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Importance: Cervical tuberculous lymphadenitis (CTL), the most frequent extrapulmonary form of tuberculosis, is currently a major health problem in Tunisia and in several regions around the world. CTL diagnosis is challenging mainly due to the paucibacillary nature of the disease and the potential misdiagnosis as cervical non-tuberculous lymphadenitis. This study demonstrates the added value of the heparin-binding hemagglutinin-interferon-gamma release assay as an immunoassay in the context of CTL., Competing Interests: The authors declare no conflict of interest.

Background: We previously reported the development of an enzyme-linked immunosorbent assay for the detection of the immunoglobulin G (IgG) response to Mycobacterium tuberculosis virulence factor - culture filtrate protein 32 (CFP32). The assay achieved high performance in comparing healthy Bacillus Calmette-Guerin-vaccinated controls with active tuberculosis (TB) patients from the Tunisian population. Herein, we aimed to assess the anti-CFP32 IgG response in suspected or confirmed active pulmonary TB individuals in different endemic settings., Methods: Serum samples were obtained from 224 donors from African and Latin American countries with variable levels of TB endemicity and different ethnical origins. Receiver operating characteristic curve was used to evaluate the performance of the serological assay., Results: The area under the curve was 0.70. The use of a cutoff level of 0.65 gave 67% and 68% sensitivity and specificity, respectively, regardless of ethnicity and endemicity. Except for the suspected Latin American group, overall multiple comparisons of medians pointed out the stability of the anti-CFP32 IgG response across the different endemic settings. Therefore, endemicity and ethnicity seem not to affect anti-CFP32 IgG response, mainly for detecting confirmed active TB individuals., Conclusions: These findings suggest that the inclusion of CFP32 epitopes in multi-antigen TB assay could attenuate serological differences related to heterogeneous endemicity and ethnicity. For this purpose, we further identified B-cell epitopes belonging to CFP32 by an in silico analysis., Competing Interests: None

The diagnosis of Tuberculous Cervical lymphadenitis (TCL) is challenging. The present study aimed to assess the performance of GeneXpert ultra (GXu) in the diagnosis of TCL on Formalin Fixed, Paraffin Embedded Tissues (FFPET). This study included 35 TCL cases confirmed by positive microbiology and/or positive GXu on Fresh Tissues (FT). The diagnostic performance parameters of GXu on FFPET were determined with reference to microbiology (positive Ziehl Neelsen and/or positive culture) and with reference to positive microbiology and/or positive GXu on FT. The GXu on FFPET was positive in 26/35 (74%) cases. With reference to positive ZN and or culture, the sensitivity, specificity, positive predictive value, and negative predictive value of GXu on FFPET were 63%, 100%, 100% and 71% respectively. With reference to positive microbiology and/or positive GXu on FT, these rates were 74%, 100%, 100% and 40% respectively. GXu on FFPET is a reliable tool for the detection of Mycobacterium tuberculosis complex particularly for cases where microbiological investigations have not been performed., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Alveolar Macrophages play a key role in the development of a robust adaptive immune response against the agent of Tuberculosis (TB), Mycobacterium tuberculosis ( M.tb ). However, macrophage response is often hampered by the production of IL-10, a potent suppressor of the host immune response. The secretion of IL-10 correlates with TB pathogenesis and persistence in host tissues. Concordantly, inhibition of IL-10 signaling, during BCG vaccination, confers higher protection against M.tb through a sustained Th1 and Th17 responses. Therefore, uncovering host effectors, underlying mycobacteria-induced expression of IL-10, may be beneficial toward the development of IL-10-blocking tools to be used either as adjuvants in preventive vaccination or as adjunct during standard treatment of TB. Here, we investigated the role of FOXO3 transcription factor in mycobacteria-induced secretion of IL-10. We observed that PI3K/Akt/FOXO3 axis regulates IL-10 expression in human macrophages. Knocking down of FOXO3 expression resulted in an increase of IL-10 production in BCG-infected macrophages. The gene reporter assay further confirmed the transcriptional regulation of IL-10 by FOXO3. In silico analysis identified four Forkhead binding motifs on the human IL-10 promoter, from which the typical FOXO3 one at position -203 was the major target as assessed by mutagenesis and CHIP binding assays. Further, we also observed a decrease in gene expression levels of the M1 typical markers (i.e., CD80 and CD86) in SiFOXO3-transfected macrophages while activation of FOXO3 led to the increase in the expression of CD86, MHCI, and MHCII. Finally, co-culture of human lymphocytes with siFOXO3-transfected macrophages, loaded with mycobacterial antigens, showed decreased expression of Th1/Th17 specific markers and a simultaneous increase in expression of IL-4 and IL-10. Taken together, we report for the first time that FOXO3 modulates IL-10 secretion in mycobacteria-infected macrophage, driving their polarization and the subsequent adaptive immune response. This work proposes FOXO3 as a potential target for the development of host-directed strategies for better treatment or prevention of TB., (Copyright © 2019 Bouzeyen, Haoues, Barbouche, Singh and Essafi.)

We previously reported that immunoreactivity of recombinant CFP32 (Rv0577), a virulence factor of Mycobacterium tuberculosis, was higher when produced in transformed Pichia pastoris as compared to transformed E. coli. In this study, we show that this difference is partly due to the N-glycosylation of the recombinant CFP32 (rCFP32) by the yeast Pichia pastoris. In addition, SDS-PAGE and western blotting analysis of Mycobacterium bovis BCG and yeast-produced rCFP32 showed the presence of a band corresponding to a homodimeric state of the protein, unlike that of rCFP32 produced in E. coli. Computational modeling indicates that a single cysteine residue at position 193 of each monomer might bond to stabilize the homodimeric state of CFP32. Computational study showed that this residue is buried inside the protein core of E. coli-produced rCFP32 suggesting that rCFP32 may adopt a different folding in P. pastoris and BCG, in which C193 is solvent exposed. Surprisingly, an enzyme-linked immunosorbent assay using a generated monoclonal antibody (14D4) reveals the presence of a differential epitope that appears to be the consequence of the protein dimerization of the yeast- and BCG-, but not E.coli- produced, CFP32 recombinant form. We conclude that, in addition to N-glycosylation, homodimeric folding significantly enhances the immunoreactivity of rCFP32 and may these post-translational modifications may factor into the structure and function of native M. tuberculosis CFP32., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Early secreted antigenic target 6 kDa (ESAT-6) and culture filtrate protein 10 kDa (CFP-10) are complex proteins secreted by Mycobacterium tuberculosis that play a major role in the pathogenesis of tuberculosis. However, studies focusing on the biological functions of ESAT-6 led to discordant results and the role of ESAT-6 remains controversial. In the present study, we aim to address a potential explanation for this discrepancy and to highlight the physiological impact of two conformational states of ESAT-6. Analysis of a recombinant form of ESAT-6 by native gel electrophoresis, size exclusion chromatography and CD spectroscopy revealed that ESAT-6 forms dimers/multimers with higher molecular weight, which disappeared under the action of the detergent amidosulfobetaine-14 (ASB), giving rise to another conformational state of the protein. NMR has further indicated that ASB-treated versus nontreated ESAT-6 adopted distinct structural forms but with no well defined tertiary structure. However, protein-protein docking analysis favored a dimeric state of ESAT-6. Interestingly, the two preparations presented opposing effects on mycobacterial infectivity, as well as macrophage survival, interferon-γ secretion and membrane pore formation. Thereafter, we generated a recombinant form of the physiological heterodimer ESAT-6/CFP-10 that ASB was also able to dissociate and which showed functions similar to those of ESAT-6 dimers/multimers. Our data suggest that, in the absence of CFP-10, the hydrophobic regions of the ESAT-6 can form dimers/multimers, mimicking the ESAT-6/CFP-10 heterodimer, whereas their dissociation generates a protein presenting entirely different activities. Overall, the present study clarifies the intriguing divergences between reports that could be attributed to the ESAT-6 oligomeric state and sheds light on its importance for a better comprehension of the physiopathology of tuberculosis., (© 2015 FEBS.)

The failure of M. bovis BCG to induce long-term protection has been endowed to its inability to escape the phagolysosome, leading to mild activation of CD8+ mediated T cell response. Induction of apoptosis in host cells plays an important role in potentiating dendritic cells-mediated priming of CD8+ T cells, a process defined as "cross-priming." Moreover, IL-10 secretion by infected cells has been reported to hamper BCG-induced immunity against Tuberculosis (TB). Previously, we have reported that apoptosis of BCG-infected macrophages and inhibition of IL-10 secretion is FOXO3 dependent, a transcription factor negatively regulated by the pro-survival activated threonine kinase, Akt. We speculate that FOXO3-mediated induction of apoptosis and abrogation of IL-10 secretion along with M. bovis BCG immunization might enhance the protection imparted by BCG. Here, we have assessed whether co-administration of a known anti-cancer Akt inhibitor, MK-2206, enhances the protective efficacy of M. bovis BCG in mice model of infection. We observed that in vitro MK-2206 treatment resulted in FOXO3 activation, enhanced BCG-induced apoptosis of macrophages and inhibition of IL-10 secretion. Co-administration of M. bovis BCG along with MK-2206 also increased apoptosis of antigen-presenting cells in draining lymph nodes of immunized mice. Further, MK-2206 administration improved BCG-induced CD4+ and CD8+ effector T cells responses and its ability to induce both effector and central memory T cells. Finally, we show that co-administration of MK-2206 enhanced the protection imparted by M. bovis BCG against Mtb in aerosol infected mice and guinea pigs. Taken together, we provide evidence that MK-2206-mediated activation of FOXO3 potentiates BCG-induced immunity and imparts protection against Mtb through enhanced innate immune response. [ABSTRACT FROM AUTHOR]

Tuberculosis, a human infectious disease caused by Mycobacterium tuberculosis (M.tb), is still a major cause of morbidity and mortality worldwide. The success of M.tb as a pathogen relies mainly on its ability to divert the host innate immune responses. One way by which M.tb maintains a persistent infection in a "silent" granuloma is to inhibit inflammation and induce an immunoregulatory phenotype in host macrophages (MΦs). However, M.tb effectors governing the switch of MΦs from the pro-inflammatory M1 to the anti-inflammatory M2 phenotype remain to be determined. The Early Secreted Antigenic Target 6 kDa or ESAT-6, has been implicated in the virulence and pathogenesis of tuberculosis. Here, we investigated roles of ESAT-6 in MΦ differentiation and polarization. We found that treatment of human monocytes with ESAT-6 did not interfere with differentiation of M1 MΦs. However, ESAT-6 promoted differentiation of M0 and M2 MΦs toward the M1 phenotype, as indicated by secretion of pro-inflammatory cytokines IL-6, IL-12, and TNF-α, and induction of a typical M1 transcriptional signature. Interestingly, we found that ESAT-6 switched terminal full activation of M1 polarized MΦs to the M2 phenotype. Indeed, in the pro-inflammatory M1 MΦs, ESAT-6 was able to inhibit IL-12 and TNF-a secretion and stimulate that of IL-10. Moreover, gene expression profiling of these cells showed that ESAT-6 induced downregulation of M1 MΦ cell surface molecules CD80 and CD86, transcription factors IRF5 and c-MAF, cytokines IL-12, IL-10, and IL-6, as well as chemokines CXCL10 and CXCL1. Overall, our findings suggest ESAT-6 as being one of the effectors used by M.tb to induce the pro-inflammatory M1 phenotype at the primo-infection; a prerequisite step to promote granuloma formation and subsequently drive the phenotype switch of MΦ polarization from M1 to M2 at a later stage of the infection. Our study improves current knowledge regarding mechanisms of virulence of M.tb and may be helpful to develop novel tools targeting ESAT-6 for a better and more efficient treatment of tuberculosis. [ABSTRACT FROM AUTHOR]

Summary: The C-type lectin DC-SIGN (CD209) is an important pathogen recognition receptor of the innate immune system. Recent studies showed that DC-SIGN is the major receptor of Mycobacterium tuberculosis on human dendritic cells and that polymorphisms in the DC-SIGN promoter region are associated with susceptibility to tuberculosis. In this light, we aimed to study the potential implication of DC-SIGN genetic variation in the predisposition to tuberculosis in a group of Tunisian patients. We thus performed an association study comprising 138 tuberculosis patients and 140 healthy controls. Sequencing of the DC-SIGN promoter region detected four polymorphisms (-939, -871, -601, and -336), but no differences in their allelic distribution were observed between the two groups. In addition, the analysis of length variation in the DC-SIGN neck region indicated extremely low levels of polymorphisms and, again, no differences between patients and controls. Our data showed therefore that neither promoter variants nor length variation in the neck region of DC-SIGN is associated with susceptibility to tuberculosis in Tunisian patients. [Copyright &y& Elsevier]