SOCS1 gene expression is increased in severe pulmonary tuberculosis

Tuberculosis severity associates with variants and eQTLs related to vascular biology and infection-induced inflammation

Background

Tuberculosis (TB) remains a major public health problem globally, even compared to COVID-19. Genome-wide studies have failed to discover genes that explain a large proportion of genetic risk for adult pulmonary TB, and even fewer have examined genetic factors underlying TB severity, an intermediate trait impacting disease experience, quality of life, and risk of mortality. No prior severity analyses used a genome-wide approach.

Methods and findings

As part of our ongoing household contact study in Kampala, Uganda, we conducted a genome-wide association study (GWAS) of TB severity measured by TBScore, in two independent cohorts of culture-confirmed adult TB cases (n = 149 and n = 179). We identified 3 SNPs (P<1.0 x 10–7) including one on chromosome 5, rs1848553, that was GWAS significant (meta-analysis p = 2.97x10-8). All three SNPs are in introns of RGS7BP and have effect sizes corresponding to clinically meaningful reductions in disease severity. RGS7BP is highly expressed in blood vessels and plays a role in infectious disease pathogenesis. Other genes with suggestive associations defined gene sets involved in platelet homeostasis and transport of organic anions. To explore functional implications of the TB severity-associated variants, we conducted eQTL analyses using expression data from Mtb-stimulated monocyte-derived macrophages. A single variant (rs2976562) associated with monocyte SLA expression (p = 0.03) and subsequent analyses indicated that SLA downregulation following MTB stimulation associated with increased TB severity. Src Like Adaptor (SLAP-1), encoded by SLA, is highly expressed in immune cells and negatively regulates T cell receptor signaling, providing a potential mechanistic link to TB severity.

Conclusions

These analyses reveal new insights into the genetics of TB severity with regulation of platelet homeostasis and vascular biology being central to consequences for active TB patients. This analysis also reveals genes that regulate inflammation can lead to differences in severity. Our findings provide an important step in improving TB patient outcomes.

MiR-342 controls Mycobacterium tuberculosis susceptibility by modulating inflammation and cell death

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) that places a heavy strain on public health. Host susceptibility to Mtb is modulated by macrophages, which regulate the balance between cell apoptosis and necrosis. However, the role of molecular switches that modulate apoptosis and necrosis during Mtb infection remains unclear. Here, we show that Mtb-susceptible mice and TB patients have relatively low miR-342-3p expression, while mice with miR-342-3p overexpression are more resistant to Mtb. We demonstrate that the miR-342-3p/SOCS6 axis regulates anti-Mtb immunity by increasing the production of inflammatory cytokines and chemokines. Most importantly, the miR-342-3p/SOCS6 axis participates in the switching between Mtb-induced apoptosis and necrosis through A20-mediated K48-linked ubiquitination and RIPK3 degradation. Our findings reveal several strategies by which the host innate immune system controls intracellular Mtb growth via the miRNA-mRNA network and pave the way for host-directed therapies targeting these pathways.

TLT2 Suppresses Th1 Response by Promoting IL-6 Production in Monocyte Through JAK/STAT3 Signal Pathway in Tuberculosis

The function of triggering receptor expressed on myeloid cell-like transcript 2 (TLT2) has not been characterized and their role in pulmonary tuberculosis (TB) remains unclear. In this study, we found that surface TLT2 was up-regulated in human monocytes of patients with active TB compared to healthy subjects. In vitro, TLT2 expression was induced in human monocyte cell line THP-1 cells after bacillus Calmette-Guérin (BCG) or Mycobacterium tuberculosis (Mtb) H37Rv infection. Knockdown of TLT2 by siRNA transfection suppressed IL-6 expression, whereas over-expression of TLT2 increased IL-6 production in THP-1 cells infected by H37Rv. TLT2⁺CD14⁺ monocytes produced higher level of IL-6 compared to TLT2^– subset in active TB patients. Western blot and immunocoprecipitation revealed that TLT2 interacted with kinase JAK1/JAK2/Tyk2 to enhance STAT3 phosphorylation. Moreover, we showed that tyrosine residues 297 and 315 of TLT2 cytoplasmic domain were involved in STAT3 activation. In monocyte/CD4⁺ T cell co-culture assay, blockage of TLT2 fusion protein facilitated IFN-γ production by CD4⁺ T cells. Plate count assay showed that monocyte-mediated bacterial killing was promoted by TLT2 fusion protein. In vivo treatment with TLT-2 fusion protein reduced IL-6 production by macrophage but increased IFN-γ production by CD4⁺ T cell in H37Rv and BCG infected mice. Furthermore, TLT2 fusion protein attenuated inflammation, and reduced bacterial load in lung of infected mice. Together, these findings demonstrate that TLT2 negatively regulates Th1 response against mycobacterial infection, which promotes IL-6 production through JAK/STAT3 signal pathway.

Genetics and evolution of tuberculosis pathogenesis: New perspectives and approaches

Tuberculosis is the most lethal infectious disease globally, but the vast majority of people who are exposed to the primary causative pathogen, Mycobacterium tuberculosis (MTB), do not develop active disease. Most people do, however, show signs of infection that remain throughout their lifetimes. In this review, we develop a framework that describes several possible transitions from pathogen exposure to TB disease and reflect on the genetics studies to address many of these. The evidence strongly supports a human genetic component for both infection and active disease, but many of the existing studies, including some of our own, do not clearly delineate what transition(s) is being explicitly examined. This can make interpretation difficult in terms of why only some people develop active disease. Nonetheless, both linkage peaks and associations with either active disease or latent infection have been identified. For transition to active disease, pathways defined as active TB altered T and B cell signaling in rheumatoid arthritis and T helper cell differentiation are significantly associated. Pathways that affect transition from exposure to infection are less clear-cut, as studies of this phenotype are less common, and a primary response, if it exists, is not yet well defined. Lastly, we discuss the role that interaction between the MTB lineage and human genetics can play in TB disease, especially severity. Severity of TB is at present the only way to study putative co-evolution between MTB and humans as it is impossible in the absence of disease to know the MTB lineage(s) to which an individual has been exposed. In addition, even though severity has been defined in multiple heterogeneous ways, it appears that MTB-human co-evolution may shape pathogenicity. Further analysis of co-evolution, requiring careful analysis of paired samples, may be the best way to completely assess the genetic basis of TB.

MiR-155-5p plays as a "janus" in the expression of inflammatory cytokines induced by T-2 toxin

Although many studies have shown that inflammatory response plays a crucial role in the various toxic effects of T-2 toxin, there are relatively few reports on the mechanism of this phenomenon. Meanwhile, accumulating evidence has shown that miR-155-5p is activated in the inflammatory response. As molecular pathways and mechanisms involved in T-2 toxin-induced inflammatory response are poorly elucidated, we assessed whether miR-155-5p is involved in the inflammation effects mediated by T-2 toxin. Treatment of RAW264.7 cells with T-2 toxin (14 nM and 12 h) resulted in inflammatory response and associated with alteration of the gene expression signature of miR-155-5p. Knockdown or overexpression of miR-155-5p both indicated that miR-155-5p positively regulated the expression of the inflammation factors. Moreover, bioinformatics prediction and luciferase assay indicated that atg3 and rheb are targets of miR-155-5p. However, atg3 and SOCS1 play positive roles in the inflammatory response regulated by miR-155-5p, while rheb plays a negative role. In addition, the in vivo study showed that single administration of T-2 toxin in mice enhances spleen immune response, which was accompanied by an overexpression of miR-155-5p. These findings indicate that miR-155-5p might have an important role associated with the inflammatory response induced by T-2 toxin. In conclusion, a dual character of miR-155-5p in inflammation response was revealed, which might exist in other reactions in which miR-155-5p is involved.

Constitutive STAT3 phosphorylation and IL-6/IL-10 co-expression are associated with impaired T-cell function in tuberculosis patients

T-cells critically contribute to protection against Mycobacterium tuberculosis infection, and impaired T-cell responses can lead to disease progression. Pro-inflammatory and immunosuppressive cytokines affect T-cells, and fine-tuned regulation of cytokine signaling via the Jak/STAT signaling pathways is crucial for appropriate T-cell function. Constitutive STAT3 phosphorylation as a consequence of aberrant cytokine signaling has been described to occur in pathognomonic T-cell responses in inflammatory and autoimmune diseases. We characterized blood samples from tuberculosis patients (n=28) and healthy contacts (n=28) from Ghana for M. tuberculosis-specific T-cell responses, constitutive cytokine production, and SOCS3 and pSTAT3 expression. Lentiviral modulation of primary CD4+ T-cells was performed to determine the effects of SOCS3 on T-cell functions. T-cells from tuberculosis patients expressed higher levels of IL-10 and IL-6 and lower levels of T helper type (TH)17 cytokines after M. tuberculosis-specific stimulation compared to healthy contacts. In addition, tuberculosis patients had higher IL-10 and IL-6 levels in the supernatants of non-stimulated immune cells and plasma samples compared to healthy contacts. Notably, aberrant cytokine expression was accompanied by high constitutive pSTAT3 levels and SOCS3 expression in T-cells. Multivariate analysis identified an IL-6/IL-10 co-expression-based principal component in tuberculosis patients that correlated with high pSTAT3 levels. SOCS3 contributed to a regulatory component, and tuberculosis patients with high SOCS3 expression showed decreased TH1 cytokine expression and impaired IL-2-induced STAT5 phosphorylation. SOCS3 over-expression in primary CD4+ T-cells confirmed the SOCS3 inhibitory function on IL-2-induced STAT5 phosphorylation. We conclude that constitutive pSTAT3 and high SOCS3 expression are influential factors that indicate impaired T-cell functions in tuberculosis patients.

Primary Role of Suppressor of Cytokine Signaling 1 in Mycobacterium bovis BCG Infection

Suppressor of cytokine signaling 1 (SOCS1) is a negative regulator of JAK/STAT signaling and is induced by mycobacterial infection. To understand the major function of SOCS1 during infection, we established a novel system in which recombinant Mycobacterium bovis bacillus Calmette-Guérin expressed dominant-negative SOCS1 (rBCG-SOCS1DN) because it would not affect the function of SOCS1 in uninfected cells. When C57BL/6 mice and RAG1^-/- mice were intratracheally inoculated with rBCG-SOCS1DN, the amount of rBCG-SOCS1DN in the lungs was significantly reduced compared to that in the lungs of mice inoculated with a vector control counterpart and wild-type BCG. However, these significant differences were not observed in NOS2^-/- mice and RAG1^-/- NOS2^-/- double-knockout mice. These findings demonstrated that SOCS1 inhibits nitric oxide (NO) production to establish mycobacterial infection and that rBCG-SOCS1DN has the potential to be a powerful tool for studying the primary function of SOCS1 in mycobacterial infection.

Upregulation of miR-196b-5p attenuates BCG uptake via targeting SOCS3 and activating STAT3 in macrophages from patients with long-term cigarette smoking-related active pulmonary tuberculosis

Background

Cigarette smoking (CS) triggers an intense and harmful inflammatory response in lungs mediated by alveolar and blood macrophages, monocytes, and neutrophils and is closely associated with prevalence of tuberculosis (TB). The risk of death in patients with long-term cigarette smoking-related pulmonary tuberculosis (LCS-PTB) is approximately 4.5 times higher than those with nonsmoking pulmonary tuberculosis (N-PTB). However, the mechanisms underlying the harmful inflammatory responses in the setting of LCS-PTB have not been well documented.

Methods

28 cases LCS-PTB patients, 22 cases N-PTB patients and 20 cases healthy volunteers were enrolled in this study. Monocytes were isolated from peripheral blood mononuclear cells. Differentiated human MDM and U937 cell were prepared with M-CSF and PMA stimulation, respectively. The miR-196b-5p, STAT1, STAT3, STAT4, STAT5A, STAT5B, STAT6, SOCS1 and SOCS3 mRNA expression were detected by qRT-PCR. Western blot was performed according to SOCS1, SOCS3, and pSTAT3 expression. The mycobacterial uptake by MDMs from different groups of patients after Bacillus Calmette–Guérin (BCG) infection and agomir-196b-5p or antagomir-196b-5p transfection were used by flow cytometry analysis. Human IL-6, IL-10 and TNF-α levels on the plasma and cell culture supernatant samples were measured using ELISA. For dual-luciferase reporter assay, the SOCS3 3′-UTR segments, containing the binding elements of miR-196b-5p or its mutant versions were synthesized as sense and antisense linkers.

Results

In this study, we found that IL-6, TNF-α production, SOCS3 mRNA expression were downregulated, while miR-196b-5p and STAT3 mRNA expression were upregulated in monocytes from LCS-PTB patients as compared to N-PTB patients. Meanwhile, we demonstrated that miR-196b-5p could target SOCS3 and activate STAT3 signaling pathway, which may possibly contribute to attenuation of BCG uptake and decrease in IL-6 and TNF-α production in macrophages.

Conclusions

Our findings revealed that CS exposure regulates inflammatory responses in monocyte/macrophages from LCS-PTB patients via upregulating miR-196b-5p, and further understanding of the specific role of miR-196b-5p in inflammatory responses mightfacilitate elucidating the pathogenesis of LCS-PTB, thus leading to the development of new therapeutic strategies for PTB patients with long-term cigarette smoking.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1654-9) contains supplementary material, which is available to authorized users.

Blood transcriptomic markers of Mycobacterium tuberculosis load in sputum

BACKGROUND

Peripheral blood transcriptome signatures that distinguish active pulmonary tuberculosis (TB) from control groups have been reported, but correlations of these signatures with sputum mycobacterial load are incompletely defined.

METHODS

We assessed the performance of published TB transcriptomic signatures in Haiti, and identified transcriptomic biomarkers of TB bacterial load in sputum as measured by Xpert® MTB/RIF molecular testing. People in Port au Prince, Haiti, with untreated pulmonary TB (n = 51) formed the study cohort: 19 people with low and 32 with high sputum Mycobacterium tuberculosis load. Peripheral whole blood transcriptomes were generated using RNA sequencing.

RESULTS

Twenty of the differentially expressed transcripts in TB vs. no TB were differentially expressed in people with low vs. high sputum mycobacterial loads. The difference between low and high bacterial load groups was independent of radiographic severity. In a published data set of transcriptomic response to anti-tuberculosis treatment, this 20-gene subset was more treatment-responsive at 6 months than the full active TB signature.

CONCLUSION

We identified genes whose transcript levels in the blood distinguish active TB with high vs. low M. tuberculosis loads in the sputum. These transcripts may reveal mechanisms of mycobacterial control of M. tuberculosis during active infection, as well as identifying potential biomarkers for bacterial response to anti-tuberculosis treatment.

SOCS Proteins as Regulators of Inflammatory Responses Induced by Bacterial Infections: A Review

Severe bacterial infections can lead to both acute and chronic inflammatory conditions. Innate immunity is the first defense mechanism employed against invading bacterial pathogens through the recognition of conserved molecular patterns on bacteria by pattern recognition receptors (PRRs), especially the toll-like receptors (TLRs). TLRs recognize distinct pathogen-associated molecular patterns (PAMPs) that play a critical role in innate immune responses by inducing the expression of several inflammatory genes. Thus, activation of immune cells is regulated by cytokines that use the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway and microbial recognition by TLRs. This system is tightly controlled by various endogenous molecules to allow for an appropriately regulated and safe host immune response to infections. Suppressor of cytokine signaling (SOCS) family of proteins is one of the central regulators of microbial pathogen-induced signaling of cytokines, principally through the inhibition of the activation of JAK/STAT signaling cascades. This review provides recent knowledge regarding the role of SOCS proteins during bacterial infections, with an emphasis on the mechanisms involved in their induction and regulation of antibacterial immune responses. Furthermore, the implication of SOCS proteins in diverse processes of bacteria to escape host defenses and in the outcome of bacterial infections are discussed, as well as the possibilities offered by these proteins for future targeted antimicrobial therapies.

Suppressors of cytokine signaling in tuberculosis

Tuberculosis (TB), a global disease mainly infected by Mycobacterium tuberculosis, remains leading public health problem worldwide. Suppressors of cytokine signaling (SOCSs) play important roles in the protection against microbial infection. However, the relationship between members of the SOCS family and tuberculosis infection remains unclear. Using peripheral blood mononuclear cells, we investigated the mRNA expression profiles of SOCS subfamilies among active TB, latent tuberculosis infection (LTBI), and healthy individuals. Our results showed that active tuberculosis subjects had higher levels of SOCS-3 mRNA, lower expressions of SOCS-2, -4, -5, -6, -7, and cytokine-inducible SH2-containing protein-1 (CIS-1) mRNAs, but not SOCS-1 mRNA than healthy and LTBI subjects. In men, LTBI patients had lower SOCS-3 than healthy subjects, and active TB patients had lower levels of SOCS-4, -5, and CIS-1 mRNAs but higher levels of SOCS-3 mRNA than healthy subjects. In women, LTBI patients had lower SOCS-3 mRNA level than healthy subjects, and active TB patients had lower CIS-1 mRNA level than healthy subjects. In non-aged adults (< 65 years old), TB patients had higher SOCS-3 mRNA and lower levels of SOCS-2, -4, -5, -6, -7, and CIS-1 mRNAs; whereas, aged TB patients (≥ 65 years old) had lower levels of SOCS-5 and CIS-1 mRNAs. These data suggest that particular SOCS members and their correlative relationships allow discrimination of active TB from healthy and LTBI subjects.

Interferon-Gamma Improves Macrophages Function against M. tuberculosis in Multidrug-Resistant Tuberculosis Patients

Background. Mycobacterium tuberculosis (M. tuberculosis) that causes tuberculosis (TB) kills millions of infected people annually especially multidrug-resistant tuberculosis (MDR-TB). On infection, macrophages recognize the mycobacteria by toll-like receptor (TLR) followed by phagocytosis and control of mycobacteria. In addition, macrophages also secrete IL-12 to induce IFN-γ production by T, which, in turn, increases the phagocytosis and oxidative burst. Individuals with defects in innate or adaptive immunity exhibit increased susceptibility to M. tuberculosis. Understanding these immunologic mechanisms will help in TB control. We aimed to investigate the immunopathologic mechanisms in MDR-TB and role of recombinant human interferon-gamma (rhIFN-γ). Study Design and Methods. Monocyte-derived macrophages (MDMs) were generated from peripheral blood mononuclear cells of MDR-TB patients and healthy subjects and were investigated for immunologic response by ELISA and flow cytometry. Results. Different functional and molecular anomalies were observed in macrophages. In addition, a defective immune response to M. tuberculosis from the patient's MDMs was characterized, which in turn improved by pretreatment with rhIFN-γ. Conclusion. This work highlights the fact that rhIFN-γ improves macrophages function against M. tuberculosis and treatment of patients with poor responsiveness to TB therapy may be needed in future to include IFN-γ as adjuvant therapy after the full characterization of pathological and molecular mechanisms in these and in other more multidrug-resistant TB patients.

Suppressor of cytokine signaling-1 and chemokine (C-X-C Motif) receptor 3 expressions are associated with caseous necrosis in granulomas from patients with tuberculous lymphadenitis

We investigated the role of suppressor of cytokine signaling-1 (SOCS1) and SOCS3 molecules in lymph nodes from tuberculous lymphadenitis patients (LNTB). Fewer T cells were noted in LNTB cases, which also had raised chemokine (C-X-C motif) receptor 3 (CXCR3) levels. In addition, we observed a positive correlation between CXCR3 and SOCS1 expression. Our data suggest that upregulation of SOCS1 molecules may contribute to the dissemination of Mycobacterium tuberculosis from granulomas.

Expression of inhibitory regulators of innate immunity in patients with active tuberculosis

BACKGROUND

Tuberculosis (TB) is an important cause of morbidity and mortality worldwide. Toll-like-receptors (TLRs) are important for the recognition of the causative agent Mycobacterium tuberculosis. Negative regulation of TLRs is necessary to control deleterious inflammatory damage, but could provide a means of immune evasion by M. tuberculosis as well.

METHODS

To obtain insight in the extent of expression of inhibitory regulators of immunity in patients with active TB, peripheral-blood-mononuclear-cells (PBMCs) and plasma were obtained from 54 TB patients and 29 healthy blood donors from Chittagong, Bangladesh. Bilateral alveolar macrophages were obtained from an infected versus a contralateral normal lung segment of 9 patients. Statistical analyses were performed using Mann-Whitney U and Wilcoxon matched pairs testing. Correlations were calculated using the Spearman rho test.

RESULTS

PBMCs harvested from TB patients demonstrated increased mRNA expression of IL-1-receptor-associated-kinase-M, suppressor-of-cytokine-signalling-3 and Toll-interacting-protein. Flow cytometry revealed enhanced expression of IL-1-receptor-like-1 (ST2) on lymphocytes. Plasma soluble ST2 was elevated in patients with TB and correlated with established TB biomarkers, most strongly with soluble interleukin-2 receptor subunit α and interleukin-8. Alveolar macrophage mRNA expression of negative TLR regulators did not differ between the infected and contralateral lung side.

CONCLUSION

These results show enhanced expression of distinct negative regulators of innate immunity in PBMCs of patients with TB and identify plasma soluble ST2 as a potential novel biomarker for TB disease activity.

Macrophage immunoregulatory pathways in tuberculosis

Macrophages, the major host cells harboring Mycobacterium tuberculosis (M.tb), are a heterogeneous cell type depending on their tissue of origin and host they are derived from. Significant discord in macrophage responses to M.tb exists due to differences in M.tb strains and the various types of macrophages used to study tuberculosis (TB). This review will summarize current concepts regarding macrophage responses to M.tb infection, while pointing out relevant differences in experimental outcomes due to the use of divergent model systems. A brief description of the lung environment is included since there is increasing evidence that the alveolar macrophage (AM) has immunoregulatory properties that can delay optimal protective host immune responses. In this context, this review focuses on selected macrophage immunoregulatory pattern recognition receptors (PRRs), cytokines, negative regulators of inflammation, lipid mediators and microRNAs (miRNAs).

Expression of M. tuberculosis-induced suppressor of cytokine signaling (SOCS) 1, SOCS3, FoxP3 and secretion of IL-6 associates with differing clinical severity of tuberculosis

Background

Appropriate immune activation of T cells and macrophages is central for the control of Mycobacterium tuberculosis infections. IFN-γ stimulated responses are lowered in tuberculosis (TB), while expression of Suppressor of Cytokine Signaling (SOCS) molecules – 1 and 3 and CD4⁺CD25⁺FoxP3⁺T regulatory cells is increased. Here we investigated the association of these molecules in regard to clinical severity of TB.

Methods

Peripheral blood mononuclear cells (PBMCs) were isolated from patients with pulmonary TB (PTB, n = 33), extra-pulmonary TB (ETB, n = 33) and healthy endemic controls (EC, n = 15). Cases were classified as moderately advanced or far advanced PTB, and less severe or severe disseminated ETB. M. tuberculosis -stimulated IFN-γ, SOCS1, SOCS3 and FoxP3 gene expression and secretion of Th1 and Th2 cytokines was measured. Statistical analysis was performed using Mann–Whitney U, Wilcoxon Rank and Kruskal Wallis non-parametric tests.

Results

In un-stimulated PBMCs, IL-6 (p = 0.018) and IL-10 (p = 0.013) secretion levels were increased in PTB while IL-10 was also increased in ETB (p = 0.003), all in comparison with EC. M. tuberculosis-stimulated IL-6 (p = 0.003) was lowered in ETB as compared with EC. SOCS1 mRNA expression in M. tuberculosis stimulated PBMCs levels in moderately advanced PTB (p = 0.022), far advanced (p = 0.014) PTB, and severe ETB (p = 0.009) were raised as compared with EC. On the other hand, SOCS1 mRNA titers were reduced in less severe ETB, in comparison with severe ETB (p = 0.027) and far advanced PTB (p = 0.016). SOCS3 mRNA accumulation was reduced in far advanced PTB (p = 0.007) and FoxP3 mRNA expression was increased in less severe ETB as compared with EC (p = 0.017).

Conclusions

The lowered SOCS1 mRNA levels in patients with less severe extra-pulmonary TB as compared to those with more severe ETB and PTB may lead to elevated IFN-γ pathway gene expression in the latter group. As localized ETB has shown to be associated with more effective Th1 immunity and adaptive responses, this suggests a role for SOCS1 in determining disease outcome in extra-pulmonary TB.