Mycobacterium bovis Bacillus Calmette-Guérin killed by extended freeze-drying reduces colitis in mice

Oroxylin A-induced Trained Immunity Promotes LC3-associated Phagocytosis in Macrophage in Protecting Mice Against Sepsis

Sepsis is defined as a dysregulated host response to infection that leads to multiorgan failure. Innate immune memory, i.e., "trained immunity", can result in stronger immune responses and provide protection against various infections. Many biological agents, including β-glucan, can induce trained immunity, but these stimuli may cause uncontrolled inflammation. Oroxylin A (OA) is an active flavonoid compound that is derived from Scutellaria baicalensis. OA is an agonist for inducing trained immunity in vivo and in vitro, and β-glucan was used as a positive control. The protective effects of OA-induced trained immunity were evaluated in mouse models that were established by either lipopolysaccharide (LPS) administration or caecal ligation and puncture (CLP). The expression of inflammatory factors and signaling pathway components involved in trained immunity was evaluated in vitro using qRT‒PCR, western blotting (WB) and enzyme-linked immunosorbent assay (ELISA). Flow cytometry and confocal microscopy were used to examine reactive oxygen species (ROS) levels and phagocytosis in trained macrophages. A PCR array was used to screen genes that were differentially expressed in trained macrophages. Here, we revealed that OA alleviated sepsis via trained immunity. OA-treated macrophages displayed increased glycolysis and mTOR phosphorylation, and mTOR inhibitors suppressed OA-induced trained immunity by effectively reprogramming macrophages. The PCR array revealed key genes in the mTOR signaling pathway in OA-treated macrophages. Furthermore, OA targeted the Dectin-1-syk axis to promote LC3-associated phagocytosis (LAP) by trained macrophages, thereby enhancing the ability of these macrophages to protect against infection. This ability could be transferred to a new host via the adoptive transfer of peritoneal macrophages. This study is the first to provide new insights into the potential of OA-induced trained immunity to be used as a strategy to protect mice against sepsis by promoting LAP by macrophages.

Efficacy of Bacillus Calmette-Guérin in Cancer Prevention and Its Putative Mechanisms

Bacillus Calmette-Guérin (BCG) is an attenuated strain of Mycobacterium bovis. Although it was developed as a prophylactic vaccine against tuberculosis (TB), researchers have also evaluated it for preventing cancer development or progression. These studies were inspired by the available data regarding the protective effects of microbial infection against cancers and an inverse relationship between TB and cancer mortality. Initial studies demonstrated the efficacy of BCG in preventing leukemia, melanoma and a few other cancers. However, mixed results were observed in later studies. Importantly, these studies have led to the successful use of BCG in the tertiary prevention of non-muscle invasive bladder cancer, wherein BCG therapy has been found to be more effective than chemotherapy. Moreover, in a recently published 60-year follow-up study, childhood BCG vaccination has been found to significantly prevent lung cancer development. In the present manuscript, we reviewed the studies evaluating the efficacy of BCG in cancer prevention and discussed its putative mechanisms. Also, we sought to explain the mixed results of BCG efficacy in preventing different cancers.

Mycobacterium potentiates protection from colorectal cancer by gut microbial alterations

Not only are many Mycobacteria pathogens, but they can act as strong non-specific immunopotentiators, generating beneficial effects on the pathogenesis of some diseases. However, there has been no direct evidence of the effect of mycobacterial species on colorectal cancer (CRC). Herein, we showed that there may be a meaningful inverse correlation between the incidence of tuberculosis and CRC based on global statistics and that heat-killed Mycobacterial tuberculosis and live Mycobacterium bovis (Bacillus Calmette-Guérin strain) could ameliorate CRC development. In particular, using a faecal microbiota transplantation and a comparison between separate housing and cohousing, we demonstrated that the gut microbiota is involved in the protective effects. The microbial alterations can be elucidated by the modulation of antimicrobial activities including those of the Reg3 family genes. Furthermore, interleukin-22 production by T helper cells contributed to the anti-inflammatory activity of Mycobacteria. Our results revealed a novel role of Mycobacteria involving gut microbial alterations in dampening inflammation-associated CRC and an immunological mechanism underlying the interaction between microbes and host immunity.

Trained Immunity Contribution to Autoimmune and Inflammatory Disorders

A dysregulated immune response toward self-antigens characterizes autoimmune and autoinflammatory (AIF) disorders. Autoantibodies or autoreactive T cells contribute to autoimmune diseases, while autoinflammation results from a hyper-functional innate immune system. Aside from their differences, many studies suggest that monocytes and macrophages (Mo/Ma) significantly contribute to the development of both types of disease. Mo/Ma are innate immune cells that promote an immune-modulatory, pro-inflammatory, or repair response depending on the microenvironment. However, understanding the contribution of these cells to different immune disorders has been difficult due to their high functional and phenotypic plasticity. Several factors can influence the function of Mo/Ma under the landscape of autoimmune/autoinflammatory diseases, such as genetic predisposition, epigenetic changes, or infections. For instance, some vaccines and microorganisms can induce epigenetic changes in Mo/Ma, modifying their functional responses. This phenomenon is known as trained immunity. Trained immunity can be mediated by Mo/Ma and NK cells independently of T and B cell function. It is defined as the altered innate immune response to the same or different microorganisms during a second encounter. The improvement in cell function is related to epigenetic and metabolic changes that modify gene expression. Although the benefits of immune training have been highlighted in a vaccination context, the effects of this type of immune response on autoimmunity and chronic inflammation still remain controversial. Induction of trained immunity reprograms cellular metabolism in hematopoietic stem cells (HSCs), transmitting a memory-like phenotype to the cells. Thus, trained Mo/Ma derived from HSCs typically present a metabolic shift toward glycolysis, which leads to the modification of the chromatin architecture. During trained immunity, the epigenetic changes facilitate the specific gene expression after secondary challenge with other stimuli. Consequently, the enhanced pro-inflammatory response could contribute to developing or maintaining autoimmune/autoinflammatory diseases. However, the prediction of the outcome is not simple, and other studies propose that trained immunity can induce a beneficial response both in AIF and autoimmune conditions by inducing anti-inflammatory responses. This article describes the metabolic and epigenetic mechanisms involved in trained immunity that affect Mo/Ma, contraposing the controversial evidence on how it may impact autoimmune/autoinflammation conditions.

Ulcerative colitis: Gut microbiota, immunopathogenesis and application of natural products in animal models

Ulcerative colitis (UC) is an inflammatory bowel disease with increasing incidence in the world, especially in developing countries. Although knowledge of its pathogenesis has progressed over the last years, some details require clarification. Studies have highlighted the role of microbial dysbiosis and immune dysfunction as essential factors that may initiate the typical high-grade inflammatory outcome. In order to better understand the immunopathophysiological aspects of UC, experimental murine models are valuable tools. Some of the most commonly used chemicals to induce colitis are trinitrobenzene sulfonic acid, oxazolone and dextran sodium sulfate. These may also be used to investigate new ways of preventing or treating UC and therefore improving targeting in human studies. The use of functional foods or bioactive compounds from plants may constitute an innovative direction towards the future of alternative medicine. Considering the above, this review focused on updated information regarding the 1. gut microbiota and immunopathogenesis of UC; 2. the most utilized animal models of the disease and their relevance; and 3. experimental application of natural products, not yet tested in clinical trials.

Mannose-capped lipoarabinomannan-induced B10 cells decrease severity of dextran sodium sulphate-induced inflammatory bowel disease in mice

Inflammatory bowel disease (IBD) is a chronic, non‐specific, inflammatory gastrointestinal disease that mainly consists of Crohn's disease and ulcerative colitis. However, the aetiology and pathogenesis of IBD are still unclear. B10 (IL‐10 producing regulatory B) cells, a subset of regulatory B cells, are known to contribute to intestinal homeostasis and the aberrant frequency of B10 cells is associated with IBD. We have recently reported that B10 cells can be induced by ManLAM (mannose‐capped lipoarabinomannan), a major cell‐wall lipoglycan of M tb (Mycobacterium tuberculosis). In the current study, the ManLAM‐induced B10 cells were adoptively transferred into IL(interleukin)‐10^−/− mice and the roles of ManLAM‐induced B10 cells were investigated in DSS (dextran sodium sulphate)‐induced IBD model. ManLAM‐induced B10 cells decrease colitis severity in the mice. The B10 cells downregulate Th1 polarization in spleen and MLNs (mesenteric lymph nodes) of DSS‐treated mice. These results suggest that IL‐10 production by ManLAM‐treated B cells contributes to keeping the balance between CD4⁺ T cell subsets and protect mice from DSS‐induced IBD.

Extended Freeze-Dried BCG Instructed pDCs Induce Suppressive Tregs and Dampen EAE

Several clinical observations have shown that Bacillus Calmette-Guérin (BCG) vaccine has beneficial impact on patients suffering from different chronic inflammatory diseases. Here we evaluated whether BCG inactivated by Extended Freeze-Drying (EFD) which circumvents all the side effects linked to the live bacteria, could influence the development of experimental autoimmune encephalomyelitis (EAE), a mouse model for Multiple Sclerosis. EFD BCG strongly attenuates inflammation, both systemically and at the central nervous system (CNS) level, alleviating EAE. Mechanistically, EFD BCG directly impacts the phenotype of plasmacytoid dendritic cells (pDCs), and promotes their ability to induce suppressive IL-10 secreting regulatory T cells (Tregs) that inhibit encephalitogenic CD4⁺ T cells. When co-cultured with human allogenic naive CD4⁺ T cells, EFD BCG exposed human pDCs similarly induce the differentiation of IL-10 producing Tregs. Our study provides evidence that EFD BCG could be used as an immunomodulator of encephalitogenic T cells in multiple sclerosis patients.

Enlarged colitogenic T cell population paradoxically supports colitis prevention through the B-lymphocyte-dependent peripheral generation of CD4(+)Foxp3(+) Treg cells

Intestinal inflammation can be induced by the reconstitution of T/B cell-deficient mice with low numbers of CD4⁺ T lymphocytes depleted of CD25⁺Foxp3⁺ regulatory T cells (Treg). Using RAG-knockout mice as recipients of either splenocytes exclusively depleted of CD25⁺ cells or FACS-purified CD4⁺CD25⁻Foxp3⁻ T cells, we found that the augmentation of potentially colitogenic naïve T cell numbers in the inoculum was unexpectedly beneficial for the suppression of colon disease and maintenance of immune homeostasis. Protection against T cell-mediated colitis correlated with a significant increment in the frequency of peripherally-induced CD4⁺CD25⁺Foxp3⁺ T (pTreg) cells, especially in the mesenteric lymph nodes, an effect that required the presence of B cells and CD4⁺CD25⁻Foxp3⁺ cells in physiological proportions. Our findings support a model whereby the interplay between B lymphocytes and a diversified naïve T cell repertoire is critical for the generation of CD4⁺CD25⁺Foxp3⁺ pTreg cells and colitis suppression.

Regulatory T-Cells at the Interface between Human Host and Pathogens in Infectious Diseases and Vaccination

Regulatory T-cells (Tregs) act at the interface of host and pathogen interactions in human infectious diseases. Tregs are induced by a wide range of pathogens, but distinct effects of Tregs have been demonstrated for different pathogens and in different stages of infection. Moreover, Tregs that are induced by a specific pathogen may non-specifically suppress immunity against other microbes and parasites. Thus, Treg effects need to be assessed not only in homologous but also in heterologous infections and vaccinations. Though Tregs protect the human host against excessive inflammation, they probably also increase the risk of pathogen persistence and chronic disease, and the possibility of disease reactivation later in life. Mycobacterium leprae and Mycobacterium tuberculosis, causing leprosy and tuberculosis, respectively, are among the most ancient microbes known to mankind, and are master manipulators of the immune system toward tolerance and pathogen persistence. The majority of mycobacterial infections occur in settings co-endemic for viral, parasitic, and (other) bacterial coinfections. In this paper, we discuss recent insights in the activation and activity of Tregs in human infectious diseases, with emphasis on early, late, and non-specific effects in disease, coinfections, and vaccination. We highlight mycobacterial infections as important models of modulation of host responses and vaccine-induced immunity by Tregs.

The interplay between bacillus Calmette-Guérin and Treg cells and its role to prevent or cure inflammatory diseases

Clinical evidence indicates that Bacillus Calmette-Guérin (BCG) vaccination exerts anti-inflammatory effects in diseases such as asthma, multiple sclerosis or Type 1 diabetes. Although the exact mechanisms for this activity remain debated, the capacity of mycobacteria to induce regulatory T cells (Tregs) in vivo has been widely reported. However, adverse events associated with live BCG prevent its repeated use, especially in immunocompromised individuals. This article reviews the preclinical data showing a potent, systemic and long-term anti-inflammatory effect in animal models of allergic asthma, inflammatory bowel disease and atherosclerosis with a preparation of BCG inactivated by Extended Freeze-Drying (EFD BCG). It also presents the characteristics of EFD BCG-induced Tregs which play a crucial role in the immunomodulation of various inflammatory diseases. Finally, it compares EFD BCG with other approaches based on the therapeutic use of Tregs in humans.

Mycobacterium bovis BCG killed by extended freeze-drying induces an immunoregulatory profile and protects against atherosclerosis

OBJECTIVES

Atherosclerosis is an inflammatory disease of the arterial wall that leads to myocardial infarction and stroke. Regulatory T cells (Tregs) and IL-10 exert significant anti-atherogenic effects in experimental models of atherosclerosis by modulating vascular inflammation. We have previously shown that Mycobacterium bovis BCG killed by extended freeze-drying (EFD BCG) decreases lung and colon inflammation by recruiting IL-10-producing Tregs. Therefore, the aim of this study was to investigate the effect of EFD BCG on the development of atherosclerosis.

DESIGN

We used two strains of atherosclerosis-prone mice: Ldlr(-/-) (four or six EFD BCG injections) and Apoe(-/-) (six injections).

RESULTS

In both models, EFD BCG significantly reduced the size of atherosclerotic lesions, increased IL-10 production and reduced the serum levels of pro-inflammatory cytokines (IL-6, IL-13, KC and tumour necrosis factor-α). Shortly after treatment with EFD BCG, the number of plasmacytoid dendritic cells (pDCs) and Foxp3(+) Tregs in the draining lymph nodes increased. EFD BCG also led to accumulation of Tregs, but not of pDCs in the spleen, and reduced activity of NF-κB and increased activity of PPAR-γ in both the spleen and vascular tissue of treated mice.

CONCLUSION

EFD BCG has atheroprotective effects through IL-10 production and Treg expansion. These findings support a novel approach to the prevention and treatment of atherosclerosis.

Probiotics increase T regulatory cells and reduce severity of experimental colitis in mice

AIM: To investigate the effect of probiotics on regulating T regulatory cells and reducing the severity of experimental colitis in mice.

METHODS: Forty C57/BL mice were randomly divided into four groups. Colitis was induced in the mice using 2,4,6-trinitrobenzene sulfonic acid (TNBS). After 10-d treatment with Bifico capsules (combined bifidobacterium, lactobacillus and enterococcus), body weight, colonic weight, colonic weight index, length of colon, and histological scores were evaluated. CD4⁺CD25⁺Foxp3⁺T cell in mesenteric lymph nodes were measured by flow cytometry, and cytokines in colonic tissue homogenates were analyzed by a cytometric bead array.

RESULTS: The colonic weight index and the colonic weight of colitis mice treated with Bifico were lower than that of TNBS-induced mice without treatment. However, colonic length and percent of body weight amplification were higher than in TNBS-induced mice without treatment. Compared with TNBS-induced mice without treatment, the level of CD4⁺CD25⁺Foxp3⁺T cells in mesenteric lymph nodes, the expression of interleukin (IL)-2, IL-4 and IL-10 in colonic tissues from colitis mice treated with Bifico were upregulated, and tumor necrosis factor-α and interferon-γ were downregulated.

CONCLUSION: Probiotics effectively treat experimental colitis by increasing CD4⁺CD25⁺Foxp3⁺T cell and regulating the balance of Th1 and Th2 cytokines in the colonic mucosa.