Fatal granuloma necrosis without exacerbated mycobacterial growth in tumor necrosis factor receptor p55 gene-deficient mice intravenously infected with Mycobacterium avium

Immunostimulatory short non-coding RNAs in the circulation of patients with tuberculosis infection

Mycobacterium tuberculosis (Mtb) infection is among the world's deadliest infectious diseases. Developing effective treatments and biomarkers for tuberculosis requires a deeper understanding of its pathobiology and host responses. Here, we report a comprehensive characterization of circulating short non-coding RNAs (sncRNAs) in plasma samples from Mtb-infected patients. We achieved this by pre-treating plasma RNAs with T4 polynucleotide kinase to convert all RNA ends to those compatible with sncRNA sequencing. We discovered a global and drastic upregulation of plasma sncRNAs in Mtb-infected patients, with tRNA-derived sncRNAs representing the most dramatically elevated class. Most of these tRNA-derived sncRNAs originated from a limited subset of tRNAs, specifically from three tRNA isoacceptors, and exhibited skewed patterns to 5'-derived fragments, such as 5' halves, 5' tRNA fragments (tRFs), and internal tRFs (i-tRFs) from the 5' regions. Further, Mtb-infected patients displayed markedly upregulated and distinct profiles of both rRNA- and mRNA-derived sncRNAs. Some of these sncRNAs, which are abundant and specific to Mtb-infected patients, robustly activated human macrophages via Toll-like receptor 7 and induced cytokine production. This drastic accumulation of circulating, immunostimulatory sncRNAs in the plasma of Mtb-infected patients offers insights into the sncRNA-driven aspects of host immune response against infectious diseases and suggests a pool of potential therapeutic targets and biomarkers.

TNFR1 Mediated Apoptosis Is Protective against Mycobacterium avium in Mice

Mycobacterium avium is an intracellular proliferating pathogen that causes chronic refractory respiratory infection. Although apoptosis induced by M. avium has been reported in vitro, the role of apoptosis against M. avium infection in vivo remains unclear. Here, we investigated the role of apoptosis in mouse models of M. avium infection. Tumor necrosis factor receptor-1 knockout mice (TNFR1-KO) andTNFR2-KO micewere used. M. avium (1 × 107 cfu/body) was administered intratracheally to mice. Apoptosis in lungs was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling and lung histology as well as cell death detection kits using BAL fluids. TNFR1-KO mice were susceptible to M. avium infection compared with TNFR2-KO and wild type mice based on the bacterial number and lung histology. Higher numbers of apoptotic cells were detected in the lungs of TNFR2-KO and wild-type mice were compared with TNFR1-KO mice. The inhalation of Z-VAD-FMK deteriorated M. avium infection compared with vehicle-inhaled controls. Overexpression of Iκ-B alpha by adenovirus vector attenuated M. avium infection. Our study showed apoptosis had an important role in innate immunity against M. avium in mice. The induction of apoptosis in M. avium-infected cells might be a new strategy to control M. avium infection.

Risk of Malignancy and Tuberculosis of Biological and Targeted Drug in Patients With Spondyloarthritis: Systematic Review and Meta-analysis of Randomized Controlled Trials

Objective: Concerns exist regarding the potential development of malignancy and tuberculosis in patients with spondyloarthritis (SpA) treated with biologics. We assessed the extent to which biologic therapy may increase the risk of malignancy and tuberculosis in patients with SpA by meta-analysis to derive estimates of sparse harmful events occurring in Randomized Controlled Trials (RCTs). Methods: A systematic literature search was conducted in PubMed, EMbase, Web of Science, the Cochrane Library, and China Biology Medicine disc for RCTs evaluating the risk of sparse harmful events of biologic therapy in patients with SpA from inception through August 9, 2021. We calculated a pooled Peto OR for malignancy and tuberculosis in biologics-treated patients vs. placebo patients. The risk of bias on the included RCTs was assessed by using Cochrane Risk of Bias tool. Results: In total, 63 studies were included in this meta-analysis, and 83 patients and 7 patients developed malignancy and tuberculosis, respectively. Overall, the risk of malignancy and tuberculosis was increased in SpA patients treated with biologics compared to placebo (malignancy: Peto OR: 2.49, 95%CI: 1.61-3.87, p < 0.001; tuberculosis: Peto OR: 5.98, 95%CI: 1.29-27.76, p = 0.022). Remarkably, compared to placebo, there was higher risk of malignancy for IL-17 inhibitors (Peto OR: 3.68, 95%CI: 1.20-11.30, p = 0.023) and small molecule targeted drugs (Peto OR: 3.08, 95%CI: 1.37-6.90, p = 0.043) in peripheral SpA, and for TNF receptor-Fc fusion protein in axial SpA (Peto OR: 7.18, 95%CI: 1.21-42.69, p = 0.030). Besides, the risk of tuberculosis was higher for anti-TNFα antibody in axial SpA (Peto OR: 6.17, 95%CI: 1.03-37.13, p = 0.046). Conclusion: This meta-analysis showed an elevated risk of malignancy in patients with peripheral SpA treated with biologics, especially for IL-17 inhibitors, and small molecule targeted drugs, a slightly increased risk of malignancy in TNF receptor-Fc fusion protein in axial SpA, and increased risk of tuberculosis in patients with axial SpA treated with anti-TNFα antibody. These findings need to be validated by studies with larger population and longer follow-up.

Infectious Complications of Biological and Small Molecule Targeted Immunomodulatory Therapies

The past 2 decades have seen a revolution in our approach to therapeutic immunosuppression. We have moved from relying on broadly active traditional medications, such as prednisolone or methotrexate, toward more specific agents that often target a single receptor, cytokine, or cell type, using monoclonal antibodies, fusion proteins, or targeted small molecules. This change has transformed the treatment of many conditions, including rheumatoid arthritis, cancers, asthma, and inflammatory bowel disease, but along with the benefits have come risks. Contrary to the hope that these more specific agents would have minimal and predictable infectious sequelae, infectious complications have emerged as a major stumbling block for many of these agents. Furthermore, the growing number and complexity of available biologic agents makes it difficult for clinicians to maintain current knowledge, and most review articles focus on a particular target disease or class of agent. In this article, we review the current state of knowledge about infectious complications of biologic and small molecule immunomodulatory agents, aiming to create a single resource relevant to a broad range of clinicians and researchers. For each of 19 classes of agent, we discuss the mechanism of action, the risk and types of infectious complications, and recommendations for prevention of infection.

A retrospective study on the risk of tuberculosis in patients with rheumatoid arthritis

Tuberculosis (TB) is an important preventable infection in patients with rheumatoid arthritis (RA). To determine the risk of TB in patients with RA by comparing with those with non-specific back pain (NSBP), and to identify the risk factors in the RA group. Medical data were retrieved from a centralized electronic database. A total of 1099 patients with RA and 2489 patients with NSBP were identified. Clinical data, comorbidities, and use of individual disease-modifying anti-rheumatic drugs (DMARDs) were retrieved. Risks of TB in patients with RA and NSBP were compared by propensity score (PS) adjusted analysis with known or potential risk factors for TB. Risk factors of TB were also determined in patients with RA. There were 14 cases of TB in RA group and 25 cases in NSBP group. Median duration of follow-up were 11.3 (0.1-21.9) years in RA group and 15.4 (0.1-24.4) years in NSBP group. The risk of TB in patients with RA was 2.53 times higher (HR 2.53; 95% CI 1.29, 4.94; p < 0.01) than in patients with NSBP. After excluding patients on DMARDs, the risk became similar (HR 2.72; 95% CI 0.81, 9.14; p = 0.11). Independent risk factors found were etanercept (HR 7.16; 95% CI 1.41, 36.30; p = 0.02), and previous TB infection (HR 25.23; 95% CI 6.99, 91.09; p < 0.001). The risk of extrapulmonary involvement between RA and NSBP groups was similar (HR 1.21; 95% CI 0.22, 6.57; p = 0.83). The risk of TB was increased in patients with RA. Anti-TNF therapy was an identified risk factor.

Predicting Human Infection Risk: Do Rodent Host Resistance Models Add Value?

Use of genetically engineered rodents is often considered a valuable exercise to assess potential safety concerns associated with the inhibition of a target pathway. When there are potential immunomodulatory risks associated with the target, these genetically modified animals are often challenged with various pathogens in an acute setting to determine the risk to humans. However, the applicability of the results from infection models is seldom assessed when significant retrospective human data become available. Thus, the purpose of the current review is to compare the outcomes of infectious pathogen challenge in mice with genetic deficiencies in TNF-α, IL17, IL23, or Janus kinase pathways with infectious outcomes caused by inhibitors of these pathways in humans. In general, mouse infection challenge models had modest utility for hazard identification and were generally only able to predict overall trends in infection risk. These models did not demonstrate significant value in evaluating specific types of pathogens that are either prevalent (ie rhinoviruses) or of significant concern (ie herpes zoster). Similarly, outcomes in mouse models tended to overestimate the severity of infection risk in human patients. Thus, there is an emerging need for more human-relevant models that have better predictive value. Large meta-analyses of multiple clinical trials or post-marketing evaluations remains the gold-standard for characterizing the true infection risk to patients.

The complexities and challenges of preventing and treating nontuberculous mycobacterial diseases

Seemingly innocuous nontuberculous mycobacteria (NTM) species, classified by their slow or rapid growth rates, can cause a wide range of illnesses, from skin ulceration to severe pulmonary and disseminated disease. Despite their worldwide prevalence and significant disease burden, NTM do not garner the same financial or research focus as Mycobacterium tuberculosis. In this review, we outline the most abundant of over 170 NTM species and inadequacies of diagnostics and treatments and weigh the advantages and disadvantages of currently available in vivo animal models of NTM. In order to effectively combat this group of mycobacteria, more research focused on appropriate animal models of infection, screening of chemotherapeutic compounds, and development of anti-NTM vaccines and diagnostics is urgently needed.

Humoral and Cellular Immune Response of European Seabass Dicentrarchus labrax Vaccinated with Heat-Killed Mycobacterium marinum (iipA::kan Mutant)

No vaccine is yet commercially available against Mycobacterium marinum, the etiological agent of fish mycobacteriosis (also known as "fish tuberculosis"). The mycobacterial gene responsible for invasion and intracellular persistence, iipA, is known to moderate M. marinum pathology in Zebrafish Danio rerio. Two doses of heat-killed, wild-type, virulent M. marinum and two doses of a heat-killed, avirulent M. marinum iipA::kan mutant strain were used in parallel to vaccinate European Seabass Dicentrarchus labrax. The fish were then challenged with live, virulent M. marinum, and the pathogenesis of the infection was monitored. High specific immunoglobulin M (IgM) response and an increase in cytokine tumor necrosis factor alpha (TNF-α) messenger RNA expression levels were observed in all vaccinated fish. At 1 month postchallenge, TNF-α expression levels increased in spleen tissues of fish vaccinated with the virulent type and in those of unvaccinated fish, whereas in the head kidney, expression was up-regulated only in unvaccinated fish. The expression then decreased, and at 2 months postchallenge, expression appeared similar in all vaccination types. The highest survival rate (75%) was recorded in the group of fish that were vaccinated with a high dose of avirulent iipA::kan mutant. The iipA::kan mutant induced a strong immune response accompanied by only modest tissue disruption. Coupled with an effective program of booster treatments, the iipA::kan mutant vaccine may be developed into a powerful preventive measure against fish mycobacteriosis.

Correlation between MBL2/CD14/TNF-α gene polymorphisms and susceptibility to spinal tuberculosis in Chinese population

Objective: The present study investigated the clinical significance of mannose-binding lectin 2 (MBL2), cluster of differentiation 14 (CD14) and tumour necrosis factor-α (TNF-α) gene polymorphisms in patients with spinal tuberculosis (TB) in Chinese population. Methods: A total of 240 patients with spinal TB were enrolled in the present study from May 2013 to August 2016 at Hangzhou Red Cross Hospital. A total of 150 age- and sex-matched healthy subjects were enrolled as controls. The genomic DNA was extracted from the peripheral blood of all subjects, and the MBL2, CD14 and TNF-α gene polymorphisms were detected by direct DNA sequencing. Results: (1) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the XY genotype at the −221G>C polymorphism as well as the Q allele and PQ genotype or an association with the QQ genotype at the +4C>T polymorphism in the MBL2 gene. (2) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the T allele and TT genotype or an association with the CT genotype at the −159C>T polymorphism in the CD14 gene. (3) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the T allele and the CT genotype or an association with the TT genotype at the TNF-857 polymorphism in the TNF-α gene. Conclusion: The −221G>C polymorphism of MBL2, the −159C>T polymorphism of CD14 and the TNF-857 polymorphism of TNF-α are risk factors for spinal TB and may be involved in the development of spinal TB in the Chinese population. These factors are indicators of susceptibility to spinal TB and require clinical attention.

Anti-mycobacterial function of macrophages is impaired in a diet induced model of type 2 diabetes

Type 2 diabetes (T2D) is one of the major risk factors for tuberculosis (TB). In this study, a diet induced murine model of T2D (DIMT2D) was developed and characterized in the context of metabolic, biochemical and histopathological features following diet intervention. Mycobacterial susceptibility was investigated using Mycobacterium fortuitum as a surrogate. Phagocytic capability of alveolar macrophages and resident peritoneal macrophages were determined by in vitro assays using mycolic acid coated beads and M. fortuitum. Results demonstrated that bacillary loads were significantly higher in liver, spleen, and lungs of diabetic mice compared to controls. Higher inflammatory lesions and impaired cytokine kinetics (TNF-α, MCP-1, IL-12, IFN-γ) were also observed in diabetic mice. Macrophages isolated from diabetic mice had lower uptake of mycolic acid coated beads, reduced bacterial internalization and killing and altered cytokine responses (TNF-α, IL-6, MCP-1). This model will be useful to further investigate different facets of host-pathogen interactions in TB-T2D.

Adventures within the speckled band: heterogeneity, angiogenesis, and balanced inflammation in the tuberculous granuloma

Recent work in a variety of animal models, including mice, zebrafish, and macaques, as well as in humans, has led to a reassessment of several tenets of mycobacterial infection. In this review, we describe new findings about the composition and dynamics of the tuberculous granuloma, the central host structure in mycobacterial infection, as well as inflammatory mediators that drive a successful anti-microbial response on one hand and pathological inflammation on the other. We highlight granuloma heterogeneity that emerges in the context of infection, the functional consequences of angiogenesis in tuberculous granulomas, and data that balanced inflammation in humans, with a central role for tumor necrosis factor, appears to play a key role in optimal defense against mycobacterial infection. These findings have suggested new and specific host-directed therapies that await further clinical exploration.

Treatment of severe non-infectious uveitis in high-risk conditions (Part 2): systemic infections; management and safety issues

INTRODUCTION

Management of patients with severe immune-mediated uveitis requires the use of immunosuppressive (IS) drugs in selected cases. This may be particularly challenging in certain patients with associated conditions, which may increase the risk of side effects or modify guidelines for the use of such drugs. Chronic viral and mycobacterial infections in the setting of non-infectious uveitis create a number of diagnostic but also therapeutic dilemmas to clinicians because they can be exacerbated by IS therapies with detrimental effects.

AREAS COVERED

In this review, we will focus on very specific chronic infections that can be affected by IS therapies: human immunodeficiency virus infection, chronic hepatitis virus infection and tuberculosis. The main aim of this review is to provide an updated and comprehensive practical guide for practitioners regarding the therapeutic decision-making and management of patients with non-infectious uveitis affected by the aforementioned infectious conditions.

EXPERT OPINION

Clinicians should be aware of the risk of viral and mycobacterial reactivation of an underlying infection during IS therapy. However, most of these conditions do not represent an absolute contraindication if one were able to apply an appropriate prior screening and close monitoring of such therapy.

IFN-γ/TNF-α ratio in response to immuno proteomically identified human T-cell antigens of Mycobacterium tuberculosis - The most suitable surrogate biomarker for latent TB infection

The enormous reservoir of latent TB infection (LTBI) poses a major hurdle for global TB control. The existing Tuberculin skin test (TST) and IFN-γ release assays (IGRAs) are found to be suboptimal for LTBI diagnosis. Previously we had taken an immunoproteomic approach and identified 10 protein fractions (contains 16 proteins), which are solely recognized by LTBI. In a cohort of 40 pulmonary TB patients (PTB) and 35 healthy household contacts (HHC), IFN-γ and TNF-α response were measured against 16 antigens by using 1:10 diluted whole blood assay. Among all the antigens, IFN-γ response to Rv2626c has shown positivity of 88.57% in HHC and 7.5% in PTB group. IFN-γ response to combination of Rv2626c + Rv3716c has demonstrated 100% positivity in HHC and 17.5% positivity in PTB respectively. Compared to individual cytokines (i.e. IFN-γ and TNF-α), ratio of IFN-γ/TNF-α has shown promising results for diagnosis of LTBI. IFN-γ/TNF-α ratio against Rv3716c and TrxC has exhibited a positivity of 94.29% in HHC and 5% in PTB group. Accession of Rv2626c and Rv3716c may improve the diagnostic performance of existing QFT-GIT. Independent of QFT-GIT assay, ratio of IFN-γ/TNF-α in response to either Rv3716c or TrxC may acts as suitable surrogate biomarker for LTBI.

Mycobacteria and autoimmunity

Mycobacterial infections can cause a variety of different manifestations. The increasing incidence of these infections worldwide brought another medical dilemma: immunological manifestations characterized by the presence of many autoantibodies and concomitant presence of autoimmune diseases. The burden of tuberculosis reactivation that emerged with immunosuppressive therapy worsened with the growing use of biological disease-modifying antirheumatic drugs (DMARDs). This review will address the relationship between the immune system and mycobacteria.

Host response to nontuberculous mycobacterial infections of current clinical importance

The nontuberculous mycobacteria are a large group of acid-fast bacteria that are very widely distributed in the environment. While Mycobacterium avium was once regarded as innocuous, its high frequency as a cause of disseminated disease in HIV-positive individuals illustrated its potential as a pathogen. Much more recently, there is growing evidence that the incidence of M. avium and related nontuberculous species is increasing in immunocompetent individuals. The same has been observed for M. abscessus infections, which are very difficult to treat; accordingly, this review focuses primarily on these two important pathogens. Like the host response to M. tuberculosis infections, the host response to these infections is of the TH1 type but there are some subtle and as-yet-unexplained differences.

Disseminated tuberculosis infection and paradoxical reaction during antimycobacterial treatment related to TNF-alpha blocker agent Infliximab

Tumor necrosis factor (TNF)-alpha inhibitors play an important role in the treatment of immun-mediated diseases such as Crohn's disease. But they also have been related to increased risk for disseminated Mycobacterium tuberculosis infections and paradoxical response to antimycobacterial treatment. Here we report a disseminated tuberculosis case and a paradoxical response to treatment after receiving TNF-inhibitor agent Infliximab for Crohn's disease. The patient had a severe clinical condition before the antimycobacterial treatment and although proper treatment was initiated his radiological findings were worsened one month after initiation of the treatment. All control microbologic tests for secondary infections were negative and this situation was accepted as a paradoxical response to antimycobacterial treatment and treatment was continued with the same regimen. At the end of the second month of the treatment, most of the symptoms disappeared and chest radiograph findings were better than the previous one. In conclusion, TNF-alpha inhibitor therapy increases risk of mycobacterial infections and patients should be examined carefully about tuberculosis before starting this therapy. Also, it is important for physicians to recognize and know how to manage paradoxical response related to TNF-alpha inhibitors during anti-tuberculosis treatment.

Dynamics of immune effector mechanisms during infection with Mycobacterium avium in C57BL/6 mice

Opportunistic infections with non-tuberculous mycobacteria such as Mycobacterium avium are receiving renewed attention because of increased incidence and difficulties in treatment. As for other mycobacterial infections, a still poorly understood collaboration of different immune effector mechanisms is required to confer protective immunity. Here we have characterized the interplay of innate and adaptive immune effector mechanisms contributing to containment in a mouse infection model using virulent M. avium strain 104 in C57BL/6 mice. M. avium caused chronic infection in mice, as shown by sustained organ bacterial load. In the liver, bacteria were contained in granuloma-like structures that could be defined morphologically by expression of the antibacterial innate effector protein Lipocalin 2 in the adjoining hepatocytes and infiltrating neutrophils, possibly contributing to containment. Circulatory anti-mycobacterial antibodies steadily increased throughout infection and were primarily of the IgM isotype. Highest levels of interferon-γ were found in infected liver, spleen and serum of mice approximately 2 weeks post infection and coincided with a halt in organ bacterial growth. In contrast, expression of tumour necrosis factor was surprisingly low in spleen compared with liver. We did not detect interleukin-17 in infected organs or M. avium-specific T helper 17 cells, suggesting a minor role for T helper 17 cells in this model. A transient and relative decrease in regulatory T cell numbers was seen in spleens. This detailed characterization of M. avium infection in C57BL/6 mice may provide a basis for future studies aimed at gaining better insight into mechanisms leading to containment of infections with non-tuberculous mycobacteria.

Toll-like receptor 6 senses Mycobacterium avium and is required for efficient control of mycobacterial infection

Mycobacterium avium has been reported to signal through both Toll-like receptor (TLR2) and TLR9. To investigate the role of TLR6 in innate immune responses to M. avium, TLR6, MyD88, TLR2, and TLR2/6 KO mice were infected with this pathogen. Bacterial burdens were higher in the lungs and livers of infected TLR6, TLR2, TLR2/6, and MyD88 KO mice compared with those in C57BL/6 mice, which indicates that TLR6 is required for the efficient control of M. avium infection. However, TLR6 KO spleen cells presented with normal M. avium induced IFN-γ responses as measured by ELISA and flow cytometry. In contrast, the production of IFN-γ in lung tissue was diminished in all studied KO mice. Furthermore, only MyD88 deficiency reduced granuloma areas in mouse livers. Moreover, we determined that TLR6 plays an important role in controlling bacterial growth within macrophages and in the production of TNF-α, IL-12, and IL-6 by M. avium infected DCs. Finally, the lack of TLR6 reduced activation of MAPKs and NF-κB in DCs. In summary, TLR6 is required for full resistance to M. avium and for the activation of DCs to produce proinflammatory cytokines.

DNA polymorphism of Mycobacterium tuberculosis PE_PGRS33 gene among clinical isolates of pediatric TB patients and its associations with clinical presentation

In vitro and in animal studies have suggested an important role for the Mycobacterium tuberculosis PE_PGRS33 protein in the pathogenesis of TB. A significant level of PE_PGRS33 gene DNA polymorphism among clinical isolates from adult tuberculosis (TB) patients and its association with clinical and epidemiological phenotypes of the disease has been found. To better understand the role of PE_PGRS33 protein in the pathogenesis pediatric TB, we investigated DNA polymorphism of the PE_PGRS33 gene among 101 of pediatric TB patients' isolates and assessed the relationship between the PE_PGRS33 sequence variation and clinical characteristics of TB. Twelve different PE_PGRS33 sequence variations representing 12 different alleles were observed among the 101 M. tuberculosis clinical isolates investigated. Of these 101 isolates, 62(59.41%) had PE_PGRS33 alleles that would result in a change in the amino acid sequence of the PE_PGRS33 protein. The degree of DNA polymorphism within individual M. tuberculosis isolates from pediatric TB patients was remarkably lower than that previously found in M. tuberculosis isolates from adults TB patients. The frequency distribution of isolates having PE_PGRS33 gene sequence variations was similar between Beijing and non-Beijing families of the pathogen. Patients having TB meningitis and negative PPD skin test results appeared to be more likely to be infected by isolates having a mutant type of the PE_PGRS33 gene than patients who had no TB meningitis (OR 2.54, 95% CI [1.11-5.84]) and patients who had positive PPD-skin test results (OR 4.26, 95% CI [1.14-12.86]), respectively. This study provides new insight into the molecular pathogenesis of pediatric TB.

Human leucocyte antigens and cytokine gene polymorphisms and tuberculosis

PURPOSE

Several genes encoding different cytokines and human leucocyte antigens (HLA) may play crucial roles in host susceptibility to tuberculosis (TB). Our objective was to investigate whether these genes might be associated with protection from or susceptibility to TB.

MATERIALS AND METHODS

Genomic DNA from patients with TB (n = 30) and ethnically matched controls (n = 30) was genotyped by using sequence-specific primers-polymerase chain reaction and sequence-specific oligonucletid methods.

RESULTS

Our results demonstrated that HLA-CwFNx0101 [P = 0.05, odds ration (OR) (95% confidence interval) = 2.269 (1.702-3.027)] allele frequency was significantly more common in TB patients than in healthy controls, and HLA-CwFNx0101 may be associated with susceptibility to TB. Analysis of cytokine allele frequencies showed that interleukin (IL)-10, -819 C and -592 C alleles was significantly more common in TB patients than in controls (pc: 0.038 and 0.017, respectively). From the IL-10 cluster, a positive significant difference was found at positions -1082 and -592 C/C (pc: 0.027 and 0.054, respectively) genotypes. Although these differences could be explained by the highest frequency of C/C and G/G homozygous patients with TB, in contrast to the control group, statistically significant differences for the C/C genotype however were lost after Bonferroni correction of the P-values.

CONCLUSION

Altogether, our results suggest that the polymorphisms in HLA (class I) and cytokine (IL-10) genes may affect the susceptibility to TB and increase the risk of developing the disease.

Mitogen-activated protein kinases p38 and ERK1/2 regulated control of Mycobacterium avium replication in primary murine macrophages is independent of tumor necrosis factor-α and interleukin-10

In macrophages, mitogen-activated protein kinases (MAPK) are critical regulators of both, mycobacterial replication and mycobacteria-induced cytokine formation. To segregate direct effects of MAPK function on mycobacterial replication from indirect, cytokine-mediated effects, we studied the growth of Mycobacterium avium strains in wild-type and tumor necrosis factor (TNF)-α- or interleukin (IL)-10-deficient bone marrow-derived murine macrophages. Using specific inhibitors of the p38- and the ERK1/2-MAPK pathways, we found that the use of SB203580 always reduced, whereas the presence of PD98059 always promoted, bacterial replication of highly virulent and intermediately virulent M. avium strains, independent of endogenous TNF-α or IL-10. The exogenous addition of TNF-α to TNF-α-deficient and wild-type M. avium-infected macrophages overrode the replication-reducing effect of SB203580, but not the replication-promoting effect of PD98059. In summary, our data demonstrate that a proper balance of MAPK activity is essential for macrophage control of M. avium growth, and that the ratio of the cytokines TNF-α and IL-10 can additionally modulate replication. Our findings indicate a novel therapeutic avenue for treating mycobacterial infections in particular by stimulating ERK1/2 or activating ERK1/2-dependent mechanisms in infected macrophages.

Genetic susceptibility in tuberculosis

The importance of host genetic factors in determining susceptibility to tuberculosis (TB) has been studied extensively using various methods, such as case-control, candidate gene and genome-wide linkage studies. Several important candidate genes like human leucocyte antigen/alleles and non-human leucocyte antigen genes, such as cytokines and their receptors, chemokines and their receptors, pattern recognition receptors (including toll-like receptors, mannose binding lectin and the dendritic cell-specific intercellular adhesion molecule-3 grabbing nonintegrin), solute carrier family 11A member 1 (formerly known as natural resistance-associated macrophage protein 1) and purinergic P2X7 receptor gene polymorphisms, have been associated with differential susceptibility to TB in various ethnic populations. This heterogeneity has been explained by host-pathogen and gene-environment interactions and evolutionary selection pressures. Although the achievements of genetics studies might not yet have advanced the prevention and treatment of TB, researchers have begun to widen their scope of investigation to encompass these practical considerations.

Innate immune defense in visceral leishmaniasis: cytokine mediated protective role by allogeneic effector cell

Antileishmanial role of mouse splenic natural killer (NK) cell was studied in allogeneic condition. In vitro data indicates that NK cells of allogeneic (C57BL/6, H2(b)) non-leishmania exposed mouse have strong antileishmanial effect against Leishmania donovani infected BALB/c (H2(d)) macrophages. Physical contact between the effector (NK cell) and the target cells (infected macrophages) is essential in this system since; cell free supernatant generated after coculturing of effector cells with infected target cells fails to elicit any antileishmanial effect. Although NK cells from allogeneic mouse are strongly attached to the infected macrophages but unable to kill it in such interaction. The antileishmanial effect of allogeneic NK cells is mediated by TNF-alpha and not by IFN-gamma. In vivo cellular therapy of established infection with NK cells from non-leishmania exposed allogeneic mouse significantly reduces the total parasite burden in the spleen of infected animal.

Latent infection and tuberculosis disease in rheumatoid arthritis patients

New drug classes, biologics, have been developed over the past 10 years based on human or chimeric antibodies against cytokines or receptors with pivotal roles in the inflammatory pathways of immune-mediated inflammatory disease. Anti-tumor necrosis factor agents carry the largest infection risk of all the biologics, predisposing patients to mycobacterial infections. Patients receiving biologics are at higher risk for developing tuberculosis. New cases of tuberculosis or reactivation of latent tuberculosis infections may occur during the course of treatment, so a high level of vigilance is highly recommended.

Decomposing health: tolerance and resistance to parasites in animals

Plant biologists have long recognized that host defence against parasites and pathogens can be divided into two conceptually different components: the ability to limit parasite burden (resistance) and the ability to limit the harm caused by a given burden (tolerance). Together these two components determine how well a host is protected against the effects of parasitism. This distinction is useful because it recognizes that hosts that are best at controlling parasite burdens are not necessarily the healthiest. Moreover, resistance and tolerance can be expected to have different effects on the epidemiology of infectious diseases and host-parasite coevolution. However, studies of defence in animals have to date focused on resistance, whereas the possibility of tolerance and its implications have been largely overlooked. The aim of our review is to (i) describe the statistical framework for analysis of tolerance developed in plant science and how this can be applied to animals, (ii) review evidence of genetic and environmental variation for tolerance in animals, and studies indicating which mechanisms could contribute to this variation, and (iii) outline avenues for future research on this topic.

Experimental tuberculosis: the role of comparative pathology in the discovery of improved tuberculosis treatment strategies

The use of laboratory animals is critical to the discovery and in vivo pre-clinical testing of new drugs and drug combinations for use in humans. M. tuberculosis infection of mice, rats, guinea pigs, rabbits and non-human primates are the most commonly used animal models of human tuberculosis. While granulomatous inflammation characterizes the most fundamental host response to M. tuberculosis aerosol infection in humans and animals, there are important species differences in pulmonary and extra-pulmonary lesion morphology which may influence responses to drug therapy. Lesions that progress to necrosis or cavitation are common, unfavorable host responses in naturally occurring tuberculosis of humans, but are not seen consistently in experimental infections in most animal model species. The importance of these unique lesion morphologies is that they represent irreversible tissue damage that can harbor persistent bacilli which are difficult to treat with standard therapies. Understanding the differences in host response to experimental tuberculosis infections may aid in selecting the most appropriate animal models to test drugs that have been rationally designed to have specific mechanisms of action in vivo. A better understanding of lesion pathogenesis across species may also aid in the identification of novel therapeutic targets or strategies that can be used alone or in combination with more conventional tuberculosis treatments in humans.

Tumor necrosis factor signaling mediates resistance to mycobacteria by inhibiting bacterial growth and macrophage death

Tumor necrosis factor (TNF), a key effector in controlling tuberculosis, is thought to exert protection by directing formation of granulomas, organized aggregates of macrophages and other immune cells. Loss of TNF signaling causes progression of tuberculosis in humans, and the increased mortality of Mycobacterium tuberculosis-infected mice is associated with disorganized necrotic granulomas, although the precise roles of TNF signaling preceding this endpoint remain undefined. We monitored transparent Mycobacterium marinum-infected zebrafish live to conduct a stepwise dissection of how TNF signaling operates in mycobacterial pathogenesis. We found that loss of TNF signaling caused increased mortality even when only innate immunity was operant. In the absence of TNF, intracellular bacterial growth and granuloma formation were accelerated and was followed by necrotic death of overladen macrophages and granuloma breakdown. Thus, TNF is not required for tuberculous granuloma formation, but maintains granuloma integrity indirectly by restricting mycobacterial growth within macrophages and preventing their necrosis.

Characterization of the deregulated immune activation occurring at late stages of mycobacterial infection in TNF-deficient mice

In the absence of TNF, mice infected with Mycobacterium avium suffer a peculiar disintegration of the granulomas, with extensive apoptosis and necrosis of their cells, occurring during the course of the infection and leading to the death of the animals within a few days of its onset. The survival time depends on the virulence of the infecting strain as well as on the dose and route of infection. Intravenously infected mice developed the typical lesions in hepatic granulomas whereas aerosol-infected animals developed them in the lung granulomas. At the onset of the development of pulmonary granuloma disintegration, extensive expansion of T cells, with intense up-regulation of activation markers, massive exacerbation of their ability to secrete IFN-gamma, and increased cytotoxic activity of both CD4(+) and CD8(+) T cells were observed. Forced expression of Bcl2 did not prevent the early death of infected TNF-deficient mice leading merely to a modest increase in survival times. The expression of the FasL on T cells was not affected but there was an intense up-regulation of the TRAIL in T cells and, in particular, myeloid cells. We thus show that an exacerbated immune response occurs in TNF-deficient hosts during M. avium infections that leads to enhanced IFN-gamma production and late up-regulation of TRAIL which may contribute to granuloma disintegration.

Decreased cytokine production in patients with nontuberculous mycobacterial lung disease

Nontuberculous mycobacteria (NTM) are intracellular pathogens that elicit a specific T-cell response characterized by the production of proinflammatory cytokines, including interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-12. However, little information exists regarding the levels of specific cytokines in patients with NTM lung disease. Therefore, we compared cytokine production in peripheral blood mononuclear cells (PBMCs) from patients with NTM lung disease with that in PBMCs from healthy controls. Pro- and anti-inflammatory cytokine production was measured by enzyme-linked immunosorbent assay in the PBMCs of 29 patients with NTM lung disease and 15 healthy controls. Phytohemagglutinin (PHA)-induced IFN-gamma production and lipopolysaccharide (LPS)-induced production of TNF-alpha and IL-12p40 were significantly lower in the PBMCs of patients with NTM lung disease than in those of the healthy controls. The production of these cytokines did not differ significantly between patients infected with Mycobacterium avium complex (MAC) and those infected with Mycobacterium abscessus; however, IL-10 production was lower in patients infected with M. abscessus than in those infected with MAC. Decreased IFN-gamma, TNF-alpha, and IL-12 production may be associated with host susceptibility to the development of MAC and M. abscessus lung disease.

Importance of T cells, gamma interferon, and tumor necrosis factor in immune control of the rapid grower Mycobacterium abscessus in C57BL/6 mice

Mycobacterium abscessus is an emerging rapidly growing mycobacterium that causes tuberculous-like lesions in humans. We studied the immune control of this organism in C57BL/6 mice challenged intravenously with 10(7) CFU. Bacteria were eliminated from both the spleen and the liver within 90 days, and liver histology showed organized granulomatous lesions. A T- and B-cell requirement was investigated by challenging Rag2-/-, Cd3epsilon-/-, and muMT-/- mice. Rag2-/- and Cd3epsilon-/- mice were significantly impaired in the ability to clear M. abscessus from the liver and spleen, and muMT-/- mice were significantly impaired in the ability to clear M. abscessus from the liver, suggesting that infection control was primarily T cell dependent in the spleen and both T and B cell dependent in the liver. The liver granulomatous response was similar to that of wild-type controls in muMT-/- mice but completely absent in Cd3epsilon-/- and Rag2-/- mice. We studied the involvement of gamma interferon (IFN-gamma) and tumor necrosis factor (TNF) by challenging C57BL/6 mice deficient in the IFN-gamma receptor (Ifngr1-/-) and in TNF (Tnf-/-). Ifngr1-/- mice were significantly impaired in M. abscessus control both in the spleen and in the liver, and granulomas were profoundly altered. The effect was even more substantial in Tnf-/- mice; they failed to control M. abscessus infection in the liver and died within 20 to 25 days after infection with many hepatic inflammatory foci and major lesions of ischemic necrosis in the liver and kidney. These features were not observed with the closely related species M. chelonae. T-cell immunity, IFN-gamma, and TNF are central factors for the control of M. abscessus in C57BL/6 mice, as they are for the control of pathogenic slowly growing mycobacteria.

Polymorphisms of interleukin-10 and tumour necrosis factor-? genes are associated with newly diagnosed and recurrent pulmonary tuberculosis

BACKGROUND AND OBJECTIVES

The genetic determinants for developing TB or having recurrent TB are unknown. The present study investigated the relationship between susceptibility to tuberculosis and human tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 genes (IL-10).

METHODS

A case-control study was conducted using two groups of cases--newly diagnosed TB (N-TB) and recurrent TB (R-TB)--and a control group.

RESULTS

One hundred and seventeen healthy controls, 80 newly diagnosed TB patients and 65 patients with recurrent TB were enrolled. There was no significant difference in the TNF-alpha-308 G/A genotype between the TB patient groups and the controls. The IL-10 -1082A alleles were markedly over-represented among the TB patient groups compared with the control subjects, however, there was no significant difference in the IL-10 genotype frequency between the N-TB and R-TB patient groups.

CONCLUSION

The -1082A allele of the IL-10 gene may be important in determining susceptibility to TB, however, the -308 allele of the TNF-alpha gene does not affect differential TB susceptibility.

Mycolactone-mediated inhibition of tumor necrosis factor production by macrophages infected with Mycobacterium ulcerans has implications for the control of infection

The pathogenicity of Mycobacterium ulcerans, the agent of Buruli ulcer, depends on the cytotoxic exotoxin mycolactone. Little is known about the immune response to this pathogen. Following the demonstration of an intracellular growth phase in the life cycle of M. ulcerans, we investigated the production of tumor necrosis factor (TNF) induced by intramacrophage bacilli of diverse toxigenesis/virulence, as well as the biological relevance of TNF during M. ulcerans experimental infections. Our data show that murine bone marrow-derived macrophages infected with mycolactone-negative strains of M. ulcerans (nonvirulent) produce high amounts of TNF, while macrophages infected with mycolactone-positive strains of intermediate or high virulence produce intermediate or low amounts of TNF, respectively. These results are in accordance with the finding that TNF receptor P55-deficient (TNF-P55 KO) mice are not more susceptible than wild-type mice to infection by the highly virulent strains but are more susceptible to nonvirulent and intermediately virulent strains, demonstrating that TNF is required to control the proliferation of these strains in animals experimentally infected by M. ulcerans. We also show that mycolactone produced by intramacrophage M. ulcerans bacilli inhibits, in a dose-dependent manner, but does not abrogate, the production of macrophage inflammatory protein 2, which is consistent with the persistent inflammatory responses observed in experimentally infected mice.

Interleukin-18 and the pathogenesis of inflammatory diseases

Several autoimmune diseases are thought to be mediated in part by interleukin (IL)-18. Many are those with associated increased interferon-gamma (IFNgamma) levels such as systemic lupus erythematosus, macrophage activation syndrome, rheumatoid arthritis, Crohn's disease, psoriasis, and graft-versus-host disease. In addition, ischemia, including acute renal failure in human beings, appears to involve IL-18. Animal studies also support the concept that IL-18 is a key player in models of lupus erythematosus, atherosclerosis, graft-versus-host disease, and hepatitis. Unexpectedly, IL-18 plays a role in appetite control and the development of obesity. IL-18 is a member of the IL-1 family; IL-1beta and IL-18 are related closely, and both require the intracellular cysteine protease caspase-1 for biological activity. The IL-18 binding protein, a naturally occurring and specific inhibitor of IL-18, neutralizes IL-18 activities and has been shown to be safe in patients. Other options for reducing IL-18 activities are inhibitors of caspase-1, human monoclonal antibodies to IL-18, soluble IL-18 receptors, and anti-IL-18 receptor monoclonal antibodies.

Pathogenesis of Mycobacterium avium infection: typical responses to an atypical mycobacterium?

Studying infections with Mycobacterium avium in mouse models has allowed the dissection of the antimycobacterial pathways of the mammalian host. Whereas the paradigm of cell-mediated immunity to intracellular pathogens has been confirmed, namely with regard to the pivotal roles of CD4+ T cells, macrophages, and the IL12-IFNgamma cytokine axis, atypical features have been uncovered such as the resistance to NO, the involvement of minor players in the induction of type 1 protective immunity (such as TLR2, CD40, and CD30), and the development of immunopathology during the infection with highly virulent strains such as the development of caseous necrosis of granulomas or the progressive emergence of severe lymphopenia.

Microarray analysis of gene expression associated with extrapulmonary dissemination of tuberculosis

OBJECTIVE

Although extrapulmonary organs are involved in 20% of patients with tuberculosis, the host genetic factors associated with the extrapulmonary dissemination of tuberculosis are not yet known. The aim of this study was to identify the host genetic factors associated with the extrapulmonary dissemination of tuberculosis by comparing gene expression profiles of patients who had recovered from extrapulmonary tuberculosis and those who had recovered from pulmonary tuberculosis.

METHODS

Five patients from each group were enrolled. Total RNA was extracted from peripheral blood mononuclear cells that had been incubated for 48 h with whole lysate of Mycobacterium tuberculosis (H37Rv, 0.5 microg/mL). Gene expression profiles were acquired using the GeneChip array and its applied systems. Gene expression profiles from five patients with previous extrapulmonary tuberculosis and one pooled control sample from five patients with previous pulmonary tuberculosis were analysed and compared. Genes that were expressed concordantly in more than 80% of arrays and that showed more than twofold changes in at least one array among samples from patients who had recovered from extrapulmonary tuberculosis were identified.

RESULTS

Compared with the control sample, the expression of 16 genes, including those for tumour necrosis factor (TNF)-alpha and cathepsin W, was increased, and the expression of 45 genes including that for TNF-receptor superfamily member 7 (TNFRSF7), was decreased in the extrapulmonary tuberculosis patients. The altered expression of the TNF-alpha, cathepsin W and TNFRSF7 genes was confirmed by quantitative RT-PCR.

CONCLUSIONS

Altered expression of the genes for TNF-alpha, cathepsin W and TNFRSF7 may be risk factors for the extrapulmonary dissemination of tuberculosis in humans.

Hypervirulence of a rough variant of the Mycobacterium abscessus type strain

We isolated a rough variant of Mycobacterium abscessus CIP 104536T during experimental infection of mice. We show that this variant has lost the ability to produce glycopeptidolipids, is hyperlethal for C57BL/6 mice infected intravenously, and induces a strong tumor necrosis factor-alpha response by murine monocyte-derived macrophages.

Impact of Biologic Agents on Infectious Diseases

Until recently, inflammatory diseases, collagen vascular diseases, inflammatory bowel diseases, and multiple sclerosis were met with a limited offering for treatment. The introduction of biologic agents has revolutionized the approach to these diseases, offering many patients freedom from disease activity staving off resultant destruction to organs and joints with marked improvement in quality of life and disability. This article focuses on the development of serious infections associated with the use of biologic agents. Presented is a synthesis of case series, reports, and systematic reviews to elucidate implicated pathogens and clinical presentations in patients being treated with biologic agents and to form a cursory backbone for prevention and treatment strategies to which clinicians prescribing these agents or encountering patients already on these agents can readily refer. Maintenance of a high index of suspicion is imperative for the prevention and appropriate treatment of serious life-threatening infections in these patients.

Execution of macrophage apoptosis by PE_PGRS33 of Mycobacterium tuberculosis is mediated by Toll-like receptor 2-dependent release of tumor necrosis factor-alpha

Combating tuberculosis requires a detailed understanding of how mycobacterial effectors modulate the host immune response. The role of the multigene PE family of proteins unique to mycobacteria in the pathogenesis of tuberculosis is still poorly understood, although certain PE_PGRS genes have been linked to virulence. Tumor necrosis factor-alpha (TNF-alpha) is essential for successfully combating tuberculosis. In this study we provide evidence that PE_PGRS33, a surface exposed protein, elicits TNF-alpha release from macrophages in a TLR2 (Toll-like receptor 2)-dependent manner. ASK1 (apoptosis signal-regulating kinase 1) is activated downstream of TLR2. ASK1 activates the MAPKs p38 and JNK. PE_PGRS33-induced signaling leads to enhanced expression of TNF-alpha and TNF receptor I (TNFRI) genes. Mycobacterium smegmatis expressing PE_ PGRS33 elicits the same effects as purified PE_PGRS33. TNF-alpha release occurs even when internalization of the bacteria is blocked by cytochalasin D, suggesting that interaction of PE_ PGRS33 with TLR2 is sufficient to trigger the effects described. Release of TNF-alpha plays the determining role in triggering apoptosis in macrophages challenged with PE_PGRS33. The death receptor-dependent signals are amplified through classical caspase 8-dependent mitochondrial release of cytochrome c, leading to the activation of caspases 9 and 3. An important aspect of our findings is that deletions within the PGRS domain (simulating those occurring in clinical strains) attenuate the TNF-alpha-inducing ability of PE_PGRS33. These results provide the first evidence that variations in the polymorphic repeats of the PGRS domain modulate the innate immune response.

Genetic control of immune-mediated necrosis of Mycobacterium avium granulomas

Intravenous infection of C57BL/6 and C57BL/10 mice with low doses of a highly virulent strain of Mycobacterium avium (ATCC 25291) led to the development of granulomas that underwent necrosis. In contrast, neither BALB/c nor DBA/1 mice developed granuloma necrosis after such infection despite a similar course of mycobacterial proliferation. Studies with C57BL/10 mice congenic for the Hc locus revealed that an intact complement C5 gene is required for granuloma necrosis. On the other hand, genetic disruption of the interleukin-10 gene in BALB/c mice made this strain susceptible to granuloma necrosis.

Lung Disease Due to the More Common Nontuberculous Mycobacteria

As the prevalence of tuberculosis (TB) declines in the developed world, the proportion of mycobacterial lung disease due to nontuberculous mycobacteria (NTM) is increasing. It is not clear whether there is a real increase in prevalence or whether NTM disease is being recognized more often because of the introduction of more sensitive laboratory techniques, and that more specimens are being submitted for mycobacterial staining and culture as the result of a greater understanding of the role of NTM in conditions such as cystic fibrosis, posttransplantation and other forms of iatrogenic immunosuppression, immune reconstitution inflammatory syndrome, fibronodular bronchiectasis, and hypersensitivity pneumonitis. The introduction of BACTEC liquid culture systems (BD; Franklin Lakes, NJ) and the development of nucleic acid amplification and DNA probes allow more rapid diagnosis of mycobacterial disease and the quicker differentiation of NTM from TB isolates. High-performance liquid chromatography, polymerase chain reaction, and restriction fragment length polymorphism analysis have helped to identify new NTM species. Although treatment regimens that include the newer macrolides are more effective than the earlier regimens, failure rates are still too high and relapse may occur after apparently successful therapy. Moreover, treatment regimens are difficult to adhere to because of their long duration, adverse effects, and interactions with the other medications that these patients require. The purpose of this article is to review the common presentations of NTM lung disease, the conditions associated with NTM lung disease, and the clinical features and treatment of the NTM that most commonly cause lung disease.

Immunological control of tuberculosis: role of tumour necrosis factor and more

Therapy of autoimmune diseases with tumour necrosis factor (TNF) neutralising agents has provided a unique opportunity to learn about the significance of TNF in the maintenance of latent bacterial infections in humans. The remarkably high incidence of tuberculosis in patients treated with TNF antagonists raises the intriguing question about the physiological role of TNF in maintaining the lifelong latency of tubercle bacilli in granulomas in infected patients. Basic research during the past decade(s) combined with thoughtful observations in human subjects with tuberculosis and autoimmune diseases has provided several potential explanations for the recurrence of tuberculosis if TNF supply is withdrawn. TNF is involved in at least four key functions that contribute towards beneficial effects on the symptoms of autoimmune disorders on the one hand, and the attenuation of immune responses against Mycobacterium tuberculosis on the other hand. These are outlined in this review: induction of apoptosis, maturation of dendritic cells, activation of antimicrobial activity in macrophages, and orchestration of leucocyte movement.

Mycobacterium abscessus infection after use of tumor necrosis factor α inhibitor therapy: case report and review of infectious complications associated with tumor necrosis factor α inhibitor use

Tumor necrosis factor alpha (TNF-alpha) inhibitors, such as infliximab and etanercept, are now frequently used in the treatment of inflammatory diseases including rheumatoid arthritis (RA) and Crohn's disease. As an apparent result of their immune modulating activity, there has been an observed association between the use of these agents and the development of a wide range of infections, most notably Mycobacterium tuberculosis. We describe a case of infection with Mycobacterium abscessus in a 67-year-old woman receiving infliximab as a component of her therapy for RA. This case, along with extensive reports in the medical literature, illustrate how treatment with inhibitors of TNF-alpha has the potential to result in a wide range of infectious complications, including rapid growing Mycobacterium.