Bovis Bacille Calmette-Guérin Infection Research Articles

Molecular detection of pre-ribosomal RNAs of Mycobacterium bovis bacille Calmette-Guérin and Mycobacterium tuberculosis to enhance pre-clinical tuberculosis drug and vaccine development

Efforts are underway globally to develop effective vaccines and drugs against M. tuberculosis (Mtb) to reduce the morbidity and mortality of tuberculosis. Improving detection of slow-growing mycobacteria could simplify and accelerate efficacy studies of vaccines and drugs in animal models and human clinical trials. Here, a real-time reverse transcription PCR (RT-PCR) assay was developed to detect pre-ribosomal RNA (pre-rRNA) of Mycobacterium bovis bacille Calmette-Guérin (BCG) and Mtb. This pre-rRNA biomarker is indicative of bacterial viability. In two different mouse models, the presence of pre-rRNA from BCG and Mtb in ex vivo tissues showed excellent agreement with slower culture-based colony-forming unit assays. The addition of a brief nutritional stimulation prior to molecular viability testing further differentiated viable but dormant mycobacteria from dead mycobacteria. This research has set the stage to evaluate pre-rRNA as a BCG and/or Mtb infection biomarker in future drug and vaccine clinical studies.

Cyclooxygenase-Derived Prostaglandin E2 Drives IL-1-Independent Mycobacterium bovis Bacille Calmette-Guérin-Triggered Skin Dendritic Cell Migration to Draining Lymph Node.

Inoculation of Mycobacterium bovis Bacille Calmette-Guérin (BCG) in the skin mobilizes local dendritic cells (DC) to the draining lymph node (dLN) in a process that remains incompletely understood. In this study, a mouse model of BCG skin infection was used to investigate mechanisms of skin DC migration to dLNs. We found enhanced transcription of cyclooxygenase (COX)-2 and production of COX-derived PGE2 early after BCG infection in skin. Animals treated with antagonists for COX or the PGE2 receptors EP2 and EP4 displayed a marked reduction in the entry of skin DCs and BCG to dLNs, uncovering an important contribution of COX-derived PGE2 in this migration process. In addition, live BCG bacilli were needed to invoke DC migration through this COX-PGE2 pathway. Having previously shown that IL-1R partially regulates BCG-induced relocation of skin DCs to dLNs, we investigated whether PGE2 release was under control of IL-1. Interestingly, IL-1R ligands IL-1α/β were not required for early transcription of COX-2 or production of PGE2 in BCG-infected skin, suggesting that the DC migration-promoting role of PGE2 is independent of IL-1α/β in our model. In DC adoptive transfer experiments, EP2/EP4, but not IL-1R, was needed on the moving DCs for full-fledged migration, supporting different modes of action for PGE2 and IL-1α/β. In summary, our data highlight an important role for PGE2 in guiding DCs to dLNs in an IL-1–independent manner.

Mycobacterium bovis Bacille-Calmette-Guérin Infection Aggravates Atherosclerosis.

Tuberculosis has been associated with increased risk of atherosclerotic cardiovascular disease. To examine whether mycobacterial infection exacerbates atherosclerosis development in experimental conditions, we infected low-density lipoprotein receptor knockout (Ldlr -/-) mice with Mycobacterium bovis Bacille-Calmette-Guérin (BCG), an attenuated strain of the Mycobacterium tuberculosis complex. Twelve-week old male Ldlr -/- mice were infected with BCG (0.3–3.0x106 colony-forming units) via the intranasal route. Mice were subsequently fed a western-type diet containing 21% fat and 0.2% cholesterol for up to 16 weeks. Age-matched uninfected Ldlr -/- mice fed with an identical diet served as controls. Atherosclerotic lesions in aorta were examined using Oil Red O staining. Changes induced by BCG infection on the immunophenotyping profile of circulating T lymphocytes and monocytes were assessed using flow cytometry. BCG infection increased atherosclerotic lesions in en face aorta after 8 weeks (plaque ratio; 0.021±0.01 vs. 0.013±0.01; p = 0.011) and 16 weeks (plaque ratio, 0.15±0.13 vs. 0.06±0.02; p = 0.003). No significant differences in plasma cholesterol or triglyceride levels were observed between infected and uninfected mice. Compared to uninfected mice, BCG infection increased systemic CD4/CD8 T cell ratio and the proportion of Ly6Clow non-classical monocytes at weeks 8 and 16. Aortic plaque ratios correlated with CD4/CD8 T cell ratios (Spearman’s rho = 0.498; p = 0.001) and the proportion of Ly6Clow non-classical monocytes (Spearman’s rho = 0.629; p < 0.001) at week 16. In conclusion, BCG infection expanded the proportion of CD4+ T cell and Ly6Clow monocytes, and aggravated atherosclerosis formation in the aortas of hyperlipidemic Ldlr -/- mice. Our results indicate that mycobacterial infection is capable of enhancing atherosclerosis development.

Dysregulation of key cytokines may contribute to increased susceptibility of diabetic mice to Mycobacterium bovis BCG infection

Diabetes is one of the major co-morbidities contributing to the high global burden of tuberculosis (TB). The increased susceptibility of individuals with type 2 diabetes (T2D) to TB is multifactorial and may influence the efficacy of vaccines. This study was undertaken to determine the early immune responses that occur following infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG) in a diet-induced murine model of T2D. The phagocytic capabilities of alveolar (AM) and resident peritoneal macrophages (RPM) were assessed using ex vivo assays. Compared to macrophages from non-diabetic mice, macrophages from diabetic animals showed decreased BCG uptake and killing and inflammatory cytokine production (TNF-α, MCP-1, IL-6, IL-1β). In vivo susceptibility to BCG was determined following intravenous infection and diabetic mice showed a trend towards increased mortality, higher bacterial burden in the lung, liver and spleen and increased inflammatory lesions compared to controls. Differences between tissue cytokines were observed as early as one day post-infection and by days 14 and 35, lung and liver TNF-α and IFN-γ levels were decreased in diabetic mice compared to controls. These results suggest that early dysregulated immune responses may influence the susceptibility of T2D mice to BCG infection.

Langerin+ CD8α+ Dendritic Cells Drive Early CD8+ T Cell Activation and IL-12 Production During Systemic Bacterial Infection.

Bloodstream infections induce considerable morbidity, high mortality, and represent a significant burden of cost in health care; however, our understanding of the immune response to bacteremia is incomplete. Langerin+ CD8α+ dendritic cells (DCs), residing in the marginal zone of the murine spleen, have the capacity to cross-prime CD8+ T cells and produce IL-12, both of which are important components of antimicrobial immunity. Accordingly, we hypothesized that this DC subset may be a key promoter of adaptive immune responses to blood-borne bacterial infections. Utilizing mice that express the diphtheria toxin receptor under control of the langerin promoter, we investigated the impact of depleting langerin+ CD8α+ DCs in a murine model of intravenous infection with Mycobacterium bovis bacille Calmette–Guerin (BCG). In the absence of langerin+ CD8α+ DCs, the immune response to blood-borne BCG infection was diminished: bacterial numbers in the spleen increased, serum IL-12p40 decreased, and delayed CD8+ T cell activation, proliferation, and IFN-γ production was evident. Our data revealed that langerin+ CD8α+ DCs play a pivotal role in initiating CD8+ T cell responses and IL-12 production in response to bacteremia and may influence the early control of systemic bacterial infections.

Hematopoietic stem cell gene therapy for IFNγR1 deficiency protects mice from mycobacterial infections

AbstractMendelian susceptibility to mycobacterial disease is a rare primary immunodeficiency characterized by severe infections caused by weakly virulent mycobacteria. Biallelic null mutations in genes encoding interferon gamma receptor 1 or 2 (IFNGR1 or IFNGR2) result in a life-threatening disease phenotype in early childhood. Recombinant interferon γ (IFN-γ) therapy is inefficient, and hematopoietic stem cell transplantation has a poor prognosis. Thus, we developed a hematopoietic stem cell (HSC) gene therapy approach using lentiviral vectors that express Ifnγr1 either constitutively or myeloid specifically. Transduction of mouse Ifnγr1−/− HSCs led to stable IFNγR1 expression on macrophages, which rescued their cellular responses to IFN-γ. As a consequence, genetically corrected HSC-derived macrophages were able to suppress T-cell activation and showed restored antimycobacterial activity against Mycobacterium avium and Mycobacterium bovis Bacille Calmette-Guérin (BCG) in vitro. Transplantation of genetically corrected HSCs into Ifnγr1−/− mice before BCG infection prevented manifestations of severe BCG disease and maintained lung and spleen organ integrity, which was accompanied by a reduced mycobacterial burden in lung and spleen and a prolonged overall survival in animals that received a transplant. In summary, we demonstrate an HSC-based gene therapy approach for IFNγR1 deficiency, which protects mice from severe mycobacterial infections, thereby laying the foundation for a new therapeutic intervention in corresponding human patients.

Healthcare-Associated Mycobacterium bovis-Bacille Calmette-Guérin (BCG) Infection in Cancer Patients Without Prior BCG Instillation.

Bacille Calmette-Guérin (BCG), an attenuated strain of Mycobacterium bovis, is widely used as adjunctive therapy for superficial bladder cancer. Intravesical administration of BCG has been associated with systemic infection. Disseminated infection due to M. bovis is otherwise uncommon. After identification of 3 patients with healthcare-associated BCG infection who had never received intravesical BCG administration, an epidemiologic study was performed. All patients with healthcare-associated BCG infection in the Barcelona tuberculosis (TB) program were reviewed from 1 January 2005 to 31 December 2015, searching for infections caused by M. bovis-BCG. Patients with healthcare-associated BCG infection who had not received intravesical BCG instillation were selected and the source of infection was investigated. Nine oncology patients with infection caused by M. bovis-BCG were studied. All had permanent central venous catheters. Catheter maintenance was performed at 4 different outpatient clinics in the same room in which other patients underwent BCG instillations for bladder cancer without required biological precautions. All patients developed pulmonary TB, either alone or with extrapulmonary disease. Catheter-related infection was considered the mechanism of acquisition based on the epidemiologic association and positive catheter cultures for BCG in patients in whom mycobacterial cultures were performed. Physicians should be alerted to the possibility of TB due to nosocomially acquired, catheter-related infections with M. bovis-BCG in patients with indwelling catheters. This problem may be more common than expected in centers providing BCG therapy for bladder cancer without adequate precautions.

Mycobacteria Manipulate G-Protein-Coupled Receptors to Increase Mucosal Rac1 Expression in the Lungs

Mycobacterium bovis bacille Calmette-Guérin (BCG) is currently the only approved vaccine against tuberculosis (TB). BCG mimics M. tuberculosis (Mtb) in its persistence in the body and is used as a benchmark to compare new vaccine candidates. BCG was originally designed for mucosal vaccination, but comprehensive knowledge about its interaction with epithelium is currently lacking. We used primary airway epithelial cells (AECs) and a murine model to investigate the initial events of mucosal BCG interactions. Furthermore, we analysed the impact of the G-protein-coupled receptors (GPCRs), CXCR1 and CXCR2, in this process, as these receptors were previously shown to be important during TB infection. BCG infection of AECs induced GPCR-dependent Rac1 up-regulation, resulting in actin redistribution. The altered distribution of the actin cytoskeleton involved the MAPK signalling pathway. Blocking of the CXCR1 or CXCR2 prior to infection decreased Rac1 expression, and increased epithelial transcriptional activity and epithelial cytokine production. BCG infection did not result in epithelial cell death as measured by p53 phosphorylation and annexin. This study demonstrated that BCG infection of AECs manipulated the GPCRs to suppress epithelial signalling pathways. Future vaccine strategies could thus be improved by targeting GPCRs.

BCG Skin Infection Triggers IL-1R-MyD88-Dependent Migration of EpCAMlow CD11bhigh Skin Dendritic cells to Draining Lymph Node During CD4+ T-Cell Priming.

The transport of antigen from the periphery to the draining lymph node (DLN) is critical for T-cell priming but remains poorly studied during infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG). To address this we employed a mouse model to track the traffic of Dendritic cells (DCs) and mycobacteria from the BCG inoculation site in the skin to the DLN. Detection of BCG in the DLN was concomitant with the priming of antigen-specific CD4+ T cells at that site. We found EpCAMlow CD11bhigh migratory skin DCs to be mobilized during the transport of BCG to the DLN. Migratory skin DCs distributed to the T-cell area of the LN, co-localized with BCG and were found in close apposition to antigen-specific CD4+ T cells. Consequently, blockade of skin DC traffic into DLN dramatically reduced mycobacterial entry into DLN and muted T-cell priming. Interestingly, DC and mycobacterial entry into the DLN was dependent on IL-1R-I, MyD88, TNFR-I and IL-12p40. In addition, we found using DC adoptive transfers that the requirement for MyD88 in BCG-triggered migration was not restricted to the migrating DC itself and that hematopoietic expression of MyD88 was needed in part for full-fledged migration. Our observations thus identify a population of DCs that contribute towards the priming of CD4+ T cells to BCG infection by transporting bacilli into the DLN in an IL-1R-MyD88-dependent manner and reveal both DC-intrinsic and -extrinsic requirements for MyD88 in DC migration.

Signaling lymphocyte-activation molecule SLAMF1 augments mycobacteria BCG-induced inflammatory response and facilitates bacterial clearance

Tuberculosis, which is caused by intracellular mycobacterium Mycobacterium tuberculosis (Mtb), remains one of the most serious global public health concerns. The mechanisms by which innate immunity regulates the inflammatory responses and affects mycobacterial infection remain unclear. In this study, signaling lymphocyte-activation molecule family 1 (SLAMF1) was significantly upregulated in Mycobacterium bovis Bacille Calmette–Guérin (BCG)-infected RAW264.7 cells. Overexpression of SLAMF1 significantly increased the production of inflammatory factors TNF-α and IL-1β, as well as chemokine MCP-1, both in vitro and in vivo upon mycobacteria BCG infection. By contrast, knockdown of SLAMF1 significantly decreased the production of TNF-α, IL-1β, and MCP-1. Western blot analysis indicated that the NF-κB signaling pathway may contribute to the elevated inflammatory response promoted by SLAMF1, as evidenced by higher levels of phosphorylated p65 and IκBα detected with SLAMF1 overexpression. Furthermore, SLAMF1 upregulation facilitated bacterial clearance in infected RAW264.7 cells and in the lungs of infected mice. In conclusion, we demonstrated that BCG infection significantly upregulated SLAMF1, which enhanced inflammatory response by activating the NF-κB signaling pathway and facilitated bacterial clearance in BCG-infected RAW264.7 cells and mice.

Augmentation of antitubercular therapy with IFNγ in a patient with dominant partial IFNγ receptor 1 deficiency

Osteomyelitis due to Mycobacterium bovis Bacille Calmette-Guerin (BCG) often develops in patients with interferon-γ receptor 1 (IFNγR1) deficiency. In these patients, susceptibility appears to be caused by impaired interleukin-12- and IFNγ-mediated immunity. Here we report the case of a one-year-old girl with dominant partial IFNγR1 deficiency who suffered from lymphadenitis and multiple sites of osteomyelitis due to BCG infection. She was allergic to isoniazid and rifampicin--the prescribed standard treatment--and required prior desensitization therapy. She was subsequently treated with these drugs, but her symptoms did not improve. IFNγ therapy was added to the antitubercular therapy, increasing the serum level of IFNγ and leading to the resolution of the lymphadenitis and osteomyelitis. In conclusion, high dose IFNγ therapy in combination with antitubercular drugs led to resolution of BCG infection in a patient with dominant partial IFNγ deficiency.

ELISPOT Refinement Using Spot Morphology for Assessing Host Responses to Tuberculosis

Tuberculosis is a global health problem. The Mycobacterium bovis Bacille Calmette Guerin (BCG) vaccine has variable efficacy (0-80%) so there is a drive to develop novel vaccines. The cytokine, interferon gamma (IFNγ), is an essential component of the protective response to M. tuberculosis (M. tb) infection and is also produced in response to BCG vaccination. Induction of an IFNγ response is used as a biomarker of successful vaccination in the assessment of new tuberculosis (TB) vaccines. The IFNγ ELISPOT assay provides an important tool for TB research. It is used for both the diagnosis of infection (T.Spot assay), and for the evaluation of the immunogenicity of new TB vaccine candidates in human clinical trials, in the non-human primate (NHP) model of TB infection studies. The ELISPOT assay captures IFNγ produced by peripheral blood mononuclear cells (PBMCs) following specific stimulation, onto a membrane so individual cells can be enumerated and the frequency of responding cells determined. Hence spot forming units (SFU) per 106 cells provide the traditional measure for ELISPOT assays. The discriminatory power of SFU is limited. In some situations, the number of SFU in BCG vaccinated, and unvaccinated, subjects was found to be similar, although the spots were observed to be larger in vaccinated subjects. Spot size potentially provides a measure of the quantity of cytokine produced by individual cells. The AID ELISPOT plate reader software used to determine frequency of spots also has the capability to determine the size of each spot. Consideration of spot size in combination with spot forming units was investigated in our studies of BCG immunogenicity. This additional readout was found to enhance the discriminatory power of the ELISPOT assay, and provide more information on the immune response to BCG vaccination and infection with M.tb.

CD8α+ and CD8α− DC subsets from BCG‐infected mice inhibit allergic Th2‐cell responses by enhancing Th1‐cell and Treg‐cell activity respectively

The hygiene hypothesis has suggested an inhibitory effect of infections on allergic diseases, but the related mechanism remains unclear. We recently reported that DCs played a critical role in Mycobacterium bovis Bacille Calmette-Guérin (BCG)-mediated inhibition of allergy, which depended on IL-12 and IL-10-related mechanisms. Here, we tested the hypothesis that BCG infection could modulate the function of DC subsets, which might in turn inhibit allergic responses through different mechanisms. We sorted CD8α(+) and CD8α(-) DCs from BCG-infected mice and tested their ability to modulate Th2-cell responses to ovalbumin (OVA) using in vitro and in vivo approaches. We found that both DC subsets could inhibit the allergic Th2-cell response in both a DC:T-cell co-culture system and after adoptive transfer. These subsets exhibited different co-stimulatory marker expression and cytokine production patterns and were different in inducing Th1 and Treg cells. Specifically, we found that CD8α(+) DCs produced higher IL-12, inducing higher Th1 cell response, while CD8α(-) DCs expressed higher ICOS-L and produced higher IL-10, inducing CD4(+) CD25(+) FoxP3(+) Treg cells with IL-10 production and membrane-bound TGF-β expression. The finding suggests that one infection may inhibit allergy by both immune deviation and regulation mechanisms through modulation of DC subsets.

Strain-Specific Differences in the Genetic Control of Two Closely Related Mycobacteria

The host response to mycobacterial infection depends on host and pathogen genetic factors. Recent studies in human populations suggest a strain specific genetic control of tuberculosis. To test for mycobacterial-strain specific genetic control of susceptibility to infection under highly controlled experimental conditions, we performed a comparative genetic analysis using the A/J- and C57BL/6J-derived recombinant congenic (RC) mouse panel infected with the Russia and Pasteur strains of Mycobacterium bovis Bacille Calmette Guérin (BCG). Bacillary counts in the lung and spleen at weeks 1 and 6 post infection were used as a measure of susceptibility. By performing genome-wide linkage analyses of loci that impact on tissue-specific bacillary burden, we were able to show the importance of correcting for strain background effects in the RC panel. When linkage analysis was adjusted on strain background, we detected a single locus on chromosome 11 that impacted on pulmonary counts of BCG Russia but not Pasteur. The same locus also controlled the splenic counts of BCG Russia but not Pasteur. By contrast, a locus on chromosome 1 which was indistinguishable from Nramp1 impacted on splenic bacillary counts of both BCG Russia and Pasteur. Additionally, dependent upon BCG strain, tissue and time post infection, we detected 9 distinct loci associated with bacillary counts. Hence, the ensemble of genetic loci impacting on BCG infection revealed a highly dynamic picture of genetic control that reflected both the course of infection and the infecting strain. This high degree of adaptation of host genetics to strain-specific pathogenesis is expected to provide a suitable framework for the selection of specific host-mycobacteria combinations during co-evolution of mycobacteria with humans.

Essential Role of IL-17A in the Formation of a Mycobacterial Infection-Induced Granuloma in the Lung

Granulomas play an essential role in the sequestration and killing of mycobacteria in the lung; however, the mechanisms of their development and maturation are still not clearly understood. IL-17A is involved in mature granuloma formation in the mycobacteria-infected lung. Therefore, IL-17A gene-knockout (KO) mice fail to develop mature granulomas in the Mycobacterium bovis bacille Calmette-Guérin (BCG)-infected lung. This study analyzed the mechanism of IL-17A-dependent mature granuloma formation in the mycobacteria-infected lung. The IL-17A KO mice showed a normal level of nascent granuloma formation on day 14 but failed to develop mature granulomas on day 28 after the BCG infection in the lung. The observation implies that IL-17A is required for the maturation of granuloma from the nascent to mature stage. TCR gammadelta T cells expressing TCR Vgamma4 or Vgamma6 were identified as the major IL-17A-producing cells that resided in the BCG-induced lung granuloma. The adoptive transfer of the IL-17A-producing TCR gammadelta T cells reconstituted granuloma formation in the IL-17A KO mice. The expression of ICAM-1 and LFA-1, which are adhesion molecules important in granuloma formation, decreased in the lung of the BCG-infected IL-17A KO mice, and their expression was induced on BCG-infected macrophages in coculture with IL-17A-producing TCR gammadelta T cells. Furthermore, IL-17A KO mice showed not only an impaired mature granuloma formation, but also an impaired protective response to virulent Mycobacterium tuberculosis. Therefore, IL-17A produced by TCR gammadelta T cells plays a critical role in the prevention of M. tuberculosis infection through the induction of mature granuloma formation.

Protective role of membrane tumour necrosis factor in the host’s resistance to mycobacterial infection

Tumour necrosis factor-α (TNF-α) plays a critical role in the recruitment and activation of mononuclear cells in mycobacterial infection. The role of membrane TNF, in host resistance against Mycobacterium bovis bacille Calmette–Guérin (BCG), was tested in knock-in mice in which the endogenous TNF was replaced by a non-cleavable and regulated allele (Δ1–12, TNFtm/tm). While 100% of mice with complete TNF deficiency (TNF−/−) succumbed to infection, 50% of TNFtm/tm mice were able to control M. bovis BCG infection and survived the experimental period. Membrane expressed TNF allowed a substantial recruitment of activated T cells and macrophages with granuloma formation and expression of bactericidal inducible nitric oxide synthase (iNOS). Using virulent Mycobacterium tuberculosis infection we confirm that membrane TNF conferred partial protection. Infection in TNFtm/tm double transgenic mice with TNF-R1 or TNF-R2 suggest protection is mediated through TNF-R2 signalling. Therefore, the data suggest that membrane-expressed TNF plays a critical role in host defence to mycobacterial infection and may partially substitute for soluble TNF.

Mycobacterium bovisBacille Calmette-Guérin Infection in the CNS Suppresses Experimental Autoimmune Encephalomyelitis and Th17 Responses in an IFN-γ-Independent Manner

Multiple sclerosis and an animal model resembling multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), are inflammatory demyelinating diseases of the CNS that are suppressed by systemic mycobacterial infection in mice and BCG vaccination in humans. Host defense responses against Mycobacterium in mice are influenced by T lymphocytes and their cytokine products, particularly IFN-gamma, which plays a protective regulatory role in EAE. To analyze the counter-regulatory role of mycobacterial infection-induced IFN-gamma in the CNS on the function of the pathological Th17 cells and the clinical outcome of EAE, we induced EAE in mice that were intracerebrally infected with Mycobacterium bovis bacille Calmette-Guerin (BCG). In this study, we demonstrate that intracerebral (i.c.) BCG infection prevented inflammatory cell recruitment to the spinal cord and suppressed the development of EAE. Concomitantly, there was a significant decrease in the frequency of myelin oligodendrocyte glycoprotein-specific IFN-gamma-producing CD4(+) T cells in the CNS. IL-17(+)CD4(+) T cell responses were significantly suppressed in i.c. BCG-infected mice following EAE induction regardless of T cell specificity. The frequency of Foxp3(+)CD4(+) T cells in these mice was equivalent to that of control mice. Intracerebral BCG infection-induced protection of EAE and suppression of myelin oligodendrocyte glycoprotein-specific IL-17(+)CD4(+) T cell responses were similar in both wild-type and IFN-gamma-deficient mice. These data show that live BCG infection in the brain suppresses CNS autoimmunity. These findings also reveal that the regulation of Th17-mediated autoimmunity in the CNS can be independent of IFN-gamma-mediated mechanisms.

Induction of cell cycle arrest and apoptosis by BCG infection in cultured human bronchial airway epithelial cells

Bronchial airway epithelial cells (BAEpC) are among the first cells to encounter M. tuberculosis following airborne infection. However, the response of BAEpC to M. tuberculosis infection has been little studied. This study investigates the response of a human BAEpC cell line (BEAS-2B) to infection with Mycobacterium bovis Bacille Calmette Guerin (BCG). Cultured human BEAS-2B cells were experimentally infected with BCG. Uninfected BEAS-2B cultures were included as controls. Following infection, BEAS-2B cells were evaluated by various methods at various time points up to 3 days. Cell proliferation was evaluated by cellular bioreduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Distribution of cells along the cell cycle was evaluated by FACS analysis of cellular DNA. Apoptotic cells were identified by cell death ELISA and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling method. Eighty-four apoptosis-relevant genes were screened by PCR gene microarray. Translation of Fas, Fas ligand (Fas-L), and Fas-associated death domain (FADD) were evaluated quantitatively by real-time PCR. Expression of Fas and FADD proteins was evaluated by immunofluorescence and Western blot. Activity of caspase-3 and caspase-8 was evaluated by colorimetric assay of their enzymatic activity. BCG infection of BEAS-2B cells inhibits proliferation, induces cell cycle arrest at the G(0)/G(1) phase, causes apoptosis, modulates transcription of multiple apoptosis-relevant genes, promotes translation of Fas, Fas-L, and FADD, upregulates expression of Fas and FADD proteins, and increases activity of caspase-3 and caspase-8. Infection with BCG does not cause any significant change in the secretion of TGF-beta. The roles of Fas and FADD as mediators of BCG-induced apoptosis in BEAS-2B cells were tested by partial blockade of Fas and FADD expression with silencing RNA. Partial blockade of Fas or FADD expression results in a decreased apoptotic response to BCG infection. In conclusion, BCG induces cell cycle arrest and apoptosis in BEAS-2B cells. BCG induced apoptosis of BEAS-2B cells via the Fas death receptor pathway.

IL-17-Mediated Regulation of Innate and Acquired Immune Response against Pulmonary Mycobacterium bovis Bacille Calmette-Guérin Infection

IL-17 is a cytokine that induces neutrophil-mediated inflammation, but its role in protective immunity against intracellular bacterial infection remains unclear. In the present study, we demonstrate that IL-17 is an important cytokine not only in the early neutrophil-mediated inflammatory response, but also in T cell-mediated IFN-gamma production and granuloma formation in response to pulmonary infection by Mycobacterium bovis bacille Calmette-Guérin (BCG). IL-17 expression in the BCG-infected lung was detected from the first day after infection and the expression depended on IL-23. Our observations indicated that gammadelta T cells are a primary source of IL-17. Lung-infiltrating T cells of IL-17-deficient mice produced less IFN-gamma in comparison to those from wild-type mice 4 wk after BCG infection. Impaired granuloma formation was also observed in the infected lungs of IL-17-deficient mice, which is consistent with the decreased delayed-type hypersensitivity response of the infected mice against mycobacterial Ag. These data suggest that IL-17 is an important cytokine in the induction of optimal Th1 response and protective immunity against mycobacterial infection.

Presentation of Interleukin-12/-23 Receptor β1 Deficiency with Various Clinical Symptoms of Salmonella Infections

Clinical disease caused by weakly pathogenic mycobacterial species, Mycobacterium bovis Bacille Calmette-Guérin (BCG) and non-tuberculous environmental mycobacteria (EM), which is known as Mendelian susceptibility to mycobacterial disease (MSMD), is a rare entity defined recently. Infections with the more virulent Mycobacterium species, M. tuberculosis, may have largely gone unnoticed in these patients due to early death. Mutations in five proteins (IFNgammaR1, IFNgammaR2, IL-12/IL-23Rbeta1, IL-12/IL-23p40 and STAT1) have been found in MSMD. These patients are prone to surprisingly few other infectious diseases mainly to salmonellosis. Here we present three IL-12/IL-23Rbeta1 deficient patients from three different families and with different genetic mutations, who presented exclusively with Salmonella infections. Bacteremia and lymph node involvement were common clinical expressions. Leukocytoclastic vasculitis developed in one of these patients. Two patients were not inoculated with BCG, the third patient did not develop BCG infection although BCG vaccine had been given twice at ages of 1 and 7 years. All three patients responded well to antibiotic treatment. In conclusion, patients with chronic, recurrent or complicated Salmonella infections should be screened for MSMD, particularly for IL-12/IL-23p40/IL-12R/-23Rbeta1 deficiency. Conversely, in patients with genetic IL-12/-23Rbeta1 deficiency a full evaluation for Salmonella infection is required. IL-12/IL-23p40/IL-12R/IL-23Rbeta1 deficiency seem to be underdiagnosed in patients with salmonellosis, and since such patients need prolonged therapy, diagnosis is important.