified CD69 mRNA as a miR-25-3p target that regulates both activation of γδ T cells and the inflammatory response. Knockdown of CD69 increased (by approximately 2-fold) interleukin-17A production of γδ T cells in vitro. To evaluate the role of exosomal miRNA on progression of periodontitis, we analyzed regional immune cells in both periodontal tissues and lymph nodes from mice with periodontitis. We found that diet-induced obesity increased the population of infiltrating pro-inflammatory immune cells in the gingiva and regional lymph nodes of these mice. Treatment with miR-25-3p inhibitors prevented the local in vivo inflammatory response in mice with periodontitis and diet-induced obesity. Finally, we showed that suppression of interleukin 17-mediated local inflammation by a miR-25-3p inhibitor alleviated (by approximately 34%) ligature-induced periodontal alveolar bone loss in mice. Taken together, these data suggest that exosomal miR-25-3p in saliva contributes to development and progression of diabetes-associated periodontitis. Discovery of additional miR-25-3p targets may provide critical insights into developing drugs to treat periodontitis by regulating γδ T cell-mediated local inflammation.

Overload of the Temporomandibular Joints Accumulates γδ T Cells in a Mouse Model of Rheumatoid Arthritis: A Morphological and Histological Evaluation

Recently, it has been reported that γδ T cells are associated with the pathology of rheumatoid arthritis (RA). However, there are many uncertainties about their relationship. In this study, we investigated the morphological and histological properties of peripheral as well as temporomandibular joints (TMJ) in a mouse model of rheumatoid arthritis with and without exposure to mechanical strain on the TMJ. Collagen antibody-induced arthritis (CAIA) was induced by administering collagen type II antibody and lipopolysaccharide to male DBA/1JNCrlj mice at 9−12 weeks of age, and mechanical stress (MS) was applied to the mandibular condyle. After 14 days, 3D morphological evaluation by micro-CT, histological staining (Hematoxylin Eosin, Safranin O, and Tartrate-Resistant Acid Phosphatase staining), and immunohistochemical staining (ADAMTS-5 antibody, CD3 antibody, CD45 antibody, RORγt antibody, γδ T cell receptor antibody) were performed. The lower jawbone was collected. The mandibular condyle showed a rough change in the surface of the mandibular condyle based on three-dimensional analysis by micro-CT imaging. Histological examination revealed bone and cartilage destruction, such as a decrease in chondrocyte layer width and an increase in the number of osteoclasts in the mandibular condyle. Then, immune-histological staining revealed accumulation of T and γδ T cells in the subchondral bone. The temporomandibular joint is less sensitive to the onset of RA, but it has been suggested that it is exacerbated by mechanical stimulation. Additionally, the involvement of γδ T cells was suggested as the etiology of rheumatoid arthritis.

Phosphoantigens are Molecular Glues that Promote Butyrophilin 3A1/2A1 Association Leading to Vγ9Vδ2 T Cell Activation

Tumor cells and pathogen-infected cells are presented to human γδ T cells based on "inside-out" signaling in which metabolites called phosphoantigens (pAgs) inside target cells are recognized by the intracellular domain of a butyrophilin protein (BTN3A1), leading to an extracellular conformational change. Here, we report that pAgs function as molecular "glues" that initiate a heteromeric association between the intracellular domains of BTN3A1 and the structurally similar BTN2A1. Working with both exogenous and endogenous pAgs, we used x-ray crystallography, mutational studies, cellular assays, synthetic probe as well as molecular dynamics investigations to determine how pAgs glue intracellular BTN3A1 and BTN2A1 together for the "inside-out" signaling that triggers γδ T cell activation. This γδ T cell-specific mode of antigen sensing creates opportunities for the development of alternative immunotherapies against cancer and infectious diseases that do not involve αβ T cells.