Programmed death (PD)-1:PD-ligand 1/PD-ligand 2 pathway inhibits T cell effector functions during human tuberculosis

Detailed phenotyping reveals diverse and highly skewed neutrophil subsets in both the blood and airways during active tuberculosis infection

Introduction

Neutrophils play a complex and important role in the immunopathology of TB. Data suggest they are protective during early infection but become a main driver of immunopathology if infection progresses to active disease. Neutrophils are now recognized to exist in functionally diverse states, but little work has been done on how neutrophil states or subsets are skewed in TB disease.

Methods

To address this, we carried out comprehensive phenotyping by flow cytometry of neutrophils in the blood and airways of individuals with active pulmonary TB with and without HIV co-infection recruited in Durban, South Africa.

Results

Active TB was associated with a profound skewing of neutrophils in the blood toward phenotypes associated with activation and apoptosis, reduced phagocytosis, reverse transmigration, and immune regulation. This skewing was also apparently in airway neutrophils, particularly the regulatory subsets expressing PDL-1 and LOX-1. HIV co-infection did not impact neutrophil subsets in the blood but was associated with a phenotypic change in the airways and a reduction in key neutrophil functional proteins cathelicidin and arginase 1.

Discussion

Active TB is associated with profound skewing of blood and airway neutrophils and suggests multiple mechanisms by which neutrophils may exacerbate the immunopathology of TB. These data indicate potential avenues for reducing neutrophil-mediated lung pathology at the point of diagnosis.

Diabetes and Infectious Diseases with a Focus on Melioidosis

Diabetes mellitus (DM) leads to impaired innate and adaptive immune responses. This renders individuals with DM highly susceptible to microbial infections such as COVID-19, tuberculosis and melioidosis. Melioidosis is a tropical disease caused by the bacterial pathogen Burkholderia pseudomallei, where diabetes is consistently reported as the most significant risk factor associated with the disease. Type-2 diabetes is observed in 39% of melioidosis patients where the risk of infection is 13-fold higher than non-diabetic individuals. B. pseudomallei is found in the environment and is an opportunistic pathogen in humans, often exhibiting severe clinical manifestations in immunocompromised patients. The pathophysiology of diabetes significantly affects the host immune responses that play a critical role in fighting the infection, such as leukocyte and neutrophil impairment, macrophage and monocyte inhibition and natural killer cell dysfunction. These defects result in delayed recruitment as well as activation of immune cells to target the invading B. pseudomallei. This provides an advantage for the pathogen to survive and adapt within the immunocompromised diabetic patients. Nevertheless, knowledge gaps on diabetes-infectious disease comorbidity, in particular, melioidosis-diabetes comorbidity, need to be filled to fully understand the dysfunctional host immune responses and adaptation of the pathogen under diabetic conditions to guide therapeutic options.

Linking S. aureus Immune Evasion Mechanisms to Staphylococcal Vaccine Failures

Vaccination arguably remains the only long-term strategy to limit the spread of S. aureus infections and its related antibiotic resistance. To date, however, all staphylococcal vaccines tested in clinical trials have failed. In this review, we propose that the failure of S. aureus vaccines is intricately linked to prior host exposure to S. aureus and the pathogen's capacity to evade adaptive immune defenses. We suggest that non-protective immune imprints created by previous exposure to S. aureus are preferentially recalled by SA vaccines, and IL-10 induced by S. aureus plays a unique role in shaping these non-protective anti-staphylococcal immune responses. We discuss how S. aureus modifies the host immune landscape, which thereby necessitates alternative approaches to develop successful staphylococcal vaccines.

Treatment Strategies for Non-Small-Cell Lung Cancer with Comorbid Respiratory Disease; Interstitial Pneumonia, Chronic Obstructive Pulmonary Disease, and Tuberculosis

Non-small cell lung cancer (NSCLC) patients are often complicated by other respiratory diseases, including interstitial pneumonia (IP), chronic obstructive pulmonary disease (COPD), and pulmonary tuberculosis (TB), and the management of which can be problematic. NSCLC patients with IP sometimes develop fatal acute exacerbation induced by pharmacotherapy, and the establishment of a safe treatment strategy is desirable. For advanced NSCLC with IP, carboplatin plus nanoparticle albumin-bound paclitaxel is a relatively safe and effective first-line treatment option. Although the safety of immune checkpoint inhibitors (ICIs) for these populations remains controversial, ICIs have the potential to provide long-term survival. The severity of COPD is an important prognostic factor in NSCLC patients. Although COPD complications do not necessarily limit treatment options, it is important to select drugs with fewer side effects on the heart and blood vessels as well as the lungs. Active TB is complicated by 2-5% of NSCLC cases during their disease course. Since pharmacotherapy, especially ICIs, reportedly induces the development of TB, the possibility of developing TB should always be kept in mind during NSCLC treatment. To date, there is no coherent review article on NSCLC with these pulmonary complications. This review article summarizes the current evidence and discusses future prospects for treatment strategies for NSCLC patients complicated with IP, severe COPD, and TB.

Mycobacterium tuberculosis-specific memory T cells in bronchoalveolar lavage of patients with pulmonary tuberculosis

BACKGROUND

Mycobacterium tuberculosis(MTB) most often infects the lungs and results in pulmonary tuberculosis(TB). MTB-specific memory T cells are able to respond quickly against antigens and help reduce the burden of pulmonary bacteria. The characteristics, function and chemotaxis axis of memory T cells in the lung remain unclear. The current study aimed to clarify the classification, function and recruitment of local antigen-specific memory T cells in the lung and the periphery blood of patients with pulmonary TB.

METHODS

A total of 85 patients with active pulmonary TB were included in the study. Bronchoalveolar lavage fluid (BALF) and Peripheral blood were collected for further detection. The cell-surface markers and intracellular staining of memory T cell subtypes were measured by flow cytometry. The level of CXCL9, CXCL10 and CXCL11 in Bronchoalveolar lavage fluid cells and peripheral blood mononuclear cells (PBMC) were measured by Real-time PCR.

RESULTS

The ratio of effective Memory T cells (TEM) were the highest in BALF of patients with pulmonary TB. In patients, CXCR3 and its ligands was increased in memory T cells of BALF compared with PBMC. IFN-γ+TNF-α+ effective Memory T cells and central memory T cells from BALF were increased after antigen stimulation. CXCR3 was higher in IFN-γ+ compared with IFN-γ- in CD4+ TCM and TEM from BALF of patients. Compared with PBMC, the PD-1 levels of terminal effector memory RA+(TEMRA) and TEM cells in CD4+ memory T cells of BALF were significantly increased. In addition, PD-1 was increased in IFN-γ+ compared with IFN-γ- in CD4+TEM from BALF of patients. There was no difference in Treg ratio between PBMC and BALF of TB patients.

CONCLUSIONS

The CXCL9/CXCL11-CXCR3 axis may participate in the chemotaxis of memory T cells from the peripheral to lung. CD4+TEM and TEMRA in BALF may have exhausted, especially the cytokine producing TEM. Our study clarified the characteristics of antigen-specific memory T cells in local lung and may have impact on strategies of therapy and vaccine.

Clinical Staphylococcus aureus inhibits human T-cell activity through interaction with the PD-1 receptor

IMPORTANCE

Therapies that target and aid the host immune defense to repel cancer cells or invading pathogens are rapidly emerging. Antibiotic resistance is among the largest threats to human health globally. Staphylococcus aureus (S. aureus) is the most common bacterial infection, and it poses a challenge to the healthcare system due to its significant ability to develop resistance toward current available therapies. In long-term infections, S. aureus further adapt to avoid clearance by the host immune defense. In this study, we discover a new interaction that allows S. aureus to avoid elimination by the immune system, which likely supports its persistence in the host. Moreover, we find that blocking the specific receptor (PD-1) using antibodies significantly relieves the S. aureus-imposed inhibition. Our findings suggest that therapeutically targeting PD-1 is a possible future strategy for treating certain antibiotic-resistant staphylococcal infections.

Molecular characterization of immunoinhibitory factors PD-1/PD-L1 in sheep

Sheep have been used as a large animal experimental model for studying infectious diseases. However, due to a lack of staining antibodies and reagents, immunological studies on sheep have not progressed. The immunoinhibitory receptor programmed death-1 (PD-1) is expressed on T lymphocytes. The interaction of PD-1 with its ligand PD-ligand 1 (PD-L1) delivers inhibitory signals and impairs proliferation, cytokine production, and cytotoxicity of T cells. We previously reported that the PD-1/PD-L1 pathway was closely associated with T-cell exhaustion and disease progression in bovine chronic infections using anti-bovine PD-L1 monoclonal antibodies (mAbs). Furthermore, we found that blocking antibodies against PD-1 and PD-L1 restore T-cell functions and could be used in immunotherapy of cattle. However, the immunological role of the PD-1/PD-L1 pathway in chronic diseases of sheep remains unknown. In this study, we identified cDNA sequences of ovine PD-1 and PD-L1 and examined the cross-activity of anti-bovine PD-L1 mAbs against ovine PD-L1 as well as the expression of PD-L1 in ovine listeriosis. The amino acid sequences of ovine PD-1 and PD-L1 share a high degree of identity and similarity with homologs from ruminants and other mammalian species. Anti-bovine PD-L1 mAb recognized ovine PD-L1 on lymphocytes in the flow cytometric assay. Furthermore, an immunohistochemical staining confirmed the PD-L1 expression on macrophages in the brain lesions of ovine listeriosis. These findings indicated that our anti-PD-L1 mAb would be useful for analyzing the ovine PD-1/PD-L1 pathway. Further research is needed to determine the immunological role of PD-1/PD-L1 in chronic diseases such as BLV infection through experimental infection of sheep.

Immune Checkpoint Inhibitors and Tuberculosis Infection in Lung Cancer: A Case Series and Systematic Review With Pooled Analysis

The association between immune checkpoint inhibitors (ICIs) and tuberculosis (TB) infection in patients with lung cancer remains largely elusive. We performed a systematic review and conducted a retrospective analysis of TB infection in patients with lung cancer and ICI exposure to assess the clinical characteristics and outcomes using PubMed, EMBASE, and the Cochrane Library. The time interval from ICI administration to diagnosis of TB between patients with and without a history of TB was compared using Kaplan-Meier analysis. A multivariate Cox regression model was used to identify potential risk factors associated with the time interval of TB development. Twenty-four studies including 53 patients with lung cancer were included. The median age of the patients was 64 years. Eight patients had a history of TB. The median time interval from ICI administration to TB diagnosis was 3 months. In retrospective analysis, 5 (1.16%, 95%CI 0.38% to 2.68%) patients with lung cancer developed TB during ICI treatment. The median time interval was 10.4 months. In a pooled analysis, the median time interval in the without-TB and with-TB groups was 7.00 and 2.35 months, respectively (P = .034). Multivariate Cox regression analyses revealed a history of TB to be an independent factor affecting the time interval of TB activation in patients with lung cancer and ICI exposure (HR 3.59; 95%CI 1.17 to 11.02; P = .026). Therefore, TB infection should be considered in patients with lung cancer during or after ICI treatment. Moreover, we found TB history to be a positive risk factor for a shorter median time interval from ICI to TB diagnosis in patients with lung cancer receiving ICI.

Beyond the Clinic: The Activation of Diverse Cellular and Humoral Factors Shapes the Immunological Status of Patients with Active Tuberculosis

Mycobacterium tuberculosis (Mtb), the etiologic agent of tuberculosis (TB), has killed nearly one billion people in the last two centuries. Nowadays, TB remains a major global health problem, ranking among the thirteen leading causes of death worldwide. Human TB infection spans different levels of stages: incipient, subclinical, latent and active TB, all of them with varying symptoms, microbiological characteristics, immune responses and pathologies profiles. After infection, Mtb interacts with diverse cells of both innate and adaptive immune compartments, playing a crucial role in the modulation and development of the pathology. Underlying TB clinical manifestations, individual immunological profiles can be identified in patients with active TB according to the strength of their immune responses to Mtb infection, defining diverse endotypes. Those different endotypes are regulated by a complex interaction of the patient's cellular metabolism, genetic background, epigenetics, and gene transcriptional regulation. Here, we review immunological categorizations of TB patients based on the activation of different cellular populations (both myeloid and lymphocytic subsets) and humoral mediators (such as cytokines and lipid mediators). The analysis of the participating factors that operate during active Mtb infection shaping the immunological status or immune endotypes of TB patients could contribute to the development of Host Directed Therapy.

STAT3 regulation of Mtb-specific T cell function in active pulmonary tuberculosis patients

BACKGROUND

Tuberculosis (TB) remains one of the most serious infectious diseases in the world. Our aim was to investigate the regulatory role of STAT3 and pSTAT3 in the regulation of T cell immunophenotype and cell function.

METHODS

Twenty-five active pulmonary tuberculosis (APTB) patients, 18 latent tuberculosis infection (LTBI) patients, and 20 healthy controls (HCs) enrolled in this study. T cell phenotype and expression of STAT3 and pSTAT3 were detected by flow cytometry.

RESULTS

Compared with HCs, the expression of pSTAT3 in CD4⁺ T and CD8⁺ T cells in peripheral blood of APTB patients was increased, and the expression was higher in pleural effusion. Multifunctional T cells that simultaneously secrete IFN-γ, TNF-α and IL-17A have higher pSTAT3 expression levels. Mtb-specific T cells from APTB patients had a higher cell frequency of the STAT3⁺ pSTAT3⁺ phenotype and a reduced cell frequency of the STAT3⁺ pSTAT3^- phenotype compared with LTBI patients. Mtb-specific T cells with STAT3⁺ pSTAT3⁺ phenotype had higher expression of PD-1 and PD-L1, while cells with STAT3⁺ pSTAT3^- phenotype had higher expression of Bcl-2.

CONCLUSIONS

STAT3 and pSTAT3 in T cells of APTB patients feature in the process of anti-apoptosis and cytokine secretion. At the same time, the higher pSTAT3 may be related to the degree of cell functional exhaustion. The pSTAT3 level of T cells is related to the infection status and may indicate the clinical activity of the disease, which provides a new idea for the clinical identification and treatment of active pulmonary tuberculosis.

Rickettsia Vaccine Candidate pVAX1-OmpB24 Stimulates TCD4+INF-γ+ and TCD8+INF-γ+ Lymphocytes in Autologous Co-Culture of Human Cells

BACKGROUND

In recent years, promising vaccination strategies against rickettsiosis have been described in experimental animal models and human cells. OmpB is considered an immunodominant antigen that is recognized by T and B cells. The aim of this study was to identify TCD4+INF-γ+ and TCD8+INF-γ+ lymphocytes in an autologous system with macrophages transfected with the vaccine candidate pVAX1-OmpB24. Lymphocytes and monocytes from 14 patients with Rickettsia were isolated from whole blood. Monocytes were differentiated into macrophages and transfected with the plasmid pVAX1-OmpB24 pVax1. Isolated lymphocytes were cultured with transfected macrophages. IFN-γ-producing TCD4+ and TCD8+ lymphocyte subpopulations were identified by flow cytometry, as was the percentage of macrophages expressing CD40+, CD80+, HLA-I and HLA-II. Also, we analyzed the exhausted condition of the T lymphocyte subpopulation by PD1 expression. Macrophages transfected with pVAX1-OmpB24 stimulated TCD4+INF-γ+ cells in healthy subjects and patients infected with R. typhi. Macrophages stimulated TCD8+INF-γ+ cells in healthy subjects and patients infected with R. rickettsii and R. felis. Cells from healthy donors stimulated with OmpB-24 showed a higher percentage of TCD4+PD1+. Cells from patients infected with R. rickettsii had a higher percentage of TCD8+PD-1+, and for those infected with R. typhi the larger number of cells corresponded to TCD4+PD1+. Human macrophages transfected with pVAX1-OmpB24 activated TCD4+IFN-γ+ and CD8+IFN-γ+ in patients infected with different Rickettsia species. However, PD1 expression played an important role in the inhibition of T lymphocytes with R. felis.

The Bidirectional Relationship between Pulmonary Tuberculosis and Lung Cancer

Lung cancer and pulmonary tuberculosis are two significant public health problems that continue to take millions of lives each year. They may have similar symptoms and, in some cases, are diagnosed simultaneously or may have a causal relationship. In tuberculosis disease, the chronic inflammation, different produced molecules, genomic changes, and fibrosis are believed to be important factors that may promote carcinogenesis. As a reverse reaction, the development of carcinogenesis and the treatment may induce the reactivation of latent tuberculosis infection. Moreover, the recently used checkpoint inhibitors are a debatable subject since they help treat lung cancer but may lead to the reactivation of pulmonary tuberculosis and checkpoint-induced pneumonitis. Pulmonary rehabilitation is an effective intervention in post-tuberculosis patients and lung cancer patients and should be recommended to improve outcomes in these pathologies.

Differential expression of programmed death 1 (PD-1) on various immune cells and its role in human leprosy

Leprosy is a chronic bacterial disease caused by Mycobacterium leprae. Leprosy patients have been found to have defects in T cells activation, which is critical to the clearance of the bacilli. Treg cell suppression is mediated by inhibitory cytokines such as IL10, IL-35 and TGF-β and its frequency is higher in leprosy patients. Activation and overexpression of programmed death 1 (PD-1) receptor is considered to one of the pathways to inhibit T-cell response in human leprosy. In the current study we address the effect of PD-1 on Tregs function and its immuno-suppressive function in leprosy patients. Flow cytometry was used to evaluate the expression of PD-1 and its ligands on various immune cells T cells, B cells, Tregs and monocytes. We observed higher expression of PD-1 on Tregs is associated with lower production of IL-10 in leprosy patients. PD-1 ligands on T cells, B cells, Tregs and monocytes found to be higher in the leprosy patients as compared to healthy controls. Furthermore, in vitro blocking of PD-1 restores the Tregs mediated suppression of Teff and increase secretion of immunosuppressive cytokine IL-10. Moreover, overexpression of PD-1 positively correlates with disease severity as well as Bacteriological Index (BI) among leprosy patients. Collectively, our data suggested that PD-1 overexpression on various immune cells is associated with disease severity in human leprosy. Manipulation and inhibition of PD-1 signaling pathway on Tregs alter and restore the Treg cell suppression activity in leprosy patients.

Immunological hyporesponsiveness in tuberculosis: The role of mycobacterial glycolipids

Glycolipids constitute a major part of the cell envelope of Mycobacterium tuberculosis (Mtb). They are potent immunomodulatory molecules recognized by several immune receptors like pattern recognition receptors such as TLR2, DC-SIGN and Dectin-2 on antigen-presenting cells and by T cell receptors on T lymphocytes. The Mtb glycolipids lipoarabinomannan (LAM) and its biosynthetic relatives, phosphatidylinositol mannosides (PIMs) and lipomannan (LM), as well as other Mtb glycolipids, such as phenolic glycolipids and sulfoglycolipids have the ability to modulate the immune response, stimulating or inhibiting a pro-inflammatory response. We explore here the downmodulating effect of Mtb glycolipids. A great proportion of the studies used in vitro approaches although in vivo infection with Mtb might also lead to a dampening of myeloid cell and T cell responses to Mtb glycolipids. This dampened response has been explored ex vivo with immune cells from peripheral blood from Mtb-infected individuals and in mouse models of infection. In addition to the dampening of the immune response caused by Mtb glycolipids, we discuss the hyporesponse to Mtb glycolipids caused by prolonged Mtb infection and/or exposure to Mtb antigens. Hyporesponse to LAM has been observed in myeloid cells from individuals with active and latent tuberculosis (TB). For some myeloid subsets, this effect is stronger in latent versus active TB. Since the immune response in individuals with latent TB represents a more protective profile compared to the one in patients with active TB, this suggests that downmodulation of myeloid cell functions by Mtb glycolipids may be beneficial for the host and protect against active TB disease. The mechanisms of this downmodulation, including tolerance through epigenetic modifications, are only partly explored.

A protein signature associated with active tuberculosis identified by plasma profiling and network-based analysis

Annually, approximately 10 million people are diagnosed with active tuberculosis (TB), and 1.4 million die of the disease. If left untreated, each person with active TB will infect 10-15 new individuals. The lack of non-sputum-based diagnostic tests leads to delayed diagnoses of active pulmonary TB cases, contributing to continued disease transmission. In this exploratory study, we aimed to identify biomarkers associated with active TB. We assessed the plasma levels of 92 proteins associated with inflammation in individuals with active TB (n = 20), latent TB (n = 14), or healthy controls (n = 10). Using co-expression network analysis, we identified one module of proteins with strong association with active TB. We removed proteins from the module that had low abundance or were associated with non-TB diseases in published transcriptomic datasets, resulting in a 12-protein plasma signature that was highly enriched in individuals with pulmonary and extrapulmonary TB and was further associated with disease severity.

Characterizing and correcting immune dysfunction in non-tuberculous mycobacterial disease

Non-tuberculous mycobacterial pulmonary disease (NTM-PD) is a chronic, progressive, and growing worldwide health burden associated with mounting morbidity, mortality, and economic costs. Improvements in NTM-PD management are urgently needed, which requires a better understanding of fundamental immunopathology. Here, we examine temporal dynamics of the immune compartment during NTM-PD caused by Mycobacterium avium complex (MAC) and Mycobactereoides abscessus complex (MABS). We show that active MAC infection is characterized by elevated T cell immunoglobulin and mucin-domain containing-3 expression across multiple T cell subsets. In contrast, active MABS infection was characterized by increased expression of cytotoxic T-lymphocyte-associated protein 4. Patients who failed therapy closely mirrored the healthy individual immune phenotype, with circulating immune network appearing to 'ignore' infection in the lung. Interestingly, immune biosignatures were identified that could inform disease stage and infecting species with high accuracy. Additionally, programmed cell death protein 1 blockade rescued antigen-specific IFN-γ secretion in all disease stages except persistent infection, suggesting the potential to redeploy checkpoint blockade inhibitors for NTM-PD. Collectively, our results provide new insight into species-specific 'immune chatter' occurring during NTM-PD and provide new targets, processes and pathways for diagnostics, prognostics, and treatments needed for this emerging and difficult to treat disease.

Host-Directed Therapies for Tuberculosis

Tuberculosis (TB) is one of the leading causes of death worldwide, consistently threatening public health. Conventional tuberculosis treatment requires a long-term treatment regimen and is associated with side effects. The efficacy of antitubercular drugs has decreased with the emergence of drug-resistant TB; therefore, the development of new TB treatment strategies is urgently needed. In this context, we present host-directed therapy (HDT) as an alternative to current tuberculosis therapy. Unlike antitubercular drugs that directly target Mycobacterium tuberculosis (Mtb), the causative agent of TB, HDT is an approach for treating TB that appropriately modulates host immune responses. HDT primarily aims to enhance the antimicrobial activity of the host in order to control Mtb infection and attenuate excessive inflammation in order to minimize tissue damage. Recently, research based on the repositioning of drugs for use in HDT has been in progress. Based on the overall immune responses against Mtb infection and the immune-evasion mechanisms of Mtb, this review examines the repositioned drugs available for HDT and their mechanisms of action.

Serial interferon-gamma release assay in lung cancer patients receiving immune checkpoint inhibitors: a prospective cohort study

Recent advancements in cancer immunotherapy using immune checkpoint inhibitors (ICIs) have received considerable attention. Although advantageous, ICI therapies cause unique immune-related adverse events (irAEs) in some patients. Moreover, infectious diseases, such as tuberculosis, have been recognized as emerging concerns during immunotherapy. We aimed to evaluate the interferon-gamma release assay (IGRA) conversion rate and active tuberculosis incidence during immunotherapy to elucidate the incidence of tuberculosis reactivation after ICI therapy induction.We prospectively assessed IGRA results in lung cancer patients who received ICI monotherapy before ICI treatment and at 6 and 12 months after ICI treatment. We also assessed computed tomography findings to determine the presence of active tuberculosis when positive IGRA results were obtained. The ICIs used were nivolumab, pembrolizumab, atezolizumab, and durvalumab.In all, 178 patients were prospectively recruited between March 2017 and March 2020. Of these, 123 completed serial IGRAs, of whom 18, 101, and 4, respectively, had positive, negative, and indeterminate IGRAs at baseline. Three and four patients, respectively, showed IGRA reversion and conversion during immunotherapy. One patient with a sustained, stable positive IGRA and one with IGRA conversion developed active pulmonary tuberculosis during immunotherapy.We found that 3.3% and 1.6% of the patients developed IGRA conversion and active tuberculosis, respectively. Of the four patients who developed IGRA conversion, one developed active pulmonary tuberculosis during immunotherapy. Another patient with sustained, stable positive IGRA developed active tuberculosis. Physicians should be alert to tuberculosis development during ICI therapy, and IGRA testing is a useful tool to assess the risk of developing active tuberculosis.

Cellular Senescence in Immunity against Infections

Cellular senescence is characterized by irreversible cell cycle arrest in response to different triggers and an inflammatory secretome. Although originally described in fibroblasts and cell types of solid organs, cellular senescence affects most tissues with advancing age, including the lymphoid tissue, causing chronic inflammation and dysregulation of both innate and adaptive immune functions. Besides its normal occurrence, persistent microbial challenge or pathogenic microorganisms might also accelerate the activation of cellular aging, inducing the premature senescence of immune cells. Therapeutic strategies counteracting the detrimental effects of cellular senescence are being developed. Their application to target immune cells might have the potential to improve immune dysfunctions during aging and reduce the age-dependent susceptibility to infections. In this review, we discuss how immune senescence influences the host’s ability to resolve more common infections in the elderly and detail the different markers proposed to identify such senescent cells; the mechanisms by which infectious agents increase the extent of immune senescence are also reviewed. Finally, available senescence therapeutics are discussed in the context of their effects on immunity and against infections.

PD-1 is expressed in cytotoxic granules of NK cells and rapidly mobilized to the cell membrane following recognition of tumor cells

The contribution of the T cell-related inhibitory checkpoint PD-1 to the regulation of NK cell activity is still not clear with contradictory results concerning its expression and role in the modulation of NK cell cytotoxicity. We provide novel key findings on the mechanism involved in the regulation of PD-1 expression on NK cell membrane and its functional consequences for the elimination of cancer cells. In contrast to freshly isolated NK cells from cancer patients, those from healthy donors did not express PD-1 on the cell membrane. However, when healthy NK cells were incubated with tumor target cells, membrane PD-1 expression increased, concurrent with the CD107a surface mobilization. This finding suggested that PD-1 was translocated to the cell membrane during NK cell degranulation after contact with target cells. Indeed, cytosolic PD-1 was expressed in freshly-isolated-NK cells and partly co-localized with CD107a and GzmB, confirming that membrane PD-1 corresponded to a pool of preformed PD-1. Moreover, NK cells that had mobilized PD-1 to the cell membrane presented a significantly reduced anti-tumor activity on PD-L1-expressing-tumor cells in vitro and in vivo, which was partly reversed by using anti-PD-1 blocking antibodies. Our results indicate that NK cells from healthy individuals express cytotoxic granule-associated PD-1, which is rapidly mobilized to the cell membrane after interaction with tumor target cells. This novel finding helps to understand how PD-1 expression is regulated on NK cell membrane and the functional consequences of this expression during the elimination of tumor cells, which will help to design more efficient NK cell-based cancer immunotherapies.

Immunosuppressive Mechanisms in Brucellosis in Light of Chronic Bacterial Diseases

Brucellosis is considered one of the major zoonoses worldwide, constituting a critical livestock and human health concern with a huge socio-economic burden. Brucella genus, its etiologic agent, is composed of intracellular bacteria that have evolved a prodigious ability to elude and shape host immunity to establish chronic infection. Brucella’s intracellular lifestyle and pathogen-associated molecular patterns, such as its specific lipopolysaccharide (LPS), are key factors for hiding and hampering recognition by the immune system. Here, we will review the current knowledge of evading and immunosuppressive mechanisms elicited by Brucella species to persist stealthily in their hosts, such as those triggered by their LPS and cyclic β-1,2-d-glucan or involved in neutrophil and monocyte avoidance, antigen presentation impairment, the modulation of T cell responses and immunometabolism. Attractive strategies exploited by other successful chronic pathogenic bacteria, including Mycobacteria, Salmonella, and Chlamydia, will be also discussed, with a special emphasis on the mechanisms operating in brucellosis, such as granuloma formation, pyroptosis, and manipulation of type I and III IFNs, B cells, innate lymphoid cells, and host lipids. A better understanding of these stratagems is essential to fighting bacterial chronic infections and designing innovative treatments and vaccines.

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.

The immunoregulatory landscape of human tuberculosis granulomas

Tuberculosis (TB) in humans is characterized by formation of immune-rich granulomas in infected tissues, the architecture and composition of which are thought to affect disease outcome. However, our understanding of the spatial relationships that control human granulomas is limited. Here, we used multiplexed ion beam imaging by time of flight (MIBI-TOF) to image 37 proteins in tissues from patients with active TB. We constructed a comprehensive atlas that maps 19 cell subsets across 8 spatial microenvironments. This atlas shows an IFN-γ-depleted microenvironment enriched for TGF-β, regulatory T cells and IDO1⁺ PD-L1⁺ myeloid cells. In a further transcriptomic meta-analysis of peripheral blood from patients with TB, immunoregulatory trends mirror those identified by granuloma imaging. Notably, PD-L1 expression is associated with progression to active TB and treatment response. These data indicate that in TB granulomas, there are local spatially coordinated immunoregulatory programs with systemic manifestations that define active TB.

Mycobacterium avium complex lung disease in a patient treated with an immune checkpoint inhibitor: A case report

Immune checkpoint inhibitors (ICIs) are becoming widely used for the treatment of various types of cancer. However, characteristic side effects, which are referred to as immune-related adverse events, may appear, and they have important clinical implications for the management of patients treated with ICIs. The development of mycobacterial infections has also been reported, but they have mostly been seen in cases with tuberculosis, and only a few cases involved non-tuberculous mycobacteriosis. We herein present the case of an 82-year-old man who was treated with nivolumab for gastric cancer. After the 22nd course of the treatment, the patient experienced loss of appetite for 1 week, and infiltration shadows were observed in the lower lobe of the left lung. Treatment for bacterial pneumonia was ineffective, and the lung field shadow gradually worsened. Mycobacterium intracellulare was detected in two consecutive sputum cultures. Thus, the patient was diagnosed with Mycobacterium avium complex (MAC) lung disease, and treatment for MAC infection was thus initiated, with subsequent improvement of the patient's condition and infiltration shadows. At 7 months after the start of treatment, the sputum cultures became negative for acid-fast bacilli. Since MAC lung disease may develop acutely during immunotherapy with ICIs, clinicians should include it in the differential diagnoses for pneumonia during immunotherapy with ICIs.

T-Cell Exhaustion in Mycobacterium tuberculosis and Nontuberculous Mycobacteria Infection: Pathophysiology and Therapeutic Perspectives

Immune exhaustion is a condition associated with chronic infections and cancers, characterized by the inability of antigen-specific T cells to eliminate the cognate antigen. Exhausted T cells display a peculiar phenotypic profile and exclusive functional characteristics. Immune exhaustion has been described in patients with Mycobacterium tuberculosis infection, and cases of tuberculosis reactivation have been reported in those treated with immune checkpoint inhibitors, drugs able to re-establish T-cells’ function. Exhausted T CD8⁺ cells’ profile has also been described in patients with infection due to nontuberculous mycobacteria. In this review, we initially provide an overview of the mechanisms leading to immune exhaustion in patients infected by Mycobacterium tuberculosis and nontuberculous mycobacteria. We then dissect the therapeutic perspectives related to immune checkpoint blockade in patients with these infections.

Pulmonary adverse events due to immune checkpoint inhibitors: A literature review

Cancer immunotherapy aims to stimulate the immune system to fight against tumors, utilizing the presentation of molecules on the surface of the malignant cells that can be recognized by the antibodies of the immune system. Immune checkpoint inhibitors, a type of cancer immunotherapy, are broadly used in different types of cancer, improving patients' survival and quality of life. However, treatment with these agents causes immune-related toxicities affecting many organs. The most frequent pulmonary adverse event is pneumonitis representing a non-infective inflammation localized to the interstitium and alveoli. Other lung toxicities include airway disease, pulmonary vasculitis, sarcoid-like reactions, infections, pleural effusions, pulmonary nodules, diaphragm myositis and allergic bronchopulmonary aspergillosis. This review aims to summarize these pulmonary adverse events, underlining the significance of an optimal expeditious diagnosis and management.

Risk of tuberculosis in patients with cancer treated with immune checkpoint inhibitors: a nationwide observational study

BACKGROUND

While some recent studies have reported the development of tuberculosis (TB) in patients exposed to immune checkpoint inhibitors (ICIs), there is limited evidence to date. Therefore, we evaluated the risk of TB in patients with cancer exposed to ICIs using the National Health Insurance claims data in South Korea.

METHODS

Patients with diagnostic codes for non-small cell lung cancer, urothelial carcinoma or melanoma between August 2017 and June 2019 were identified. The incidence rate and standardized incidence ratio (SIR) of TB were calculated for both the ICI exposure and non-exposure groups. The risk of TB according to ICI exposure was assessed using a multivariable Cox regression model.

RESULTS

During the study period, 141 550 patients with cancer and 916 new TB cases were identified. Among the 5037 patients exposed to ICIs, 20 were diagnosed with TB at a median of 2.2 months after the ICI was initiated. The crude incidence rate of TB per 100,000 person-years was 675.8 (95% CI 412.8 to 1043.8) for the ICI exposure group and 599.1 (95% CI 560.5 to 639.6) for the non-exposure group. The SIR for TB was 8.1 (95% CI 8.0 to 8.2) in the ICI exposure group. After adjusting for potential confounding factors, ICI treatment was not significantly associated with an increased risk of TB (HR: 0.73; 95% CI 0.47 to 1.14).

CONCLUSIONS

While the incidence of TB in cancer patients exposed to ICIs was eightfold higher than in the general population, the risk of patients with cancer developing TB did not significantly differ according to ICI exposure.

Comparisons of Underlying Mechanisms, Clinical Efficacy and Safety Between Anti-PD-1 and Anti-PD-L1 Immunotherapy: The State-of-the-Art Review and Future Perspectives

Over the past decade, diverse PD-1/PD-L1 blockades have demonstrated significant clinical benefit in across a wide range of tumor and cancer types. With the increasing number of PD-1/PD-L1 blockades available in the market, differences between the clinical performance of each of them started to be reported. Here, we provide a comprehensive historical and biological perspective regarding the underlying mechanism and clinical performance of PD-1/PD-L1 blockades, with an emphasis on the comparisons of their clinical efficacy and safety. The real-world evidence indicated that PD-1 blockade may be more effective than the PD-L1, though no significant differences were found as regards to their safety profiles. Future head-to-head studies are warranted for direct comparison between them. Finally, we summarize the yet to be elucidated questions and future promise of anti-PD-1/PD-L1 immunotherapy, including a need to explore novel biomarkers, novel combinatorial strategies, and their clinical use on chronic infection.

PGE2 displays immunosuppressive effects during human active tuberculosis

Prostaglandin E2 (PGE2), an active lipid compound derived from arachidonic acid, regulates different stages of the immune response of the host during several pathologies such as chronic infections or cancer. In fact, manipulation of PGE2 levels was proposed as an approach for countering the Type I IFN signature of tuberculosis (TB). However, very limited information regarding the PGE2 pathway in patients with active TB is currently available. In the present work, we demonstrated that PGE2 exerts a potent immunosuppressive action during the immune response of the human host against Mycobacterium tuberculosis (Mtb) infection. Actually, we showed that PGE2 significantly reduced the surface expression of several immunological receptors, the lymphoproliferation and the production of proinflammatory cytokines. In addition, PGE2 promoted autophagy in monocytes and neutrophils cultured with Mtb antigens. These results suggest that PGE2 might be attenuating the excessive inflammatory immune response caused by Mtb, emerging as an attractive therapeutic target. Taken together, our findings contribute to the knowledge of the role of PGE2 in the human host resistance to Mtb and highlight the potential of this lipid mediator as a tool to improve anti-TB treatment.

Readministration of Pembrolizumab after Treatment of Tuberculosis Activated by Initial Pembrolizumab Therapy

Increasing the T-cell immune response to Mycobacterium tuberculosis with an anti-programmed cell death 1 (anti-PD-1) antibody may ultimately have detrimental effects. We present the case of a patient with advanced non-small cell lung cancer who developed active tuberculosis (TB) after initial treatment with pembrolizumab, an anti-PD-1 antibody. Pembrolizumab was resumed after completing anti-TB treatment, and no relapse of TB was observed clinically or radiologically. Checkpoint inhibitor-related pneumonitis (CIP) is first suspected when a pulmonary shadow presents during treatment with an anti-PD-1 antibody. It is sometimes difficult to diagnose CIP using computed tomographic images alone. Careful testing, including bacterial examinations and bronchoscopic biopsy, should be performed.

Tuberculosis following programmed cell death receptor-1 (PD-1) inhibitor in a patient with non-small cell lung cancer. Case report and literature review

Immune checkpoint inhibitors (ICIs)-anti-programmed death-1 (PD-1) and their ligands (PD-L1 and PD-L2) have become widely used in the treatment of several malignancies. Many immune-related adverse events (irAEs) have been linked to these agents. Nonetheless, tuberculosis (TB) reactivation during their use is increasingly recognized and reported. Herein, we present a 58-year-old lady with advanced non-small cell lung cancer (NSCLC) ALK-negative, EGFR wild, and PD-L1 immune histochemistry (IHC) strongly positive in 95% of tumor cells, on ongoing treatment with Pembrolizumab as a first-line monotherapy. Our patient presented with 1-week history of productive cough and high-grade fever. Further workup yielded the diagnosis of pulmonary tuberculosis after her Pembrolizumab sixth cycle with positive AFB smear and TB PCR from BAL (rifampin resistance not detected), with negative HIV status. Hence, immunotherapy was held, and patient was commenced on anti-TB regimen. History revealed contact with active TB patient over the past decade, without previous documentation of latent TB or previous TB infection. Her sputum AFB smear remained persistently positive 4 weeks through anti-TB regimen course. Later, the patient was discharged after her sputum was cleared from AFB (two negative sets). In light of pembrolizumab mechanism of action as an immune checkpoint inhibitor, we suspected its implication on reactivating latent TB which was observed in our patient demonstrating features of pulmonary tuberculosis. She was not re-challenged with Pembrolizumab following TB diagnosis.

Lactate Metabolism and Signaling in Tuberculosis and Cancer: A Comparative Review

Infection with Mycobacterium tuberculosis (Mtb) leading to tuberculosis (TB) disease continues to be a major global health challenge. Critical barriers, including but not limited to the development of multi-drug resistance, lack of diagnostic assays that detect patients with latent TB, an effective vaccine that prevents Mtb infection, and infectious and non-infectious comorbidities that complicate active TB, continue to hinder progress toward a TB cure. To complement the ongoing development of new antimicrobial drugs, investigators in the field are exploring the value of host-directed therapies (HDTs). This therapeutic strategy targets the host, rather than Mtb, and is intended to augment host responses to infection such that the host is better equipped to prevent or clear infection and resolve chronic inflammation. Metabolic pathways of immune cells have been identified as promising HDT targets as more metabolites and metabolic pathways have shown to play a role in TB pathogenesis and disease progression. Specifically, this review highlights the potential role of lactate as both an immunomodulatory metabolite and a potentially important signaling molecule during the host response to Mtb infection. While long thought to be an inert end product of primarily glucose metabolism, the cancer research field has discovered the importance of lactate in carcinogenesis and resistance to chemotherapeutic drug treatment. Herein, we discuss similarities between the TB granuloma and tumor microenvironments in the context of lactate metabolism and identify key metabolic and signaling pathways that have been shown to play a role in tumor progression but have yet to be explored within the context of TB. Ultimately, lactate metabolism and signaling could be viable HDT targets for TB; however, critical additional research is needed to better understand the role of lactate at the host-pathogen interface during Mtb infection before adopting this HDT strategy.

Low-Density Granulocytes Affect T-SPOT.TB Assay by Inhibiting the Production of Interferon-γ in T Cells via PD-L1/PD-1 Pathway

Background

T-SPOT TB (T-SPOT) assay is widely used for detection of Mycobacterium tuberculosis infection that is based on the detection of M. tuberculosis-specific interferon-γ-secreting T cells (ISCs) in peripheral blood mononuclear cells (PBMCs). Recently, high frequencies of low-density granulocytes (LDGs) were found in the PBMCs of tuberculosis patients. Whether these LDGs affect the detection of T-SPOT has not been investigated. The impact of LDGs on T-SPOT assay and related mechanism were investigated in this study.

Methods

The correlations between the frequencies of LDGs and the results of T-SPOT were analyzed. T-SPOT with LDG-removed PBMCs and PBMCs with exogenous addition of LDGs were performed. The possible mechanism was explored by detecting the levels of negative immune regulatory molecules on LDGs. The impact of programmed death ligand 1 (PD-L1) on T-SPOT was evaluated and confirmed by function blocking with neutralizing antibody.

Results

The positive rates of T-SPOT and ISCs in tuberculosis patients with low LDGs frequency (n = 22) were significantly higher than those with high LDGs frequency (n = 39). Removal or exogenous addition of LDGs significantly increased or decreased the ISCs and the positive rate of T-SPOT. The frequencies of interferon-γ-producing T cells were negatively correlated with the frequencies of LDGs. The expression of PD-L1 was significantly elevated on LDGs. Pretreatment of LDGs with anti-PD-L1 antibody significantly counteracted the impact of LDGs on T-SPOT. Treatment of PBMCs with anti-PD-L1 antibody resulted in comparable ISCs with that of LDG removal.

Conclusion

LDGs can inhibit the production of interferon-γ in T cells and decrease the positive rated of T-SPOT assay via highly expressed PD-L1.

A decrease in PPD specific CD4 T cell CD38 and HLA-DR expression in pulmonary tuberculosis patients after 8 weeks of therapy correlates with successful anti-tuberculosis treatment

Tuberculosis (TB) is a major health problem in Indonesia with a million new cases each year. The CD4 T cell adaptive immune response against Mycobacterium tuberculosis (MTB) is central to the control of this disease. We investigated whether standard therapy of TB causes changes to these cells in the early stages of treatment. To do this we took blood samples from 2 groups of TB patients in Banda Aceh, Indonesia; one from a group of patients before treatment, and the other from a group who become smear negative after 8 weeks treatment. MTB specific CD4 T cells were identified by ex vivo stimulation with PPD and flow cytometric measurement of intracellular cytokines and surface markers. We found no difference in total PPD specific CD4 T cells between the groups, but that the proportion of these cells CD38 + HLA-DR+ was significantly lower in the treatment group. This decrease was not specific to Interferon gamma (IFNg), Interleukin-2 (IL-2) or Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) producing cells. Our findings show that anti-MTB treatment affects the adaptive immune response, and that measuring the decrease of the PPD specific CD4 T cell CD38+HLA-DR+ phenotype could be a useful parameter for determination of treatment success.

The enhancement of Th1 immune response by anti-PD-L1 antibody in cattle infected with Mycobacterium avium subsp. paratuberculosis

Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic enteritis of ruminants. Previous studies have shown that programmed death-ligand 1 (PD-L1) is associated with the disease progression, and PD-L1 blockade activates MAP-specific Th1 responses in vitro. Here, we performed anti-PD-L1 antibody administration using 2 MAP-infected cattle at the late subclinical stage of infection. After administration, bacterial shedding was reduced or maintained at a low level. Additionally, MAP-specific Th1 cytokine production was upregulated, and CD69 expression was increased in T cells. Collectively, the treatment has a potential as a novel control method against Johne's disease.

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.

Depression and recovery of IL-17A secretion in mitogen responses in patients with active tuberculosis-a prospective observational study

BACKGROUND/PURPOSE

T-helper cell 17 (Th17) is a distinct subset of CD4+ T lymphocytes that is important in the pathogenesis of Mycobacterium tuberculosis infection. This study aims to investigate the characteristics of interleukin (IL)-17A and Th17-related cytokines after stimulation with phytohemagglutinin in patients with active tuberculosis (TB).

METHODS

This prospective cohort study enrolled patients with culture-confirmed active TB. QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was performed upon TB diagnosis and at 2 months after TB treatment. Their non-TB-specific secretion of IL-17A and Th17-related cytokines were measured in supernatants of mitogen tubes in QFT-GIT and compared to those of active TB contacts with or without latent TB infection. We analyzed the association between IL-17A secretions and TB presentation and treatment outcomes.

RESULTS

A total of 108 patients with TB and 64 non-TB cases were enrolled. The secretion of IL-17A, IL-21, IL-23, and IL-6 were lower in active TB patients upon TB diagnosis. In active TB patients, lower IL-17A secretions were associated with higher grades of sputum smear. In the multivariate analysis, lower IL-17A secretions served as an independent factor associated with 2-month culture non-conversion (odds ratio 23.04, 95% confidence interval [CI] 1.69-84.78) and on-treatment mortality (hazard ratio 28.54, 95% CI 1.30-99.25). The levels of IL-23, and IL-6 significantly increased after 2 months of anti-TB treatment.

CONCLUSION

The non-TB-specific IL-17A secretions were lower in active TB patients upon TB diagnosis and associated with higher disease severity and worse treatment outcomes. Trend of recovery of the depressed Th17-related cytokines was noted after effective anti-TB treatment.

Neutrophil autophagy during human active tuberculosis is modulated by SLAMF1

Neutrophils infected with Mycobacterium tuberculosis (Mtb) predominate in tuberculosis patients' lungs. Neutrophils phagocytose the pathogen, but the mechanism of pathogen elimination is controversial. Macroautophagy/autophagy, a crucial mechanism for several neutrophil functions, can be modulated by immunological mediators. The costimulatory molecule SLAMF1 can act as a microbial sensor in macrophages being also able to interact with autophagy-related proteins. Here, we demonstrate for the first time that human neutrophils express SLAMF1 upon Mtb-stimulation. Furthermore, SLAMF1 was found colocalizing with LC3B⁺ vesicles, and activation of SLAMF1 increased neutrophil autophagy induced by Mtb. Finally, tuberculosis patients' neutrophils displayed reduced levels of SLAMF1 and lower levels of autophagy against Mtb as compared to healthy controls. Altogether, these results indicate that SLAMF1 participates in neutrophil autophagy during active tuberculosis.Abbreviations: AFB: acid-fast bacilli; BafA1: bafilomycin A₁; CLL: chronic lymphocytic leukemia; DPI: diphenyleneiodonium; EVs: extracellular vesicles; FBS: fetal bovine serum; HD: healthy donors; HR: high responder (tuberculosis patient); IFNG: interferon gamma; IL1B: interleukin 1 beta; IL17A: interleukin 17A; IL8: interleukin 8; LR: low responder (tuberculosis patient); mAb: monoclonal antibody; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK14/p38: mitogen-activated protein kinase 14; Mtb: Mycobacterium tuberculosis; Mtb-Ag: Mycobacterium tuberculosis, Strain H37Rv, whole cell lysate; NETs: neutrophils extracellular traps; PPD: purified protein derivative; ROS: reactive oxygen species; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; SLAMF1: signaling lymphocytic activation molecule family member 1; TB: tuberculosis; TLR: toll like receptor.

Increased phagocytosis in the presence of enhanced M2-like macrophage responses correlates with increased primary and latent HSV-1 infection

After HSV-1 infection, macrophages infiltrate early into the cornea, where they play an important role in HSV-1 infection. Macrophages are divided into M1 or M2 groups based on their activation. M1 macrophages are pro-inflammatory, while M2 macrophages are anti-inflammatory. Macrophage phenotypes can shift between M1 or M2 in vitro and in vivo following treatment with specific cytokines. In this study we looked at the effect of M2 macrophages on HSV-1 infectivity using mice either lacking M2 (M2-/-) or overexpressing M2 (M2-OE) macrophages. While presence or absence of M2 macrophages had no effect on eye disease, we found that over expression of M2 macrophages was associated with increased phagocytosis, increased primary virus replication, increased latency, and increased expression of pro- and anti-inflammatory cytokines. In contrast, in mice lacking M2 macrophages following infection phagocytosis, replication, latency, and cytokine expression were similar to wild type mice. Our results suggest that enhanced M2 responses lead to higher phagocytosis, which affected both primary and latent infection but not reactivation.

Tuberculosis-Cancer Parallels in Immune Response Regulation

Mycobacterium tuberculosis and cancer are two diseases with proclivity for the development of resistance to the host immune system. Mechanisms behind resistance can be host derived or disease mediated, but they usually depend on the balance of pro-inflammatory to anti-inflammatory immune signals. Immunotherapies have been the focus of efforts to shift that balance and drive the response required for diseases eradication. The immune response to tuberculosis has widely been thought to be T cell dependent, with the majority of research focused on T cell responses. However, the past decade has seen greater recognition of the importance of the innate immune response, highlighting factors such as trained innate immunity and macrophage polarization to mycobacterial clearance. At the same time, there has been a renaissance of immunotherapy treatments for cancer since the first checkpoint inhibitor passed clinical trials, in addition to work highlighting the importance of innate immune responses to cancer. However, there is still much to learn about host-derived responses and the development of resistance to new cancer therapies. This review examines the similarities between the immune responses to cancer and tuberculosis with the hope that their commonalities will facilitate research collaboration and discovery.

Severe pulmonary infections complicating nivolumab treatment for lung cancer: a report of two cases

BACKGROUND

Immunotherapy represents a recent milestone in the treatment of lung cancer, particularly with the rapidly expanding development of monoclonal antibodies targeting checkpoint inhibitors in the programmed cell death-1 (PD-1) pathway, such as nivolumab and pembrolizumab. Classical auto-immune side effects of these treatments, often called immune-related adverse events (irAEs), can affect multiple organs, including the lungs in which potentially life-threatening pneumonitis may require rapid treatment with high doses of corticosteroids. Nevertheless, the occurrence of severe infections in cancer patients treated with nivolumab, outside the context of immunosuppressive therapy, is a complication that has rarely been reported in the literature.

CLINICAL CASES

We report two cases of severe pulmonary infection with unusual microbes, Mycobacterium tuberculosis and Aspergillus fumigatus, in patients treated with nivolumab for non-small cell lung cancer.

CONCLUSION

Ruling out pulmonary infections may require extensive investigation, as these may have an atypical presentation due to immunomodulation. Furthermore, treating the patient with corticosteroids for immune-related pneumonia could lead to a fatal outcome in this context. This report highlights the importance of excluding the presence of opportunistic infections and tuberculosis before considering immune-related pulmonary toxicity with or without a history of prior corticosteroid use. These cases also emphasize the potential value of tuberculosis screening in patients treated with PD-1 checkpoint inhibitors.

DHX36, BAX, and ARPC1B May Be Critical for the Diagnosis and Treatment of Tuberculosis

Background

Tuberculosis (TB) is usually caused by Mycobacterium tuberculosis, which has the highest mortality rate among infectious diseases. This study is designed to identify the key genes affecting the diagnosis and treatment of TB.

Methods

GSE54992, which included 39 peripheral blood mononuclear cell (PBMC) samples, was extracted from the Gene Expression Omnibus database. After the samples were classified into type and time groups by limma package, the differentially expressed genes (DEGs) were analyzed using the Analysis of Variance. Using pheatmap package, hierarchical cluster analysis was performed for the DEGs. Then, the key modules correlated with TB were selected using the WGCNA package. Finally, functional and pathway enrichment analyses were carried out using clusterProfiler package.

Results

The DEGs in subclusters 3, 6, 7, and 8 were chosen for further analyses. Based on WGCNA analysis, blue and green modules in type group and pink module in time group were selected as key modules. From the key modules, 9 (including BAX and ARPC1B) hub genes in type group and 6 (including DHX36) hub genes in time group were screened. Through pathway enrichment analysis, the TNF signaling pathway was enriched for the green module.

Conclusion

DHX36, BAX, and ARPC1B might be key genes acting in the mechanisms of TB. Besides, the TNF signaling pathway might also be critical for the diagnosis and therapy of the disease.

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.

Defective Antigen Presentation Leads to Upregulation of PD1 and IL-10 in HIV-TB Co-Infection

Human immunodeficiency virus-tuberculosis (HIV-TB) co-infection poses a challenge to the immunologists in developing new diagnostic and therapeutic tools. Mechanisms behind the breakdown of the immune defense of the co-infected individual are poorly known. Numerous studies in HIV alone have revealed the role of PD1, TAP, and IL-10, but not in co-infection. The interaction of the 2 distinct bugs, which is resulting in domination over the host immune system, is still a lacuna. Hence, we aimed to portray functions of IL-10, TAP, and PD1 molecules in HIV-TB co-infection. Co-culture cells challenged with γ-irradiated M.Tb under various conditions resulted in high interleukin (IL)-10 secretion and high percentage of PD1 expression on CD8 T cells, which might be due to defective antigen presentation of TAP on dendritic cells and macrophages. Herein our observations provide an insight into the escape mechanisms by M.Tb in HIV-infected individuals from the host immune responses leading to TB co-infection.

Programmed cell death protein 1 (PD-1) in infection

Exhausted and dysfunctional T cells triggered by infection and cancer render the immune system unable to eliminate these pathogens. Pharmacologic blockade of the surface receptors that inhibit T-cell function has shown remarkable success in patients with various malignancies. In this Review, we discuss the emerging evidence of inhibiting checkpoint pathways as a potential role in controlling or clearing infectious diseases. Though interesting tendencies, much work is still needed in order to develop safe strategies that can be translated into clinically relevant outcomes in patients with infections.

Characteristics of Circulating CD4+ T Cell Subsets in Patients with Mycobacterium avium Complex Pulmonary Disease

Although prevalence of Mycobacterium avium complex pulmonary disease (MAC-PD) is increasing, limited data are available regarding vulnerability to Mycobacterium avium complex (MAC) infections. To understand the pathobiology of interaction between MAC and host-immunity, it is important to understand the characteristics for circulating T cells in terms of the immunological phenotype and functional correlates in MAC-PD. We aimed to characterize immunophenotype, cytokine profile, and immune inhibitory receptors of circulating CD4⁺ T cells in MAC-PD patients. We enrolled 71 MAC-PD and 20 control individuals. Flow cytometric analysis was performed to determine T cell subsets and immune checkpoint markers. Ex vivo cytokine productions in response to MAC were determined using enzyme-linked immunosorbent assay. The frequencies of CD4⁺ T cells and CD4⁺IL-17⁺ T cells decreased, while CD4⁺IL-4⁺ T cells and CD4⁺CD25⁺Foxp3⁺ T cells increased in peripheral blood mononuclear cells (PBMCs) of MAC-PD individuals upon MAC stimulation compared with those cells in healthy donor-PBMCs. Additionally, we found increased PD-1, CTLA-4, and TIM-3-expressing T cells in MAC- PD individuals in response to MAC-stimulation, indicating that suppressed T cell-mediated response is associated with the susceptibility to MAC infection. These results may help to explain impaired T cell-mediated responses and pave the way for better strategies to achieve protective immunity against MAC infection.

Tuberculosis and Biologic Therapies: Anti-Tumor Necrosis Factor-α and Beyond

Biologic drugs have revolutionized the treatment of certain hematologic, autoimmune, and malignant diseases, but they may place patients at risk for reactivation or acquisition of tuberculosis. This risk is highest with the tumor necrosis factor-alpha (TNF-α) inhibitors. Amongst this class of drugs, the monoclonal antibodies (infliximab, adalimumab, golimumab) and antibody fragment (certolizumab) carry an increased risk compared to the soluble receptor fusion molecule, etanercept. Treatment of latent TB is critical to decrease the risk of reactivation. Data continues to emerge regarding tuberculosis risk associated with novel biologics targeting cytokines involved in tuberculosis control.

Diagnostic Usefulness of Cytokine and Chemokine Levels in the Cerebrospinal Fluid of Patients with Suspected Tuberculous Meningitis

In this study, we investigated the diagnostic utility of the cytokine profile of the cerebrospinal fluid (CSF) and enzyme-linked immunospot (ELISPOT) assays of patients with suspected tuberculous meningitis (TBM). We prospectively enrolled adult patients with suspected TBM, and CSF specimens were analyzed for 18 cytokines/chemokines and soluble programmed death protein 1 (PD-1) and programmed death ligand 1 (PD-L1). Enzyme-linked immunospot assays were performed on mononuclear cells from the CSF (CSF-MCs) and peripheral blood (PBMCs). A total of 87 patients with meningitis, including 42 TBM-suspected patients and 45 non-TBM patients, were enrolled. Excluding the 32 patients with possible TBM, 10 patients with TBM and 45 patients with non-TBM were finally analyzed. Levels of adenosine deaminase (ADA), interleukin 12 subunit β (IL-12p40), IL-13, macrophage inflammatory protein α (MIP-1α), and soluble PD-1 and PD-L1 in the CSF were significantly higher in the TBM group than in the non-TBM group (P < 0.05). The optimal cutoff values for the sensitivities and specificities of the test methods for diagnosing TBM with small samples of 10 cases of definite or probable TBM were as follows: ADA > 6.95 U/L, 70% and 81%; IL-12p40 > 52.04 pg/mL, 80% and 73%; IL-13 > 0.44 pg/mL, 90% and 47%; MIP-1α > 8.83 pg/mL, 80% and 62%; soluble PD-1 > 35.87 pg/mL, 80% and 63%; soluble PD-L1 > 24.19 pg/mL, 80% and 61%; CSF-MC ELISPOT > 13.5 spots/250,000 CSF-MC, 30% and 91%; and PBMC ELISPOT > 14 spots/250,000 PBMCs, 50% and 78%, respectively. Therefore, CSF IL-12p40, IL-13, MIP-1α, and soluble PD-1 and PD-L1 concentrations appear to be useful adjuncts for diagnosing TBM.