Innate immune recognition in tuberculosis infection

Association Between Plasma Exosomes S100A9/C4BPA and Latent Tuberculosis Infection Treatment: Proteomic Analysis Based on a Randomized Controlled Study

Background

Identifying host plasma exosome proteins associated with host response to latent tuberculosis infection (LTBI) treatment might promote our understanding of tuberculosis (TB) pathogenesis and provide useful tools for implementing the precise intervention.

Methods

Based on an open-label randomized controlled trial (RCT) aiming to evaluate the short-course regimens for LTBI treatment, plasma exosomes from pre- and post-LTBI treatment were retrospectively detected by label-free quantitative protein mass spectrometry and validated by a parallel reaction monitoring method for participants with changed or not changed infection testing results after LTBI treatment. Eligible participants for both screening and verification sets were randomly selected from the based-RCT in a 1:1 ratio by age and gender. Reversion was defined as a decrease in IFN-γ levels from >0.70 IU/ml prior to treatment to 0.20 IU/ml within 1 week of treatment. The predictive ability of the candidate proteins was evaluated by receiver operating characteristic (ROC) analysis.

Results

Totally, two sample sets for screening (n = 40) and validation (n = 60) were included. Each of them included an equal number of subjects with persistent positive or reversed QuantiFERON-TB Gold In-Tube (QFT) results after LTBI. A total of 2,321 exosome proteins were detected and 102 differentially expressed proteins were identified to be associated with QFT reversion. Proteins with high confidence and original values intact were selected to be further verified. Totally, 9 downregulated proteins met the criteria and were validated. After verification, C4BPA and S100A9 were confirmed to be still significantly downregulated (fold change <0.67, p < 0.05). The respective areas under the ROC curve were 0.73 (95% CI: 0.57–0.89) and 0.69 (95% CI: 0.52–0.86) for C4BPA and S100A9, with a combined value of 0.78 (95% CI: 0.63–0.93). The positive and negative predictive values for combined markers were 70.10% (95% CI: 50.22–86.30%) and 55.63% (95% CI: 29.17–61.00%).

Conclusion

Our findings suggest that downregulated C4BPA and S100A9 in plasma exosomes might be associated with a host positive response to LTBI treatment. Further studies are warranted to verify the findings and potential underlying mechanisms in varied populations with a larger sample size.

Gene expression tryptophan aspartate coat protein in determining latent tuberculosis infection using immunocytochemistry and real time polimerase chain reaction

Background

Tuberculosis (TB) remains a major cause of morbidity and mortality worldwide. Problem of Latent Tuberculosis Infection (LTBI) is increasing in number especially in countries with high TB incidence rate, such as Indonesia. Although not every LTBI will become active TB, if untreated and not handled appropriately it can still be a source of transmission and may increase the rate of resistance to the first-line TB drugs. Mycobacterium tuberculosis as a cause of tuberculosis disease is an intracellular pathogens that survives within the phagosome of host macrophages. Several host factors are involved in this process, including the Tryptophan Aspartate-containing Coat Protein (TACO). TACO is a protein recruited and retained by viable Mycobacterium tuberculosis on the surface of the phagosome membrane to maintain its survival in phagosome, because the presence of TACO plays an important role in inhibiting the fusion of phagosomes and lysosomes.

Objective

the aim of this studyis to assess the difference of gene expression TACO protein in Latent Tuberculosis Infection (LTBI) and healthy people.

Method

A preliminary studyof mRNA examination of TACO protein using Immunocytochemistry (ICC) and Real Time-Polimerase Chain Reaction (RT-PCR) method by a PCR Light Cycler 2.0 machine (Roche) in LTBI and healthy groups.

Results

18 samples of peripheral blood monocyte cells (PBMCs) were collected and divided into 2 groups. We found that there was a significantly difference between the 2 groups of samples.

Conclusion

Further research is required to consider that the measurement of TACO expression using RT-PCRcan used as one of the other method to determine LTBI.

Human Properdin Modulates Macrophage: Mycobacterium bovis BCG Interaction via Thrombospondin Repeats 4 and 5

Mycobacterium tuberculosis can proficiently enter macrophages and diminish complement activation on its cell surface. Within macrophages, the mycobacterium can suppress macrophage apoptosis and survive within the intracellular environment. Previously, we have shown that complement regulatory proteins such as factor H may interfere with pathogen–macrophage interactions during tuberculosis infection. In this study, we show that Mycobacterium bovis BCG binds properdin, an upregulator of the complement alternative pathway. TSR4+5, a recombinant form of thrombospondin repeats 4 and 5 of human properdin expressed in tandem, which is an inhibitor of the alternative pathway, was also able to bind to M. bovis BCG. Properdin and TSR4+5 were found to inhibit uptake of M. bovis BCG by THP-1 macrophage cells in a dose-dependent manner. Quantitative real-time PCR revealed elevated pro-inflammatory responses (TNF-α, IL-1β, and IL-6) in the presence of properdin or TSR4+5, which gradually decreased over 6 h. Correspondingly, anti-inflammatory responses (IL-10 and TGF-β) showed suppressed levels of expression in the presence of properdin, which gradually increased over 6 h. Multiplex cytokine array analysis also revealed that properdin and TSR4+5 significantly enhanced the pro-inflammatory response (TNF-α, IL-1β, and IL-1α) at 24 h, which declined at 48 h, whereas the anti-inflammatory response (IL-10) was suppressed. Our results suggest that properdin may interfere with mycobacterial entry into macrophages via TSR4 and TSR5, particularly during the initial stages of infection, thus affecting the extracellular survival of the pathogen. This study offers novel insights into the non-complement related functions of properdin during host–pathogen interactions in tuberculosis.

Evasion of Innate and Adaptive Immunity by Mycobacterium tuberculosis

Through thousands of years of reciprocal coevolution, Mycobacterium tuberculosis has become one of humanity's most successful pathogens, acquiring the ability to establish latent or progressive infection and persist even in the presence of a fully functioning immune system. The ability of M. tuberculosis to avoid immune-mediated clearance is likely to reflect a highly evolved and coordinated program of immune evasion strategies that interfere with both innate and adaptive immunity. These include the manipulation of their phagosomal environment within host macrophages, the selective avoidance or engagement of pattern recognition receptors, modulation of host cytokine production, and the manipulation of antigen presentation to prevent or alter the quality of T-cell responses. In this article we review an extensive array of published studies that have begun to unravel the sophisticated program of specific mechanisms that enable M. tuberculosis and other pathogenic mycobacteria to persist and replicate in the face of considerable immunological pressure from their hosts. Unraveling the mechanisms by which M. tuberculosis evades or modulates host immune function is likely to be of major importance for the development of more effective new vaccines and targeted immunotherapy against tuberculosis.

Pattern recognition receptors and cytokines in Mycobacterium tuberculosis infection--the double-edged sword?

Tuberculosis, an infectious disease caused by Mycobacterium tuberculosis (Mtb), remains a major cause of human death worldwide. Innate immunity provides host defense against Mtb. Phagocytosis, characterized by recognition of Mtb by macrophages and dendritic cells (DCs), is the first step of the innate immune defense mechanism. The recognition of Mtb is mediated by pattern recognition receptors (PRRs), expressed on innate immune cells, including toll-like receptors (TLRs), complement receptors, nucleotide oligomerization domain like receptors, dendritic cell-specific intercellular adhesion molecule grabbing nonintegrin (DC-SIGN), mannose receptors, CD14 receptors, scavenger receptors, and FCγ receptors. Interaction of mycobacterial ligands with PRRs leads macrophages and DCs to secrete selected cytokines, which in turn induce interferon-γ- (IFNγ-) dominated immunity. IFNγ and other cytokines like tumor necrosis factor-α (TNFα) regulate mycobacterial growth, granuloma formation, and initiation of the adaptive immune response to Mtb and finally provide protection to the host. However, Mtb can evade destruction by antimicrobial defense mechanisms of the innate immune system as some components of the system may promote survival of the bacteria in these cells and facilitate pathogenesis. Thus, although innate immunity components generally play a protective role against Mtb, they may also facilitate Mtb survival. The involvement of selected PRRs and cytokines on these seemingly contradictory roles is discussed.

Potential association of pulmonary tuberculosis with genetic polymorphisms of toll-like receptor 9 and interferon-gamma in a Chinese population

Background

Association studies have been employed to investigate the relationships between host single nucleotide polymorphisms (SNPs) and susceptibility to pulmonary Tuberculosis (PTB). However, such candidate genetic markers have not been widely studied in Chinese population, especially with respect to the disease development from latent M. tuberculosis infection (LTBI).

Methods

In this case–control study, 44 candidate SNPs were examined in a total of 600 participants (PTB patients, LTBI controls and healthy controls without M. tuberculosis infection) from Zhengzhou, China. The two groups of controls were frequency matched on gender and age with PTB patients. Genotyping was carried out by the Illumina Golden Gate assay.

Results

When comparing PTB patients with LTBI controls but not healthy controls without M. tuberculosis infection, significant associations with disease development were observed for TLR9 1174 A/G, TLR9 1635 A/G and IFNG 2109G/A. The two loci in TLR9 were in LD in our study population (r²=0.96, D’=1.00). A combined effect of the genotypes associated with increased risk of PTB (i.e. TLR9 1174G/G and IFNG 2109 A/A) was found when comparing PTB patients with LTBI controls (p=0.004) but not with healthy controls without infection (p=0.433).

Conclusions

Potential associations between TLR9 and IFN-γ genetic polymorphisms and PTB were observed in a Chinese population which supports further study of the roles played by TLR9/IFN-γ pathway during the development of PTB.

Heat shock proteins: stimulators of innate and acquired immunity

Adjuvants were reintroduced into modern immunology as the dirty little secret of immunologists by Janeway and thus began the molecular definition of innate immunity. It is now clear that the binding of pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs) on antigen presenting cells (APCs) activates the innate immune response and provides the host with a rapid mechanism for detecting infection by pathogens and initiates adaptive immunity. Ironically, in addition to advancing the basic science of immunology, Janeway's revelation on induction of the adaptive system has also spurred an era of rational vaccine design that exploits PRRs. Thus, defined PAMPs that bind to known PRRs are being specifically coupled to antigens to improve their immunogenicity. However, while PAMPs efficiently activate the innate immune response, they do not mediate the capture of antigen that is required to elicit the specific responses of the acquired immune system. Heat shock proteins (HSPs) are molecular chaperones that are found complexed to client polypeptides and have been studied as potential cancer vaccines. In addition to binding PRRs and activating the innate immune response, HSPs have been shown to both induce the maturation of APCs and provide chaperoned polypeptides for specific triggering of the acquired immune response.

Differential trafficking of TLR1 I602S underlies host protection against pathogenic mycobacteria

We recently identified I602S as a frequent single-nucleotide polymorphism of human TLR1 that greatly inhibits cell surface trafficking, confers hyporesponsiveness to TLR1 agonists, and protects against the mycobacterial diseases leprosy and tuberculosis. Because mycobacteria are known to manipulate the TLR system to their advantage, we hypothesize that the hyporesponsive 602S variant may confer protection by enabling the host to overcome this immune subversion. We report that primary human monocytes and macrophages from homozygous TLR1 602S individuals are resistant to mycobacterial-induced downregulation of macrophage MHC class II, CD64, and IFN-γ responses compared with individuals who harbor the TLR1 602I variant. Additionally, when challenged with mycobacterial agonists, macrophages from TLR1 602S/S individuals resist induction of host arginase-1, an enzyme that depletes cellular arginine stores required for the production of antimicrobial reactive nitrogen intermediates. The differences in cell activation mediated by TLR1 602S and TLR1 602I are observed upon stimulation with soluble mycobacterial-derived agonists but not with whole mycobacterial cells. Taken together, these results suggest that the TLR1 602S variant protects against mycobacterial disease by preventing soluble mycobacterial products, perhaps released from granulomas, from disarming myeloid cells prior to their encounter with whole mycobacteria.

The role of airway epithelial cells in response to mycobacteria infection

Airway epithelial cells (AECs) are part of the frontline defense against infection of pathogens by providing both a physical barrier and immunological function. The role of AECs in the innate and adaptive immune responses, through the production of antimicrobial molecules and proinflammatory factors against a variety of pathogens, has been well established. Tuberculosis (TB), a contagious disease primarily affecting the lungs, is caused by the infection of various strains of mycobacteria. In response to mycobacteria infection, epithelial expression of Toll-like receptors and surfactant proteins plays the most prominent roles in the recognition and binding of the pathogen, as well as the initiation of the immune response. Moreover, the antimicrobial substances, proinflammatory factors secreted by AECs, composed a major part of the innate immune response and mediation of adaptive immunity against the pathogen. Thus, a better understanding of the role and mechanism of AECs in response to mycobacteria will provide insight into the relationship of epithelial cells and lung immunocytes against TB, which may facilitate our understanding of the pathogenesis and immunological mechanism of pulmonary tuberculosis disease.

Polymorphic allele of human MRC1 confer protection against tuberculosis in a Chinese population

Mannose receptor is a member of the C-type lectin receptor family involved in pathogen molecular-pattern recognition, and plays a critical role in shaping host immune response. Single nucleotide polymorphisms (SNPs) in the MRC1 gene may affect expression levels and differences in the structure and function of proteins in different individuals, thereby affecting individual susceptibility to pulmonary tuberculosis. However, to date, MRC1 polymorphisms associated with susceptibility to pulmonary tuberculosis have not yet been reported. The present study aimed to investigate potential associations of SNPs in the MRC1 gene with pulmonary tuberculosis in a Chinese population. Six SNPs (G1186A, G1195A, T1212C, C1221G, C1303T and C1323T) in exon 7 of the MRC1 gene were genotyped using the PCR and DNA sequencing methods in the pulmonary tuberculosis patients and the healthy controls. Linkage disequilibrium analysis was performed between polymorphic sites. The study found that the allele frequency of G1186A (rs34039386) of the MRC1 gene in a Chinese population was higher in the pulmonary tuberculosis group than the healthy control group. There was a significant difference in frequency distribution between the two groups (P = 0.037; OR = 0.76; 95% CI, 0.58-0.98). Genotypic analysis also indicated that the AG genotypes in a Chinese population were significantly correlated with pulmonary tuberculosis (P < 0.01; OR = 0.57; 95% CI, 0.37-0.87). After adjustment for age and gender, G1186A sites were found to be dominant (P < 0.01; OR = 0.59; 95% CI, 0.40-0.87), over-dominant (P = 0.045; OR = 0.69; 95% CI, 0.47-0.99) and additive models (P = 0.041; OR = 0.76; 95% CI, 0.59-0.99) in association with pulmonary tuberculosis. But, no association was found between the other 5 SNPs (G1195A, T1212C, C1221G, C1303T and C1323T) and tuberculosis (P > 0.05). This study is the first to report that genetic variants in the MRC1 gene can be associated with pulmonary tuberculosis in a Chinese population, and may reduce the risk of infecting pulmonary tuberculosis. This also provides a new experimental basis to clarify the pathogenesis of pulmonary tuberculosis.

LMP2/LMP7 gene variant: a risk factor for intestinal Mycobacterium tuberculosis infection in the Chinese population

BACKGROUND AND AIMS

Low molecular mass protein-2 (LMP2) and low molecular mass protein-7 (LMP7) genes play a critical role in foreign antigen processing on the major histocompatibility complex-I CD8(+) cytotoxic T-lymphocyte pathway. This study was designed to investigate whether the sequence variants in the LMP2/LMP7 coding region were associated with intestinal Mycobacterium tuberculosis (M. tuberculosis) infection or with the co-infection of pulmonary tuberculosis.

METHODS

A total of 168 patients with intestinal tuberculosis and 235 normal controls were recruited for this study. Two polymorphisms of LMP2 (Arg60-His) and LMP7 (Gln145-Lys) were identified by polymerase chain reaction-restriction fragment length polymorphism method. The associations of the LMP2/LMP7 genotype and haplotype with intestinal M. tuberculosis infection were assessed by using logistic regression analysis.

RESULTS

The results revealed that LMP7 position codon 145 Lys/Lys and Gln/Lys alleles in the coding region were associated with the infection of intestinal M. tuberculosis (P=0.003, odds ratio [OR]= 3.86 and P < 0.001, OR = 2.28, respectively). Meanwhile, the Arg-Lys and Cys-Lys haplotypes exhibited significant relation to the intestinal M. tuberculosis infection (P= 0.006, OR=1.87; P=0.021, OR=1.83, respectively). No significant associations were observed for any of the single-nucleotide polymorphism genotypes or haplotypes with the co-infection of pulmonary tuberculosis (P > 0.05).

CONCLUSIONS

The results indicated that the genetic variant within the LMP2/LMP7 gene would increase the risk of intestinal M. tuberculosis infection.

Aerosol vaccines for tuberculosis: a fine line between protection and pathology

Pulmonary delivery of vaccines against airborne infection is being investigated worldwide, but there is limited effort directed at developing inhaled vaccines for tuberculosis (TB). This review addresses some of the challenges confronting vaccine development for TB and attempts to link these challenges to the promises of mucosal immunity offered by pulmonary delivery. There are several approaches working toward this goal including subunit vaccines, recombinant strains, a novel vaccine strain Mycobacterium w, and DNA vaccine approaches. While it is clear that lung-resident adaptive immunity is an attainable goal, vaccine platforms must ensure that damage to the lung is limited during both vaccination and when memory cells respond to pathogenic infection.

TLR-2 independent recognition of Mycobacterium tuberculosis by CD11c+ pulmonary cells from old mice

The elderly are particularly susceptible to infectious diseases such as influenza, bacterial pneumonia, and tuberculosis. Current vaccines are only partially protective in old age, which makes the elderly a critical target group for the development of new vaccine strategies. The recognition of pathogens via toll like receptors (TLR) and the subsequent generation of pro-inflammatory cytokines has generated interest in incorporating TLR agonists into new vaccines to enhance immunogenicity. However, TLR function is reportedly decreased in old age, leading to questions regarding the benefit of including TLR agonists into vaccines for the elderly. It is critical that we understand the function and role of TLRs in aged hosts prior to approving new TLR based adjuvants for vaccines that will be delivered to the elderly. In this study we determine the ability of TLRs on pulmonary macrophages from old mice to recognize and respond to infection with the virulent pathogen Mycobacterium tuberculosis (M. tb). Although pulmonary (CD11c(+)) cells from old mice were fully capable of producing cytokines in response to M. tb infection, we demonstrate that in contrast to young mice, M. tb induced cytokine production occurred independently of TLR-2. Our data indicate that the inclusion of TLR-2 agonists into new vaccines may not be fully effective in the elderly population. Investigation into such age-related differences in TLR function is of critical importance for the design of effective vaccines that will protect the elderly against infectious diseases.