Biology subjects

Brosch, R.

Publications and source records attributed to Brosch, R..

16 recordsLinked to original sources

bioRxiv2026

Pulmonary delivery of antigen-enhanced BCG overcomes safety barriers in immunocompromised hosts and protects against TB in the absence of adaptive immunity.

The low efficacy of Bacille Calmette-Guerin (BCG) in preventing pulmonary tuberculosis (TB) underscores the need for improved TB vaccines. Recombinant BCG (rBCG) strains secreting the virulence-associated effector molecule ESAT-6 from Mycobacterium tuberculosis (Mtb) markedly improve efficacy and immunogenicity in animal models of TB but have been considered unsuitable for clinical translation due to safety concerns identified in intravenous SCID mouse models. Here, we demonstrate that pulmonary delivery fundamentally reshapes the safety and protective efficacy of the ESAT-6-secreting rBCG strains, BCG::RD1 and BCG::ESAT6-PE25SS. In sharp contrast to intravenous delivery, pulmonary administration was markedly better tolerated, improved survival, and reduced systemic dissemination and brain pathology of severely immunocompromised mice. Strikingly, pulmonary rBCG vaccination also conferred superior protection against aerosol Mtb challenge in wild-type, type 2 diabetic, and adaptive immunity-deficient Rag1-/- and Rag2-/-Il2rg-/- mice, with BCG::RD1 showing the strongest adaptive immunity-independent protection. Mechanistically, pulmonary rBCG vaccination promoted lung innate immune activation, expansion of myeloid-biased progenitors in the bone marrow, and enhanced antimycobacterial activity of macrophages, consistent with trained innate immunity. Collectively, these findings reveal that pulmonary vaccination largely overcomes safety concerns of ESAT-6-secreting rBCG strains and provide preclinical evidence for a viable strategy to improve protection against TB in immunocompromised individuals.

immunology↗

bioRxiv2025

Improved Immune Responses and Tuberculosis Protection by Aerosol Vaccination with recombinant BCG expressing ESX-1 from Mycobacterium marinum

The currently licensed anti-tuberculosis (TB) vaccine, Mycobacterium bovis BCG, provides limited protection against pulmonary TB in adolescents and adults, the main cause of TB transmission and mortality. To obtain an improved BCG-based vaccine candidate with increased immune signaling but still low virulence, we have previously generated a recombinant BCG strain named BCG::ESX-1Mmar, which is heterologously expressing ESX-1 functions of Mycobacterium marinum and thereby modulates the host innate immune responses via phagosomal rupture-associated induction of type I interferon production and enhanced inflammasome activity, leading to superior protection against TB disease in murine infection models. As protection may also vary with the route of vaccination, here, we have explored aerosol vaccination relative to subcutaneous vaccination, using BCG Pasteur and BCG::ESX-1Mmar. We found that mice vaccinated via the aerosol route with BCG Pasteur or BCG::ESX-1Mmar both yielded higher frequencies of CD4+ and CD8+ T effector memory (TEM) cells in the lungs compared to subcutaneously immunised mice, whereas comparable poly-functional Th1 (IL-2, TNF- and IFN-{gamma}) cytokine-producing subsets were observed in the spleens of all vaccinated mice. Significantly higher IL-17 responses without severe lung pathology were seen in the lungs of aerosol-vaccinated mice associated to local and transient inflammatory cytokine responses and immune cell infiltrations. Aerosol vaccination also elicited high amounts of humoral IgG and IgM responses in the bronchoalveolar lavage fluid and induced substantial lung CD69+ CD103+ T resident memory (TRM) cells, containing both CD4+ and CD8+ T subsets, in the airways of immunised mice, whereas this was not the case for subcutaneous vaccination. These effects led to significant improved protection against M. tuberculosis and reduced lung pathology in aerosol-vaccinated mice compared to subcutaneously vaccinated mice. Moreover, BCG::ESX-1Mmar induced enhanced T-cell immunity and superior protection compared to parental BCG Pasteur for both vaccination routes and thereby represents an interesting candidate for developing improved vaccination strategies against TB. Author summaryAnti-tuberculosis vaccine efficacy is influenced by multiple parameters, including the immunogenicity of the vaccine strain, the type of preclinical host model used, and the route of vaccination. Given recent advances in the field of mucosal vaccination, in the current study we were particularly interested to explore and compare aerosol-based vaccination with standard subcutaneous vaccination in a C57BL/6J mouse model using our recently developed recombinant BCG::ESX-1Mmar vaccine candidate in comparison with parental BCG Pasteur. Our results show that in this setting the protective efficacy of mucosal vaccination was superior to subcutaneous vaccination for both vaccine strains, whereby the use of BCG::ESX-1Mmar induced additional benefits in terms of bacterial load reduction compared to standard BCG Pasteur. Taken together, we propose that aerosol vaccination using BCG::ESX-1Mmar as live-attenuated vaccine candidate is a promising and powerful combination for obtaining improved protection against an M. tuberculosis challenge, a concept that can now be tested in other animal models in a perspective of a putative clinical trial.

microbiology↗

bioRxiv2025

Nitrate-responsive Mycobacterial Intracytoplasmic Membranes dampen Inflammation during Mycobacterium tuberculosis Infection

Subcellular compartmentalization of metabolic processes is a main feature of prokaryotic and eukaryotic architecture. Environmental bacteria generate intracytoplasmic membranes (ICMs) as a crucial strategy to adapt their metabolism to environmental changes. While pathogenic intracellular bacteria also perceive various stressful stimuli during host interactions, the subsequent re-organization of their internal architecture has not been explored. Using cryo-electron tomography, we show that Mycobacterium tuberculosis (Mtb), a major human pathogen, is able to form ICMs outside and inside host cells in a strain-dependent manner. We characterize these Mycobacterial intracytoplasmic Membranes (MIMs) as nitrate-induced structures involved in regulation of metabolism. Furthermore, we uncover that MIM formation during macrophage infection correlates with the ability of Mtb to dampen cellular inflammatory responses. Our findings reveal a previously uncharacterized cytoplasmic structure in Mtb and link it to a functional mechanism that enables the bacterium to adapt to its intracellular niche.

microbiology↗

bioRxiv2025

Disease progression is associated with differential neutrophil maturation in Mycobacterium tuberculosis-infected macaques

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is associated with clinical diversity and outcomes ranging from latent TB to active TB with distinct pathophysiologies. However, our understanding of the innate immune mechanisms related to the protection or progression of TB is limited. Among innate immune cells, the role of neutrophils is not fully elucidated, as they have been shown to exhibit both protective and harmful capacities in TB. This duality suggests possible differences in the nature and type of neutrophils present during the infection, generating different effects. We hypothesized that Mtb infection induces changes in neutrophil phenotype and function, influencing the infection outcomes. In order to decipher the link between neutrophils and disease progression, we used a cynomolgus macaque model of human TB. Based on clinical, bacteriological, and positron emission tomography with X-ray computed tomography (PET/CT) scan parameters, animals were stratified into two categories: animals that rapidly progressed to an active form of TB, designated as "fast progressors", and "slow progressors", which include low symptomatic or asymptomatic animals. In this study, we identified transcriptomic signatures of type I interferons and neutrophil degranulation in macaques with fast progression to active TB, which were not observed in animals with slow TB progression. Unsuppervised mass cytometry analysis showed the emergence of blood immature neutrophils (CD101+ CD10-) in fast progressing animals. In addition, circulating neutrophils from infected animals displayed capacities to modulate TNF- production and cytotoxic function of CD8 T cells in a contact-dependent mechanism. In the lungs, neutrophils infiltration in granuloma was higher in fast progressors and specifically located in the lymphocyte-rich region in lesions. These data suggest that specific neutrophil subpopulations are associated with disease progression. Furthermore, these data suggest that neutrophils may modulate CD8 T cells functions, which in turn contribute to the loss of Mtb control and fuel inflammation. AUTHORS SUMMARYMycobacterium tuberculosis (Mtb) infection in humans is associated with a wide range of disease progression, ranging from latent tuberculosis (TB) to active TB. Understanding immune factors leading to the control of the infection or disease progression is essential to identify new biomarkers and targets for host-directed therapies. Innate immunity plays an important role in inflammatory imbalance observed in active TB, among which neutrophils have both beneficial and detrimental roles. Using a macaque model developing a broad range of clinical forms of TB, we seek to understand the links between neutrophils and disease progression. We found that rapid progression to active TB leads to type I interferon signalling and neutrophil activation. In the blood, immature neutrophils were enriched when the disease progressed. In case of severe TB, Neutrophils also infiltrate a specific region of lung TB lesions rich in T lymphocytes, whereas they could modulate CD8 T cells. Our study provides new insights into the role of neutrophils in TB progression.

immunology↗

bioRxiv2025

Evaluation of the role of whiB6 and kdpDE in the dominant multidrug resistant clone Mycobacterium tuberculosis B0/W148

Multidrug resistant (MDR) strains of Mycobacterium tuberculosis represent an obstacle to eradicating tuberculosis (TB) due to the low treatment success rate of MDR TB. Among them, the MDR B0/W148 clone has recently evolved from the M. tuberculosis Beijing lineage 2 and widely disseminated in Russia and Europe. To get more insights into the genetic factors underlying the evolutionary success of the MDR M. tuberculosis B0/W148 clone in addition to environmental and patient-related features, we focused on two mutations specific from this clone that are found in the transcriptional regulators WhiB6 and KdpDE and investigated in a H37Rv strain background the transcriptional profile associated with these mutations and their impact on the in vitro and in vivo growth characteristics. Through the construction and use of H37Rv{Delta}whiB6, H37Rv{Delta}kdpDE, and complemented strains, we found that both mutations did not impair the in vitro growth of M. tuberculosis in standard mycobacterial growth media. The mutation T51P in whiB6 prevented the upregulation of 9 genes in the esx-1 core region and 44 genes elsewhere in the genome, while the deletion of two nucleotides in kdpD leads to a fusion protein of KdpD with KdpE that inhibits the transcriptional activity of KdpE. Both mutations did not lead to hypervirulence in a mouse infection model. These results point to the role of other MDR B0/W148 specific mutations in the wide geographic diffusion of this clone, and/or put in question a hypothesized hypervirulence as driving factor for this large dissemination. ImportanceHuman tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis, remains a global public health issue estimated to have been responsible for 1.25 million deaths in 2023. Multidrug resistant (MDR) strains of M. tuberculosis, resistant to rifampicin and isoniazid, lead to lower treatment success. Among them, the MDR B0/W148 clone has widely disseminated in Russia and Europe. To get more insights into the genetic factors underlying the evolutionary success of this clone, we investigated two strain-specific mutations found in the transcriptional regulators WhiB6 and KdpDE. By constructing and analysing laboratory M. tuberculosis strains carrying these specific mutations, we found numerous changes in their transcriptional profiles, whereas we observed only little impact of these mutations on virulence of M. tuberculosis in a mouse infection model. Our study provides new insights into the transcriptional landscape of the selected MDR strains, although no direct connection to virulence could be established.

microbiology↗

bioRxiv2024

A marine sponge-associated mycobacterium closely related to Mycobacterium tuberculosis

Reconstructing the evolutionary origins of Mycobacterium tuberculosis, the causative agent of human tuberculosis, has helped identify bacterial factors that have led to the tubercle bacillus becoming such a formidable human pathogen. Here we report the discovery and detailed characterization of an exceedingly slow growing mycobacterium that is closely related to M. tuberculosis for which we have proposed the species name Mycobacterium spongiae sp. nov., (strain ID: FSD4b-SM). The bacterium was isolated from a marine sponge, taken from the waters of the Great Barrier Reef in Queensland, Australia. Comparative genomics revealed that, after the opportunistic human pathogen Mycobacterium decipiens, M. spongiae is the most closely related species to the M. tuberculosis complex reported to date, with 80% shared average nucleotide identity and extensive conservation of key M. tuberculosis virulence factors, including intact ESX secretion systems and associated effectors. Proteomic and lipidomic analyses showed that these conserved systems are functional in FSD4b-SM, but that it also produces cell wall lipids not previously reported in mycobacteria. We investigated the virulence potential of FSD4b-SM in mice and found that, while the bacteria persist in lungs for 56 days after intranasal infection, no overt pathology was detected. The similarities with M. tuberculosis, together with its lack of virulence, motivated us to investigate the potential of FSD4b-SM as a vaccine strain and as a genetic donor of the ESX-1 genetic locus to improve BCG immunogenicity. However, neither of these approaches resulted in superior protection against M. tuberculosis challenge compared to BCG vaccination alone. The discovery of M. spongiae adds to our understanding of the emergence of the M. tuberculosis complex and it will be another useful resource to refine our understanding of the factors that shaped the evolution and pathogenesis of M. tuberculosis.

microbiology↗

bioRxiv2023

An oxadiazole-based compound potentiates anti- tuberculosis treatment by increasing host resistance via zinc poisoning

Anti-tuberculosis drugs, mostly developed over 60 years ago, combined with a poorly effective vaccine, have failed to eradicate tuberculosis. More worryingly, multi-resistant strains of Mycobacterium tuberculosis are constantly emerging. Innovative strategies are thus urgently needed to improve tuberculosis treatment. Recently, host-directed therapy has emerged as a promising strategy to be used in adjunct with existing or future antibiotics, by improving innate immunity or limiting immunopathology. Here, using high content imaging, we identified novel 1,2,4-oxadiazole-based compounds, that allow human macrophages to control MTB replication. Genome-wide gene expression analysis revealed that these molecules induced zinc remobilization inside cells, resulting in bacterial zinc intoxication. More importantly, we also demonstrated that, upon treatment with these novel compounds, M. tuberculosis became even more sensitive to anti-tuberculosis drugs, in vitro and in vivo, in a mouse model of tuberculosis. Manipulation of heavy metal homeostasis holds thus great promise to be exploited to develop host-directed therapeutic interventions.

microbiology↗

bioRxiv2022

A comprehensive update to the Mycobacterium tuberculosis H37Rv reference genome

H37Rv is the most widely used M. tuberculosis strain. Its genome is globally used as the M. tuberculosis reference sequence. We developed Bact-Builder, a pipeline that leverages consensus building to generate complete and highly accurate gap-closed bacterial genomes and applied it to three independently sequenced cultures of a parental H37Rv laboratory stock. Two of the 4,417,942 base-pair long H37Rv assemblies were 100% identical, with the third differing by a single nucleotide. Compared to the existing H37Rv reference, the new sequence contained approximately 6.4 kb additional base pairs encoding ten new regions. These regions included insertions in PE/PPE genes and new paralogs of esxN and esxJ, which were differentially expressed compared to the reference genes. Additional sequencing and assembly with Bact-Builder confirmed that all 10 regions were also present in widely accepted strains of H37Rv: NR123 and TMC102. Bact-builder shows promise as an improved method to perform extremely accurate and reproducible de novo assemblies of bacterial genomes. Furthermore, our findings provide important updates to the primary tuberculosis reference genome.

microbiology↗

bioRxiv2022

The C terminus of the mycobacterium ESX-1 secretion system substrate ESAT-6 is required for phagosomal membrane damage and virulence

Mycobacterium tuberculosis and its close relative Mycobacterium marinum infect macrophages and induce the formation of granulomas, organized macrophage-rich immune aggregates. These mycobacterial pathogens can accelerate and co-opt granuloma formation for their benefit, using the specialized secretion system ESX-1, a key virulence determinant. ESX-1-mediated virulence is attributed to the damage it causes to the membranes of macrophage phagosomal compartments, within which the bacteria reside. This phagosomal damage, in turn, has been attributed to the membranolytic activity of ESAT-6, the major secreted substrate of ESX-1. However, mutations that perturb ESAT- 6s membranolytic activity often result in global impairment of ESX-1 secretion. This has precluded an understanding of the causal and mechanistic relationships between ESAT-6 membranolysis and ESX-1-mediated virulence. Here, we identify two conserved residues in the unstructured C-terminal tail of ESAT-6 required for phagosomal damage, granuloma formation and virulence. Importantly, these ESAT-6 mutants have near- normal levels of secretion, far higher than the minimal threshold we establish is needed for ESX-1-mediated virulence early in infection. Unexpectedly, these loss-of-function ESAT-6 mutants retain the ability to lyse acidified liposomes. Thus, ESAT-6s virulence functions in vivo can be uncoupled from this in vitro surrogate assay. These uncoupling mutants highlight an enigmatic functional domain of ESAT-6 and provide key tools to investigate the mechanism of phagosomal damage and virulence. Significance StatementTuberculosis (TB), an ancient disease of humanity, continues to be a major cause of worldwide death. The causative agent of TB, Mycobacterium tuberculosis, and its close pathogenic relative Mycobacterium marinum, initially infect, evade, and exploit macrophages, a major host defense against invading pathogens. Within macrophages, mycobacteria reside within host membrane-bound compartments called phagosomes. Mycobacterium-induced damage of the phagosomal membranes is integral to pathogenesis, and this activity has been attributed the specialized mycobacterial secretion system ESX-1, and particularly to ESAT-6, its major secreted protein. Here, we show that the integrity of the unstructured ESAT-6 C-terminus is required for macrophage phagosomal damage, granuloma formation, and virulence.

microbiology↗

bioRxiv2021

Proteome remodeling in the Mycobacterium tuberculosis PknG knockout: molecular evidence for the role of this kinase in cell envelope biogenesis and hypoxia response.

Mycobacterium tuberculosis, the etiological agent of tuberculosis, is among the deadliest human pathogens. One of M. tuberculosiss pathogenic hallmarks is its ability to persist in a dormant state in the host for long periods, reinitiating the infectious cycle when favorable environmental conditions are found. Thus, it is not surprising that this pathogen has developed different mechanisms to withstand the stressful conditions found in the host. In particular, the Ser/Thr protein kinase PknG has gained special relevance since it regulates nitrogen metabolism and facilitates bacterial survival inside macrophages. Nevertheless, the molecular mechanisms underlying these effects are far from being elucidated. To further investigate these issues, we performed quantitative proteomics analyses of protein extracts from M. tuberculosis H37Rv and a mutant derivative lacking pknG. Our results showed that in the absence of PknG the mycobacterial proteome was remodeled since 5.7% of the proteins encoded by M. tuberculosis presented significant changes in its relative abundance when compared to the wild-type strain. The main biological processes affected by pknG deletion were the biosynthesis of cell envelope components and the response to hypoxic conditions. As many as 13 DosR-regulated proteins were underrepresented in the pknG deletion mutant, including the distinctive Hrp-1, which was found to be 12-fold decreased according to Parallel Reaction Monitoring experiments. Altogether, the results presented here allow us to postulate that PknG regulation of bacterial adaptation to stress conditions might be an important mechanism underlying its reported effect on intracellular bacterial survival.

biochemistry↗

bioRxiv2020

Both adaptive immunity and IL-1R1 dependent signals improve clearance of cytosolic virulent mycobacteria in vivo

Mycobacterium tuberculosis infections claim more than a million lives each year and better treatments or vaccines are required. A crucial pathogenicity factor is translocation from the phago-lysosomes to the cytosol upon phagocytosis by macrophages. The translocation from the phago-lysosome into the cytosol is an ESX-1 dependent process as previously shown in vitro. Here we show that in vivo, mycobacteria also translocate to the cytosol but mainly when host immunity is compromised. We observed only low numbers of cytosolic bacilli in mice, armadillo, zebrafish and patient material infected with M. tuberculosis, M. marinum or M. leprae. In contrast, when innate or adaptive immunity was compromised, as in SCID or IL-1R1 deficient mice, a significant number of cytosolic M. tuberculosis bacilli were detected in lungs of infected mice. Taken together, M. tuberculosis infection is controlled by adaptive immune responses as well as IL-1R1-mediated signals that result in clearance of cells containing cytosolic mycobacteria in vivo. ImportanceFor decades, Mycobacterium tuberculosis is one of the deathliest pathogens known. Despite infecting approximately one third of the human population, no effective treatment or vaccine is available. A crucial pathogenicity factor is the subcellular localization, as M. tuberculosis can translocate from the phago-lysosome to the cytosol in macrophages. The situation in vivo is more complicated. In this study we establish that high level cytosolic escape of mycobacteria can indeed occur in vivo, but mainly when host resistance is compromised. The IL-1 pathway is crucial for the control of the number of cytosolic mycobacteria. The establishment that immune signals result in clearance of cells containing cytosolic mycobacteria, connects two important fields: cell-biology and immunology which is vital for the understanding of the pathology of M. tuberculosis.

cell biology↗

bioRxiv2020

Phthiocerol dimycocerosates from Mycobacterium tuberculosis increase the membrane activity of bacterial effectors and host receptors

Mycobacterium tuberculosis (Mtb) synthesizes a variety of atypical lipids that are exposed at the cell surface and help the bacterium infect macrophages and escape elimination by the cells immune responses. In the present study, we investigate the mechanism of action of one family of hydrophobic lipids, the phthiocerol dimycocerosates (DIM/PDIM), major lipid virulence factors. DIM are transferred from the envelope of Mtb to host membranes during infection. Using the polarity-sensitive fluorophore C-Laurdan, we visualized that DIM increase the membrane polarity of a supported lipid bilayer put in contact with mycobacteria, even beyond the site of contact. We observed that DIM activate the complement receptor 3, a predominant receptor for phagocytosis of Mtb by macrophages. DIM also increased the activity of membrane-permeabilizing effectors of Mtb, among which the virulence factor EsxA. This is consistent with previous observations that DIM help Mtb disrupt host cell membranes. Taken together, our data show that transferred DIM spread within the target membrane, remodel lipid organization and increase the activity of host cell receptors and bacterial effectors, diverting in a nonspecific manner host cell functions. We therefore bring new insight into the molecular mechanisms by which DIM increase Mtbs capability to escape the cells immune responses.

microbiology↗

bioRxiv2019

The antibiotic bedaquiline activates host macrophage innate immune resistance to bacterial infection

Antibiotics are widely used in the treatment of bacterial infections. Although known for their microbicidal activity, antibiotics may also interfere with the hosts immune system. Here we analyzed the effects of bedaquiline (BDQ), an inhibitor of the mycobacterial ATP synthase, on human macrophages. Genome-wide gene expression analysis revealed that BDQ reprogramed macrophages into potent bactericidal phagocytes. We found that 1,495 genes were differentially expressed in M. tuberculosis-infected macrophages incubated with the drug, with an over-representation of genes involved in metabolism, lysosome biogenesis and activation. BDQ treatment triggered a variety of antimicrobial defense mechanisms, including nitric oxide production, phagosome-lysosome fusion, and autophagy. These effects were associated with activation of transcription factor EB (TFEB), involved in the transcription of lysosomal genes, resulting in enhanced intracellular killing of different bacterial species that were naturally insensitive to BDQ. Thus, BDQ could be used as a host-directed therapy against a wide range of bacterial infections.

immunology↗

bioRxiv2019

Mycobacterium abscessus virulence traits unraveled by transcriptomic profiling in amoeba and macrophages

Free-living amoebae might represent an evolutionary niche. In order to get more insights into the potential amoebal training ground for Mycobacterium abscessus, we characterized its full transcriptome in amoeba (Ac) and macrophages (M{varphi}), as well as the Mycobacterium chelonae intra-Ac transcriptome for comparison. Up-regulated genes in Ac allowed M. abscessus to resist environmental stress and induce defense mechanisms, as well as showing switch from carbohydrate carbon sources to fatty acid metabolism. Eleven genes implicated in the adaptation to intracellular stress, were mutated, with all but one confirmed to be involved in M. abscessus intra-M{varphi} survival. Cloning two of these genes in M. chelonae increased its intra-M{varphi} survival. One mutant was particularly attenuated in M{varphi} that corresponded to the deletion of an Eis N-acetyl transferase protein (MAB_4532c). Taken together, M. abscessus transcriptomes revealed the intracellular lifestyle of the mycobacteria, with Ac largely contributing to the enhancement of M. abscessus intra-M{varphi} survival.

microbiology↗

bioRxiv2018

RD5-mediated lack of PE_PGRS and PPE-MPTR export in BCG vaccine strains results in strong reduction of antigenic repertoire but little impact on protection

Tuberculosis is the deadliest infectious disease worldwide. Although the BCG vaccine is widely used, it does not efficiently protect against pulmonary tuberculosis and an improved tuberculosis vaccine is therefore urgently needed. Mycobacterium tuberculosis uses different ESX/Type VII secretion (T7S) systems to transport proteins important for virulence and host immune responses. We recently reported that secretion of T7S substrates belonging to the mycobacteria-specific Pro-Glu (PE) and Pro-Pro-Glu (PPE) proteins of the PGRS (polymorphic GC-rich sequences) and MPTR (major polymorphic tandem repeat) subfamilies required both a functional ESX-5 system and a functional PPE38/71 protein for secretion. Inactivation of ppe38/71 and the resulting loss of PE_PGRS/PPE-MPTR secretion were linked to increased virulence of M. tuberculosis strains. Here, we show that a predicted total of 89 PE_PGRS/PPE-MPTR surface proteins are not exported by certain animal-adapted strains of the M. tuberculosis complex including M. bovis. This {Delta}ppe38/71-associated secretion defect therefore also occurs in the M. bovis-derived tuberculosis vaccine BCG and could be restored by introduction of the M. tuberculosis ppe38-locus. Epitope mapping of the PPE-MPTR protein PPE10, further allowed us to monitor T-cell responses in splenocytes from BCG/M. tuberculosis immunized mice, confirming the dependence of PPE10-specific immune-induction on ESX-5/PPE38-mediated secretion. Restoration of PE_PGRS/PPE-MPTR secretion in recombinant BCG neither altered global antigenic presentation or activation of innate immune cells, nor protective efficacy in two different mouse vaccination-infection models. This unexpected finding stimulates a reassessment of the immunomodulatory properties of PE_PGRS/PPE-MPTR proteins, some of which are contained in vaccine formulations currently in clinical evaluation.

microbiology↗

bioRxiv2017

Predicting susceptibility to tuberculosis based on gene expression profiling in dendritic cells

Tuberculosis (TB) is a deadly infectious disease, which kills millions of people every year. The causative pathogen, Mycobac-terium tuberculosis (MTB), is estimated to have infected up to a third of the worlds population; however, only approximately 10% of infected healthy individuals progress to active TB. Despite evidence for heritability, it is not currently possible to predict who may develop TB. To explore approaches to classify susceptibility to TB, we infected with MTB dendritic cells (DCs) from putatively resistant individuals diagnosed with latent TB, and from susceptible individuals that had recovered from active TB. We measured gene expression levels in infected and non-infected cells and found hundreds of differentially expressed genes between susceptible and resistant individuals in the non-infected cells. We further found that genetic polymorphisms nearby the differentially expressed genes between susceptible and resistant individuals are more likely to be associated with TB susceptibility in published GWAS data. Lastly, we trained a classifier based on the gene expression levels in the non-infected cells, and demonstrated decent performance on our data and an independent data set. Overall, our promising results from this small study suggest that training a classifier on a larger cohort may enable us to accurately predict TB susceptibility.

genomics↗