Extracellular Mycobacterial DNA-binding Protein 1 Participates in Mycobacterium-Lung Epithelial Cell Interaction through Hyaluronic Acid

Recombinant mycobacterial DNA-binding protein 1 with post-translational modifications boosts IFN-gamma production from BCG-vaccinated individuals' blood cells in combination with CpG-DNA

Tuberculosis remains a large health threat, despite the availability of the tuberculosis vaccine, BCG. As BCG efficacy gradually decreases from adolescence, BCG-Prime and antigen-booster may be an efficient strategy to confer vaccine efficacy. Mycobacterial DNA-binding protein 1 (MDP1, namely Rv2986c, hupB or HU) is a major Mycobacterium tuberculosis protein that induces vaccine-efficacy by co-administration with CpG DNA. To produce MDP1 for booster-vaccine use, we have created recombinant MDP1 produced in both Escherichia coli (eMDP1) and Mycolicibacterium smegmatis (mMDP1), an avirulent rapid-growing mycobacteria. We tested their immunogenicity by checking interferon (IFN)-gamma production by stimulated peripheral blood cells derived from BCG-vaccinated individuals. Similar to native M. tuberculosis MDP1, we observed that most lysin resides in the C-terminal half of mMDP1 are highly methylated. In contrast, eMDP1 had less post-translational modifications and IFN-gamma stimulation. mMDP1 stimulated the highest amount of IFN-gamma production among the examined native M. tuberculosis proteins including immunodominant MPT32 and Antigen 85 complex. MDP1-mediated IFN-gamma production was more strongly enhanced when combined with a new type of CpG DNA G9.1 than any other tested CpG DNAs. Taken together, these results suggest that the combination of mMDP1 and G9.1 possess high potential use for human booster vaccine against tuberculosis.

Evaluation of cytokine profiles related to Mycobacterium tuberculosis latent antigens using a whole-blood assay in the Philippines

Introduction

There is no useful method to discriminate between latent tuberculosis infection (LTBI) and active pulmonary tuberculosis (PTB). This study aimed to investigate the potential of cytokine profiles to discriminate between LTBI and active PTB using whole-blood stimulation with Mycobacterium tuberculosis (MTB) antigens, including latency-associated antigens.

Materials and methods

Patients with active PTB, household contacts of active PTB patients and community exposure subjects were recruited in Manila, the Philippines. Peripheral blood was collected from the participants and used for whole-blood stimulation (WBS) with either the early secretory antigenic target and the 10-kDa culture filtrate protein (ESAT-6/CFP-10), Rv3879c or latency-associated MTB antigens, including mycobacterial DNA-binding protein 1 (MDP-1), α-crystallin (Acr) and heparin-binding hemagglutinin (HBHA). Multiple cytokine concentrations were analyzed using the Bio-Plex™ multiplex cytokine assay.

Results

A total of 78 participants consisting of 15 active PTB patients, 48 household contacts and 15 community exposure subjects were eligible. The MDP-1-specific IFN-γ level in the active PTB group was significantly lower than that in the household contact group (p < 0.001) and the community exposure group (p < 0.001). The Acr-specific TNF-α and IL-10 levels in the active PTB group were significantly higher than those in the household contact (TNF-α; p = 0.001, IL-10; p = 0.001) and community exposure (TNF-α; p < 0.001, IL-10; p = 0.01) groups. However, there was no significant difference in the ESAT-6/CFP-10-specific IFN-γ levels among the groups.

Conclusion

The patterns of cytokine profiles induced by latency-associated MTB antigens using WBS have the potential to discriminate between LTBI and active PTB. In particular, combinations of IFN-γ and MDP-1, TNF-α and Acr, and IL-10 and Acr are promising. This study provides the first demonstration of the utility of MDP-1-specific cytokine responses in WBS.

The heparin-binding hemagglutinin protein of Mycobacterium tuberculosis is a nucleoid-associated protein

Nucleoid-associated proteins (NAPs) regulate multiple cellular processes such as gene expression, virulence, and dormancy throughout bacterial species. NAPs help in the survival and adaptation of Mycobacterium tuberculosis (Mtb) within the host. Fourteen NAPs have been identified in Escherichia coli; however, only seven NAPs are documented in Mtb. Given its complex lifestyle, it is reasonable to assume that Mtb would encode for more NAPs. Using bioinformatics tools and biochemical experiments, we have identified the heparin-binding hemagglutinin (HbhA) protein of Mtb as a novel sequence-independent DNA-binding protein which has previously been characterized as an adhesion molecule required for extrapulmonary dissemination. Deleting the carboxy-terminal domain of HbhA resulted in a complete loss of its DNA-binding activity. Atomic force microscopy showed HbhA-mediated architectural modulations in the DNA, which may play a regulatory role in transcription and genome organization. Our results showed that HbhA colocalizes with the nucleoid region of Mtb. Transcriptomics analyses of a hbhA KO strain revealed that it regulates the expression of ∼36% of total and ∼29% of essential genes. Deletion of hbhA resulted in the upregulation of ∼73% of all differentially expressed genes, belonging to multiple pathways suggesting it to be a global repressor. The results show that HbhA is a nonessential NAP regulating gene expression globally and acting as a plausible transcriptional repressor.

Limited proteolysis of mycobacterial DNA-binding protein 1 with an extended, lysine-rich, intrinsically disordered region to unveil posttranslational modifications

The basic, intrinsically disordered regions of eukaryotic histones and their bacterial counterparts are presumed to act as signaling hubs to regulate the compaction of chromosomes or nucleoids and various DNA processes such as gene expression, recombination, and DNA replication. Posttranslational modifications (PTMs) on these regions are pivotal in regulating chromosomal or nucleoid compaction and DNA processes. However, the low sequence complexity and the presence of short lysine-rich repeats in the regions have hindered the accurate determination of types and locations of PTMs using conventional proteomic procedures. We described a limited proteolysis protocol using trypsin to analyze PTMs on mycobacterial DNA-binding protein 1 (MDP1), a nucleoid-associated protein in mycobacterial species that possesses an extended, lysine-rich, intrinsically disordered region in its C-terminal domain. This limited proteolysis approach successfully revealed significant methylation on many lysine residues in the C-terminal domain of MDP1 purified from Mycobacterium tuberculosis, which was lacking in the corresponding region of recombinant MDP1 expressed in Escherichia coli.

Diminishing of Helicobacter pylori adhesion to Cavia porcellus gastric epithelial cells by BCG vaccine mycobacteria

Mycobacterium bovis onco-BCG bacilli used in immunotherapy of bladder cancer are candidates for training of immune cells towards microbial pathogens. Increasing antibiotic resistance of gastric pathogen Helicobacter pylori (Hp) prompts the search for new anti-Hp and immunomodulatory formulations. Colonization of gastric mucosa by Hp through mucin 5 AC (MUC5AC) ligands could potentially be a therapeutic target. The aim of this study was to examine the ability of onco-BCG mycobacteria to reduce Hp adhesion to gastric epithelial cells using Cavia porcellus model. Animals were inoculated per os with 0.85% NaCl, Hp alone, onco-BCG alone or with onco-BCG and Hp. After 7/28 days Mucin5AC and Hp binding to gastric epithelium were assessed in gastric tissue specimens by staining with anti-Mucin5AC and anti-Hp antibodies, respectively, both fluorescently labeled. Primary gastric epithelial cells were treated ex vivo with live Hp or Hp surface antigens (glycine extract or lipopolysaccharide) alone or with onco-BCG. In such cells MUC5AC and Hp binding were determined as above. Mycobacteria reduced the amount of MUC5AC animals infected with Hp and in gastric epithelial cells pulsed in vitro with Hp components. Decrease of MUC5AC driven in cell cultures in vitro and in gastric tissue exposed ex vivo to mycobacteria was related to diminished adhesion of H. pylori bacilli. Vaccine mycobacteria by diminishing the amount of MUC5AC in gastric epithelial cells may reduce Hp adhesion.

Absorption, metabolism, and functions of hyaluronic acid and its therapeutic prospects in combination with microorganisms: A review

Hyaluronic acid (HA) is key to the stability of the internal environment of tissues. HA content in tissues gradually decreases with age, causing age-related health problems. Exogenous HA supplements are used to prevent or treat these problems including skin dryness and wrinkles, intestinal imbalance, xerophthalmia, and arthritis after absorption. Moreover, some probiotics are able to promote endogenous HA synthesis and alleviate symptoms caused by HA loss, thus introducing potential preventative or therapeutic applications of HA and probiotics. Here, we review the oral absorption, metabolism, and biological function of HA as well as the potential role of probiotics and HA in increasing the efficacy of HA supplements.

Bacterial nucleoid-associated protein HU as an extracellular player in host-pathogen interaction

HU protein is a member of nucleoid-associated proteins (NAPs) and is an important regulator of bacterial virulence, pathogenesis and survival. NAPs are mainly DNA structuring proteins that influence several molecular processes by binding the DNA. HU´s indispensable role in DNA-related processes in bacteria was described. HU protein is a necessary bacterial transcription factor and is considered to be a virulence determinant as well. Less is known about its direct role in host-pathogen interactions. The latest studies suggest that HU protein may be secreted outside bacteria and be a part of the extracellular matrix. Moreover, HU protein can be internalized in a host cell after bacterial infection. Its role in the host cell is not well described and further studies are extremely needed. Existing results suggest the involvement of HU protein in host cell immune response modulation in bacterial favor, which can help pathogens resist host defense mechanisms. A better understanding of the HU protein’s role in the host cell will help to effective treatment development.

Monitoring IgG against Mycobacterium tuberculosis proteins in an Asian elephant cured of tuberculosis that developed from long-term latency

Tuberculosis (TB) is fatal in elephants, hence protecting elephants from TB is key not only in the conservation of this endangered animal, but also to prevent TB transmission from elephants to humans. Most human TB cases arise from long-term asymptomatic infections. Significant diagnostic challenges remain in the detection of both infection and disease development from latency in elephants due to their huge bodies. In this study, we assessed cryopreserved sera collected for over 16 years, from the first Japanese treatment case of elephant TB. Semi-quantification of IgG levels to 11 proteins showed high detection levels of 3 proteins, namely ESAT6/CFP10, MPB83 and Ag85B. The level of IgG specific to these 3 antigens was measured longitudinally, revealing high and stable ESAT6/CFP10 IgG levels regardless of onset or treatment. Ag85B-specifc IgG levels were largely responsive to onset or treatment, while those of MPB83 showed intermediate responses. These results suggest that ESAT6/CFP10 is immunodominant in both asymptomatic and symptomatic phases, making it useful in the detection of infection. On the other hand, Ag85B has the potential to be a marker for the prediction of disease onset and in the evaluation of treatment effectiveness in elephants.

TLR-9 Plays a Role in Mycobacterium leprae-Induced Innate Immune Activation of A549 Alveolar Epithelial Cells

The respiratory tract is considered the main port of entry of Mycobacterium leprae, the causative agent of leprosy. However, the great majority of individuals exposed to the leprosy bacillus will never manifest the disease due to their capacity to develop protective immunity. Besides acting as a physical barrier, airway epithelium cells are recognized as key players by initiating a local innate immune response that orchestrates subsequent adaptive immunity to control airborne infections. However, to date, studies exploring the interaction of M. leprae with the respiratory epithelium have been scarce. In this work, the capacity of M. leprae to immune activate human alveolar epithelial cells was investigated, demonstrating that M. leprae-infected A549 cells secrete significantly increased IL-8 that is dependent on NF-κB activation. M. leprae was also able to induce IL-8 production in human primary nasal epithelial cells. M. leprae-treated A549 cells also showed higher expression levels of human β-defensin-2 (hβD-2), MCP-1, MHC-II and the co-stimulatory molecule CD80. Furthermore, the TLR-9 antagonist inhibited both the secretion of IL-8 and NF-κB activation in response to M. leprae, indicating that bacterial DNA sensing by this Toll-like receptor constitutes an important innate immune pathway activated by the pathogen. Finally, evidence is presented suggesting that extracellular DNA molecules anchored to Hlp, a histone-like protein present on the M. leprae surface, constitute major TLR-9 ligands triggering this pathway. The ability of M. leprae to immune activate respiratory epithelial cells herein demonstrated may represent a very early event during infection that could possibly be essential to the generation of a protective response.

The Known Unknowns of the Immune Response to Coccidioides

Coccidioidomycosis, otherwise known as Valley Fever, is caused by the dimorphic fungi Coccidioides immitis and C. posadasii. While most clinical cases present with self-limiting pulmonary infection, dissemination of Coccidioides spp. results in prolonged treatment and portends higher mortality rates. While the structure, genome, and niches for Coccidioides have provided some insight into the pathogenesis of disease, the underlying immunological mechanisms of clearance or inability to contain the infection in the lung are poorly understood. This review focuses on the known innate and adaptive immune responses to Coccidioides and highlights three important areas of uncertainty and potential approaches to address them. Closing these gaps in knowledge may enable new preventative and therapeutic strategies to be pursued.

Evaluation of a booster tuberculosis vaccine containing mycobacterial DNA-binding protein 1 and CpG oligodeoxynucleotide G9.1 using a Guinea pig model that elicits immunity to Bacillus Calmette-Guérin

Tuberculosis is a major threat to global health and its increased incidence in adolescents as well as onset in the elderly presents a serious problem. One strategy to control tuberculosis involves taking advantage of Bacillus Calmette-Guérin's (BCG) superior effects on childhood tuberculosis. Accordingly, here we aimed to develop a booster vaccine for adults who received the BCG vaccine during early childhood. Therefore, we first devised a system to assess the efficacy of a candidate booster vaccine. Specifically, variant strain BCG-II, a minor component of BCG-Tokyo strain, which elicits weak immunity, was administered to guinea pigs. Vaccine-induced immunity and protection against Mycobacterium tuberculosis (Mtb) infection were evaluated using skin delayed-type hypersensitivity (DTH) and Mtb colony forming unit counts in organs, respectively. Candidate booster vaccine containing the mycobacterial DNA-binding protein 1 (MDP1) as antigen and CpG oligodeoxynucleotide G9.1 as adjuvant increased T-bet expression and IFN-γ production in human peripheral blood mononuclear cells. Intradermal administration of MDP1 or MDP1 and G9.1 to unimmunized guinea pigs produced DTH on MDP1-inoculated skin. Boosting BCG-II-primed guinea pigs with this protocol effectively enhanced DTH against MDP1 and protection against Mtb infection, particularly when combined with G9.1. The candidate vaccine may contribute to efforts to prevent tuberculosis.

Extracellular matrix-inspired inhalable aerogels for rapid clearance of pulmonary tuberculosis

Tuberculosis (TB) remains a leading cause of death from a single infectious agent, and limiting the spread of multidrug-resistant TB (MDR-TB) is now an urgent global health priority. Essential to the persistence of this disease is the ability of Mycobacterium tuberculosis (Mtb) to circumvent host defenses by infecting lung macrophages to create a cellular niche for its survival and proliferation. This has urged the development of new therapeutic strategies that act through mechanisms distinct from conventional antibiotics, and thus are effective against MDR bacteria, while being able to efficiently kill persister Mtb cells in infected host macrophages. Here, we report a new class of gel-like microparticle aerosols, or 'aerogels', designed to exploit metabolic vulnerabilities of Mtb pathogens and TB-infected macrophages to enable preferential delivery of synergistic peptide-antibiotic combinations for potent and rapid antitubercular therapy. This is achieved by formulating aerogels through the supramolecular assembly of a de novo designed anti-TB peptide and the extracellular matrix (ECM)-derived polysaccharide, hyaluronic acid (HA). Importantly, HA serves as a nutrient source for Mtb cells during tissue invasion and proliferation, and is recognized by CD44 receptors highly expressed on lung macrophages during TB infection. By exploiting this metabolic substrate for pathogen targeting, HA aerogels are shown to avidly bind and kill both drug-sensitive and drug-resistant mycobacteria, while being efficiently internalized into macrophage host cells in vitro and in vivo to clear Mtb persisters. This multifaceted bioactivity suggests aerogels may serve as a versatile inhalable platform upon which novel biomaterials-enabled therapeutics can be developed to rapidly clear pulmonary MDR-TB.

A protein fragment of Rv3194c located on mycobacterial cell surface efficiently prevents adhesion of recombinant Mycobacterium smegmatis, and promises a new anti-adhesive drug

Adhesins are virulence factors expressed on the surfaces of pathogenic bacteria that mediate pathogen-host interactions, a critical step in the infection process. Here, we show that the Mycobacterium tuberculosis protease Rv3194c functions not only as an enzyme but as an adhesin. The heterologous Rv3194c protein was purified from Escherichia coli and was shown to bind to hyaluronic acid (HA). The HA-binding site was identified as a 20 amino acid peptide between residues 91 and 110 (P91-110). Rv3194c bound to A549 alveolar basal epithelial cells and the interaction was abolished by the addition of hyaluronidase or P91-110. Experimental infection in vitro revealed that Rv3194c participates in the attachment of recombinant Mycobacterium smegmatis (Rv3194c/MS) to A549 cells, and P91-110 treatment of A549 cells largely inhibited the Rv3194c/MS-A549 cell interaction. To provide in vivo evidence, we constructed a reporter strain of M. smegmatis that expressed a derivative of the firefly luciferase that is shifted to red (FFlucRT) in combination with Rv3194c (Rv3194c + FFlucRT/MS) to infect mice and monitor the progression of the disease. In mice, Rv3194c dramatically enhanced M. smegmatis persistence and induced lesions in the lungs. In addition, treatment of intratracheal Rv3194c + FFlucRT/MS- infected mice with P91-110 significantly suppressed the growth of Rv3194c + FFlucRT/MS in vivo and reduced pathological injury caused by infection of the lung with Rv3194c + FFlucRT/MS. Taken together, these results demonstrate that Rv3194c functions as an HA-binding adhesin and that P91-110 may have the potential for treating and preventing mycobacterial infection.

Metabolic adaptation to glycolysis is a basic defense mechanism of macrophages for Mycobacterium tuberculosis infection

Macrophages are major components of tuberculosis (TB) granulomas and are responsible for host defenses against the intracellular pathogen, Mycobacterium tuberculosis. We herein showed the strong expression of hypoxia-inducible factor-1α (HIF-1α) in TB granulomas and more rapid death of HIF-1α-conditional knockout mice than wild-type (WT) mice after M. tuberculosis infection. Although interferon-γ (IFN-γ) is a critical host-protective cytokine against intracellular pathogens, HIF-1-deficient macrophages permitted M. tuberculosis growth even after activation with IFN-γ. These results prompted us to investigate the role of HIF-1α in host defenses against infection. We found that the expression of lactate dehydrogenase-A (LDH-A) was controlled by HIF-1α in M. tuberculosis-infected macrophages IFN-γ independently. LDH-A is an enzyme that converts pyruvate to lactate and we found that the intracellular level of pyruvate in HIF-1α-deficient bone marrow-derived macrophages (BMDMs) was significantly higher than in WT BMDMs. Intracellular bacillus replication was enhanced by an increase in intracellular pyruvate concentrations, which were decreased by LDH-A. Mycobacteria in phagosomes took up exogenous pyruvate more efficiently than glucose, and used it as the feasible carbon source for intracellular growth. These results demonstrate that HIF-1α prevents the hijacking of pyruvate in macrophages, making it a fundamental host-protective mechanism against M. tuberculosis.

Significance of a histone-like protein with its native structure for the diagnosis of asymptomatic tuberculosis

Tuberculosis causes the highest mortality among all single infections. Asymptomatic tuberculosis, afflicting one third of the global human population, is the major source as 5–10% of asymptomatic cases develop active tuberculosis during their lifetime. Thus it is one of important issues to develop diagnostic tools for accurately detecting asymptomatic infection. Mycobacterial DNA-binding protein 1 (MDP1) is a major protein in persistent Mycobacterium tuberculosis and has potential for diagnostic use in detecting asymptomatic infection. However, a previous ELISA-based study revealed a specificity problem; IgGs against MDP1 were detected in both M. tuberculosis-infected and uninfected individuals. Although the tertiary structures of an antigen are known to influence antibody recognition, the MDP1 structural details have not yet been investigated. The N-terminal half of MDP1, homologous to bacterial histone-like protein HU, is predicted to be responsible for DNA-binding, while the C-terminal half is assumed as totally intrinsically disordered regions. To clarify the relationship between the MDP1 tertiary structure and IgG recognition, we refined the purification method, which allow us to obtain a recombinant protein with the predicted structure. Furthermore, we showed that an IgG-ELISA using MDP1 purified by our refined method is indeed useful in the detection of asymptomatic tuberculosis.

AbmR (Rv1265) is a novel transcription factor of Mycobacterium tuberculosis that regulates host cell association and expression of the non-coding small RNA Mcr11

Gene regulatory networks used by Mycobacterium tuberculosis (Mtb) during infection include many genes of unknown function, confounding efforts to determine their roles in Mtb biology. Rv1265 encodes a conserved hypothetical protein that is expressed during infection and in response to elevated levels of cyclic AMP. Here, we report that Rv1265 is a novel auto‐inhibitory ATP‐binding transcription factor that upregulates expression of the small non‐coding RNA Mcr11, and propose that Rv1265 be named ATP‐binding mcr11regulator (AbmR). AbmR directly and specifically bound DNA, as determined by electrophoretic mobility shift assays, and this DNA‐binding activity was enhanced by AbmR’s interaction with ATP. Genetic knockout of abmR in Mtb increased abmR promoter activity and eliminated growth phase‐dependent increases in mcr11 expression during hypoxia. Mutagenesis identified arginine residues in the carboxy terminus that are critical for AbmR’s DNA‐binding activity and gene regulatory function. Limited similarity to other DNA‐ or ATP‐binding domains suggests that AbmR belongs to a novel class of DNA‐ and ATP‐binding proteins. AbmR was also found to form large organized structures in solution and facilitate the serum‐dependent association of Mtb with human lung epithelial cells. These results indicate a potentially complex role for AbmR in Mtb biology.

G-Quadruplex-Forming DNA Aptamers Inhibit the DNA-Binding Function of HupB and Mycobacterium tuberculosis Entry into Host Cells

The entry and survival of Mycobacterium tuberculosis (Mtb) within host cells is orchestrated partly by an essential histone-like protein HupB (Rv2986c). Despite being an essential drug target, the lack of structural information has impeded the development of inhibitors targeting the indispensable and multifunctional C-terminal domain (CTD) of HupB. To bypass the requirement for structural information in the classical drug discovery route, we generated a panel of DNA aptamers against HupB protein through systemic evolution of ligands by exponential (SELEX) enrichment. Two G-quadruplex-forming high-affinity aptamers (HupB-4T and HupB-13T) were identified, each of which bound two distinct sites on full-length HupB, with an estimated K_D of ∼1.72 μM and ∼0.17 μM, respectively, for the high-affinity sites. While HupB-4T robustly inhibited DNA-binding activity of HupB in vitro, both the aptamers recognized surface-located HupB and significantly blocked Mtb entry into THP-1 monocytic cells (p < 0.0001). In summary, DNA aptamers generated in this study block DNA-binding activity of HupB, inhibit virulent Mtb infection in host cells, and demonstrate aptamers to be inhibitors of HupB functions. This study also illustrates the utility of SELEX in developing inhibitors against essential targets for whom structural information is not available.

Pursuing Intracellular Pathogens with Hyaluronan. From a 'Pro-Infection' Polymer to a Biomaterial for 'Trojan Horse' Systems

Hyaluronan (HA) is among the most important bioactive polymers in mammals, playing a key role in a number of biological functions. In the last decades, it has been increasingly studied as a biomaterial for drug delivery systems, thanks to its physico-chemical features and ability to target and enter certain cells. The most important receptor of HA is ‘Cluster of Differentiation 44’ (CD44), a cell surface glycoprotein over-expressed by a number of cancers and heavily involved in HA endocytosis. Moreover, CD44 is highly expressed by keratinocytes, activated macrophages and fibroblasts, all of which can act as ‘reservoirs’ for intracellular pathogens. Interestingly, both CD44 and HA appear to play a key role for the invasion and persistence of such microorganisms within the cells. As such, HA is increasingly recognised as a potential target for nano-carriers development, to pursuit and target intracellular pathogens, acting as a ‘Trojan Horse’. This review describes the biological relationship between HA, CD44 and the entry and survival of a number of pathogens within the cells and the subsequent development of HA-based nano-carriers for enhancing the intracellular activity of antimicrobials.

Hyaluronate lyase activity of Streptococcus suis serotype 2 and modulatory effects of hyaluronic acid on the bacterium's virulence properties

Background

Streptococcus suis serotype 2 is a major swine pathogen and zoonotic agent worldwide causing mainly meningitis and septicemia. Hyaluronate lyases are enzymes that degrade hyaluronic acid, a major constituent of animal tissues, and have been reported as virulence factors in various bacterial species. Since the hyaluronate lyase of S. suis has been considered ambiguously as a virulence factor, we screened 50 isolates from the three major clonal complexes found in North America (sequence type [ST] 1, ST25, and ST28) known to differ in their degree of virulence in order to link the presence or absence of this activity with the degree of virulence. Moreover, the effect of exogenous hyaluronic acid on S. suis virulence factor gene expression and the pro-inflammatory response of brain macrovascular endothelial cells (BMEC) was also investigated.

Results

We found that all but one ST1 isolates (high virulence) were devoid of hyaluronate lyase activity whereas all ST25 (intermediate virulence) and ST28 (low virulence) isolates possessed the activity. A 2 bp insertion was responsible for the lack of activity in ST1 strains. Since the most virulent isolates did not degrade hyaluronic acid, this tissue component may be found during the infectious process. Therefore, we investigated its effect on S. suis and host cells. Hyaluronic acid was found to modulate S. suis adhesion to BMEC, to increase S. suis virulence factor expression, and to enhance pro-inflammatory cytokine secretion by BMEC.

Conclusions

These findings suggest that S. suis hyaluronate lyase does not represent a critical virulence factor in its active form. However, exogenous hyaluronic acid that is likely to interact with S. suis and host cells during the course of infection appears to modulate several virulence determinants of the bacterium, in addition to promote inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1692-9) contains supplementary material, which is available to authorized users.

A mycobacterial phosphoribosyltransferase promotes bacillary survival by inhibiting oxidative stress and autophagy pathways in macrophages and zebrafish

Mycobacterium tuberculosis employs various strategies to modulate host immune responses to facilitate its persistence in macrophages. The M. tuberculosis cell wall contains numerous glycoproteins with unknown roles in pathogenesis. Here, by using Concanavalin A and LC-MS analysis, we identified a novel mannosylated glycoprotein phosphoribosyltransferase, encoded by Rv3242c from M. tuberculosis cell walls. Homology modeling, bioinformatic analyses, and an assay of phosphoribosyltransferase activity in Mycobacterium smegmatis expressing recombinant Rv3242c (MsmRv3242c) confirmed the mass spectrometry data. Using Mycobacterium marinum-zebrafish and the surrogate MsmRv3242c infection models, we proved that phosphoribosyltransferase is involved in mycobacterial virulence. Histological and infection assays showed that the M. marinum mimG mutant, an Rv3242c orthologue in a pathogenic M. marinum strain, was strongly attenuated in adult zebrafish and also survived less in macrophages. In contrast, infection with wild type and the complemented ΔmimG:Rv3242c M. marinum strains showed prominent pathological features, such as severe emaciation, skin lesions, hemorrhaging, and more zebrafish death. Similarly, recombinant MsmRv3242c bacteria showed increased invasion in non-phagocytic epithelial cells and longer intracellular survival in macrophages as compared with wild type and vector control M. smegmatis strains. Further mechanistic studies revealed that the Rv3242c- and mimG-mediated enhancement of intramacrophagic survival was due to inhibition of autophagy, reactive oxygen species, and reduced activities of superoxide dismutase and catalase enzymes. Infection with MsmRv3242c also activated the MAPK pathway, NF-κB, and inflammatory cytokines. In summary, we show that a novel mycobacterial mannosylated phosphoribosyltransferase acts as a virulence and immunomodulatory factor, suggesting that it may constitute a novel target for antimycobacterial drugs.

Immunity against Mycobacterium tuberculosis and the risk of biologic anti-TNF-α reagents

A third of the world's population is exposed to Mycobacterium tuberculosis in their lifetime. Over eight million people develop a tuberculosis (TB) illness and 1.3 million people die from the disease every year. Acquired immunity (cytotoxic CD8+ T cells (CBT), Th1 CD4+ helper T cells) macrophages, and dendritic cells all play important roles in TB infection. Recently, it is well established that innate immunity as well plays a definitive role in the development of TB immunity under the effects of several cytokines, microbicidal proteins and Toll-like receptors. Meanwhile, the introduction and widespread use of biological disease-modifying anti-rheumatic reagents over the last 15 years worldwide has dramatically advanced and improved the standard care and prognosis of patients with rheumatoid arthritis (RA) and juvenile idiopathic arthritis (JIA). However, as clinical experience with these drugs has grown, the risk of granulomatous infections, especially disseminated TB and fungal infections, has become apparent, especially because having RA or JIA may innately increase the risk of infection (bacterial, viral and fungal). The knowledge of basic immunology has also advanced over the past 10 years and adult and pediatric rheumatologists should increase their understanding of this dynamic between arthritis diseases, anti-TNF-α medications, and TB. This review will provide an up-to-date discussion of both the immunology of the TB organism in the human host and the pathophysiologic mechanisms of the TNF-α blockers in the development of secondary (disseminated) tuberculosis.

Interaction of alveolar epithelial cells with CFP21, a mycobacterial cutinase-like enzyme

Mycobacterium tuberculosis (M. tb), an intracellular pathogen, has the ability to infect alveolar epithelial cells (AEC) also in addition to alveolar macrophages. The virulence of M. tb is attributed to proteins encoded by genomic regions of deletion (RD) and till date 16 such regions (RD1-RD16) have been identified. Culture filtrate protein 21 (CFP21), a RD2 secretory protein, is a cutinase-like enzyme that possesses esterase and lipolytic activity. It is hypothesized that CFP21 could be playing a role in M. tb virulence by disrupting the host cell integrity. In this study, recombinant CFP21 was expressed and purified. The in vitro exposure of type I (WI26) and type II (A549) AEC to CFP21 resulted in a significant decline in their cellular viability by inducing cell apoptosis. However, the cytotoxic effects were more pronounced in WI26 cells than in A549 cells. The analysis of immune responses in CFP21-treated AEC exhibited significant production of reactive oxygen species and anti-inflammatory cytokine TGF-β which indicated oxidative stress-mediated cell death. These results show that CFP21 could play an important role in M. tb pathogenesis by disrupting the host alveolar barrier and thereby facilitating mycobacterial dissemination.

Highly immunoreactive antibodies against the rHup-F2 fragment (aa 63-161) of the iron-regulated HupB protein of Mycobacterium tuberculosis and its potential for the serodiagnosis of extrapulmonary and recurrent tuberculosis

HupB is an iron-regulated protein in Mycobacterium tuberculosis that functions as a positive regulator of mycobactin biosynthesis. It is essential for the growth and survival of the pathogen inside macrophages. Previously, using the full-length rHupB of M. tuberculosis, we demonstrated high levels of anti-HupB antibodies in the serum of pulmonary tuberculosis (TB) and, interestingly, extrapulmonary TB patients with negligible levels in household contacts and healthy controls. Here, we used three antigenic fragments of HupB, namely the recombinant HupB-F1 (aa 1-71), HupB-F2 (aa 63-161) and HupB-F3 (aa 164-214), as antigens in enzyme-linked immunosorbent assay (ELISA) to screen serum from TB patients. HupB-F2 showed enhanced immunoreactivity with serum from patients with pulmonary TB (three groups consisting of new cases, defaulters and recurrent cases) and extrapulmonary TB, with negligible levels in normal healthy controls. The negative correlation of the anti-(HupB-F2) antibodies with serum iron was maximal, with a Pearson's correlation coefficient value of -0.415. The study, in addition to strengthening the diagnostic potential of HupB, reflected the superior performance of HupB-F2 as an antigen in screening pulmonary and extrapulmonary TB.

[Molecular mechanisms of dormancy and drug tolerance in mycobacteria]

Instead of rapid multiplication, pathogenic mycobacteria, such as Mycobacterium tuberculosis are likely to have acquired slow but long life. Host immunity affords desirable non-competitive environment for M tuberculosis in human lungs, where this pathogen slowly grows or arrests growing, which avoids rapid loss of living places. Mycobacterial DNA-binding protein 1 (MDP1), a unique histone-like protein associating mycobacterial GC-rich DNA, has pivotal role in realizing such slow life and pathogenesis including drug tolerance to isoniazid.

Mycobacterial laminin-binding histone-like protein mediates collagen-dependent cytoadherence

When grown in the presence of exogenous collagen I, Mycobacterium bovis BCG was shown to form clumps. Scanning electron microscopy examination of these clumps revealed the presence of collagen fibres cross-linking the bacilli. Since collagen is a major constituent of the eukaryotic extracellular matrices, we assayed BCG cytoadherence in the presence of exogenous collagen I. Collagen increased the interaction of the bacilli with A549 type II pneumocytes or U937 macrophages, suggesting that BCG is able to recruit collagen to facilitate its attachment to host cells. Using an affinity chromatography approach, we have isolated a BCG collagen-binding protein corresponding to the previously described mycobacterial laminin-binding histone-like protein (LBP/Hlp), a highly conserved protein associated with the mycobacterial cell wall. Moreover, Mycobacterium leprae LBP/Hlp, a well-characterized adhesin, was also able to bind collagen I. Finally, using recombinant fragments of M. leprae LBP/Hlp, we mapped the collagen-binding activity within the C-terminal domain of the adhesin. Since this protein was already shown to be involved in the recognition of laminin and heparan sulphate-containing proteoglycans, the present observations reinforce the adhesive activities of LBP/Hlp, which can be therefore considered as a multifaceted mycobacterial adhesin, playing an important role in both leprosy and tuberculosis pathogenesis.

Novel feature of Mycobacterium avium subsp. paratuberculosis, highlighted by characterization of the heparin-binding hemagglutinin adhesin

Mycobacterium avium subsp. paratuberculosis comprises two genotypically defined groups, known as the cattle (C) and sheep (S) groups. Recent studies have reported phenotypic differences between M. avium subsp. paratuberculosis groups C and S, including growth rates, infectivity for macrophages, and iron metabolism. In this study, we investigated the genotypes and biological properties of the virulence factor heparin-binding hemagglutinin adhesin (HBHA) for both groups. In Mycobacterium tuberculosis, HBHA is a major adhesin involved in mycobacterium-host interactions and extrapulmonary dissemination of infection. To investigate HBHA in M. avium subsp. paratuberculosis, we studied hbhA polymorphisms by fragment analysis using the GeneMapper technology across a large collection of isolates genotyped by mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) and IS900 restriction fragment length polymorphism (RFLP-IS900) analyses. Furthermore, we analyzed the structure-function relationships of recombinant HBHA proteins of types C and S by heparin-Sepharose chromatography and surface plasmon resonance (SPR) analyses. In silico analysis revealed two forms of HBHA, corresponding to the prototype genomes for the C and S types of M. avium subsp. paratuberculosis. This observation was confirmed using GeneMapper on 85 M. avium subsp. paratuberculosis strains, including 67 strains of type C and 18 strains of type S. We found that HBHAs from all type C strains contain a short C-terminal domain, while those of type S present a long C-terminal domain, similar to that produced by Mycobacterium avium subsp. avium. The purification of recombinant HBHA from M. avium subsp. paratuberculosis of both types by heparin-Sepharose chromatography highlighted a correlation between their affinities for heparin and the lengths of their C-terminal domains, which was confirmed by SPR analysis. Thus, types C and S of M. avium subsp. paratuberculosis may be distinguished by the types of HBHA they produce, which differ in size and adherence properties, thereby providing new evidence that strengthens the genotypic differences between the C and S types of M. avium subsp. paratuberculosis.

Interaction of Mycobacterium leprae with human airway epithelial cells: adherence, entry, survival, and identification of potential adhesins by surface proteome analysis

This study examined the in vitro interaction between Mycobacterium leprae, the causative agent of leprosy, and human alveolar and nasal epithelial cells, demonstrating that M. leprae can enter both cell types and that both are capable of sustaining bacterial survival. Moreover, delivery of M. leprae to the nasal septum of mice resulted in macrophage and epithelial cell infection in the lung tissue, sustaining the idea that the airways constitute an important M. leprae entry route into the human body. Since critical aspects in understanding the mechanisms of infection are the identification and characterization of the adhesins involved in pathogen-host cell interaction, the nude mouse-derived M. leprae cell surface-exposed proteome was studied to uncover potentially relevant adhesin candidates. A total of 279 cell surface-exposed proteins were identified based on selective biotinylation, streptavidin-affinity purification, and shotgun mass spectrometry; 11 of those proteins have been previously described as potential adhesins. In vitro assays with the recombinant forms of the histone-like protein (Hlp) and the heparin-binding hemagglutinin (HBHA), considered to be major mycobacterial adhesins, confirmed their capacity to promote bacterial attachment to epithelial cells. Taking our data together, they suggest that the airway epithelium may act as a reservoir and/or portal of entry for M. leprae in humans. Moreover, our report sheds light on the potentially critical adhesins involved in M. leprae-epithelial cell interaction that may be useful in designing more effective tools for leprosy control.

Characterization of Rv0394c gene encoding hyaluronidase and chondrosulfatase from Mycobacterium tuberculosis

It has been demonstrated that Mycobacterium tuberculosis can utilize hyaluronan (HA) as an alternative carbon resource; however, the gene responsible for HA utilization has not been identified. We overexpressed the soluble product of the Rv0394c gene from M. tuberculosis H37Rv in Escherichia coli and purified it using affinity chromatography and anion exchange chromatography. The hyaluronidase and chondrosulfatase activities of the purified recombinant protein Rv0394c (rRv0394c) were detected and quantitatively measured. Analysis of nucleotide and derived amino acid sequences of the Rv0394c gene revealed that homologs of this gene were conserved in pathogenic mycobacteria, but absent in non-pathogenic mycobacteria. In the current study, we provide novel identification and characterization of a gene encoding hyaluronidase and chondrosulfatase in M. tuberculosis.

BtaE, an adhesin that belongs to the trimeric autotransporter family, is required for full virulence and defines a specific adhesive pole of Brucella suis

Brucella is responsible for brucellosis, one of the most common zoonoses worldwide that causes important economic losses in several countries. Increasing evidence indicates that adhesion of Brucella spp. to host cells is an important step to establish infection. We have previously shown that the BmaC unipolar monomeric autotransporter mediates the binding of Brucella suis to host cells through cell-associated fibronectin. Our genome analysis shows that the B. suis genome encodes several additional potential adhesins. In this work, we characterized a predicted trimeric autotransporter that we named BtaE. By expressing btaE in a nonadherent Escherichia coli strain and by phenotypic characterization of a B. suis ΔbtaE mutant, we showed that BtaE is involved in the binding of B. suis to hyaluronic acid. The B. suis ΔbtaE mutant exhibited a reduction in the adhesion to HeLa and A549 epithelial cells compared with the wild-type strain, and it was outcompeted by the wild-type strain in the binding to HeLa cells. The knockout btaE mutant showed an attenuated phenotype in the mouse model, indicating that BtaE is required for full virulence. BtaE was immunodetected on the bacterial surface at one cell pole. Using old and new pole markers, we observed that both the BmaC and BtaE adhesins are consistently associated with the new cell pole, suggesting that, in Brucella, the new pole is functionally differentiated for adhesion. This is consistent with the inherent polarization of this bacterium, and its role in the invasion process.

Effect of mycobacterial secretory proteins on the cellular integrity and cytokine profile of type II alveolar epithelial cells

Background:

Pulmonary tuberculosis (TB) is caused by Mycobacterium tuberculosis (M. tb). In lungs, alveolar macrophages and type II alveolar epithelial cells serve as a replicative niche for this pathogen. Secretory proteins released by actively replicating tubercle bacilli are known to interact with host cells at the initial stages of infection. To understand the role of these cells in TB pathogenesis, it is important to identify the mycobacterial components involved in interaction with alveolar epithelial cells.

Materials and Methods:

We fractionated the whole secretory proteome of M. tb H₃₇Rv into 10 narrow molecular mass fractions (A1-A10; <20 kDa to >90 kDa) that were studied for their binding potential with A549; type II alveolar epithelial cell line. We also studied the consequences of this interaction in terms of change in epithelial cell viability by MTT assay and cytokine release by ELISA.

Results:

Our results show that several mycobacterial proteins bind and confer cytolysis in epithelial cells. Amongst all the fractions, proteins ranging from 35-45 kDa (A5) exhibited highest binding to A549 cells with a consequence of cytolysis of these cells. This fraction (A5) also led to release of various cytokines important in anti-mycobacterial immunity.

Conclusion:

Fraction A5 (35-45 kDa) of mycobacterial secretory proteome play an important role in mediating M. tb interaction with type II alveolar epithelial cells with the consequences detrimental for the TB pathogenesis. Further studies are being carried out to identify the candidate proteins from this region.

The role of the mycobacterial DNA-binding protein 1 (MDP1) from Mycobacterium bovis BCG in host cell interaction

BACKGROUND

Mycobacterium tuberculosis differs from most pathogens in its ability to multiply inside monocytes and to persist during long periods of time within granuloma in a status of latency. A class of proteins called mycobacterial histone-like proteins has been associated with regulation of replication and latency, but their precise role in the infection process has yet to be uncovered. Our study aimed at defining the impact of the histone-like protein MDP1 from M. bovis BCG (mycobacterial DNA-binding protein 1, corresponding to Rv2986c from M. tuberculosis) on early steps of infection.

RESULTS

Previously, a BCG (Bacillus Calmette Guérin) strain had been generated by antisense-technique exhibiting reduced MDP1 expression. This strain was now used to analyse the impact of reduced amount of MDP1 on the interaction with human blood monocytes, macrophage lines and PBMC (peripheral blood mononuclear cells). MDP1 was revealed to be required for growth at acidic pH and for intracellular replication in human blood monocytes. Down-regulation of MDP1 resulted in reduced secretion of the cytokine IL-1β by infected human PBMC. In addition, a reduction of MDP1 expression had a major impact on the formation of fused multi-nucleated macrophages. In monocyte preparations from human blood as well as in human and mouse macrophage cell lines, both the percentage of multi-nucleated cells and the number of nuclei per cell were much enhanced when the monocytes were infected with BCG expressing less MDP1.

CONCLUSION

MDP1 from M. bovis BCG affects the growth at acidic pH and the intracellular replication in human monocytes. It furthermore affects cytokine secretion by host cells, and the formation of fused multi-nucleated macrophages. Our results suggest an important role of MDP1 in persistent infection.

A novel mechanism of growth phase-dependent tolerance to isoniazid in mycobacteria

Tuberculosis remains one of the most deadly infectious diseases worldwide and is a leading public health problem. Although isoniazid (INH) is a key drug for the treatment of tuberculosis, tolerance to INH necessitates prolonged treatment, which is a concern for effective tuberculosis chemotherapy. INH is a prodrug that is activated by the mycobacterial enzyme, KatG. Here, we show that mycobacterial DNA-binding protein 1 (MDP1), which is a histone-like protein conserved in mycobacteria, negatively regulates katG transcription and leads to phenotypic tolerance to INH in mycobacteria. Mycobacterium smegmatis deficient for MDP1 exhibited increased expression of KatG and showed enhanced INH activation compared with the wild-type strain. Expression of MDP1 was increased in the stationary phase and conferred growth phase-dependent tolerance to INH in M. smegmatis. Regulation of KatG expression is conserved between M. smegmatis and Mycobacterium tuberculosis complex. Artificial reduction of MDP1 in Mycobacterium bovis BCG was shown to lead to increased KatG expression and susceptibility to INH. These data suggest a mechanism by which phenotypic tolerance to INH is acquired in mycobacteria.

The role of airway epithelial cells in response to mycobacteria infection

Airway epithelial cells (AECs) are part of the frontline defense against infection of pathogens by providing both a physical barrier and immunological function. The role of AECs in the innate and adaptive immune responses, through the production of antimicrobial molecules and proinflammatory factors against a variety of pathogens, has been well established. Tuberculosis (TB), a contagious disease primarily affecting the lungs, is caused by the infection of various strains of mycobacteria. In response to mycobacteria infection, epithelial expression of Toll-like receptors and surfactant proteins plays the most prominent roles in the recognition and binding of the pathogen, as well as the initiation of the immune response. Moreover, the antimicrobial substances, proinflammatory factors secreted by AECs, composed a major part of the innate immune response and mediation of adaptive immunity against the pathogen. Thus, a better understanding of the role and mechanism of AECs in response to mycobacteria will provide insight into the relationship of epithelial cells and lung immunocytes against TB, which may facilitate our understanding of the pathogenesis and immunological mechanism of pulmonary tuberculosis disease.

Mobility of late endosomal and lysosomal markers on phagosomes analyzed by fluorescence recovery after photobleaching

During phagosome maturation, the late endosomal marker Rab7 and the lysosomal marker LAMP1 localize to the phagosomes. We investigated the mobility of Rab7 and LAMP1 on the phagosomes in macrophages by fluorescence recovery after photobleaching (FRAP) analysis. Rab7 was mobile between the phagosomal membrane and the cytosol in macrophages that ingested latex beads during phagosome maturation. The addition of interferon-γ (IFN-γ) restricted this mobility, suggesting that Rab7 is forced to bind to the phagosomal membrane by IFN-γ-mediated activation. Immobilization of LAMP1 on the phagosomes was observed irrespective of IFN-γ-activation. We further examined the mobility of Rab7 on the phagosomes containing Mycobacterium bovis BCG by FRAP analysis. The rate of fluorescence recovery for Rab7 on mycobacterial phagosomes was lower than that on the phagosomes containing latex beads, suggesting that mycobacteria impaired the mobility of Rab7 and arrested phagosome maturation.

A histone-like protein of mycobacteria possesses ferritin superfamily protein-like activity and protects against DNA damage by Fenton reaction

Iron is an essential metal for living organisms but its level must be strictly controlled in cells, because ferrous ion induces toxicity by generating highly active reactive oxygen, hydroxyl radicals, through the Fenton reaction. In addition, ferric ion shows low solubility under physiological conditions. To overcome these obstacles living organisms possess Ferritin superfamily proteins that are distributed in all three domains of life: bacteria, archaea, and eukaryotes. These proteins minimize hydroxyl radical formation by ferroxidase activity that converts Fe²⁺ into Fe³⁺ and sequesters iron by storing it as a mineral inside a protein cage. In this study, we discovered that mycobacterial DNA-binding protein 1 (MDP1), a histone-like protein, has similar activity to ferritin superfamily proteins. MDP1 prevented the Fenton reaction and protects DNA by the ferroxidase activity. The K_m values of the ferroxidase activity by MDP1 of Mycobacterium bovis bacillus Calmette-Guérin (BCG-3007c), Mycobacterium tuberculosis (Rv2986c), and Mycobacterium leprae (ML1683; ML-LBP) were 0.292, 0.252, and 0.129 mM, respectively. Furthermore, one MDP1 molecule directly captured 81.4±19.1 iron atoms, suggesting the role of this protein in iron storage. This study describes for the first time a ferroxidase-iron storage protein outside of the ferritin superfamily proteins and the protective role of this bacterial protein from DNA damage.

Rab GTPases regulating phagosome maturation are differentially recruited to mycobacterial phagosomes

Mycobacterium tuberculosis (M. tb) is an intracellular pathogen that can replicate within infected macrophages. The ability of M. tb to arrest phagosome maturation is believed to facilitate its intracellular multiplication. Rab GTPases regulate membrane trafficking, but details of how Rab GTPases regulate phagosome maturation and how M. tb modulates their localization during inhibiting phagolysosome biogenesis remain elusive. We compared the localization of 42 distinct Rab GTPases to phagosomes containing either Staphylococcus aureus or M. tb. The phagosomes containing S. aureus were associated with 22 Rab GTPases, but only 5 of these showed similar localization kinetics as the phagosomes containing M. tb. The Rab GTPases responsible for phagosome maturation, phagosomal acidification and recruitment of cathepsin D were examined in macrophages expressing the dominant-negative form of each Rab GTPase. LysoTracker staining and immunofluorescence microscopy revealed that Rab7, Rab20 and Rab39 regulated phagosomal acidification and Rab7, Rab20, Rab22b, Rab32, Rab34, Rab38 and Rab43 controlled the recruitment of cathepsin D to the phagosome. These results suggest that phagosome maturation is achieved by a series of interactions between Rab GTPases and phagosomes and that differential recruitment of these Rab GTPases, except for Rab22b and Rab43, to M. tb-containing phagosomes is involved in arresting phagosome maturation and inhibiting phagolysosome biogenesis.

Characterization of the Mycobacterium avium subsp. paratuberculosis laminin-binding/histone-like protein (Lbp/Hlp) which reacts with sera from patients with Crohn's disease

Mycobacterium avium subsp. paratuberculosis (Map) causes a chronic enteric disease in ruminants, called paratuberculosis or Johne's disease. The current model proposes that after ingestion by the host, Map crosses the intestinal barrier via internalization by the M cells. Experimental observations suggest, however, that Map may also transcytose the intestinal wall via the enterocytes, but the mechanisms involved in this process remain poorly understood. Cytoadherence assays performed on epithelial cells with Map revealed that the addition of laminin to the cell culture increases adhesion. A Map protein was isolated by heparin-Sepharose chromatography and identified as a laminin-binding protein like. The gene encoding this protein named Lbp/Hlp was identified in the Map genome sequence at locus MAP3024 (annotated Hup B). The deduced Map Lbp/Hlp amino acid sequence reveals 80% identity with that reported for other mycobacteria. The C-terminal domain involved in adhesion is mainly composed of arginine and lysine residues modified by methylation. In vitro tests demonstrated that recombinant Lbp/Hlp binds laminin, heparin, collagen and epithelial cells. Interestingly, we found that this adhesin corresponds to the antigen described as the target of pANCA and serum antibodies of patients with Crohn's disease.

A structure-based approach for mapping adverse drug reactions to the perturbation of underlying biological pathways

Adverse drug reactions (ADR), also known as side-effects, are complex undesired physiologic phenomena observed secondary to the administration of pharmaceuticals. Several phenomena underlie the emergence of each ADR; however, a dominant factor is the drug's ability to modulate one or more biological pathways. Understanding the biological processes behind the occurrence of ADRs would lead to the development of safer and more effective drugs. At present, no method exists to discover these ADR-pathway associations. In this paper we introduce a computational framework for identifying a subset of these associations based on the assumption that drugs capable of modulating the same pathway may induce similar ADRs. Our model exploits multiple information resources. First, we utilize a publicly available dataset pairing drugs with their observed ADRs. Second, we identify putative protein targets for each drug using the protein structure database and in-silico virtual docking. Third, we label each protein target with its known involvement in one or more biological pathways. Finally, the relationships among these information sources are mined using multiple stages of logistic-regression while controlling for over-fitting and multiple-hypothesis testing. As proof-of-concept, we examined a dataset of 506 ADRs, 730 drugs, and 830 human protein targets. Our method yielded 185 ADR-pathway associations of which 45 were selected to undergo a manual literature review. We found 32 associations to be supported by the scientific literature.

Differential recruitment of CD63 and Rab7-interacting-lysosomal-protein to phagosomes containing Mycobacterium tuberculosis in macrophages

M.tb is an intracellular pathogen which survives within the phagosomes of host macrophages by inhibiting their fusion with lysosomes. Here, it has been demonstrated that a lysosomal glycoprotein, CD63, is recruited to the majority of M.tb phagosomes, while RILP shows limited localization. This is consistent with the author's findings that CD63, but not RILP, is recruited to the phagosomes in macrophages expressing the dominant negative form of Rab7. These results suggest that M.tb phagosomes selectively fuse with endosomes and lysosomes to escape killing activity while acquiring nutrients.

Adhesion to and invasion of pulmonary epithelial cells by the F15/LAM4/KZN and Beijing strains of Mycobacterium tuberculosis

Globally, specific genotypes of Mycobacterium tuberculosis have been shown to dominate in patients, suggesting that these are more successful pathogens. One such genotype, the F15/LAM4/KZN (KZN) family of M. tuberculosis, has predominated in KwaZulu-Natal, South Africa, since the early 1990s. This strain recently evolved from multidrug-resistant to extensively drug-resistant (XDR). The ability of M. tuberculosis strains belonging to the Beijing family, the KZN family, strains with unique DNA fingerprint patterns and laboratory strains (H37Rv and H37Ra) to adhere to and invade a human alveolar (A549) and a human bronchial (BBM) epithelial cell line was investigated. All strains displayed greater adhesion to and invasion of A549 cells as compared to BBM cells. The Beijing and KZN strains combined showed greater adhesion (28 %) than the unique strains (5 %) (P <0.05). The XDR variant of KZN invaded A549 cells more effectively than the other isolates. These results suggest that the successful spread of the Beijing and KZN strains might be related to their interaction with alveolar epithelium.

Mycobacteria exploit host hyaluronan for efficient extracellular replication

In spite of the importance of hyaluronan in host protection against infectious organisms in the alveolar spaces, its role in mycobacterial infection is unknown. In a previous study, we found that mycobacteria interact with hyaluronan on lung epithelial cells. Here, we have analyzed the role of hyaluronan after mycobacterial infection was established and found that pathogenic mycobacteria can grow by utilizing hyaluronan as a carbon source. Both mouse and human possess 3 kinds of hyaluronan synthases (HAS), designated HAS1, HAS2, and HAS3. Utilizing individual HAS-transfected cells, we show that HAS1 and HAS3 but not HAS2 support growth of mycobacteria. We found that the major hyaluronan synthase expressed in the lung is HAS1, and that its expression was increased after infection with Mycobacterium tuberculosis. Histochemical analysis demonstrated that hyaluronan profoundly accumulated in the granulomatous legion of the lungs in M. tuberculosis-infected mice and rhesus monkeys that died from tuberculosis. We detected hyaluronidase activity in the lysate of mycobacteria and showed that it was critical for hyaluronan-dependent extracellular growth. Finally, we showed that L-Ascorbic acid 6-hexadecanoate, a hyaluronidase inhibitor, suppressed growth of mycobacteria in vivo. Taken together, our data show that pathogenic mycobacteria exploit an intrinsic host-protective molecule, hyaluronan, to grow in the respiratory tract and demonstrate the potential usefulness of hyaluronidase inhibitors against mycobacterial diseases.

Mycobacterium tuberculosis and Mycobacterium bovis are major bacterial pathogens that kill approximately 2 million people annually by causing tuberculosis. The M. tuberculosis complex has several strategies to parasitize the host. After infection is established, these pathogens are rarely eliminated from the host, and nowadays approximately a third of the world's human population is infected with the Mycobacterium tuberculosis complex. The elucidation of the parasitic mechanisms of the M. tuberculosis complex is important for the development of novel strategies against the disease. The major portal entry of M. tuberculosis complex is through the respiratory tract. On the surface of the airway, hyaluronan retains bactericidal enzymes so that they are “ready-to-use”, protecting tissues from invading pathogens. Furthermore, fragmented hyaluronan produced as a result of infection is used by the immune system as a sensor of infection. Thus, hyaluronan plays a pivotal role in host defenses in the respiratory tract. However, in this study, we observed that the M. tuberculosis complex utilizes hyaluronan as a carbon source for multiplication. We also found that the M. tuberculosis complex has hyaluronidase activity and showed that it is critical for hyaluronan-dependent growth of the M. tuberculosis complex. This study demonstrates a novel parasitic mechanism of the M. tuberculosis complex and suggests that mycobacterial hyaluronidase is a potential drug target.

Lipocalin 2-dependent inhibition of mycobacterial growth in alveolar epithelium

Mycobacterium tuberculosis invades alveolar epithelial cells as well as macrophages. However, the role of alveolar epithelial cells in the host defense against M. tuberculosis remains unknown. In this study, we report that lipocalin 2 (Lcn2)-dependent inhibition of mycobacterial growth within epithelial cells is required for anti-mycobacterial innate immune responses. Lcn2 is secreted into the alveolar space by alveolar macrophages and epithelial cells during the early phase of respiratory mycobacterial infection. Lcn2 inhibits the in vitro growth of mycobacteria through sequestration of iron uptake. Lcn2-deficient mice are highly susceptible to intratracheal infection with M. tuberculosis. Histological analyses at the early phase of mycobacterial infection in Lcn2-deficient mice reveal increased numbers of mycobacteria in epithelial cell layers, but not in macrophages, in the lungs. Increased intracellular mycobacterial growth is observed in alveolar epithelial cells, but not in alveolar macrophages, from Lcn2-deficient mice. The inhibitory action of Lcn2 is blocked by the addition of endocytosis inhibitors, suggesting that internalization of Lcn2 into the epithelial cells is a prerequisite for the inhibition of intracellular mycobacterial growth. Taken together, these findings highlight a pivotal role for alveolar epithelial cells during mycobacterial infection, in which Lcn2 mediates anti-mycobacterial innate immune responses within the epithelial cells.