Tim-3 pathway affects NK cell impairment in patients with active tuberculosis

Upregulation of CD226 on subsets of T cells and NK cells is associated with upregulated adhesion molecules and cytotoxic factors in patients with tuberculosis

Human T cells and natural killer (NK) cells are major effector cells of innate immunity exerting potential immune surveillance against tuberculosis infection. CD226 is an activating receptor playing vital roles in the functions of T cells and NK cells during HIV infection and tumorigenesis. However, CD226 is a less-studied activating receptor during Mycobacterium tuberculosis (Mtb) infection. In this study, we used peripheral blood from tuberculosis patients and healthy donors to evaluate CD226 immunoregulation functions from two independent cohorts using Flow cytometry. Here, we found that a subset of T cells and NK cells that constitutively express CD226 exhibit a distinct phenotype in TB patients. In fact, the proportions of CD226⁺ and CD226^- cell subsets differ between healthy people and tuberculosis patients, and the expression of immune checkpoint molecules (TIGIT, NKG2A) and adhesion molecules (CD2, CD11a) in CD226⁺ and CD226^- subsets of T cells and NK cells exhibits special regulatory roles. Furthermore, CD226⁺ subsets produced more IFN-γ and CD107a than CD226^- subsets in tuberculosis patients. Our results imply that CD226 may be a potential predictor of disease progression and clinical efficacy in tuberculosis by mediating the cytotoxic capacity of T cells and NK cells.

Immune checkpoint modulating T cells and NK cells response to Mycobacterium tuberculosis infection

Many subversive mechanisms promote the occurrence and development of chronic infectious diseases and cancer, among which the down-regulated expression of immune-activating receptors and the enhanced expression of immune-inhibitory receptors accelerate the occurrence and progression of the disease. Recently, the use of immune checkpoint inhibitors has shown remarkable efficacy in the treatment of tumors in multiple organs. However, the expression of immune checkpoint molecules on natural killer (NK) cells by Mycobacterium tuberculosis (Mtb) infection and its impact on NK cell effector functions have been poorly studied. In this review, we focus on what is currently known about the expression of various immune checkpoints in NK cells following Mtb infection and how it alters NK cell-mediated host cytotoxicity and cytokine secretion. Unraveling the function of NK cells after the infection of host cells by Mtb is crucial for a comprehensive understanding of the innate immune mechanism of NK cells involved in tuberculosis and the evaluation of the efficacy of immunotherapies using immune checkpoint inhibitors to treat tuberculosis. In view of some similarities in the immune characteristics of T cells and NK cells, we reviewed the molecular mechanism of the interaction between T cells and Mtb, which can help us to further understand and explore the specific interaction mechanism between NK cells and Mtb.

Using TBAg/PHA Ratio for Monitoring TB Treatment: A Prospective Multicenter Study

The way to monitor tuberculosis (TB) treatment is extremely lacking in clinical practice. The aim of the study is to assess the role of the TBAg/PHA ratio in the treatment monitoring of TB. TB patients were followed up for 6 months and serial T-SPOT.TB (T-SPOT) assays were performed. In patients with successful treatment outcomes, the ESAT-6 sfc, CFP-10 sfc, and TBAg/PHA ratio all showed a decreased trend after the initiation of treatment. Conversely, PHA sfc showed an increased trend after 2 months of treatment. However, these indicators had moderate performance in distinguishing between before and after 6 months of treatment, and the AUC ranged from 0.702 to 0.839. Notably, the TBAg/PHA ratio in patients without risk factors was of important value in differentiation between before and after treatment. The optimal AUC of TBAg/PHA ratio reached up to 0.890. Patients with unsuccessful treatment outcomes showed persistently high levels of TBAg/PHA ratio. The TBAg/PHA ratio in patients after 6 months of treatment showed a certain potential in distinguishing between patients with successful and unsuccessful treatment outcomes. A further calculation of the TBAg/PHA ratio in T-SPOT assay has potential value in the treatment monitoring of TB, but further confirmation is needed.

CD39 pathway inhibits Th1 cell function in tuberculosis

The role of CD39 pathway in Th1 cell function in tuberculosis (TB) is rarely elucidated. The present study aims to investigate the modulating mechanism of CD39 pathway during Mycobacterium tuberculosis (MTB) infection. CD39 expression was examined on host immune cells among patients with TB. The relationship between CD39 expression and Th1 cell function was analysed. Patients with TB displayed dramatically higher CD39 expression on Th1 cells than healthy controls, and a significantly increased expression of surface markers, including activation, exhaustion and apoptosis markers, were noted in CD39⁺ Th1 cells in comparison with CD39⁻ Th1 cells. Conversely, CD39 expression on Th1 cells was associated with diminished number of polyfunctional cells producing Th1‐type cytokines, and CD39⁺ Th1 cells showed obviously lower proliferation potential. Notably, tetramer analysis demonstrated a predominant CD39 expression on TB‐specific CD4⁺ cells, which was associated with higher apoptosis and lower cytokine‐producing ability. Transcriptome sequencing identified 27 genes that were differentially expressed between CD39⁺ and CD39⁻ Th1 cells, such as IL32, DUSP4 and RGS1. Inhibition of CD39 pathway could enhance the activation, proliferation and cytokine‐producing ability of Th1 cells. Furthermore, there was a significantly negative correlation between CD39 expression on Th1 cells and nutritional status indicators such as lymphocyte count and albumin levels, and we observed a significant decline in CD39 expression on Th1 cells after anti‐TB treatment. CD39 is predominantly expressed on TB‐specific Th1 cells and correlated with their exhausted function, which suggests that CD39 could serve as a prominent target for TB therapy.

Towards efficient immunotherapy for bacterial infection

The emergence of multiantibiotic-resistant bacteria, often referred to as superbugs, is leading to infections that are increasingly difficult to treat. Further, bacteria have evolved mechanisms by which they subvert the immune response, meaning that even antibiotic-sensitive bacteria can persist through antibiotic therapy. For these reasons, a broad range of viable therapeutic alternatives or conjunctions to traditional antimicrobial therapy are urgently required to reduce the burden of disease threatened by antibiotic resistance. Immunotherapy has emerged as a leading treatment option in cancer, and researchers are now attempting to apply this to infectious disease. This review summarizes and discusses the recent advances in the field and highlights current and future perspectives of using immunotherapies to treat bacterial infections.

Tim-3 enhances brain inflammation by promoting M1 macrophage polarization following intracerebral hemorrhage in mice

Macrophage polarization contributes to brain inflammation following spontaneous intracerebral hemorrhage (ICH). T cell immunoglobulin and mucin domain-3 (Tim-3) has been identified to induce macrophage mediated inflammation following ICH. However, the regulation of Tim-3 on macrophage polarization following ICH has not been fully studied. In current experiment, we explored Tim-3 expression, macrophage polarization, brain water content and neurological function in WT and Tim-3^-/^- ICH mice. In addition, downstream transcriptional factor TRIF and IRF3 were also analyzed. We found that ICH promoted Tim-3 expression and M1 polarization in the perihematomal region of WT mice, leading to increased brain water content and neurological impairment. However, deletion of Tim-3 expression attenuated M1 polarization, decreased rain water content and improved neurological function of ICH mice. Furthermore, Tim-3 signal promoted transcriptional factors TRIF and IRF3 levels, regulating macrophage polarization. The data suggested that Tim-3 played a crucial role in the macrophage polarization and brain inflammation following ICH, and might represent a promising way in ICH therapy.

Statins reduce the expressions of Tim-3 on NK cells and NKT cells in atherosclerosis

3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors (statins) have an immuno-regulatory effect in addition to lowing-lipids. Accumulated evidence showed that the expressions of T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) on natural killer (NK) cells increased in atherosclerotic patients and animal models. In this study, 14 patients treated with rosuvastatin and 12 patients with atorvastatin for more than 3 months were included and 20 patients without statins treatment as control. Both statins treatment reduced the expressions of Tim-3 on NK cells and their subtypes, natural killer T (NKT) cells and CD3⁺ T cells, and increased the proportions of NKT cells among peripheral blood mononuclear cells, accompanied by the decreased levels of total cholesterol, low density lipoprotein, and increased ratios of high density lipoprotein to cholesterol. These may contribute to the functions of statins in the treatment of atherosclerosis.

Application of ImmunoScore Model for the Differentiation between Active Tuberculosis and Latent Tuberculosis Infection as Well as Monitoring Anti-tuberculosis Therapy

Tuberculosis (TB) is a leading global public health problem. To achieve the end TB strategy, non-invasive markers for diagnosis and treatment monitoring of TB disease are urgently needed, especially in high-endemic countries such as China. Interferon-gamma release assays (IGRAs) and tuberculin skin test (TST), frequently used immunological methods for TB detection, are intrinsically unable to discriminate active tuberculosis (ATB) from latent tuberculosis infection (LTBI). Thus, the specificity of these methods in the diagnosis of ATB is dependent upon the local prevalence of LTBI. The pathogen-detecting methods such as acid-fast staining and culture, all have limitations in clinical application. ImmunoScore (IS) is a new promising prognostic tool which was commonly used in tumor. However, the importance of host immunity has also been demonstrated in TB pathogenesis, which implies the possibility of using IS model for ATB diagnosis and therapy monitoring. In the present study, we focused on the performance of IS model in the differentiation between ATB and LTBI and in treatment monitoring of TB disease. We have totally screened five immunological markers (four non-specific markers and one TB-specific marker) and successfully established IS model by using Lasso logistic regression analysis. As expected, the IS model can effectively distinguish ATB from LTBI (with a sensitivity of 95.7% and a specificity of 92.1%) and also has potential value in the treatment monitoring of TB disease.

Innate Immune Responses to Tuberculosis

Tuberculosis remains one of the greatest threats to human health. The causative bacterium, Mycobacterium tuberculosis, is acquired by the respiratory route. It is exquisitely adapted to humans and is a prototypic intracellular pathogen of macrophages, with alveolar macrophages being the primary conduit of infection and disease. However, M. tuberculosis bacilli interact with and are affected by several soluble and cellular components of the innate immune system which dictate the outcome of primary infection, most commonly a latently infected healthy human host, in whom the bacteria are held in check by the host immune response within the confines of tissue granuloma, the host histopathologic hallmark. Such individuals can develop active TB later in life with impairment in the immune system. In contrast, in a minority of infected individuals, the early host immune response fails to control bacterial growth, and progressive granulomatous disease develops, facilitating spread of the bacilli via infectious aerosols. The molecular details of the M. tuberculosis-host innate immune system interaction continue to be elucidated, particularly those occurring within the lung. However, it is clear that a number of complex processes are involved at the different stages of infection that may benefit either the bacterium or the host. In this article, we describe a contemporary view of the molecular events underlying the interaction between M. tuberculosis and a variety of cellular and soluble components and processes of the innate immune system.

Increased Tim-3 expression in peripheral NK cells predicts a poorer prognosis and Tim-3 blockade improves NK cell-mediated cytotoxicity in human lung adenocarcinoma

T cell immunoglobulin- and mucin-domain-containing molecule-3 (Tim-3) has been shown to play an important role in mediating NK-cell function in human diseases. However, the relationship between Tim-3 expression in natural killer (NK) cells and human lung adenocarcinoma remains unclear. We therefore investigated the expression of Tim-3 in NK cells and explored the effect of Tim-3 blockade on NK cell-mediated activity in human lung adenocarcinoma. Upregulated expression of Tim-3 on CD3-CD56+ cells (P<0.05) and CD3-CD56(dim) cells (P<0.05) of patients with lung adenocarcinoma was detected by flow cytometry. Moreover, Tim-3 expression in CD3-CD56+ NK cells was higher in patients with lung adenocarcinoma with lymph node metastasis (LNM) (P<0.05) or with tumor stage T3-T4 (P<0.05). Tim-3 expression in CD56(dim) NK-cell subset was higher in patients with tumor size ≥3cm (P<0.05), or LNM (P<0.05) or with tumor stage T3-T4 (P<0.05). Further analysis showed that higher expressions of Tim-3 on both CD3-CD56+ NK cells and CD56(dim) NK-cell subset were independently correlated with shorter overall survival of patients with lung adenocarcinoma (log-rank test, P=0.0418, 0.0406, respectively). Importantly, blockade of Tim-3 signaling with anti-Tim-3 antibodies resulted in the increased cytotoxicity and IFN-γ production of peripheral NK cells from patients with lung adenocarcinoma. Our data indicate that Tim-3 expression in NK cells can function as a prognostic biomarker in human lung adenocarcinoma and support that Tim-3 could be a new target for an immunotherapeutic strategy.