Mycobacteria induce TPL-2 mediated IL-10 in IL-4-generated alternatively activated macrophages

Leishmania surface molecule lipophosphoglycan-TLR2 interaction moderates TPL2-mediated TLR2 signalling for parasite survival

Leishmania donovani, a protozoan parasite, resides and replicates in macrophages and inflicts the potentially fatal disease visceral leishmaniasis (VL). The parasite-expressed surface lipophosphoglycan (LPG) was implicated in binding TLR2 on NK cells, but the modus operandi of its disease-promoting influence remained unknown. As TPL2, a member of the MAPK module in mammalian macrophages, was implicated in the anti-inflammatory immune response and promoting pathogen survival, we investigated the possibility of TPL2-directed LPG-TLR2 signalling in Leishmania infection. We observed that TLR2 or TPL2 blockade differentially influenced the TLR2 ligand proteoglycan (PGN)-induced p38MAPK and ERK-1/2 activation. TLR2 blockade abrogated the PGN-induced TPL2 activation. L. donovani infection impaired the Akt activation whereas, upon TPL2 inhibition, the infection fails to control Akt phosphorylation. In L. donovani-infected macrophages, TLR2 blocking negatively affected p38, Akt and TPL2 phosphorylation while ERK1/2 phosphorylation increased relative to the infection alone. TPL2 blockade reduced TGF-β, but increased TNF-α expression and diminished amastigote count in macrophages. While exploring stimulation patterns of TLR2 ligands, LPG, unlike PGN, selectively increased TLR2 expression in macrophages. LPG blockade increased p38MAPK and AKT, but slightly affected ERK-1/2 and significantly reduced TPL2 phosphorylation from L. donovani-infected macrophages. Molecular docking and molecular dynamics analysis drew a parallel between LPG's glycan chain lengths with the frequency of interaction with TLR2 which might impact TLR2 signalling. Therefore, the parasite regulates the TLR2 signalling via TPL2 when elicited by LPG-TLR2 interaction for pathogenesis.

Macrophage innate training induced by IL-4 and IL-13 activation enhances OXPHOS driven anti-mycobacterial responses

Macrophages are a highly adaptive population of innate immune cells. Polarization with IFNγ and LPS into the 'classically activated' M1 macrophage enhances pro-inflammatory and microbicidal responses, important for eradicating bacteria such as Mycobacterium tuberculosis. By contrast, 'alternatively activated' M2 macrophages, polarized with IL-4, oppose bactericidal mechanisms and allow mycobacterial growth. These activation states are accompanied by distinct metabolic profiles, where M1 macrophages favor near exclusive use of glycolysis, whereas M2 macrophages up-regulate oxidative phosphorylation (OXPHOS). Here, we demonstrate that activation with IL-4 and IL-13 counterintuitively induces protective innate memory against mycobacterial challenge. In human and murine models, prior activation with IL-4/13 enhances pro-inflammatory cytokine secretion in response to a secondary stimulation with mycobacterial ligands. In our murine model, enhanced killing capacity is also demonstrated. Despite this switch in phenotype, IL-4/13 trained murine macrophages do not demonstrate M1-typical metabolism, instead retaining heightened use of OXPHOS. Moreover, inhibition of OXPHOS with oligomycin, 2-deoxy glucose or BPTES all impeded heightened pro-inflammatory cytokine responses from IL-4/13 trained macrophages. Lastly, this work identifies that IL-10 attenuates protective IL-4/13 training, impeding pro-inflammatory and bactericidal mechanisms. In summary, this work provides new and unexpected insight into alternative macrophage activation states in the context of mycobacterial infection.

Genetic Polymorphism of Tumor Necrosis Factor-Alpha, Interferon-Gamma and Interleukin-10 and Association With Risk of Mycobacterium Tuberculosis Infection

BACKGROUND

Mycobacterium tuberculosis has become the leading cause of morbidity and death in humans worldwide. Thus, genetic variability of the host plays a major role in human susceptibility to the pathogen, among others. Therefore, the objective of this finding was to assess the association of genetic polymorphisms of cytokines with tuberculosis infection.

METHOD

A cross-sectional study was conducted between January and May 2018. Five ml of whole blood was collected and extracted the genomic DNA through simple salting out method. The patterns of genetic polymorphism were determined by amplification refractory method PCR using specific primers. Finally, the PCR run on electrophoresis of agarose gel and the band was visualized under UV light. A logistical regression model has been adapted to assess the association of genetic polymorphisms with tubercular infection. In order to determine the association between the explanatory and outcome variable, the odds ratio with 95% CI was calculated. P < 0.05 is a statistically significant value.

RESULT

In present study, the frequency of TNF-α -308 G allele and GG genotype OR (95% CI)= 0.20 (0.11-0.37), and OR (95% CI)= 0.29 (0.18-0.46)), respectively) and IFN-γ +874 A allele and AA genotype OR (95% CI)= 3.80 (2.11-6.86) and (OR (95% CI)= 1.61(1.13-2.28), respectively) were significantly associated with tuberculosis incidence. In contrast, there is no significant correlation between IL-10 -1082 A and AA of allele and genotype, respectively in tuberculosis patients (p > 0.05) was evident.

CONCLUSION

From our finding, the genetic variability of TNF-α -308 A and IFN-γ +874 alleles are the potent host genetic risk factors associated with tuberculosis infection.

Tumor progression locus 2 (TPL2) in tumor-promoting Inflammation, Tumorigenesis and Tumor Immunity

Over the years, tumor progression locus 2 (TPL2) has been identified as an essential modulator of immune responses that conveys inflammatory signals to downstream effectors, subsequently modulating the generation and function of inflammatory cells. TPL2 is also differentially expressed and activated in several cancers, where it is associated with increased inflammation, malignant transformation, angiogenesis, metastasis, poor prognosis and therapy resistance. However, the relationship between TPL2-driven inflammation, tumorigenesis and tumor immunity has not been addressed. Here, we reconcile the function of TPL2-driven inflammation to oncogenic functions such as inflammation, proliferation, apoptosis resistance, angiogenesis, metastasis, immunosuppression and immune evasion. We also address the controversies reported on TPL2 function in tumor-promoting inflammation and tumorigenesis, and highlight the potential role of the TPL2 adaptor function in regulating the mechanisms leading to pro-tumorigenic inflammation and tumor progression. We discuss the therapeutic implications and limitations of targeting TPL2 for cancer treatment. The ideas presented here provide some new insight into cancer pathophysiology that might contribute to the development of more integrative and specific anti-inflammatory and anti-cancer therapeutics.

Helminth Coinfection Alters Monocyte Activation, Polarization, and Function in Latent Mycobacterium tuberculosis Infection

Helminth infections are known to influence T and B cell responses in latent tuberculosis infection (LTBI). Whether helminth infections also modulate monocyte responses in helminth-LTBI coinfection has not been fully explored. To this end, we examined the activation, polarization, and function of human monocytes isolated from individuals with LTBI with (n = 25) or without (n = 25) coincident Strongyloides stercoralis infection (S. stercoralis-positive and S. stercoralis-negative respectively). Our data reveal that the presence of S. stercoralis infection is associated with lower frequencies of monocytes expressing CD54, CD80, CD86 at baseline (absence of stimulation) and in response to mycobacterial-Ag stimulation than monocytes from S. stercoralis-negative individuals. In contrast, S. stercoralis infection was associated with higher frequencies of M2-like monocytes, as determined by expression of CD206 and CD163. Monocytes from S. stercoralis-positive individuals had a reduced capacity to phagocytose or exhibit respiratory burst activity following mycobacterial-Ag or LPS stimulation and were less capable of expression of IL-1β, TNF-α, IL-6, and IL-12 at baseline and/or following Ag stimulation compared with those without S. stercoralis infection. In addition, definitive treatment of S. stercoralis infection resulted in a significant reversal of the altered monocyte function 6 mo after anthelmintic therapy. Finally, T cells from S. stercoralis-positive individuals exhibited significantly lower activation at baseline or following mycobacterial-Ag stimulation. Therefore, our data highlight the induction of dampened monocyte activation, enhanced M2 polarization, and impaired monocyte function in helminth-LTBI coinfection. Our data also reveal a different mechanism by which helminth infection modulates immune function in LTBI.

MiR-1178 regulates mycobacterial survival and inflammatory responses in Mycobacterium tuberculosis-infected macrophages partly via TLR4

Tuberculosis is chronic respiratory infectious disease and is caused by the infection of Mycobacterium tuberculosis (M.tb). Macrophages play an important role in host immune response against M.tb infection, which is regulated by various factors, including microRNAs (miRNAs). The present study aimed to examine the in vitro functional role of miR-1178 in mycobacterial survival and inflammatory responses induced by M.tb infection in human macrophages. Our results showed that M.tb infection increased the expression of miR-1178 in human macrophages (HTP-1 and U937 cells) in a concentration- and time-dependent manner. Overexpression of miR-1178 enhanced the intracellular growth of mycobacteria during M.tb infection, while knockdown of miR-1178 suppressed the mycobacteria survival. Overexpression of miR-1178 also significantly attenuated the accumulation of proinflammatory cytokines including interferon-γ (IFN-γ), interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) in the M.tb-infected macrophages, while knockdown of miR-1178 caused enhancement in these proinflammatory cytokines in the M.tb-infected macrophage. Bioinformatics analysis and luciferase reporter assay showed that toll-like receptor 4 (TLR4) was a direct target of miR-1178, and miR-1178 negatively regulated the expression of TLR4. In addition, enforced expression of TLR4 attenuated the effects of miR-1178 overexpression on promoting the production of proinflammatory cytokines including IFN-γ, IL-6, IL-1β, and TNF-α in the M.tb-infected macrophages. Collectively, our findings showed that overexpression of miR-1178 promoted mycobacteria survival and miR-1178 also modulated the immune response of M.tb-infected macrophages partly via targeting TLR4.