PD-1/PD-L1 Pathway Modulates Macrophage Susceptibility to Mycobacterium tuberculosis Specific CD8+ T cell Induced Death

Promoter methylation and increased expression of PD-L1 in patients with active tuberculosis

The PD-1/PD-L1 pathway plays a pivotal role in T cell activity and is involved in the pathophysiology of Mycobacterium tuberculosis (MTB) infection. DNA methylation is a mechanism that modulates PD-L1 expression in cancer cells. However, its effect on PD-L1 expression in macrophages after MTB infection remains unknown. We prospectively enrolled patients with active tuberculosis (TB) and non-TB subjects. The expression of PD-L1 and methylation-related genes in peripheral blood mononuclear cells (PBMCs) were investigated and their correlation with disease severity and treatment outcomes were examined. PD-L1 promoter methylation status was evaluated using bisulfite sequencing. Immunohistochemistry (IHC) and immunofluorescence (IF) staining were used to visualize PD-L1- and TET-1-expressing cells in lung tissues from patients with TB and in macrophage cell lines with MTB-related stimulation. In total, 80 patients with active TB and 40 non-TB subjects were enrolled in the analysis. Patients with active TB had significantly higher expression of PD-L1, DNMT3b, TET1, TET2, and lower expression of DNMT1, compared to that in the non-TB subjects. The expression of PD-L1 and TET-1 was significantly associated with 1-month smear and culture non-conversion. IHC and IF staining demonstrated the co-localization of PD-L1- and TET-1-expressing macrophages in patients with pulmonary TB and in human macrophage cell lines after MTB-related stimulation. DNMT inhibition and TET-1 knockdown in human macrophages increased and decreased PD-L1 expression, respectively. Overall, PD-L1 expression is increased in patients with active TB and is correlated with treatment outcomes. DNA methylation is involved in modulating PD-L1 expression in human macrophages.

The evolving landscape of IL-10, IL-22 and IL-26 in pleurisy especially in tuberculous pleurisy

Pleurisy can be categorized as primary or secondary, arising from immunological, tumorous, or microbial conditions. It often results in lung structure damage and the development of various respiratory issues. Among the different types, tuberculous pleurisy has emerged as a prominent focus for both clinical and scientific investigations. The IL-10 family, known for its anti-inflammatory properties in the human immune system, is increasingly being studied for its involvement in the pathogenesis of pleurisy. This review aims to present a detailed overview of the intricate role of IL-10 family members (specifically IL-10, IL-22, and IL-26) in human and animal pleuritic diseases or relevant animal models. These insights could serve as valuable guidance and references for further studies on pleurisy and potential therapeutic strategies.

Absence of PD-L1 signaling hinders macrophage defense against Mycobacterium tuberculosis via upregulating STAT3/IL-6 pathway

The blockade of programmed death-ligand 1 (PD-L1) pathway has been clinically used in cancer immunotherapy, while its effects on infectious diseases remain elusive. Roles of PD-L1 signaling in the macrophage-mediated innate immune defense against M.tb is unclear. In this study, the outcomes of tuberculosis (TB) in wild-type (WT) mice treated with anti-PD-1/PD-L1 therapy and macrophage-specific Pdl1-knockout (Pdl1ΔΜΦ) mice were compared. Treatment with anti-PD-L1 or anti-PD-1 benefited protection against M.tb infection in WT mice, while Pdl1ΔΜΦ mice exhibited the increased susceptibility to M.tb infection. Mechanistically, the absence of PD-L1 signaling impaired M.tb killing by macrophages. Furthermore, elevated STAT3 activation was found in PD-L1-deficient macrophages, leading to increased interleukin (IL)-6 production and reduced inducible nitric oxide synthase (iNOS) expression. Inhibiting STAT3 phosphorylation partially impeded the increase in IL-6 production and restored iNOS expression in these PD-L1-deficient cells. These findings provide valuable insights into the complexity and mechanisms underlying anti-PD-L1 therapy in the context of tuberculosis.

Expression of HLA-DR and KLRG1 enhances the cytotoxic potential and cytokine secretion capacity of CD3+ T cells in tuberculosis patients

BACKGROUND

Human T cells play an important role in immunity against tuberculosis (TB) infection. Activating receptor HLA-DR and inhibitory receptor KLRG1 are critical regulators of T cell function during viral infection and tumorigenesis, but they have been less studied in TB infection.

METHODS

In this study, we explored the relationship between CD3+ T cell expression of HLA-DR and KLRG1 receptors and function against TB infection. Flow cytometry was conducted to assess the immunomodulatory effects of HLA-DR and KLRG1 receptors on CD3+ T cells in patients with different TB infection status.

RESULTS

We found activating receptors HLA-DR, NKG2C, CD57 and NKP46, and inhibitory receptors KLRG1 and KIR on CD3+ T cells in different TB infection status showed different distribution patterns; the cytotoxic potential and cytokine secretion capacity of CD3+ T cells after Mtb-specific antigen stimulation were significantly enhanced in TB infection groups. Further studies revealed HLA-DR+ T and KLRG1+ T cells expressed higher activating and inhibitory receptors than the negative population. In addition, the expression of cytotoxic potential and cytokine secretion capacity of HLA-DR+ T and KLRG1+ T cells was significantly higher than that of HLA-DR- T and KLRG1- T cells.

CONCLUSIONS

Expression of HLA-DR and KLRG1 enhances the cytotoxic potential and cytokine secretion capacity of CD3+ T cells in TB patients, suggesting CD3+ T cells expressing HLA-DR and KLRG1 are important effector cell phenotypes involved in the host anti-TB infection. HLA-DR and KLRG1 expressed by CD3+ T cells may be potential predictive markers of TB disease progression and clinical immune assessment.

Impact of PD-L1 Gene Polymorphisms and Interactions with Cooking with Solid Fuel Exposure on Tuberculosis

INTRODUCTION

Given that PD-L1 is a crucial immune checkpoint in regulating T-cell responses, the aim of this study was to explore the impact of PD-L1 gene polymorphisms and the interaction with cooking with solid fuel on susceptibility to tuberculosis (TB) in Chinese Han populations.

METHODS

A total of 503 TB patients and 494 healthy controls were enrolled in this case-control study. Mass spectrometry technology was applied to genotype rs2297136 and rs4143815 of PD-L1 genes. The associations between single nucleotide polymorphism (SNPs) and TB were assessed using unconditional logistic regression analysis. Marginal structural linear odds models were used to estimate the gene-environment interactions.

RESULTS

Compared with genotype CC, genotypes GG and CG+GG at rs4143815 locus were significantly associated with susceptibility to TB (OR: 3.074 and 1.506, respectively, p < 0.05). However, no statistical association was found between rs2297136 SNP and TB risk. Moreover, the relative excess risk of interaction between rs4143815 of the PD-L1 gene and cooking with solid fuel was 2.365 (95% CI: 1.922-2.809), suggesting positive interactions with TB susceptibility.

CONCLUSION

The rs4143815 polymorphism of the PD-L1 gene was associated with susceptibility to TB in Chinese Han populations. There were significantly positive interactions between rs4143815 and cooking with solid fuel.

Recent advances in understanding the human host immune response in tuberculous meningitis

Tuberculous meningitis (TBM), the most severe form of tuberculosis, causes death in approximately 25% cases despite antibiotic therapy, and half of survivors are left with neurological disability. Mortality and morbidity are contributed to by a dysregulated immune response, and adjunctive host-directed therapies are required to modulate this response and improve outcomes. Developing such therapies relies on improved understanding of the host immune response to TBM. The historical challenges in TBM research of limited in vivo and in vitro models have been partially overcome by recent developments in proteomics, transcriptomics, and metabolomics, and the use of these technologies in nested substudies of large clinical trials. We review the current understanding of the human immune response in TBM. We begin with M. tuberculosis entry into the central nervous system (CNS), microglial infection and blood-brain and other CNS barrier dysfunction. We then outline the innate response, including the early cytokine response, role of canonical and non-canonical inflammasomes, eicosanoids and specialised pro-resolving mediators. Next, we review the adaptive response including T cells, microRNAs and B cells, followed by the role of the glutamate-GABA neurotransmitter cycle and the tryptophan pathway. We discuss host genetic immune factors, differences between adults and children, paradoxical reaction, and the impact of HIV-1 co-infection including immune reconstitution inflammatory syndrome. Promising immunomodulatory therapies, research gaps, ongoing challenges and future paths are discussed.

Pulmonary Tuberculosis Following Immune Checkpoint Inhibitor Treatment for Recurrent Maxillary Squamous Cell Carcinoma

Immune checkpoint inhibitors (ICIs) like nivolumab and pembrolizumab are effective treatments for recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN). However, they can lead to immune-related adverse events (irAEs) and tuberculosis (TB) reactivation. We present a case of a 79-year-old male with recurrent maxillary squamous cell carcinoma treated with pembrolizumab, cisplatin, and 5-fluorouracil. The patient developed a fever, and pulmonary TB development was confirmed. Prolonged TB treatment was required, and ICI treatment was discontinued. The patient ultimately opted for palliative care due to aggressive tumor growth. TB development during ICI treatment is a rare but important concern, especially in TB-endemic areas. Vigilant monitoring and screening might be essential to manage this risk in cancer patients with R/M SCCHN receiving ICIs.

Mycobacterium tuberculosis: immune response, biomarkers, and therapeutic intervention

Although tuberculosis (TB) is an infectious disease, the progression of the disease following Mycobacterium tuberculosis (MTB) infection is closely associated with the host's immune response. In this review, a comprehensive analysis of TB prevention, diagnosis, and treatment was conducted from an immunological perspective. First, we delved into the host's immune response mechanisms against MTB infection as well as the immune evasion mechanisms of the bacteria. Addressing the challenges currently faced in TB diagnosis and treatment, we also emphasized the importance of protein, genetic, and immunological biomarkers, aiming to provide new insights for early and personalized diagnosis and treatment of TB. Building upon this foundation, we further discussed intervention strategies involving chemical and immunological treatments for the increasingly critical issue of drug-resistant TB and other forms of TB. Finally, we summarized TB prevention, diagnosis, and treatment challenges and put forward future perspectives. Overall, these findings provide valuable insights into the immunological aspects of TB and offer new directions toward achieving the WHO's goal of eradicating TB by 2035.

New Immunological Markers in Chromoblastomycosis-The Importance of PD-1 and PD-L1 Molecules in Human Infection

The pathogenesis of chromoblastomycosis (CBM) is associated with Th2 and/or T regulatory immune responses, while resistance is associated with a Th1 response. However, even in the presence of IFN-γ, fungi persist in the lesions, and the reason for this persistence is unknown. To clarify the factors associated with pathogenesis, this study aimed to determine the polarization of the cellular immune response and the densities of cells that express markers of exhaustion in the skin of CBM patients. In the skin of patients with CBM, a moderate inflammatory infiltrate was observed, characterized primarily by the occurrence of histiocytes. Analysis of fungal density allowed us to divide patients into groups that exhibited low and high fungal densities; however, the intensity of the inflammatory response was not related to mycotic loads. Furthermore, patients with CBM exhibited a significant increase in the number of CD4+ and CD8+ cells associated with a high density of IL-10-, IL-17-, and IFN-γ-producing cells, indicating the presence of a chronic and mixed cellular immune response, which was also independent of fungal load. A significant increase in the number of PD-1+ and PD-L1+ cells was observed, which may be associated with the maintenance of the fungus in the skin and the progression of the disease.

From immunology to artificial intelligence: revolutionizing latent tuberculosis infection diagnosis with machine learning

Latent tuberculosis infection (LTBI) has become a major source of active tuberculosis (ATB). Although the tuberculin skin test and interferon-gamma release assay can be used to diagnose LTBI, these methods can only differentiate infected individuals from healthy ones but cannot discriminate between LTBI and ATB. Thus, the diagnosis of LTBI faces many challenges, such as the lack of effective biomarkers from Mycobacterium tuberculosis (MTB) for distinguishing LTBI, the low diagnostic efficacy of biomarkers derived from the human host, and the absence of a gold standard to differentiate between LTBI and ATB. Sputum culture, as the gold standard for diagnosing tuberculosis, is time-consuming and cannot distinguish between ATB and LTBI. In this article, we review the pathogenesis of MTB and the immune mechanisms of the host in LTBI, including the innate and adaptive immune responses, multiple immune evasion mechanisms of MTB, and epigenetic regulation. Based on this knowledge, we summarize the current status and challenges in diagnosing LTBI and present the application of machine learning (ML) in LTBI diagnosis, as well as the advantages and limitations of ML in this context. Finally, we discuss the future development directions of ML applied to LTBI diagnosis.

Immunotherapy and biomarkers in patients with lung cancer with tuberculosis: Recent advances and future Directions

Lung cancer (LC) and tuberculosis (TB) are two major global public health problems, and the incidence of LC-TB is currently on the rise. Therefore effective clinical interventions are crucial for LC-TB. The aim of this review is to provide up-to-date information on the immunological profile and therapeutic biomarkers in patients with LC-TB. We discuss the immune mechanisms involved, including the immune checkpoints that play an important role in the treatment of patients with LC-TB. In addition, we explore the susceptibility of patients with LC to TB and summarise the latest research on LC-TB. Finally, we discuss future prospects in this field, including the identification of potential targets for immune intervention. In conclusion, this review provides important insights into the complex relationship between LC and TB and highlights new advances in the detection and treatment of both diseases.

Site-specific transgene integration in chimeric antigen receptor (CAR) T cell therapies

Chimeric antigen receptor (CAR) T cells and natural killer (NK) cells are genetically engineered immune cells that can detect target antigens on the surface of target cells and eliminate them following adoptive transfer. Recent progress in CAR-based therapies has led to outstanding clinical success in certain patients with leukemias and lymphomas and offered therapeutic benefits to those resistant to conventional therapies. The universal approach to stable CAR transgene delivery into the T/NK cells is the use of viral particles. Such approaches mediate semi-random transgene insertions spanning the entire genome with a high preference for integration into sites surrounding highly-expressed genes and active loci. Regardless of the variable CAR expression level based on the integration site of the CAR transgene, foreign integrated DNA fragments may affect the neighboring endogenous genes and chromatin structure and potentially change a transduced T/NK cell behavior and function or even favor cellular transformation. In contrast, site-specific integration of CAR constructs using recent genome-editing technologies could overcome the limitations and disadvantages of universal random gene integration. Herein, we explain random and site-specific integration of CAR transgenes in CAR-T/NK cell therapies. Also, we tend to summarize the methods for site-specific integration as well as the clinical outcomes of certain gene disruptions or enhancements due to CAR transgene integration. Also, the advantages and limitations of using site-specific integration methods are discussed in this review. Ultimately, we will introduce the genomic safe harbor (GSH) standards and suggest some appropriate safety prospects for CAR integration in CAR-T/NK cell therapies.

Site-specific transgene integration in chimeric antigen receptor (CAR) T cell therapies

Chimeric antigen receptor (CAR) T cells and natural killer (NK) cells are genetically engineered immune cells that can detect target antigens on the surface of target cells and eliminate them following adoptive transfer. Recent progress in CAR-based therapies has led to outstanding clinical success in certain patients with leukemias and lymphomas and offered therapeutic benefits to those resistant to conventional therapies. The universal approach to stable CAR transgene delivery into the T/NK cells is the use of viral particles. Such approaches mediate semi-random transgene insertions spanning the entire genome with a high preference for integration into sites surrounding highly-expressed genes and active loci. Regardless of the variable CAR expression level based on the integration site of the CAR transgene, foreign integrated DNA fragments may affect the neighboring endogenous genes and chromatin structure and potentially change a transduced T/NK cell behavior and function or even favor cellular transformation. In contrast, site-specific integration of CAR constructs using recent genome-editing technologies could overcome the limitations and disadvantages of universal random gene integration. Herein, we explain random and site-specific integration of CAR transgenes in CAR-T/NK cell therapies. Also, we tend to summarize the methods for site-specific integration as well as the clinical outcomes of certain gene disruptions or enhancements due to CAR transgene integration. Also, the advantages and limitations of using site-specific integration methods are discussed in this review. Ultimately, we will introduce the genomic safe harbor (GSH) standards and suggest some appropriate safety prospects for CAR integration in CAR-T/NK cell therapies.

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.

Mycobacterium avium subsp. paratuberculosis antigens induce cellular immune responses in cattle without causing reactivity to tuberculin in the tuberculosis skin test

Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic progressive granulomatous enteritis leading to diarrhea, weight-loss, and eventual death in ruminants. Commercially available vaccine provides only partial protection against MAP infection and can interfere with the use of current diagnostic tests for bovine tuberculosis in cattle. Here, we characterized immune responses in calves to vaccines containing four truncated MAP antigens as a fusion (Ag85A^202-347-SOD^1-72-Ag85B^173-330-74F^{1-148+669-786}), either displayed on protein particles, or expressed as a soluble recombinant MAP (rMAP) fusion protein as well as to commercially available Silirum^® vaccine. The rMAP fusion protein elicited the strongest antigen-specific antibody responses to both PPDA and recombinant antigen and strong and long-lasting T-cell immune responses to these antigens, as indicated by increased production of IFN-γ and IL-17A in antigen-stimulated whole blood cultures. The MAP fusion protein particle vaccine induced minimal antibody responses and weak IFN-γ responses but stimulated IL-17A responses to recombinant antigen. The immune response profile of Silirum^® vaccine was characterized by weak antibodies and strong IFN-γ and IL-17A responses to PPDA. Transcription analysis on antigen-stimulated leukocytes from cattle vaccinated with rMAP fusion protein showed differential expression of several immune response genes and genes involved in costimulatory signaling, TLR4, TLR2, PTX3, PTGS2, PD-L1, IL1B, IL2, IL6, IL12B, IL17A, IL22, IFNG, CD40, and CD86. Moreover, the expression of several genes of immune pathways correlated with cellular immune responses in the rMAP fusion protein vaccinated group. These genes have key roles in pathways of mycobacterial immunity, including autophagy, manipulation of macrophage-mediated killing, Th17- and regulatory T cells- (Treg) mediated responses. Calves vaccinated with either the rMAP fusion protein or MAP fusion protein particle vaccine did not induce reactivity to PPDA and PPDB in a comparative cervical skin test, whereas Silirum^® induced reactivity to these tuberculins in most of the vaccinated animals. Overall, our results suggest that a combination of recombinant MAP antigens in the form of a soluble fusion protein vaccine are capable of inducing strong antigen-specific humoral and a balanced Th1/Th17-cell immune response. These findings, together with the absence of reactivity to tuberculin, suggest this subunit vaccine could provide protective immunity against intracellular MAP infection in cattle without compromising the use of current bovine tuberculosis surveillance test.

Reinventing the human tuberculosis (TB) granuloma: Learning from the cancer field

Tuberculosis (TB) remains one of the deadliest infectious diseases in the world and every 20 seconds a person dies from TB. An important attribute of human TB is induction of a granulomatous inflammation that creates a dynamic range of local microenvironments in infected organs, where the immune responses may be considerably different compared to the systemic circulation. New and improved technologies for in situ quantification and multimodal imaging of mRNA transcripts and protein expression at the single-cell level have enabled significantly improved insights into the local TB granuloma microenvironment. Here, we review the most recent data on regulation of immunity in the TB granuloma with an enhanced focus on selected in situ studies that enable spatial mapping of immune cell phenotypes and functions. We take advantage of the conceptual framework of the cancer-immunity cycle to speculate how local T cell responses may be enhanced in the granuloma microenvironment at the site of Mycobacterium tuberculosis infection. This includes an exploratory definition of "hot", immune-inflamed, and "cold", immune-excluded TB granulomas that does not refer to the level of bacterial replication or metabolic activity, but to the relative infiltration of T cells into the infected lesions. Finally, we reflect on the current knowledge and controversy related to reactivation of active TB in cancer patients treated with immune checkpoint inhibitors such as PD-1/PD-L1 and CTLA-4. An understanding of the underlying mechanisms involved in the induction and maintenance or disruption of immunoregulation in the TB granuloma microenvironment may provide new avenues for host-directed therapies that can support standard antibiotic treatment of persistent TB disease.

Multidisciplinary approach to treatment with immune checkpoint inhibitors in patients with HIV, tuberculosis, or underlying autoimmune diseases

We reviewed the available information on the use of immune checkpoint inhibitors (ICIs) in populations with special conditions, namely, patients with HIV, tuberculosis, or underlying autoimmune disease. Available data show that treatment with ICIs is safe in patients with HIV; it is advisable, however, that these patients receive adequate antiretroviral therapy and have an undetectable viral load before ICIs are initiated. Tuberculosis reactivation has been reported with the use of ICIs, possibly due to immune dysregulation. Tuberculosis has also been associated with the use of immunosuppressors to treat immune-related adverse events (irAEs). Active tuberculosis must be ruled out in patients with symptoms or signs, and selected patients may benefit from screening for latent tuberculosis infection, although more data are required. Limited data exist regarding the safety of ICIs in patients with cancer and autoimmune disease. Data from observational studies suggest that up to 29% of patients with a preexisting autoimmune disease treated with an ICI present with an autoimmune disease flare, and 30% present with a de novo irAE of any type. The frequency of flares appears to differ according to the type of ICI received, with higher rates associated with PD-1/PD-L1 inhibitors. The most common autoimmune diseases for which patients reported flares with ICI therapy are rheumatoid arthritis, other inflammatory arthritis, and psoriasis. Most studies have reported flares or de novo irAEs associated with ICIs that were mild to moderate, with low rates of discontinuation and no deaths due to flares. Therefore, the use of ICIs in these patients is possible, but careful monitoring is required.

Novel immunosuppressive effect of FK506 by upregulation of PD-L1 via FKBP51 in heart transplantation

The calcineurin inhibitor-FK506-is a first-line immunosuppressant that regulates T-cell secretion of IL-2 and other cytokines. However, the mechanism of its protective effect on target cells and its role on tumor recurrence and interaction with anti-tumor immune checkpoint inhibitors, such as PD-L1 blocking, are still unclear. Here, in a murine heart transplantation model, we observed the upregulation of programmed death-ligand 1 (PD-L1) expression by FK506 in both dendritic cells (DCs) and allografts. Blocking PD-L1 during FK506 treatment increased IFN-γ and TNF-α expression, enhanced CD4⁺ and CD8⁺ T-cell proliferation, and suppressed Treg differentiation. Moreover, PD-L1 decreased T-cell infiltration and induced T cell apoptosis in both the spleen and graft. PD-L1 was not only required in FK506-mediated immunosuppression but also upregulated by FK506. Treatment with SAFit2, a FKBP51 selective inhibitor, reduced the expression of PD-L1 on DCs and the grafts and interfered with the immunosuppressive effect of FK506, suggesting that the mechanism depends on FK506-binding protein (FKBP) 51 expression. Overall, our results add new insights into the role of FK506, not only on T-cell cytokine secretion but also on co-inhibitory molecular regulation and target cell immune privilege.

Macrophage Differentiation and Polarization Regulate the Release of the Immune Checkpoint Protein V-Domain Ig Suppressor of T Cell Activation

Recently, the V-domain immunoglobulin suppressor of T-cell activation (VISTA) was identified as a negative immune checkpoint regulator (NCR) that is mainly expressed in hematopoietic cells. Preclinical studies have shown that VISTA blockade results in impeded tumor growth and improved survival. Nevertheless, little is known about the physiological role of VISTA expression in macrophages. This study focused on the differential expression of VISTA in human monocytes and macrophages in order to elucidate a putative role of VISTA regulation upon macrophage polarization and activation. We observed that human peripheral monocytes constitutively release soluble VISTA, which was regulated via matrix metalloproteinases. However, monocyte stimulation with cytokines that induce macrophage differentiation, such as granulocyte-macrophage colony–stimulating (GM-CSF) and macrophage colony-stimulating factor (M-CSF), substantially reduced soluble VISTA release. VISTA release was further affected by various pro- and anti-inflammatory stimuli that led to macrophage polarization, where activated M1 macrophages generally released more VISTA than M2 macrophages. Additionally, we observed that stimulation of activated macrophages with the toll-like receptor 4 ligand lipopolysaccharide (LPS) led to a further decrease of soluble VISTA release. Moreover, we found that soluble VISTA impairs T cell cytotoxic activity but did not induce their programmed death. Our results suggest that VISTA is constantly produced and released in the peripheral blood where it may contribute to peripheral tolerance.

The Role of Immune Checkpoint Molecules on Macrophages in Cancer, Infection, and Autoimmune Pathologies

Immune checkpoint inhibitors have revolutionized immunotherapy against various cancers over the last decade. The use of checkpoint inhibitors results in remarkable re-activation of patients’ immune system, but is also associated with significant adverse events. In this review, we emphasize the importance of cell-type specificity in the context of immune checkpoint-based interventions and particularly focus on the relevance of macrophages. Immune checkpoint blockade alters the dynamic macrophage phenotypes and thereby substantially manipulates therapeutical outcome. Considering the macrophage-specific immune checkpoint biology, it seems feasible to ameliorate the situation of patients with severe side effects and even increase the probability of survival for non-responders to checkpoint inhibition. Apart from malignancies, investigating immune checkpoint molecules on macrophages has stimulated their fundamental characterization and use in other diseases as well, such as acute and chronic infections and autoimmune pathologies. Although the macrophage-specific effect of checkpoint molecules has been less studied so far, the current literature shows that a macrophage-centered blockade of immune checkpoints as well as a stimulation of their expression represents promising therapeutic avenues. Ultimately, the therapeutic potential of a macrophage-focused checkpoint therapy might be maximized by diagnostically assessing individual checkpoint expression levels on macrophages, thereby personalizing an effective treatment approach for each patient having cancer, infection, or autoimmune diseases.

PD-L1 Expression in Monocytes Correlates with Bacterial Burden and Treatment Outcomes in Active Pulmonary Tuberculosis

The PD-1/PD-L1 pathway is critical in T cell biology; however, the role of the PD-1/PD-L1 pathway in clinical characteristics and treatment outcomes in pulmonary tuberculosis (PTB) patients is unclear. We prospectively enrolled PTB, latent TB infection (LTBI), and non-TB, non-LTBI subjects. The expression of PD-1/PD-L1 on peripheral blood mononuclear cells (PBMCs) was measured and correlated with clinical characteristics and treatment outcomes in PTB patients. Immunohistochemistry and immunofluorescence were used to visualize PD-1/PD-L1-expressing cells in lung tissues from PTB patients and from murine with heat-killed MTB (HK-MTB) treatment. A total of 76 PTB, 40 LTBI, and 28 non-TB, non-LTBI subjects were enrolled. The expression of PD-1 on CD4+ T cells and PD-L1 on CD14+ monocytes was significantly higher in PTB cases than non-TB subjects. PTB patients with sputum smear/culture unconversion displayed higher PD-L1 expression on monocytes. PD-L1-expressing macrophages were identified in lung tissue from PTB patients, and co-localized with macrophages in murine lung tissues. Mycobacterium tuberculosis (MTB) whole cell lysate/EsxA stimulation of human and mouse macrophages demonstrated increased PD-L1 expression. In conclusion, increased expression of PD-L1 on monocytes in PTB patients correlated with higher bacterial burden and worse treatment outcomes. The findings suggest the involvement of the PD-1/PD-L1 pathway in MTB-related immune responses.

Bcl2 negatively regulates Protective Immune Responses During Mycobacterial Infection

We previously reported that M. tb on its own as well as together with HIV inhibits macrophage apoptosis by upregulating the expression of Bcl2 and Inhibitor of Apoptosis (IAP). In addition, recent reports from our lab showed that stimulation of either macrophages or BMDCs results in the significant upregulation of Bcl2. In this report, we delineate the role of Bcl2 in mediating defense responses from dendritic cells (BMDCs) during mycobacterial infection. Inhibiting Bcl2 led to a significant decrease in intracellular bacterial burden in BMDCs. To further characterize the role of Bcl2 in modulating defense responses, we inhibited Bcl2 in BMDCs as well as human PBMCs to monitor their activation and functional status in response to mycobacterial infection and stimulation with M. tb antigen Rv3416. Inhibiting Bcl2 generated protective responses including increased expression of co-stimulatory molecules, oxidative burst, pro-inflammatory cytokine expression and autophagy. Finally, co-culturing human PBMCs and BMDCs with antigen-primed T cells increased their proliferation, activation and effector function. These results point towards a critical role for Bcl2 in regulating BMDCs defense responses to mycobacterial infection.

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.

Lower IL-7 Receptor Expression of Monocytes Impairs Antimycobacterial Effector Functions in Patients with Tuberculosis

Altered monocyte differentiation and effector functions characterize immune pathogenesis of tuberculosis. IL-7 is an important factor for proliferation of T cells and impaired IL-7 sensitivity due to decreased IL-7 receptor α-chain (IL-7Rα) expression was found in patients with acute tuberculosis. Peripheral blood monocytes have moderate IL-7Rα expression and increased IL-7Rα levels were described for inflammatory diseases. In this study, we investigated a potential role of IL-7 and IL-7Rα expression for monocyte functions in tuberculosis. We analyzed the phenotype of monocytes in the blood from tuberculosis patients (n = 33), asymptomatic contacts of tuberculosis patients (contacts; n = 30), and healthy controls (n = 20) from Ghana by multicolor flow cytometry. Mycobacterial components were analyzed for their capacity to induce IL-7Rα expression in monocytes. Functional effects of monocyte to IL-7 were measured during signaling and by using an antimycobacterial in vitro kill assay. Monocytes were more frequent in peripheral blood from patients with tuberculosis and especially higher proportions of CD14⁺/CD16⁺ (M1/2) monocytes with increased PD-L1 expression characterized acute tuberculosis. IL-7Rα expression was decreased particularly on M1/2 monocytes from patients with tuberculosis and aberrant low expression IL-7Rα correlated with high PD-L1 levels. Constitutive low pSTAT5 levels of monocytes ex vivo and impaired IL-7 response confirmed functionally decreased monocyte IL-7 sensitivity of patients with tuberculosis. Mycobacteria and mycobacterial cell wall components induced IL-7 receptor expression in monocytes and IL-7 boosted mycobacterial killing by monocyte-derived macrophages in vitro. We demonstrated impaired monocyte IL-7 receptor expression as well as IL-7 sensitivity in tuberculosis with potential effects on antimycobacterial effector functions.

Emerging Role of Exosomes in Tuberculosis: From Immunity Regulations to Vaccine and Immunotherapy

Exosomes are cell-derived nanovesicles carrying protein, lipid, and nucleic acid for secreting cells, and act as significant signal transport vectors for cell-cell communication and immune modulation. Immune-cell-derived exosomes have been found to contain molecules involved in immunological pathways, such as MHCII, cytokines, and pathogenic antigens. Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains one of the most fatal infectious diseases. The pathogen for tuberculosis escapes the immune defense and continues to replicate despite rigorous and complicate host cell mechanisms. The infected-cell-derived exosomes under this circumstance are found to trigger different immune responses, such as inflammation, antigen presentation, and activate subsequent pathways, highlighting the critical role of exosomes in anti-MTB immune response. Additionally, as a novel kind of delivery system, exosomes show potential in developing new vaccination and treatment of tuberculosis. We here summarize recent research progress regarding exosomes in the immune environment during MTB infection, and further discuss the potential of exosomes as delivery system for novel anti-MTB vaccines and therapies.

Epithelioid granulomatous lesions express abundant programmed death ligand-1 (PD-L1): a discussion of adverse events in anti-PD-1 antibody-based cancer immunotherapy

The immune system is often called a double-edged sword, due to the inextricable link between cancer immunity and allergy/autoimmunity. Intriguingly, a growing number of cases have been reported in which PD-1 blockade triggers the exacerbation of tuberculosis (TB), an organ-invasive granulomatous disease caused by bacterial infection. As a result, the exacerbation of TB is now considered a severe adverse effect of nivolumab and pembrolizumab. In this letter, we report the strong expression of PD-L1 in epithelioid granulomatous lesions in tuberculosis, sarcoidosis, Crohn's disease, and foreign body granuloma. In addition, we discussed the exacerbation of tuberculosis after anti-PD-1 antibody-based cancer immunotherapy.

Biomimetic Anti-PD-1 Peptide-Loaded 2D FePSe3 Nanosheets for Efficient Photothermal and Enhanced Immune Therapy with Multimodal MR/PA/Thermal Imaging

Metal phosphorous trichalcogenides (MPX3) are novel 2D nanomaterials that have recently been exploited as efficient photothermal-chemodynamic agents for cancer therapy. As a representative MPX3, FePSe3 has the potential to be developed as magnetic resonance imaging (MRI) and photoacoustic imaging (PAI) agents due to the composition of Fe and the previously revealed PA signal. Here, a FePSe3-based theranostic agent, FePSe3@APP@CCM, loaded with anti-PD-1 peptide (APP) as the inner component and CT26 cancer cell membrane (CCM) as the outer shell is reported, which acts as a multifunctional agent for MR and PA imaging and photothermal and immunotherapy against cancer. FePSe3@APP@CCM induces highly efficient tumor ablation and suppresses tumor growth by photothermal therapy under near-infrared laser excitation, which further activates immune responses. Moreover, APP blocks the PD-1/PD-L1 pathway to activate cytotoxic T cells, causing strong anticancer immunity. The combined therapy significantly prolongs the lifespan of experimental mice. The multimodal imaging and synergistic therapeutic effects of PTT and its triggered immune responses and APP-related immunotherapy are clearly demonstrated by in vitro and in vivo experiments. This work demonstrates the potential of MPX3-based biomaterials as novel theranostic agents.

Diverse immune environments in human lung tuberculosis granulomas assessed by quantitative multiplexed immunofluorescence

The precise nature of the local immune responses in lung tuberculosis (TB) granulomas requires a comprehensive understanding of their environmental complexities. At its most basic level, a granuloma is a compact, organized immune aggregate of macrophages surrounded by myeloid, B and T cells. We established two complementary multiplex immunolabeling panels to simultaneously evaluate the myeloid and lymphocytic contexture of 14 human lung TB granulomas in formalin-fixed paraffin-embedded tissue samples. We observed diverse CD3+ and CD8+ T-cell and CD20+ B lymphocyte compositions of the granuloma immune environment and a relatively homogeneous distribution of all myeloid cells. We also found significant associations between CD8+ T-cell densities and the myeloid marker CD11b and phagocytic cell marker CD68. In addition, significantly more CD68+ macrophages and CD8+ T cells were found in Mycobacterium tuberculosis-infected granulomas, as detected by Ziehl-Neelsen staining. FOXP3 expression was predominately found in a small subset of CD4+ T cells in different granulomas. As the success or failure of each granuloma is determined by the immune response within that granuloma at a local and not a systemic level, we attempted to identify the presence of reactive T cells based on expression of the T-cell activation marker CD137 (4-1BB) and programmed cell death-1 (PD-1). Only a small fraction of the CD4+ and CD8+ T cells expressed PD-1. CD137 expression was found only in a very small fraction of the CD4+ T cells in two granulomas. Our results also showed that multinucleated giant cells showed strong PD-L1 but not CTLA-4 membrane staining. This study offers new insights into the heterogeneity of immune cell infiltration in lung TB granulomas, suggesting that each TB granuloma represents a unique immune environment that might be independently influenced by the local adaptive immune response, bacterial state, and overall host disease status.

Tumor-regulated macrophage type 2 differentiation promotes immunosuppression in laryngeal squamous cell carcinoma

AIMS

Tumor-associated macrophage (TAM) residing in tumor microenvironment as the major niche cell made remarkable contribution to tumor growth. However, the functional role of macrophage and its different differentiating state as well as the regulating mechanism in laryngeal squamous cell carcinoma (LSCC) remains not fully clear.

MATERIALS AND METHODS

LSCC samples were collected from patients. Human peripheral blood mononuclear cells (PBMC) were collected from volunteers' blood, and used for macrophage induction. Enzyme-Linked Immunosorbent Assay (ELISA) was performed to detect proinflammatory cytokines. Immunostaining was prepared to observe tumor tissues.

KEY FINDINGS

Here, we found the number of type 2 macrophage (MΦ2) and PDL-1 expression was increased in LSCC that was correlated with poor prognosis in patients with LSCC. Tumor cells induced macrophage into type 2 differentiation by TGF-β/Smad3 signaling. The primed MΦ2 produced IL-10 by activating JAK/STAT signaling that promoted PDL-1 expression in tumor cells leading to its immunosuppression. Inhibition of JAK/STAT signaling promoted tumor cells death from immune cells killing by regulating PDL-1 expression. Targeting cytokines TGF-β or IL-10 synergistically enhances the sensitivity of tumors to chemotherapy in vivo.

SIGNIFICANCE

In conclusion, our findings showed tumor cells and MΦ2 were bilaterally regulated through cytokines production that integrally advanced tumor progression through boosting anti-tumor immunity. It provides insight to develop immune strategies synergy with chemotherapy in treating laryngeal squamous cell carcinoma.

Immune checkpoint inhibitors and tuberculosis: an old disease in a new context

Tuberculosis, the leading cause of infection-related death in developing regions, is a leading cause of morbidity and mortality worldwide. Screening for, and treatment of, latent Mycobacterium tuberculosis infection is routine before initiation of anti-tumour necrosis factor α (anti-TNFα) agents in the management of psoriasis, Crohn's disease, and rheumatoid arthritis. By contrast, screening for latent tuberculosis before immune checkpoint inhibitor treatment in cancer is not routine, despite the increasing number of reports of primary infection with M tuberculosis or reactivation of latent M tuberculosis infection during such treatment. We present our experience with M tuberculosis screening in 70 patients who underwent immune checkpoint inhibitor therapy for metastatic skin cancer. Based on our understanding of the interaction between M tuberculosis and the immune system, we present the argument for tuberculosis screening before immune checkpoint inhibitor therapy and its use when considering anti-TNFα treatment for severe immune-related adverse events. We call for increased vigilance during immune checkpoint inhibition until its effects on tuberculosis pathophysiology are fully ascertained.

Fighting Persistence: How Chronic Infections with Mycobacterium tuberculosis Evade T Cell-Mediated Clearance and New Strategies To Defeat Them

Chronic bacterial infections are caused by pathogens that persist within their hosts and avoid clearance by the immune system. Treatment and/or detection of such pathogens is difficult, and the resulting pathologies are often deleterious or fatal. There is an urgent need to develop protective vaccines and host-directed therapies that synergize with antibiotics to prevent pathogen persistence and infection-associated pathologies. However, many persistent pathogens, such as Mycobacterium tuberculosis, actively target the very host pathways activated by vaccination. These immune evasion tactics blunt the effectiveness of immunization strategies and are impeding progress to control these infections throughout the world. Therefore, it is essential that M. tuberculosis immune evasion-related pathogen virulence strategies are considered to maximize the effectiveness of potential new treatments. In this review, we focus on how Mycobacterium tuberculosis infects antigen-presenting cells and evades effective immune clearance by the adaptive response through (i) manipulating antigen presentation, (ii) repressing T cell-activating costimulatory molecules, and (iii) inducing ligands that drive T cell exhaustion. In this context, we will examine the challenges that bacterial virulence strategies pose to developing new vaccines. We will then discuss new approaches that will help dissect M. tuberculosis immune evasion mechanisms and devise strategies to bypass them to promote long-term protection and prevent disease progression.

Functional and mechanistic advantage of the use of a bifunctional anti-PD-L1/IL-15 superagonist

BACKGROUND

Anti(α)-programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) monotherapy fails to provide durable clinical benefit for most patients with carcinoma. Recent studies suggested that strategies to reduce immunosuppressive cells, promote systemic T-cell responses and lymphocyte trafficking to the tumor microenvironment (TME) may improve efficacy. N-809 is a first-in-class bifunctional agent comprising the interleukin (IL)-15 superagonist N-803 fused to two αPD-L1 domains. Thus, N-809 can potentially stimulate effector immune cells through IL-15 and block immunosuppressive PD-L1. Here, we examined the antitumor efficacy and immunomodulatory effects of N-809 versus N-803+αPD-L1 combination.

METHODS

The ability of N-809 to block PD-L1 and induce IL-15-dependent immune effects was examined in vitro and in vivo. Antitumor efficacy of N-809 or N-803+αPD-L1 was evaluated in two murine carcinoma models and an extensive analysis of immune correlates was performed in the tumor and tumor-draining lymph node (dLN).

RESULTS

We demonstrate that N-809 blocks PD-L1 and induces IL-15-dependent immune effects. N-809 was well-tolerated and reduced 4T1 lung metastasis, decreased MC38 tumor burden and increased survival versus N-803+αPD-L1. Compared with N-803+αPD-L1, N-809 enhanced natural killer (NK) and CD8+ T-cell activation and function in the dLN and TME, relating to increased gene expression associated with interferon and cytokine signaling, lymphoid compartment, costimulation and cytotoxicity. The higher number of TME CD8+ T cells was attributed to enhanced infiltration, not in situ expansion. Increased TME NK and CD8+ T-cell numbers correlated with augmented chemokine ligands and receptors. Moreover, in contrast to N-803+αPD-L1, N-809 reduced immunosuppressive regulatory T cells (Treg), monocytic myeloid-derived suppressor cells (M-MDSC) and M2-like macrophages in the TME.

CONCLUSIONS

Our results suggest that N-809 functions by a novel immune mechanism to promote antitumor efficacy. Foremost, N-809 enhances intratumoral lymphocyte numbers by increasing trafficking via altered chemokine levels in the TME and chemokine receptor expression on CD8+ T cells and NK cells. In addition, N-809 reduces immunosuppressive and pro-tumorigenic immune cells in the TME, including Treg, M2-like macrophages and M-MDSC. Overall, these novel effects of N-809 promote an inflamed TME, leading to lower tumor burden and increased survival. These results provide mechanistic insight and rationale supporting the potential clinical study of N-809 in patients with carcinoma.

Anti-PD-1 immunotherapy leads to tuberculosis reactivation via dysregulation of TNF-α

Previously, we developed a 3-dimensional cell culture model of human tuberculosis (TB) and demonstrated its potential to interrogate the host-pathogen interaction (Tezera et al., 2017a). Here, we use the model to investigate mechanisms whereby immune checkpoint therapy for cancer paradoxically activates TB infection. In patients, PD-1 is expressed in Mycobacterium tuberculosis (Mtb)-infected lung tissue but is absent in areas of immunopathology. In the microsphere model, PD-1 ligands are up-regulated by infection, and the PD-1/PD-L1 axis is further induced by hypoxia. Inhibition of PD-1 signalling increases Mtb growth, and augments cytokine secretion. TNF-α is responsible for accelerated Mtb growth, and TNF-α neutralisation reverses augmented Mtb growth caused by anti-PD-1 treatment. In human TB, pulmonary TNF-α immunoreactivity is increased and circulating PD-1 expression negatively correlates with sputum TNF-α concentrations. Together, our findings demonstrate that PD-1 regulates the immune response in TB, and inhibition of PD-1 accelerates Mtb growth via excessive TNF-α secretion.

The Diverse Function of PD-1/PD-L Pathway Beyond Cancer

The recent success of PD-1 and PD-L1 blockade in cancer therapy illustrates the important role of the PD-1/PD-L1 pathway in the regulation of antitumor immune responses. However, signaling regulated by the PD-1/PD-L pathway is also associated with substantial inflammatory effects that can resemble those in autoimmune responses, chronic infection, and sepsis, consistent with the role of this pathway in balancing protective immunity and immunopathology, as well as in homeostasis and tolerance. Targeting PD-1/PD-L1 to treat cancer has shown benefits in many patients, suggesting a promising opportunity to target this pathway in autoimmune and inflammatory disorders. Here, we systematically evaluate the diverse biological functions of the PD-1/PD-L pathway in immune-mediated diseases and the relevant mechanisms that control these immune reactions.

Inhibition of the PD-1/PD-L1 signaling pathway enhances innate immune response of alveolar macrophages to mycobacterium tuberculosis in mice

BACKGROUND

Mycobacterium tuberculosis (TB) is a pathogen that consequently leads to TB infection, which remains a significant global health concern. Programmed death 1 (PD-1)/programmed death-ligand 1 (PD-L1) signaling pathway is critical for terminating immune responses. The present study aimed to elucidate the regulatory role of the PD-1/PD-L1 signaling pathway in alveolar macrophages against Mycobacterium TB in mice.

METHODS

Specific pathogen free mice were initially prepared for Mycobacterium TB model establishment. The alveolar macrophages of the successfully modeled rats were evaluated to determine the levels of PD-1, PD-L1, AKT, mTOR, TNF-α, NF-κB, IL-2, IL-4, IL-6, IL-10, IL-17, IL-17A, and IFN-γ. The surface makers of macrophages (CD11c, CD16, CD86, CD163, CD206, CX3CR-1 and CSF-1R), level of ROS, apoptosis and cell cycle, were all assessed.

RESULTS

Elevated levels of PD-1 and PD-L1, decreased levels of AKT and mTOR, along with elevated levels of TNF-α, NF-κB, IL-17, IL-2, IL-6, IL-17A and IFN-γ were identified in the alveolar macrophages infected with Mycobacterium TB, while an opposite trend was observed when PD-1/PD-L1 signaling pathway was inhibited. Additionally, elevated protein levels of CD11c, CD16 and CD86, as well as an increased rate of positive ROS and cell apoptosis, levels of Bax, and a diminished percentage of alveolar macrophages at the S and G2/M stages were detected in the event of Mycobacterium TB infection. A contrasting trend to the aforementioned findings was detected when the PD-1/PD-L1 signaling pathway was inhibited.

CONCLUSION

Taken together, these results suggested that inhibition of the PD-1/PD-L1 signaling pathway enhanced the innate immune response of alveolar macrophages to Mycobacterium TB in mice.

Checkpoint Inhibition and Infectious Diseases: A Good Thing?

The mammalian immune system has evolved the capacity to detect and destroy tumor cells. Tumors utilize multiple strategies to evade host immune surveillance, including the induction of the checkpoint molecules cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) to suppress antitumor immunity. Pharmacologic blockade of these molecules with checkpoint inhibitors (CPIs) restores T cell function and prolongs survival in patients with various malignancies. Emerging evidence suggests that the same checkpoint pathways may play a crucial role during infections. Indeed, CPIs appear promising as immunotherapeutic agents in infectious diseases, although their efficacy varies depending on pathogen-, cell-, and organ-specific factors. More research will be necessary to clarify the effects and safety of CPIs on clinically relevant outcomes of human infection.