Correlation of virulence, lung pathology, bacterial load and delayed type hypersensitivity responses after infection with different Mycobacterium tuberculosis genotypes in a BALB/c mouse model

Ag85B with c-di-AMP as mucosal adjuvant showed immunotherapeutic effects on persistent Mycobacterium tuberculosis infection in mice

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains the leading cause of mortality by a single infectious agent in the world. M. tuberculosis infection could also result in clinical chronic infection, known as latent TB infection (LTBI). Compared to the current limited treatment, several subunit vaccines showed immunotherapeutic effects and were included in clinical trials. In this study, a subunit vaccine of Ag85B with a novel mucosal adjuvant c-di-AMP (Ag85B:c-di-AMP) was delivered intranasally to a persistent M. tuberculosis H37Ra infection mouse model, which also presented the asymptomatic characteristics of LTBI. Compared with Ag85B immunization, Ag85B:c-di-AMP vaccination induced stronger humoral immune responses, significantly higher CD4+ T cells recruitment, enhanced Th1/Th2/Th17 profile response in the lung, decreased pathological lesions of the lung, and reduced M. tuberculosis load in mice. Taken together, Ag85B:c-di-AMP mucosal route immunization provided an immunotherapeutic effect on persistent M. tuberculosis H37Ra infection, and c-di-AMP, as a promising potential mucosal adjuvant, could be further used in therapeutic or prophylactic vaccine strategies for persistent M. tuberculosis infection as well as LTBI.

Shape variation in cranium, mandible and teeth in selected mouse strains

There are different strains of laboratory mouse used in many different fields. These strains differ anatomically. In order to determine these anatomical differences, shape analysis was conducted according to species. CD-1, C57bl/6 and Balb-c strains were preferred to study these differences. Forty-eight adult mouse strains belonging to these strains were utilized. The bones were photographed and geometric morphometry was applied to these photographs. Principal Component Analysis was applied to determine shape variations. In Principal component 1 for cranium, CD-1 and C57bl/6 strain groups showed different shape variations, while Balb-c strain group showed similar shape variations to the other strain groups. Principal Component 1 for the mandible separated the CD-1 and C57bl/6 strain groups in terms of shape variation. Principal Component 2 explained most of the variation between the C57bl/6 and CD-1 lineage groups. In PC1 for molars, the CD-1 group showed a different shape variation from the other groups. Mahalanobis distances and Procrustes distances were measured using Canonical variance analysis to explain the differences between the lineage groups. These measurements were statistically significant. For cranium, in canonical variate 1, CD-1 group of mouse and Balb-c group of mouse were separated from each other. In canonical variate 2, C57bl/6 group of mouse were separated from the other groups. For mandible, Balb-c group of mouse in canonical variate 1 and CD-1 group of mouse in canonical variate 2 were separated from the other groups. For molars, CD-1 group of mouse in canonical variate 1 and Balb-c group of mouse in canonical variate 2 were separated from the other groups. It was thought that these anatomical differences could be caused by genotypic factors as well as dietary differences and many different habits that would affect the way their muscles work.

The Evolution of Diagnostic Techniques in the Paleopathology of Tuberculosis: A Scoping Review

Tuberculosis (TB) is an ancient chronic infectious disease that remains a global health concern. In human remains, the most common and characteristic clinical signs are the skeletal modifications involving the spine, such as in Pott's disease. Diagnosing TB in ancient human remains is challenging. Therefore, in this systematic review, the authors investigated the studies assessing molecular diagnosis of Pott's disease in ancient human remains with the intention to survey the literature, map the evidence, and identify gaps and future perspectives on TB in paleopathology. Our systematic review offers a full contextualization of the history of Pott's disease in ancient times. Our search strategy was performed between August 2022 and March 2023. The authors initially identified 340 records, and 74 studies were finally included and assessed for qualitative analysis. Due to non-specific clinical signs associated with TB, how best to diagnose tuberculosis in human remains still represents a central point. Nevertheless, ancient DNA (aDNA) analysis, lipid biomarkers, and spoligotyping might be extremely useful tools in the study of TB in human remains. Moreover, we propose the extraction and study of immune response genes involved in innate and adaptive immunity versus Mycobacterium spp. as an innovative and vastly overlooked approach in TB paleopathology. Complementary methodologies should be integrated to provide the best approach to the study of TB in human remains.

Natural mutations in the sensor kinase of the PhoPR two-component regulatory system modulate virulence of ancestor-like tuberculosis bacilli

The molecular factors and genetic adaptations that contributed to the emergence of Mycobacterium tuberculosis (MTB) from an environmental Mycobacterium canettii-like ancestor, remain poorly investigated. In MTB, the PhoPR two-component regulatory system controls production and secretion of proteins and lipid virulence effectors. Here, we describe that several mutations, present in phoR of M. canettii relative to MTB, impact the expression of the PhoP regulon and the pathogenicity of the strains. First, we establish a molecular model of PhoR and show that some substitutions found in PhoR of M. canettii are likely to impact the structure and activity of this protein. Second, we show that STB-K, the most attenuated available M. canettii strain, displays lower expression of PhoP-induced genes than MTB. Third, we demonstrate that genetic swapping of the phoPR allele from STB-K with the ortholog from MTB H37Rv enhances expression of PhoP-controlled functions and the capacities of the recombinant strain to colonize human macrophages, the MTB target cells, as well as to cause disease in several mouse infection models. Fourth, we extended these observations to other M. canettii strains and confirm that PhoP-controlled functions are expressed at lower levels in most M. canettii strains than in M. tuberculosis. Our findings suggest that distinct PhoR variants have been selected during the evolution of tuberculosis bacilli, contributing to higher pathogenicity and persistence of MTB in the mammalian host.

BORC complex specific components and Kinesin-1 mediate autophagy evasion by the autophagy-resistant Mycobacterium tuberculosis Beijing strain

Autophagy induction by starvation has been shown to enhance lysosomal delivery to mycobacterial phagosomes, resulting in the restriction of the Mycobacterium tuberculosis reference strain H37Rv. In contrast to H37Rv, our previous study showed that strains belonging to the notorious M. tuberculosis Beijing genotype could evade autophagic elimination. Our recent RNA-Seq analysis also discovered that the autophagy-resistant M. tuberculosis Beijing strain (BJN) evaded autophagic control by upregulating the expression of Kxd1, a BORC complex component, and Plekhm2, both of which function in lysosome positioning towards the cell periphery in host macrophages, thereby suppressing enhanced lysosomal delivery to its phagosome and sparing the BJN from elimination as a result. In this work, we further characterised the other specific components of the BORC complex, BORC5-8, and Kinesin proteins in autophagy resistance by the BJN. Depletion of BORCS5-8 and Kinesin-1, but not Kinesin-3, reverted autophagy avoidance by the BJN, resulting in increased lysosomal delivery to the BJN phagosomes. In addition, the augmented lysosome relocation towards the perinuclear region could now be observed in the BJN-infected host cells depleted in BORCS5-8 and Kinesin-1 expressions. Taken together, the data uncovered new roles for BORCS5-8 and Kinesin-1 in autophagy evasion by the BJN.

Clinical strains of Mycobacterium tuberculosis exhibit differential lipid metabolism-associated transcriptome changes in in vitro cholesterol and infection models

Many studies have identified host-derived lipids, characterised by the abundance of cholesterol, as a major source of carbon nutrition for Mycobacterium tuberculosis during infection. Members of the Mycobacterium tuberculosis complex are biologically different with regards to degree of disease, host range, pathogenicity and transmission. Therefore, the current study aimed at elucidating transcriptome changes during early infection of pulmonary epithelial cells and on an in vitro cholesterol-rich minimal media, in M. tuberculosis clinical strains F15/LAM4/KZN and Beijing, and the laboratory H37Rv strain. Infection of pulmonary epithelial cells elicited the upregulation of fadD28 and hsaC in both the F15/LAM4/KZN and Beijing strains and the downregulation of several other lipid-associated genes. Growth curve analysis revealed F15/LAM4/KZN and Beijing to be slow growers in 7H9 medium and cholesterol-supplemented media. RNA-seq analysis revealed strain-specific transcriptomic changes, thereby affecting different metabolic processes in an in vitro cholesterol model. The differential expression of these genes suggests that the genetically diverse M. tuberculosis clinical strains exhibit strain-specific behaviour that may influence their ability to metabolise lipids, specifically cholesterol, which may account for phenotypic differences observed during infection.

Host cell transcriptomic response to the multidrug-resistant Mycobacterium tuberculosis clonal outbreak Beijing strain reveals its pathogenic features

The upsurge of multidrug-resistant infections has rendered tuberculosis the principal cause of death among infectious diseases. A clonal outbreak multidrug-resistant triggering strain of Mycobacterium tuberculosis was identified in Kanchanaburi Province, labelled "MKR superspreader," which was found to subsequently spread to other regions, as revealed by prior epidemiological reports in Thailand. Herein, we showed that the MKR displayed a higher growth rate upon infection into host macrophages in comparison with the H37Rv reference strain. To further elucidate MKR's biology, we utilized RNA-Seq and differential gene expression analyses to identify host factors involved in the intracellular viability of the MKR. A set of host genes function in the cellular response to lipid pathway was found to be uniquely up-regulated in host macrophages infected with the MKR, but not those infected with H37Rv. Within this set of genes, the IL-36 cytokines which regulate host cell cholesterol metabolism and resistance against mycobacteria attracted our interest, as our previous study revealed that the MKR elevated genes associated with cholesterol breakdown during its growth inside host macrophages. Indeed, when comparing macrophages infected with the MKR to H37Rv-infected cells, our RNA-Seq data showed that the expression ratio of IL-36RN, the negative regulator of the IL-36 pathway, to that of IL-36G was greater in macrophages infected with the MKR. Furthermore, the MKR's intracellular survival and increased intracellular cholesterol level in the MKR-infected macrophages were diminished with decreased IL-36RN expression. Overall, our results indicated that IL-36RN could serve as a new target against this emerging multidrug-resistant M. tuberculosis strain.

The Emergence of Novel Spoligotypes of Highly Drug-Resistant Mycobacterium tuberculosis Isolates in Fujian, China

Background

Here, we aimed to determine the population structure of Mycobacterium tuberculosis (MTB) genotypes in Fujian and explore risk factors associated with infection with the Beijing genotype. We also explored the association between Beijing genotype and drug resistance.

Methods

Representative MTB isolates obtained during provincial-level routine anti-tuberculosis drug resistance surveillance conducted since 2013 in 11 Fujian counties were analyzed using McSpoligotyping. In vitro drug susceptibilities to anti-tuberculosis drugs were determined using the standard Löwenstein–Jensen proportion method.

Results

Overall, 477 MTB isolates were included in the study, of which 245 isolates belonged to the Beijing genotype family and 232 possessed non-Beijing genotypes. Ultimately, a total of 204 spoligotypes were identified that included 58 spoligotype international types (SITs) from the SITVITWEB database and 146 novel spoligotypes. As compared to patients <25 years of age (control group), elderly patients (≥65 years of age) were more likely to be infected with non-Beijing genotypes [aOR 18.69, 95% CI (5.80–60.26)], with risk of infection with non-Beijing genotypes increasing with age [aOR 3.73, 95% CI (1.67–8.30) for patients 45–64 years of age]. Additionally, as compared to isolates with Beijing and other non-Beijing genotypes, significantly greater proportions of isolates with novel spoligotypes exhibited PTO- and PAS-resistance. Moreover, a markedly higher proportion of isolates with novel spoligotypes exhibited OFX-resistance as compared to isolates with other non-Beijing genotypes.

Conclusion

Our data demonstrated that the Beijing genotype is the predominant MTB sublineage in Fujian and that the prevalence rate of infection with this MTB genotype decreases with advancing patient age. Notably, the prevalence rate of this genotype in Fujian TB patients is relatively lower than in other regions of China. In addition, the emergence of novel spoligotypes of highly drug-resistant MTB isolates highlights the urgent need for ongoing molecular genotyping surveillance in Fujian.

Cyclic-di-AMP Phosphodiesterase Elicits Protective Immune Responses Against Mycobacterium tuberculosis H37Ra Infection in Mice

Many antigens from Mycobacterium tuberculosis (M. tuberculosis) have been demonstrated as strong immunogens and proved to have application potential as vaccine candidate antigens. Cyclic di-AMP (c-di-AMP) as a bacterial second messenger regulates various bacterial processes as well as the host immune responses. Rv2837c, the c-di-AMP phosphodiesterase (CnpB), was found to be relative to virulence of M. tuberculosis and interference with host innate immune response. In this study, recombinant CnpB was administered subcutaneously to mice. We found that CnpB had strong immunogenicity and induced high levels of humoral response and lung mucosal immunity after M. tuberculosis intranasally infection. CnpB immunization stimulated splenocyte proliferation and the increasing number of activated NK cells but had little effects on Th1/Th2 cellular immune responses in spleens. However, CnpB induced significant Th1/Th2 cellular immune responses with a decreased number of T and B cells in the lungs, and significantly recruits of CD4+ and CD8+ T cells after M. tuberculosis attenuated strain H37Ra infection. Besides, we first reported that CnpB could stimulate IFN-β expression transitorily and inhibit the autophagy of macrophages in vitro. In mice intranasally infection model, CnpB immunization alleviated pathological changes and reduced M. tuberculosis H37Ra loads in the lungs. Thus, our results suggested that CnpB interferes with host innate and adaptive immune responses and confers protection against M. tuberculosis respiratory infection, which should be considered in vaccine development as well as a drug target.

Dropping mortality by increasing connectivity in plant epidemics

Pathogen introduction in plant communities can cause serious impacts and biodiversity losses that may take a long time to manage and restore. Effective control of epidemic spreading in the wild is a problem of paramount importance because of its implications in conservation and potential economic losses. Understanding the mechanisms that hinder pathogen propagation is, therefore, crucial. Usual modelization approaches in epidemic spreading are based in compartmentalized models, without keeping track of pathogen concentrations during spreading. In this contribution we present and fully analyze a dynamical model for plant epidemic spreading based on pathogen abundances. The model, which is defined on top of network substrates, is amenable to a deep mathematical analysis in the absence of a limit in the amount of pathogen a plant can tolerate before dying. In the presence of such death threshold, we observe that the fraction of dead plants peaks at intermediate values of network connectivity, and mortality decreases for large average degrees. We discuss the implications of our results as mechanisms to halt infection propagation.

Elevated IL-35 level and iTr35 subset increase the bacterial burden and lung lesions in Mycobacterium tuberculosis-infected mice

This study aimed to investigate the relationship between interleukin (IL)-35 level and IL-35-producing regulatory T cells (iTr35 subset) in Mycobacterium tuberculosis (Mtb)-infected mice. After the mice were injected with Mtb strain H37R via tail vein, the bacterial burden, lung lesions, and the impact of immune suppression on the infected mice were respectively assessed. The results, when compared with the control mice, showed that the mRNA expression levels of the p35 and Epstein-Barr virus-induced gene 3 of IL-35 were significantly increased in the Mtb-infected mouse spleen at 4 or 8 weeks post-infection and their protein expression levels were concurrently increased in the lungs of the mice, especially in 8 week infected mice. In addition, the levels of serum IL-35 and the iTr35 subset in the spleen of mice were also increased in 4 or 8 weeks post-infection compared with the control mice. Importantly, the high bacterial burden and lung lesions and the low mouse weight were found at 8 week post-infection. Therefore, the mice infected with Mtb resulted in elevating IL-35 level and iTr35 subset and increasing bacterial burden and lung lesions. The findings from the study suggest IL-35 and iTr35 cells may exert an immune suppression role in chronic Mtb-infected mice.

Pleiotropic Effect of IL-6 Produced by B-Lymphocytes During Early Phases of Adaptive Immune Responses Against TB Infection

The role of B cells migrating to the lung and forming follicles during tuberculosis (TB) inflammation is still the subject of debate. In addition to their antibody production and antigen-presenting functions, B cells secrete different cytokines and chemokines, thus participating in complex networks of innate and adaptive immunity. Importantly, lung B-cells produce high amounts of the pleiotropic gp130 cytokine IL-6. Its role during TB infection remains controversial, partly due to the fact that IL-6 is produced by different cell types. To investigate the impact of IL-6 produced by B cells on TB susceptibility and immune responses, we established a mouse strain with specific IL-6 deficiency in B cells (CD19cre-IL-6fl/fl, B-IL-6KO) on the B6 genetic background. Selective abrogation of IL-6 in B cells resulted in shortening the lifespan of TB-infected B-IL-6KO mice compare to the wild-type controls. We provide evidence that at the initial TB stages B cells serve as a critical source of IL-6. In the lung, the effect of IL-6 deficiency in B cells is associated rather with B and T cell functioning, than with macrophage polarization. TB-infected B-IL-6KO mice displayed diminished sizes of B cells themselves, CD4⁺IFN-γ⁺, Th17⁺, and CD4⁺CXCR5⁺ follicular T cell populations. The pleiotropic effect of B-cell-derived IL-6 on T-cells demonstrated in our study bridges two major lymphocyte populations and sheds some light on B- and T-cells interactions during the stage of anti-TB response when the host switches on a plethora of acquired immune reactions.

Dual RNA Sequencing of Mycobacterium tuberculosis-Infected Human Splenic Macrophages Reveals a Strain-Dependent Host-Pathogen Response to Infection

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb), leading to pulmonary and extrapulmonary TB, whereby Mtb is disseminated to many other organs and tissues. Dissemination occurs early during the disease, and bacteria can be found first in the lymph nodes adjacent to the lungs and then later in the extrapulmonary organs, including the spleen. The early global gene expression response of human tissue macrophages and intracellular clinical isolates of Mtb has been poorly studied. Using dual RNA-seq, we have explored the mRNA profiles of two closely related clinical strains of the Latin American and Mediterranean (LAM) family of Mtb in infected human splenic macrophages (hSMs). This work shows that these pathogens mediate a distinct host response despite their genetic similarity. Using a genome-scale host–pathogen metabolic reconstruction to analyze the data further, we highlight that the infecting Mtb strain also determines the metabolic response of both the host and pathogen. Thus, macrophage ontogeny and the genetic-derived program of Mtb direct the host–pathogen interaction.

The autophagy-resistant Mycobacterium tuberculosis Beijing strain upregulates KatG to evade starvation-induced autophagic restriction

Mycobacterium tuberculosis utilizes several mechanisms to block phagosome–lysosome fusion to evade host cell restriction. However, induction of host cell autophagy by starvation was shown to overcome this block, resulting in enhanced lysosomal delivery to mycobacterial phagosomes and the killing of the M. tuberculosis reference strain H37Rv. Nevertheless, our previous studies found that strains belonging to the M. tuberculosis Beijing genotype can resist starvation-induced autophagic elimination, though the mycobacterial factors involved remain unclear. In this study, we showed that KatG expression is upregulated in the autophagy-resistant M. tuberculosis Beijing strain (BJN) during autophagy induction by the starvation of host macrophages, while such increase was not observed in the H37Rv. KatG depletion using the CRISPR-dCas9 interference system in the BJN resulted in increased lysosomal delivery to its phagosome and decreased its survival upon autophagy induction by starvation. As KatG functions by catabolizing ROS, we determined the source of ROS contributing to the starvation-induced autophagic elimination of mycobacteria. Using siRNA-mediated knockdown, we found that Superoxide dismutase 2, which generates mitochondrial ROS but not NADPH oxidase 2, is important for the starvation-induced lysosomal delivery to mycobacterial phagosomes. Taken together, these findings showed that KatG is vital for the BJN to evade starvation-induced autophagic restriction.

The Effects Of Tempe Extract On The Oxidative Stress Marker And Lung Pathology In Tuberculosis Wistar Rat

Background and Objective — Tempe (fermented soybean) has the potential as an affordable nutritional support alternative during tuberculosis (TB) infection. The purpose of the study was to assess the efficacy of supplementation with the ethanolic extract of Tempe on the oxidative stress markers alleviation and histological changes in male Wistar rats infected with Mycobacterium tuberculosis. Material and Methods — Thirty-five male Wistar rats were divided randomly into five groups and infected by Mycobacterium tuberculosis strain H37RV intratracheally. Total antioxidant capacity (TAC) and Thiobarbituric Acid Reaction (TBARS) levels were assessed using a colorimetric method while C-reactive protein (CRP) was measured by Elisa method. The lung damage was scored using histopathological parameters. Results — There were no significant differences in the TBARS levels and CRP concentrations compared to control. Tempe extract increased the TAC level at 200 (p=0.011), 400 (p=0.027), and 800 (p=0.029) kg/body weight concentrations compared to control. Perivasculitis and alveolitis mean scores were lower (p<0.05) than control in all supplement groups. Additionally, the mean scores of peribronchiolitis among supplementation groups were decreased (p<0.05) in the 200 and 800 mg/kg body weight, while the granuloma mean score was lower in the 800 mg/kg body weight compared to control. Conclusions — Tempe extract may have a weak efficacy in improving the antioxidant capacity and lung histological condition in TB rat models.

Extremely lethal and hypervirulent Mycobacterium tuberculosis strain cluster emerging in Far East, Russia

Mycobacterium tuberculosis strains of the early ancient sublineage of the Beijing genotype are mostly drug susceptible and mainly circulate in East Asia. We have recently discovered two clusters of this sublineage emerging in the Asian part of Russia (VNTR-defined 1071-32 and 14717-15 types) and, to our surprise, both were strongly MDR/XDR-associated. Here, we evaluated their pathogenic features. The clinical isolates and reference laboratory strain H37Rv were investigated in the C57BL/6 mouse model to assess their virulence and lethality properties. The BACTEC MGIT 960 system was used to study the in vitro growth characteristics. In the murine model, strains 396 (14717-15-cluster, from Buryatia, Far East) and 6691 (1071-32-cluster, from Omsk, Siberia) demonstrated contrasting properties. The 396-infected group had significantly higher mortality, more weight loss, higher bacterial burden, and more severe lung pathology. Furthermore, compared to the previously published data on other Russian epidemic Beijing strains (B0/W148, CAO, Central Asian Russian), strain 396 demonstrated the highest mortality. Under the in vitro growth experiment, cluster 14717-15 isolates had significantly shorter lag-phase. To conclude, low-virulent MDR strain 6691 belongs to the Beijing 1071-32-cluster widespread across FSU countries but at low prevalence. This corresponds to common expectation that multiple drug resistance mutations reduce fitness and virulence. In contrast, highly lethal and hypervirulent MDR strain 396 represents an intriguing Beijing 14717-15 cluster predominant only in Buryatia, Far East (16%), sporadically found beyond it, but not forming clusters of transmission. Further in-depth study of this most virulent Russian Beijing cluster is warranted.

The within-host evolution of antimicrobial resistance in Mycobacterium tuberculosis

Tuberculosis (TB) has been responsible for the greatest number of human deaths due to an infectious disease in general, and due to antimicrobial resistance (AMR) in particular. The etiological agents of human TB are a closely-related group of human-adapted bacteria that belong to the Mycobacterium tuberculosis complex (MTBC). Understanding how MTBC populations evolve within-host may allow for improved TB treatment and control strategies. In this review, we highlight recent works that have shed light on how AMR evolves in MTBC populations within individual patients. We discuss the role of heteroresistance in AMR evolution, and review the bacterial, patient and environmental factors that likely modulate the magnitude of heteroresistance within-host. We further highlight recent works on the dynamics of MTBC genetic diversity within-host, and discuss how spatial substructures in patients' lungs, spatiotemporal heterogeneity in antimicrobial concentrations and phenotypic drug tolerance likely modulates the dynamics of MTBC genetic diversity in patients during treatment. We note the general characteristics that are shared between how the MTBC and other bacterial pathogens evolve in humans, and highlight the characteristics unique to the MTBC.

Parallel in vivo experimental evolution reveals that increased stress resistance was key for the emergence of persistent tuberculosis bacilli

Pathogenomic evidence suggests that Mycobacterium tuberculosis (MTB) evolved from an environmental ancestor similar to Mycobacterium canettii, a rare human pathogen. Although the adaptations responsible for this transition are poorly characterized, the ability to persist in humans seems to be important. We set out to identify the adaptations contributing to the evolution of persistence in MTB. We performed an experimental evolution of eight M. canettii populations in mice; four populations were derived from the isolate STB-K (phylogenomically furthest from MTB) and four from STB-D (closest to MTB), which were monitored for 15 and 6 cycles, respectively. We selected M. canettii mutants with enhanced persistence in vivo compared with the parental strains, which were phenotypically closer to MTB. Genome sequencing of 140 mutants and complementation analysis revealed that mutations in two loci were responsible for enhanced persistence. Most of the tested mutants were more resistant than their parental strains to nitric oxide, an important effector of immunity. Modern MTB were similarly more resistant to nitric oxide than M. canettii. Our findings demonstrate phenotypic convergence during experimental evolution of M. canettii, which mirrors natural evolution of MTB. Furthermore, they indicate that the ability to withstand host-induced stresses was key for the emergence of persistent MTB.

Characterisation of secretome-based immune responses of human leukocytes infected with various Mycobacterium tuberculosis lineages

Background

Differences in immune responses against different lineages of Mycobacterium tuberculosis (Mtb), and by different types of immune cell, are still poorly understood. We aimed to compare the secretome-based immune responses among three Mtb lineages and among immune-cell types. The immune responses were also investigated during infection and when the bacilli had been eliminated from the immune cells.

Methods

Human primary leukocytes were infected with strains representing three lineages of Mtb (East-Asian, Indo-Oceanic and Euro-American). Label-free GeLC MS/MS proteomic analysis of secretomes was performed. The response of each immune-cell type was compared with the appropriate interactome database for each.

Results

The expression pattern of proteins secreted by Mtb-infected leukocytes differed among Mtb lineages. The ancestral lineage (IO lineage) had a greater ability to activate MMP14 (associated with leukocyte migration) than did the more recent lineages (EA and EuA). During infection, proteins secreted by macrophages, dendritic cells, neutrophils and B-cells were associated with cell proliferation. Following clearance of Mtb, proteins associated with interferon signaling were found in macrophages, dendritic cells and neutrophils: proteins associated with antigen processing were found in B-cells and regulatory T-cells. Expression of immune response-related proteins from many immune-cell types might be suppressed by Mtb infection. Our study has provided a better insight into the host-pathogen interaction and immune response against different Mtb lineages.

Mycobacterium tuberculosis Beijing Lineage and Risk for Tuberculosis in Child Household Contacts, Peru

Few studies have prospectively compared the relative transmissibility and propensity to cause disease of Mycobacterium tuberculosis Beijing strains with other human-adapted strains of the M. tuberculosis complex. We assessed the effect of Beijing strains on the risk for M. tuberculosis infection and disease progression in 9,151 household contacts of 2,223 culture-positive pulmonary tuberculosis (TB) patients in Lima, Peru. Child contacts exposed to Beijing strains were more likely than child contacts exposed to non-Beijing strains to be infected at baseline, by 12 months of follow-up, and during follow-up. We noted an increased but nonsignificant tendency for child contacts to develop TB. Beijing strains were not associated with TB in adult contacts. These findings suggest that Beijing strains are more transmissible in children than are non-Beijing strains.

Lysosome repositioning as an autophagy escape mechanism by Mycobacterium tuberculosis Beijing strain

Induction of host cell autophagy by starvation was shown to enhance lysosomal delivery to mycobacterial phagosomes, resulting in the restriction of Mycobacterium tuberculosis reference strain H37Rv. Our previous study showed that strains belonging to M. tuberculosis Beijing genotype resisted starvation-induced autophagic elimination but the factors involved remained unclear. Here, we conducted RNA-Seq of macrophages infected with the autophagy-resistant Beijing strain (BJN) compared to macrophages infected with H37Rv upon autophagy induction by starvation. Results identified several genes uniquely upregulated in BJN-infected macrophages but not in H37Rv-infected cells, including those encoding Kxd1 and Plekhm2, which function in lysosome positioning towards the cell periphery. Unlike H37Rv, BJN suppressed enhanced lysosome positioning towards the perinuclear region and lysosomal delivery to its phagosome upon autophagy induction by starvation, while depletion of Kxd1 and Plekhm2 reverted such effects, resulting in restriction of BJN intracellular survival upon autophagy induction by starvation. Taken together, these data indicated that Kxd1 and Plekhm2 are important for the BJN strain to suppress lysosome positioning towards the perinuclear region and lysosomal delivery into its phagosome during autophagy induction by starvation to evade starvation-induced autophagic restriction.

Transcriptional response to the host cell environment of a multidrug-resistant Mycobacterium tuberculosis clonal outbreak Beijing strain reveals its pathogenic features

Tuberculosis is a global public health problem with emergence of multidrug-resistant infections. Previous epidemiological studies of tuberculosis in Thailand have identified a clonal outbreak multidrug-resistant strain of Mycobacterium tuberculosis in the Kanchanaburi province, designated “MKR superspreader”, and this particular strain later was found to also spread to other regions. In this study, we elucidated its biology through RNA-Seq analyses and identified a set of genes involved in cholesterol degradation to be up-regulated in the MKR during the macrophage cell infection, but not in the H37Rv reference strain. We also found that the bacterium up-regulated genes associated with the ESX-1 secretion system during its intracellular growth phase, while the H37Rv did not. All results were confirmed by qRT-PCR. Moreover, we showed that compounds previously shown to inhibit the mycobacterial ESX-1 secretion system and cholesterol utilisation, and FDA-approved drugs known to interfere with the host cholesterol transportation were able to decrease the intracellular survival of the MKR when compared to the untreated control, while not that of the H37Rv. Altogether, our findings suggested that such pathways are important for the MKR’s intracellular growth, and potentially could be targets for the discovery of new drugs against this emerging multidrug-resistant strain of M. tuberculosis.

Pathology of TB/COVID-19 Co-Infection: The phantom menace

Tuberculosis (TB) and coronavirus disease 2019 (COVID-19) are currently the two main causes of death among infectious diseases. There is an increasing number of studies trying to elucidate the interactions between Mycobacterium tuberculosis and SARS-CoV-2. Some of the first case reports point to a worsening of respiratory symptoms in co-infected TB/COVID-19 individuals. However, data from the cohort studies has shown some conflicting results. This study proposes to conduct a systematic review on the current literature on TB/COVID-19 co-infection cohorts, evaluating clinical and epidemiological data, focusing on its implications to the immune system. From an immunological perspective, the TB/COVID-19 co-infection has the potential to converge in a "perfect storm". The disorders induced by each pathogen to the immunomodulation tend to induce an unbalanced inflammatory response, which can promote the progression and worsening of both diseases. Understanding the nature of the interactions between M. tuberculosis and SARS-CoV-2 will be crucial for the development of therapeutic strategies against co-infection.

The recent trend in mycobacterial strain diversity among extra pulmonary lymph node tuberculosis and their association with drug resistance and the host immunological response in South India

Background

Tuberculosis (TB) though primarily affects the lungs it may also affect the other parts of the body and referred as extra pulmonary (EPTB). This study is focused on understanding the genetic diversity and molecular epidemiology of Mycobacterium tuberculosis (M.tb) among tuberculous lymphadenitis (TBL), a form of EPTB patients identified in Chennai, Tamil Nadu.

Methods

The genetic diversity was identified by performing spoligotyping on the M.tb clinical isolates that were recovered from lymph node samples. A total of 71 M.tb isolates were recovered from extra pulmonary lymph node samples and subjected to Drug susceptibility testing and spoligotyping was carried out. In addition, immunological characterization from blood of same individuals from whom M.tb was isolated was carried out between the two major lineages groups East African Indian 3 (EAI3) and non-EAI3 strains by ELISA. The results of spoligotyping patterns were compared with the world Spoligotyping Database of Institute Pasteur de Guadeloupe (SpolDB4).

Results

We found 41 spoligotype patterns and their associated lineages. Out of 41 spoligotype pattern, only 22 patterns are available in the spoldB4 database with Spoligotype international Type (SIT) number and remaining patterns were orphan strains without SIT number. The most predominant spoligotype lineage that was found in lymph node sample in this region of India was EAI (36), followed by central Asian strain (CAS) (6), T1 (5), Beijing (3), Latin American & Mediterranean (LAM) (2), U (1), X2 (1) and orphan (22). In addition to EAI, CAS and Beijing, our study identified the presence of orphan and unique spoligotyping patterns in Chennai region. We observed six drug resistant isolates. Out of six drug resistant isolates, four were resistant to isoniazid drug and associated with EAI family. Moreover, we observed increased levels of type 2 and type 17 cytokine profiles between EAI3 and non-EAI family, infected individuals.

Conclusions

The study confirms that EAI lineage to be the most predominant lineages in EPTB patients with lymphadenitis and were found to have increased type 1 and type 17 proinflammatory cytokine profiles.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-020-05597-0.

Sequential Co-infection of Heligmosomoides polygyrus and Mycobacterium tuberculosis Determine Lung Macrophage Polarization and Histopathological Changes

BACKGROUND

Tuberculosis is a chronic infection caused by Mycobacterium tuberculosis (M.tb), which needs proper macrophage activation for control. It has been debated whether the co-infection with helminth will affect the immune response to mycobacterial infection.

OBJECTIVE

To determine the effect of sequential co-infection of Heligmosomoides polygyrus (H.pg) nematodes and M.tb on T cell responses, macrophages polarization and lung histopathological changes.

METHOD

This study used 49 mice divided into 7 treatment groups, with different sequence of infection of M.tb via inhalation and H.pg via oral ingestion for 8 and 16 weeks. T cells response in the lung, intestine, and peripheral blood were determined by flow cytometry. Cytokines (IL-4, IFN-γ, TGB-β1, and IL-10) were measured in peripheral blood using ELISA. Lung macrophage polarization were determined by the expression of iNOS (M1) or Arginase 1 (M2). Mycobacterial count were done in lung tissue. Lung histopathology were measured using Dorman's semiquantitative score assessing peribronchiolitis, perivasculitis, alveolitis, and granuloma formation.

RESULT

M.tb infection induced Th1 response and M1 macrophage polarization, while H.pg infection induced Th2 and M2 polarization. In sequential co-infection, the final polarization of macrophage was dictated by the sequence of co-infection. However, all groups with M.tb infection showed the same degree of mycobacterial count in lung tissues and lung tissue histopathological changes.

CONCLUSION

Sequential co-infection of H.pg and M.tb induces different T cell response which leads to different macrophage polarization in lung tissue. Helminth infection induced M2 lung macrophage polarization, but did not cause different mycobacterial count nor lung histopathological changes.

Chemical p38 MAP kinase inhibition constrains tissue inflammation and improves antibiotic activity in Mycobacterium tuberculosis-infected mice

Host-modulating therapies have become an important focus in the development of novel concepts for improved management of tuberculosis (TB). Previous in vitro studies revealed that the p38 MAP kinase signaling pathway coordinates several inflammatory and stress responses in Mycobacterium tuberculosis (Mtb)-infected host cells. Here we extend these findings and show that in vivo treatment of Mtb-infected C57BL/6 mice with doramapimod, a p38 MAP-kinase inhibitor, results in reduced inflammation, granuloma formation and lung pathology. Moreover, doramapimod, together with standard antibiotic treatment, significantly reduced lung and spleen mycobacterial loads compared to antibiotic treatment alone. Our in vivo data suggest the opportunity to repurpose p38 MAPK inhibitors for adjunct host directed therapies. We also provide first data on safety of p38 MAPK inhibition which is of relevance for future application of these substances in inflammatory diseases and concomitant TB.

Activation of M1 Macrophages in Response to Recombinant TB Vaccines With Enhanced Antimycobacterial Activity

Pulmonary tuberculosis (TB) is a difficult-to-eliminate disease. Although the Bacille Calmette–Guérin (BCG) vaccine against Mycobacterium tuberculosis (MTB) has been available for decades, its efficacy is variable and has lessened over time. Furthermore, the BCG vaccine no longer protects against newly emerged Beijing strains which are responsible for many current infections in adults. Development of a novel vaccine is urgently needed. In this study, we first tested the efficacy of our recombinant BCG vaccines rBCG1 and rBCG2, compared to parental BCG, against MTB strain H37Ra in mice. Both the bacterial load and the level of lymphocyte infiltration decreased dramatically in the three groups treated with vaccine, especially rBCG1 and rBCG2. Furthermore, the Th1 and Th17 responses increased and macrophage numbers rose in the vaccination groups. Th1-mediated production of cytokines TNF-α, IFN-γ, and MCP-1 as well as M1-polarized cells all increased in lung tissue of the rBCG1 and rBCG2 groups. Clodronate-induced depletion of macrophages reduced the level of protection. Based on these results, we conclude that rBCG vaccines induce a significant increase in the number of M1 macrophages, which augments their potential as TB vaccine candidates.

Association between bacterial homoplastic variants and radiological pathology in tuberculosis

BACKGROUND

Understanding how pathogen genetic factors contribute to pathology in TB could enable tailored treatments to the most pathogenic and infectious strains. New strategies are needed to control drug-resistant TB, which requires longer and costlier treatment. We hypothesised that the severity of radiological pathology on the chest radiograph in TB disease was associated with variants arising independently, multiple times (homoplasies) in the Mycobacterium tuberculosis genome.

METHODS

We performed whole genome sequencing (Illumina HiSeq2000 platform) on M. tuberculosis isolates from 103 patients with drug-resistant TB in Lima between 2010 and 2013. Variables including age, sex, HIV status, previous TB disease and the percentage of lung involvement on the pretreatment chest radiograph were collected from health posts of the national TB programme. Genomic variants were identified using standard pipelines.

RESULTS

Two mutations were significantly associated with more widespread radiological pathology in a multivariable regression model controlling for confounding variables (Rv2828c.141, RR 1.3, 95% CI 1.21 to 1.39, p<0.01; rpoC.1040 95% CI 1.77 to 2.16, RR 1.9, p<0.01). The rpoB.450 mutation was associated with less extensive radiological pathology (RR 0.81, 95% CI 0.69 to 0.94, p=0.03), suggestive of a bacterial fitness cost for this mutation in vivo. Patients with a previous episode of TB disease and those between 10 and 30 years of age also had significantly increased radiological pathology.

CONCLUSIONS

This study is the first to compare the M. tuberculosis genome to radiological pathology on the chest radiograph. We identified two variants significantly positively associated with more widespread radiological pathology and one with reduced pathology. Prospective studies are warranted to determine whether mutations associated with increased pathology also predict the spread of drug-resistant TB.

Host defense mechanisms against Mycobacterium tuberculosis

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), remains the leading cause of death worldwide from a single infectious pathogen. Mtb is a paradigmatic intracellular pathogen that primarily invades the lungs after host inhalation of bacteria-containing droplets via the airway. However, the majority of Mtb-exposed individuals can spontaneously control the infection by virtue of a robust immune defense system. The mucosal barriers of the respiratory tract shape the first-line defense against Mtb through various mucosal immune responses. After arriving at the alveoli, the surviving mycobacteria further encounter a set of host innate immune cells that exert multiple cellular bactericidal functions. Adaptive immunity, predominantly mediated by a range of different T cell and B cell subsets, is subsequently activated and participates in host anti-mycobacterial defense. During Mtb infection, host bactericidal immune responses are exquisitely adjusted and balanced by multifaceted mechanisms, including genetic and epigenetic regulation, metabolic regulation and neuroendocrine regulation, which are indispensable for maintaining host immune efficiency and avoiding excessive tissue injury. A better understanding of the integrated and equilibrated host immune defense system against Mtb will contribute to the development of rational TB treatment regimens especially novel host-directed therapeutics.

Impact of Strain Competition on Bacterial Resistance in Immunocompromised Populations

Despite the risk of emerging drug resistance that occurs with the frequent use of antimicrobial agents, targeted and prophylactic antibiotics have been considered crucial to opportunistic infection management among the HIV/AIDS-immunocompromised. As we recently demonstrated, the disrupted selective pressures that occur in AIDS-prevalent host populations increase the probability of novel emergence. This effect is concerning, given that bacterial strains unresponsive to first-line antibiotics can be particularly dangerous to hosts whose immune response is insufficient to fight infection in the absence of antibiotic support. While greater host susceptibility within a highly immunocompromised population may offer a fitness advantage to drug-resistant bacterial strains, this advantage could be mitigated by increased morbidity and mortality among the AIDS-immunocompromised. Using a Susceptible-Exposed-Infectious-Recovered (SEIR) epidemiological model parameterized to reflect conditions in an AIDS-prevalent host population, we examine the evolutionary relationship between drug-sensitive and -resistant strains of Mycobacterium tuberculosis. We explore this relationship when the fitness of the resistant strain is varied relative to that of the sensitive strain to investigate the likely long-term multi-strain dynamics of the AIDS-mediated increased emergence of drug resistance.

Impact of chemorophylaxis policy for AIDS-immunocompromised patients on emergence of bacterial resistance

Chemoprophylaxis (antibiotic prophylaxis) is a long relied-upon means of opportunistic infection management among HIV/AIDS patients, but its use represents an evolutionary tradeoff: Despite the benefits of chemoprophylaxis, widespread use of antibiotics creates a selective advantage for drug-resistant bacterial strains. Especially in the developing world, with combined resource limitations, antibiotic misuse, and often-poor infection control, the emergence of antibiotic resistance may pose a critical health risk. Extending previous work that demonstrated that this risk is heightened when a significant proportion of the population is HIV/AIDS-immunocompromised, we work to address the relationship between HIV/AIDS patients' use of antibiotic chemoprophylaxis and the emergence of resistance. We apply an SEIR compartmental model, parameterized to reflect varying percentages of chemoprophylaxis use among HIV/AIDS+ patients in a resource-limited setting, to investigate the magnitude of the risk of prophylaxis-associated emergence versus the individual-level benefits it is presumed to provide. The results from this model suggest that, while still providing tangible benefits to the individual, chemoprophylaxis is associated with negligible decreases in population-wide morbidity and mortality from bacterial infection, and may also fail to provide assumed efficacy in reduction of TB prevalence.

Translocation of Mycobacterium tuberculosis after experimental ingestion

Human tuberculosis is a life-threatening infection following the inhalation of Mycobacterium tuberculosis, while the closely related bacteria Mycobacterium bovis and Mycobacterium canettii are thought to be transmitted by ingestion. To explore whether M. tuberculosis could also infect individuals by ingestion, male BALBc mice were fed 2 x 10⁶ CFUs of M. tuberculosis Beijing or phosphate-buffered saline as a negative control, over a 28-day experiment. While eight negative control mice remained disease-free, M. tuberculosis was identified in the lymph nodes and lungs of 8/14 mice and in the spleens of 4/14 mice by microscopy, PCR-based detection and culture. Whole-genome sequencing confirmed the identity of the inoculum and the tissue isolates. In these genetically identical mice, the dissemination of M. tuberculosis correlated with the results of the culture detection of four intestinal bacteria. These observations indicate that ingested M. tuberculosis mycobacteria can translocate, notably provoking lymphatic tuberculosis.

Linking Individual Natural History to Population Outcomes in Tuberculosis

Background

Substantial individual heterogeneity exists in the clinical manifestations and duration of active tuberculosis. We sought to link the individual-level characteristics of tuberculosis disease to observed population-level outcomes.

Methods

We developed an individual-based, stochastic model of tuberculosis disease in a hypothetical cohort of patients with smear-positive tuberculosis. We conceptualized the disease process as consisting of 2 states—progression and recovery—including transitions between the 2. We then used a Bayesian process to calibrate the model to clinical data from the prechemotherapy era, thus identifying the rates of progression and recovery (and probabilities of transition) consistent with observed population-level clinical outcomes.

Results

Observed outcomes are consistent with slow rates of disease progression (median doubling time: 84 days, 95% uncertainty range 62–104) and a low, but nonzero, probability of transition from disease progression to recovery (median 16% per year, 95% uncertainty range 11%–21%). Other individual-level dynamics were less influential in determining observed outcomes.

Conclusions

This simplified model identifies individual-level dynamics—including a long doubling time and low probability of immune recovery—that recapitulate population-level clinical outcomes of untreated tuberculosis patients. This framework may facilitate better understanding of the population-level impact of interventions acting at the individual host level.

Emergence of antibiotic resistance in immunocompromised host populations: A case study of emerging antibiotic resistant tuberculosis in AIDS patients

OBJECTIVE

The evolution of antibiotic resistance is far outpacing the development of new antibiotics, causing global public health concern about infections that will increasingly be unresponsive to antimicrobials. This risk of emerging antibiotic resistance may be meaningfully altered in highly AIDS-immunocompromised populations. Such populations fundamentally alter the bacterial evolutionary landscape in two ways, which we seek to model and analyze. First, widespread, population-level immunoincompetence creates a novel host environment with disrupted selective pressures. Second, within AIDS-prevalent populations, the recommendation that antibiotics be taken to treat and prevent opportunistic infection raises the risk of selection for drug-resistant pathogens.

DESIGN

To determine the impact of HIV/AIDS on the emergence of antibiotic resistance-specifically in the developing world where high prevalence and economic challenges complicate disease management.

METHODS

We present an SEIR epidemiological model of bacterial infection, and parametrize it to capture HIV/AIDS-attributable emergence of resistance under conditions of both high and low HIV/AIDS prevalence.

RESULTS

We demonstrate that HIV/AIDS-immunocompromised hosts can be responsible for a disproportionately greater contribution to emergence of resistance than would be expected based on population-wide HIV/AIDS prevalence alone.

CONCLUSIONS

As such, the AIDS-immunocompromised have the potential become wellsprings of novel, resistant, opportunistic pathogen strains that can propagate into the broader global community. We discuss how public health policies for HIV/AIDS management can shape the evolutionary environment for opportunistic bacterial infections.

Ample glycosylation in membrane and cell envelope proteins may explain the phenotypic diversity and virulence in the Mycobacterium tuberculosis complex

Multiple regulatory mechanisms including post-translational modifications (PTMs) confer complexity to the simpler genomes and proteomes of Mycobacterium tuberculosis (Mtb). PTMs such as glycosylation play a significant role in Mtb adaptive processes. The glycoproteomic patterns of clinical isolates of the Mycobacterium tuberculosis complex (MTBC) representing the lineages 3, 4, 5 and 7 were characterized by mass spectrometry. A total of 2944 glycosylation events were discovered in 1325 proteins. This data set represents the highest number of glycosylated proteins identified in Mtb to date. O-glycosylation constituted 83% of the events identified, while 17% of the sites were N-glycosylated. This is the first report on N-linked protein glycosylation in Mtb and in Gram-positive bacteria. Collectively, the bulk of Mtb glycoproteins are involved in cell envelope biosynthesis, fatty acid and lipid metabolism, two-component systems, and pathogen-host interaction that are either surface exposed or located in the cell wall. Quantitative glycoproteomic analysis revealed that 101 sites on 67 proteins involved in Mtb fitness and survival were differentially glycosylated between the four lineages, among which 64% were cell envelope and membrane proteins. The differential glycosylation pattern may contribute to phenotypic variabilities across Mtb lineages. The study identified several clinically important membrane-associated glycolipoproteins that are relevant for diagnostics as well as for drug and vaccine discovery.

The pathogenesis of tuberculous meningitis

Tuberculosis (TB) remains a leading cause of death globally. Dissemination of TB to the brain results in the most severe form of extrapulmonary TB, tuberculous meningitis (TBM), which represents a medical emergency associated with high rates of mortality and disability. Via various mechanisms the Mycobacterium tuberculosis (M.tb) bacillus disseminates from the primary site of infection and overcomes protective barriers to enter the CNS. There it induces an inflammatory response involving both the peripheral and resident immune cells, which initiates a cascade of pathologic mechanisms that may either contain the disease or result in significant brain injury. Here we review the steps from primary infection to cerebral disease, factors that contribute to the virulence of the organism and the vulnerability of the host and discuss the immune response and the clinical manifestations arising. Priorities for future research directions are suggested.

Virulence of Mycobacterium tuberculosis Clinical Isolates Is Associated With Sputum Pre-treatment Bacterial Load, Lineage, Survival in Macrophages, and Cytokine Response

It is uncertain whether differences in Mycobacterium tuberculosis (Mtb) virulence defined in vitro influence clinical tuberculosis pathogenesis, transmission, and mortality. We primarily used a macrophage lysis model to characterize the virulence of Mtb isolates collected from 153 Vietnamese adults with pulmonary tuberculosis. The virulence phenotypes were then investigated for their relationship with sputum bacterial load, bacterial lineages, bacterial growth, and cytokine responses in macrophages. Over 6 days of infection, 34 isolates (22.2%) showed low virulence (< 5% macrophages lysed), 46 isolates (30.1%) showed high virulence (≥90% lysis of macrophages), and 73 isolates (47.7%) were of intermediate virulence (5–90% macrophages lysed). Highly virulent isolates were associated with an increased bacterial load in patients' sputum before anti-tuberculosis therapy (P = 0.02). Isolate-dependent virulence phenotype was consistent in both THP-1 and human monocyte-derived macrophages. High virulence isolates survived better and replicated in macrophages one hundred fold faster than those with low virulence. Macrophages infected with high virulence isolates produced lower concentrations of TNF-α and IL-6 (P = 0.002 and 0.0005, respectively), but higher concentration of IL-1β (P = 5.1 × 10⁻⁵) compared to those infected with low virulence isolates. High virulence was strongly associated with East Asian/Beijing lineage [P = 0.002, Odd ratio (OR) = 4.32, 95% confident intervals (CI) 1.68–11.13]. The association between virulence phenotypes, bacterial growth, and proinflammatory cytokines in macrophages suggest the suppression of certain proinflammatory cytokines (TNF-α and IL-6) but not IL-1β allows better intracellular survival of highly virulent Mtb. This could result in rapid macrophage lysis and higher bacterial load in sputum of patients infected with high virulence isolates, which may contribute to the pathogenesis and success of the Beijing lineage.

Risk factors of multidrug-resistant tuberculosis: A global systematic review and meta-analysis

OBJECTIVES

Since the risk of multidrug-resistant tuberculosis (MDR-TB) may depend on the setting, we aimed to determine the associations of risk factors of MDR-TB across different regions.

METHODS

A systematic review and meta-analysis was performed with Pubmed and Embase databases. Information was retrieved on 37 pre-defined risk factors of MDR-TB. We estimated overall Mantel-Haenszel odds ratio as a measure of the association.

RESULTS

Factors of previous TB disease and treatment are the most important risk factors associated with MDR-TB. There was also a trend towards increased risk of MDR-TB for patients 40 years and older, unemployed, lacking health insurance, smear positive, with non-completion and failure of TB treatment, showing adverse drug reaction, non-adherent, HIV positive, with COPD and with M. Tuberculosis Beijing infection. Effect modification by geographical area was identified for several risk factors such as male gender, married patients, urban domicile, homelessness and history of imprisonment.

CONCLUSIONS

Assessment of risk factors of MDR-TB should be conducted regionally to develop the most effective strategy for MDR-TB control. Across all regions, factors associated with previous TB disease and treatment are essential risk factors, indicating the appropriateness of diagnosis, treatment and monitoring are an important requirements.

Biology of clinical strains of Mycobacterium tuberculosis with varying levels of transmission

Transmission of Mycobacterium tuberculosis bacilli from one individual to another is the basis of the disease process. While considerable emphasis has been placed on the role of host mechanisms of resistance in establishing or preventing new infection, far less has been expended on understanding possible factors operative at the bacterial level. In this study we established a panel of clinical isolates of M. tuberculosis strains obtained from the Western Cape region of South Africa, each of which had been carefully tracked in terms of their degree of transmission in the community. Each of the panel were used to infect guinea pigs with 15-20 bacilli by aerosol exposure and the course of the infection then determined. Strains with different degrees of transmission could not be distinguished in terms of their capacity to grow in the main target organs of infected animals. However, rather surprisingly, while strains with no evidence of transmission [NOT] in general caused moderate to severe lung damage, this parameter in animals infected with highly transmitted [HT] strains was mostly mild. In terms of TH1 immunity these signals were strongest in these latter animals, as was IL-17 gene expression, whereas minimal signals for regulatory molecules including IL-10 and FoxP3 were seen across the entire panel. In terms of T cell numbers, responses of both CD4 and CD8 were both far faster and far higher in animals infected with the HT strains. At the gene expression level we observed a major three-fold difference [both up and down] between NOT and HT strains, but in terms of proteins of key interest only a few [including PD-L1 and HIF-3] showed major differences between the two groups. Overall, it was apparent that NOT strains were far more inflammatory that HT strains, and appeared to trigger a much larger number of genes, possibly explaining the observed damage to the lungs and progressive pathology. In contrast, the HT strains, while equally virulent, were more immunogenic and developed much stronger T cell responses, while keeping lung damage to a minimum. Hence, in terms of trying to explain the capacity of these strains to cause transmission, these results are clearly paradoxical.

Humane Endpoints for Guinea Pigs Used for Mycobacterium tuberculosis Vaccine Research

Guinea pigs are a commonly used model for tuberculosis vaccine research. Loss of body weight is the most frequently described humane endpoint for animals used in these studies. During a chronic study, we noted labored breathing in some tuberculosis-infected guinea pigs. To develop consistent humane endpoints for these guinea pigs, we performed an observational study using multiple clinical signs. A combination of body weight loss, labored breathing, and activity level during handling estimated the time to euthanasia within approximately 7 d. Histologic severity scores of lesions in the cranial or caudal lung lobe (or both) supported clinical endpoints. This study presents humane endpoints for the refinement of studies using guinea pigs in tuberculosis research.

The Troika Host-Pathogen-Extrinsic Factors in Tuberculosis: Modulating Inflammation and Clinical Outcomes

The already enormous burden caused by tuberculosis (TB) will be further aggravated by the association of this disease with modern epidemics, as human immunodeficiency virus and diabetes. Furthermore, the increasingly aging population and the wider use of suppressive immune therapies hold the potential to enhance the incidence of TB. New preventive and therapeutic strategies based on recent advances on our understanding of TB are thus needed. In particular, understanding the intricate network of events modulating inflammation in TB will help to build more effective vaccines and host-directed therapies to stop TB. This review integrates the impact of host, pathogen, and extrinsic factors on inflammation and the almost scientifically unexplored complexity emerging from the interactions between these three factors. We highlight the exciting data showing a contribution of this troika for the clinical outcome of TB and the need of incorporating it when developing novel strategies to rewire the immune response in TB.

Ready Experimental Translocation of Mycobacterium canettii Yields Pulmonary Tuberculosis

Mycobacterium canettii, which has a smooth colony morphology, is the tuberculous organism retaining the most genetic traits from the putative last common ancestor of the rough-morphology Mycobacterium tuberculosis complex. To explore whether M. canettii can infect individuals by the oral route, mice were fed phosphate-buffered saline or 10⁶M. canettii mycobacteria and sacrificed over a 28-day experiment. While no M. canettii was detected in negative controls, M. canettii-infected mice yielded granuloma-like lesions for 4/4 lungs at days 14 and 28 postinoculation (p.i.) and positive PCR detection of M. canettii for 5/8 mesenteric lymph nodes at days 1 and 3 p.i. and 5/6 pooled stools collected from day 1 to day 28 p.i. Smooth M. canettii colonies grew from 68% of lungs and 36% of spleens and cervical lymph nodes but fewer than 20% of axillary lymph nodes, livers, brown fat samples, kidneys, or blood samples throughout the 28-day experiment. Ready translocation in mice after digestive tract challenge demonstrates the potential of ingested M. canettii organisms to relocate to distant organs and lungs. The demonstration of this relocation supports the possibility that populations may be infected by environmental M. canettii.

Impact of Genetic Diversity on the Biology of Mycobacterium tuberculosis Complex Strains

Tuberculosis (TB) remains the most deadly bacterial infectious disease worldwide. Its treatment and control are threatened by increasing numbers of multidrug-resistant (MDR) or nearly untreatable extensively drug-resistant (XDR) strains. New concepts are therefore urgently needed to understand the factors driving the TB epidemics and the spread of different strain populations, especially in association with drug resistance. Classical genotyping and, more recently, whole-genome sequencing (WGS) revealed that the world population of tubercle bacilli is more diverse than previously thought. Several major phylogenetic lineages can be distinguished, which are associated with their sympatric host population. Distinct clonal (sub)populations can even coexist within infected patients. WGS is now used as the ultimate approach for differentiating clinical isolates and for linking phenotypic to genomic variation from lineage to strain levels. Multiple lines of evidence indicate that the genetic diversity of TB strains translates into pathobiological consequences, and key molecular mechanisms probably involved in differential pathoadaptation of some main lineages have recently been identified. Evidence also accumulates on molecular mechanisms putatively fostering the emergence and rapid expansion of particular MDR and XDR strain groups in some world regions. However, further integrative studies will be needed for complete elucidation of the mechanisms that allow the pathogen to infect its host, acquire multidrug resistance, and transmit so efficiently. Such knowledge will be key for the development of the most effective new diagnostics, drugs, and vaccination strategies.

Heterogeneity in tuberculosis

Infection with Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), results in a range of clinical presentations in humans. Most infections manifest as a clinically asymptomatic, contained state that is termed latent TB infection (LTBI); a smaller subset of infected individuals present with symptomatic, active TB. Within these two seemingly binary states, there is a spectrum of host outcomes that have varying symptoms, microbiologies, immune responses and pathologies. Recently, it has become apparent that there is diversity of infection even within a single individual. A good understanding of the heterogeneity that is intrinsic to TB - at both the population level and the individual level - is crucial to inform the development of intervention strategies that account for and target the unique, complex and independent nature of the local host-pathogen interactions that occur in this infection. In this Review, we draw on model systems and human data to discuss multiple facets of TB biology and their relationship to the overall heterogeneity observed in the human disease.

Genotyping and Prevalence of Pyrazinamide- and Moxifloxacin-Resistant Tuberculosis in China, 2000 to 2010

We investigated the prevalence, trends, and risk factors for pyrazinamide (PZA) and moxifloxacin (MOX) resistance among tuberculosis (TB) cases in China and also analyzed the population structure of Mycobacterium tuberculosis strains. All the M. tuberculosis strains enrolled in this study were collected from the national TB prevalence surveys. Each strain was genotyped by analyzing the regions of RD105 and IS6110 in the NTF region. The Bactec MGIT 960 system was used to detect the drug susceptibility of M. tuberculosis isolates to PZA and MOX. Based on the genotyping results, 241 (66.4%) strains were classified as Beijing genotype in 2000, which was significantly lower than in 2010 (76.2%, P < 0.01). The proportion of the modern Beijing genotype increased significantly from 49.6% in 2000 to 68.1% in 2010 (P < 0.01), while no significant difference was observed in the rate of ancient Beijing genotype between 2000 and 2010 (P = 0.676). In addition, we found that the proportion of PZA resistance in 2010 (15.0%) was significantly higher than that in 2000 (9.6%, P = 0.04). For MOX, there were more MOX-resistant isolates detected in 2010 (7.7%) than in 2000 (3.0%). In conclusion, our data demonstrate that the Beijing genotype was the predominant M. tuberculosis lineage during the past decade. The proportion of Beijing genotype isolates significantly increased from 2000 to 2010, largely due to an increase in the modern Beijing sublineage. In addition, resistance to PZA and MOX increased significantly in China between 2000 and 2010.

Proteomics for the Investigation of Mycobacteria

The physiology of Mycobacterium tuberculosis, the causative agent of tuberculosis, is being studied with intensity. However, despite the genomic and transcriptomic data available today, the pathogenic potential of these bacteria remains poorly understood. Therefore, proteomic approaches seem relevant in studying mycobacteria. This review covers the main stages in the proteomic analysis methods used to study mycobacteria. The main achievements in the area of M. tuberculosis proteomics are described in general. Special attention is paid to the proteomic features of the Beijing family, which is widespread in Russia. Considering that the proteome is a set of all the proteins in the cell, post-translational modifications of mycobacterium proteins are also described.