A structural overview of mycobacterial adhesins: Key biomarkers for diagnostics and therapeutics

IgG antibody response to Mycobacterium tuberculosis curli pili (MTP) in people from different geographical regions in Sub-Saharan Africa

Previously, a slot blot or an indirect enzyme-linked immunosorbent assay (ELISA) using a synthetic or purified MTP antigen, conceptually demonstrated IgG antibody induction in pulmonary TB patients, albeit with small sample sizes and differing sensitivity. Therefore, we evaluated an IgG MTP ELISA in larger populations from The Gambia (n = 549), Uganda (n = 161), and South Africa (n = 193), comprising human immunodeficiency virus (HIV) positive and negative, with microbiologically confirmed active TB. The association between the IgG level and demographic characteristics was determined by multivariate logistic regression. The sensitivity (44.8-61.2 %) and specificity (33.4-78.5 %) varied in the three cohorts. Anti-MTP antibody titres differed between the TB positive and negative groups within the South African and The Gambian cohorts (p < 0.001), but not in Uganda (p = 0.35). Antibodies were detected in HIV positive and negative patients and were reduced at 6-month follow-up after treatment (p > 0.067). The study verified previous findings that anti-MTP antibodies, and therefore MTP antigen, are produced during active TB. However, the accuracy of the MTP-IgG ELISA was low, and is therefore not suitable as a target product profile in the high burden TB areas investigated. Further studies are needed to clarify the variable reactivities in different geographical areas.

Glycan-mediated adhesion mechanisms in antibiotic-resistant bacteria

Bacterial adhesins play a central role in host-pathogen interactions, with many specifically targeting glycans to mediate bacterial colonization, influence infection dynamics, and evade host immune responses. In this review, we focus on bacterial pathogens identified by the World Health Organization as critical threats to public health and in urgent need of new treatments. We summarize glycoconjugate targets identified in the literature across 19 bacterial genera and species. This comprehensive review provides a foundation for the development of innovative therapeutic strategies to effectively combat these pathogens.

Reinforcing cancer immunotherapy with engineered porous hollow mycobacterium tuberculosis loaded with tumor neoantigens

BACKGROUND

Enhancing antigen cross-presentation is essential for the development of a tumor neoantigen vaccine. One approach is to stimulate antigen-presenting cells (APCs) to uptake neoantigens. Mycobacterium tuberculosis (MTb) contains pathogen-associated molecular patterns (PAMPs) recognized by APCs and adhesion molecules that facilitate MTb invasion of APCs. Therefore, we suggest using MTb as a carrier to enhance APC phagocytosis of neoantigens, thereby promoting antigen cross-presentation.

METHODS

The successful preparation of the MTb carrier (phMTb) was confirmed through electron and confocal microscopy. Fluorescence microscopy was used to detect PAMPs and adhesion molecules on phMTb as well as to observe its role in aiding dendritic cells (DCs) in antigen uptake into endosomes or lysosomes. Flow cytometry was used to assess the retention of PAMPs and adhesion molecules on phMTb, investigate antigen uptake by DCs, evaluate their activation and maturation status, examine the presentation of tumor neoantigens, and analyze immune cells in draining lymph nodes and tumor tissues. The efficacy of phMTb vaccine formulations in combination with anti-programmed cell death protein 1 (PD-1) antibody therapy was assessed using the MC38 mouse tumor models. Adverse effects were evaluated through H&E staining of major organs, assessment of reproductive capability and detection of biochemical indices.

RESULTS

The engineered porous hollow phMTb carrier successfully encapsulated model tumor neoantigens, with or without the adjuvant CpG. The phMTb retained PAMPs and adhesion molecules on its surface, similar to the parental MTb, thereby enhancing DC uptake of phMTb and its formulations containing tumor neoantigens and CpG. Vaccines formulated with phMTb facilitated DC maturation, activation, cross-presentation of tumor neoantigens, and promoted migration of phMTb-laden DCs to lymph nodes, enhancing effector and memory CD8+ T lymphocyte function. In murine tumor models, immunization with phMTb-formulated neoantigen vaccines elicited a robust tumor-specific cytotoxic T lymphocyte immune response with minimal adverse effects. Additionally, vaccination with phMTb-formulated neoantigen vaccines effectively reversed the tumor's immune-suppressive microenvironment. Concurrent administration of the PD-1 antibody with the phMTb-formulated neoantigen vaccine exhibited significant synergistic therapeutic effects.

CONCLUSIONS

The results of our study highlight the potential clinical translation of personalized tumor neoantigen vaccines using the phMTb carrier.

Mycobacterium tuberculosis: The Mechanism of Pathogenicity, Immune Responses, and Diagnostic Challenges

BACKGROUND

The infection caused by Mycobacterium tuberculosis arises from a complex interplay between the host immune system and the bacteria. Early and effective treatment of this disease is of great importance in order to prevent the emergence of drug-resistant strains. This necessitates the availability of fast and reliable diagnostic methods for managing affected cases. One reason why this study is significant is the lack of a comprehensive review in this field that thoroughly examines the importance, pathogenesis, and diagnosis of M. tuberculosis. Therefore, the aim of this review is to provide updated information on M. tuberculosis.

METHODS

We investigate the virulence factors, pathogenicity, and diagnostic methods of this bacterium, alongside the clinical symptoms and interpretation of different types of tuberculosis, including cerebral, miliary, nerve, and tubercular tuberculosis.

RESULTS

Mycobacterium tuberculosis acts as the causative agent of human tuberculosis and is regarded as one of the most adaptable human pathogens. M. tuberculosis possesses several virulence factors that help the bacterium evade mucous barriers. The rise of multidrug-resistant tuberculosis (MDR-TB) in both developing and industrialized countries emphasizes the need for rapid diagnostic methods.

CONCLUSIONS

Non-protein virulence factors play a crucial role in the pathogenicity of Mycobacterium tuberculosis (M. tuberculosis). The bacterial cell membrane contains proteins that modulate the host immune response. For instance, ESAT-6, either alone or in combination with CFP-10, reduces immune activity. While molecular techniques-such as DNA microarray, luciferase reporter assay, polymerase chain reaction (PCR), DNA and RNA probes, next-generation sequencing, and whole-genome sequencing-offer rapid, sensitive, and specific detection of M. tuberculosis, these methods are expensive and require technical expertise.

In silico design of Mycobacterium tuberculosis multi-epitope adhesin protein vaccines

Mycobacterium tuberculosis (Mtb) adhesin proteins are promising candidates for subunit vaccine design. Multi-epitope Mtb vaccine and diagnostic candidates were designed using immunoinformatic tools. The antigenic potential of 26 adhesin proteins were determined using VaxiJen 2.0. The truncated heat shock protein 70 (tnHSP70), 19 kDa antigen lipoprotein (lpqH), Mtb curli pili (MTP), and Phosphate transport protein S1 (PstS1) were selected based on the number of known epitopes on the Immune Epitope Database (IEDB). B- and T-cell epitopes were identified using BepiPred2.0, ABCpred, SVMTriP, and IEDB, respectively. Population coverage was analysed using prominent South African specific alleles on the IEDB. The allergenicity, physicochemical characteristics and tertiary structure of the tri-fusion proteins were determined. The in silico immune simulation was performed using C-ImmSim. Three truncated sequences, with predicted B and T cell epitopes, and without allergenicity or signal peptides were linked by three glycine-serine residues, resulting in the stable, hydrophilic molecules, tnlpqH-tnPstS1-tnHSP70 (64,86 kDa) and tnMTP-tnPstS1-tnHSP70 (63,96 kDa). Restriction endonuclease recognition sequences incorporated at the N- and C-terminal ends of each construct, facilitated virtual cloning using Snapgene, into pGEX6P-1, resulting in novel, highly immunogenic vaccine candidates (0,912-0,985). Future studies will involve the cloning, recombinant protein expression and purification of these constructs for downstream applications.

Mycobacterial biofilms: Understanding the genetic factors playing significant role in pathogenesis, resistance and diagnosis

Even though the genus Mycobacterium is a diverse group consisting of a majority of environmental bacteria known as non-tuberculous mycobacteria (NTM), it also contains some of the deadliest pathogens (Mycobacterium tuberculosis) in history associated with chronic disease called tuberculosis (TB). Formation of biofilm is one of the unique strategies employed by mycobacteria to enhance their ability to survive in hostile conditions. Biofilm formation by Mycobacterium species is an emerging area of research with significant implications for understanding its pathogenesis and treatment of related infections, specifically TB. This review provides an overview of the biofilm-forming abilities of different species of Mycobacterium and the genetic factors influencing biofilm formation with a detailed focus on M. tuberculosis. Biofilm-mediated resistance is a significant challenge as it can limit antibiotic penetration and promote the survival of dormant mycobacterial cells. Key genetic factors promoting biofilm formation have been explored such as the mmpL genes involved in lipid transport and cell wall integrity as well as the groEL gene essential for mature biofilm formation. Additionally, biofilm-mediated antibiotic resistance and pathogenesis highlighting the specific niches, sites of infection along with the possible mechanisms of biofilm dissemination have been discussed. Furthermore, drug targets within mycobacterial biofilm and their role as potential biomarkers in the development of rapid diagnostic tools have been highlighted. The review summarises the current understanding of the complex nature of Mycobacterium biofilm and its clinical implications, paving the way for advancements in the field of disease diagnosis, management and treatment against its multi-drug resistant species.

Spray-dried pH-sensitive chitosan microparticles loaded with Mycobacterium bovis BCG intended for supporting treatment of Helicobacter pylori infection

Gram-negative spiral-shaped Helicobacter pylori (Hp) bacteria induce the development of different gastric disorders. The growing resistance of Hp to antibiotics prompts to search for new therapeutic formulations. A promising candidate is Mycobacterium bovis BCG (BCG) with immunomodulatory properties. Biodegradable mucoadhesive chitosan is a good carrier for delivering BCG mycobacteria to the gastric mucosal environment. This study aimed to show whether BCG bacilli are able to increase the phagocytic activity of Cavia porcellus-guinea pig macrophages derived from the bone marrow towards fluorescently labeled Escherichia coli. Furthermore, to encapsulate live BCG bacilli, in spray-dried chitosan microparticles (CHI-MPs), and assess the pH-dependent release of mycobacteria in pH conditions mimicking gastric (acidic) or gut (alkaline) milieu. Microparticles (MPs) were made of chitosan and coated with Pluronic F-127-(Plur) or N-Acetyl-D-Glucosamine-(GlcNAc) to increase the MPs resistance to low pH or to increase anti-Hp effect, respectively. Spray-drying method was used for microencapsulation of live BCG. The biosafety of tested CHI-MPs has been confirmed using cell models in vitro and the model of guinea pig in vivo. The CHI-MPs loaded with BCG released live mycobacteria at pH 3.0 (CHI-GlcNAc-MPs) or pH 8.0. (CHI-Plur-MPs). The CHI-MPs loaded with live BCG can be used for per os inoculation of Cavia porcellus to check the effectiveness of delivered mycobacteria in increasing anti-H. pylori host response.

Cigarette Smoking as a Risk Factor for Tuberculosis in Adults: Epidemiology and Aspects of Disease Pathogenesis

It has been noted by the World Health Organisation that cases of tuberculosis in 2022 globally numbered 10.6 million, resulting in 1.3 million deaths, such that TB is one of the infectious diseases causing the greatest morbidity and mortality worldwide. Since as early as 1918, there has been an ongoing debate as to the relationship between cigarette smoking and TB. However, numerous epidemiological studies, as well as meta-analyses, have indicated that both active and passive smoking are independent risk factors for TB infection, development of reactivation TB, progression of primary TB, increased severity of cavitary disease, and death from TB, among several other considerations. With this considerable body of evidence confirming the association between smoking and TB, it is not surprising that TB control programmes represent a key potential preventative intervention. In addition to coverage of the epidemiology of TB and its compelling causative link with smoking, the current review is also focused on evidence derived from clinical- and laboratory-based studies of disease pathogenesis, most prominently the protective anti-mycobacterial mechanisms of the alveolar macrophage, the primary intracellular refuge of M. tuberculosis. This section of the review is followed by an overview of the major strategies utilised by the pathogen to subvert these antimicrobial mechanisms in the airway, which are intensified by the suppressive effects of smoke inhalation on alveolar macrophage function. Finally, consideration is given to a somewhat under-explored, pro-infective activity of cigarette smoking, namely augmentation of antibiotic resistance due to direct effects of smoke per se on the pathogen. These include biofilm formation, induction of cellular efflux pumps, which eliminate both smoke-derived toxicants and antibiotics, as well as gene modifications that underpin antibiotic resistance.

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.

A computational method for the prediction and functional analysis of potential Mycobacterium tuberculosis adhesin-related proteins

OBJECTIVES

Mycobacterial adherence plays a major role in the establishment of infection within the host. Adhesin-related proteins attach to host receptors and cell-surface components. The current study aimed to utilize in-silico strategies to determine the adhesin potential of conserved hypothetical (CH) proteins.

METHODS

Computational analysis was performed on the whole Mycobacterium tuberculosis H37Rv proteome using a software program for the prediction of adhesin and adhesin-like proteins using neural networks (SPAAN) to determine the adhesin potential of CH proteins. A robust pipeline of computational analysis tools: Phyre2 and pFam for homology prediction; Mycosub, PsortB, and Loctree3 for subcellular localization; SignalP-5.0 and SecretomeP-2.0 for secretory prediction, were utilized to identify adhesin candidates.

RESULTS

SPAAN revealed 776 potential adhesins within the whole MTB H37Rv proteome. Comprehensive analysis of the literature was cross-tabulated with SPAAN to verify the adhesin prediction potential of known adhesin (n = 34). However, approximately a third of known adhesins were below the probability of adhesin (Pad) threshold (Pad ≥0.51). Subsequently, 167 CH proteins of interest were categorized using essential in-silico tools.

CONCLUSION

The use of SPAAN with supporting in-silico tools should be fundamental when identifying novel adhesins. This study provides a pipeline to identify CH proteins as functional adhesin molecules.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Mycobacterium bovis BCG increase the selected determinants of monocyte/macrophage activity, which were diminished in response to gastric pathogen Helicobacter pylori

High antibiotic resistance of gastric pathogen Helicobacter pylori (Hp) and the ability to escape the host immune response prompt searching for therapeutic immunomodulators. Bacillus Calmette-Guerin (BCG) vaccine with Mycobacterium bovis (Mb) is a candidate for modulation the activity of immunocompetent cells, and onco-BCG formulation was successfully used in immunotherapy of bladder cancer. We determined the influence of onco-BCG on the phagocytic capacity of human THP-1 monocyte/macrophage cells, using the model of Escherichia coli bioparticles and Hp fluorescently labeled. Deposition of cell integrins CD11b, CD11d, CD18, membrane/soluble lipopolysaccharide (LPS) receptors, CD14 and sCD14, respectively, and the production of macrophage chemotactic protein (MCP)-1 were determined. Furthermore, a global DNA methylation, was also assessed. Human THP-1 monocytes/macrophages (TIB 202) primed or primed and restimulated with onco-BCG or Hp, were used for assessment of phagocytosis towards E. coli or Hp, surface (immunostaining) or soluble activity determinants, and global DNA methylation (ELISA). THP-1 monocytes/macrophages primed/restimulated with BCG showed increased phagocytosis capacity towards E. coli fluorescent particles, elevated expression of CD11b, CD11d, CD18, CD14, sCD14, increased MCP-1 secretion and DNA methylation. Preliminary results indicate that BCG mycobacteria may also induce the phagocytosis of H. pylori by THP-1 monocytes. Priming or priming and restimulation of monocytes/macrophages with BCG resulted in an increased activity of these cells, which was negatively modulated by Hp.

Unraveling Major Proteins of Mycobacterium tuberculosis Envelope

Abstract:

Although treatable, resistant form of tuberculosis (TB) has posed a major impediment to the effective TB control programme. As the Mycobacterium tuberculosis cell envelope is closely associated with its virulence and resistance, it is very important to understand the cell envelope for better treatment of causative pathogens. Cell membrane plays a crucial role in imparting various cell functions. Proteins being the functional moiety, it is impossible to characterize the functional properties based on genetic analysis alone. Proteomic based research has indicated mycobacterial envelope as a good source of antigens/proteins. Envelope/membrane and associated proteins have an anticipated role in biological processes, which could be of vital importance to the microbe, and hence could qualify as drug targets. This review provides an overview of the prominent and biologically important cell envelope and highlights the different functions offered by the proteins associated with it. Selective targeting of the mycobacterial envelope offers an untapped opportunity to address the problems associated with the current drug regimen and also will lead to the development of more potent and safer drugs against all forms of tuberculous infections.

Mycobacterial Adhesion: From Hydrophobic to Receptor-Ligand Interactions

Adhesion is crucial for the infective lifestyles of bacterial pathogens. Adhesion to non-living surfaces, other microbial cells, and components of the biofilm extracellular matrix are crucial for biofilm formation and integrity, plus adherence to host factors constitutes a first step leading to an infection. Adhesion is, therefore, at the core of pathogens’ ability to contaminate, transmit, establish residency within a host, and cause an infection. Several mycobacterial species cause diseases in humans and animals with diverse clinical manifestations. Mycobacterium tuberculosis, which enters through the respiratory tract, first adheres to alveolar macrophages and epithelial cells leading up to transmigration across the alveolar epithelium and containment within granulomas. Later, when dissemination occurs, the bacilli need to adhere to extracellular matrix components to infect extrapulmonary sites. Mycobacteria causing zoonotic infections and emerging nontuberculous mycobacterial pathogens follow divergent routes of infection that probably require adapted adhesion mechanisms. New evidence also points to the occurrence of mycobacterial biofilms during infection, emphasizing a need to better understand the adhesive factors required for their formation. Herein, we review the literature on tuberculous and nontuberculous mycobacterial adhesion to living and non-living surfaces, to themselves, to host cells, and to components of the extracellular matrix.

Model systems for optical trapping: the physical basis and biological applications

The micromechanical methods, among which optical trapping and atomic force microscopy have a special place, are widespread currently in biology to study molecular interactions between different biological objects. Optical trapping is reported to be quite applicable to study the mechanical properties of surface structures onto bacterial (pili and flagella) and eukaryotic (filopodia) cells. The review briefly summarizes the physical basis of optical trapping, as well as the principles of calculating the van der Waals, electrostatic, and donor-acceptor forces when two microparticles or a microparticle and a flat surface are used. Three main types of model systems (abiotic, biotic, and mixed) used in trapping experiments are described, and the peculiarities of manipulation with living (bacteria, fungal spores, etc.) and non-spherical objects (e.g., rod-shaped bacteria) are summarized.

Aptamer-Based Diagnostic Systems for the Rapid Screening of TB at the Point-of-Care

The transmission of Tuberculosis (TB) is very rapid and the burden it places on health care systems is felt globally. The effective management and prevention of this disease requires that it is detected early. Current TB diagnostic approaches, such as the culture, sputum smear, skin tuberculin, and molecular tests are time-consuming, and some are unaffordable for low-income countries. Rapid tests for disease biomarker detection are mostly based on immunological assays that use antibodies which are costly to produce, have low sensitivity and stability. Aptamers can replace antibodies in these diagnostic tests for the development of new rapid tests that are more cost effective; more stable at high temperatures and therefore have a better shelf life; do not have batch-to-batch variations, and thus more consistently bind to a specific target with similar or higher specificity and selectivity and are therefore more reliable. Advancements in TB research, in particular the application of proteomics to identify TB specific biomarkers, led to the identification of a number of biomarker proteins, that can be used to develop aptamer-based diagnostic assays able to screen individuals at the point-of-care (POC) more efficiently in resource-limited settings.

Structural features of HtpGMtb and HtpG-ESAT6Mtb vaccine antigens against tuberculosis: Molecular determinants of antigenic synergy and cytotoxicity modulation

Vaccine development against tuberculosis is an urgent need as the only available vaccine, M. bovis Bacillus Calmette Guerin (BCG), is unable to provide significant protection in adults. Among newly identified antigens, Rv2299c is an excellent candidate for the rational design of an effective multi-antigenic TB vaccine. Also, when fused to the T cell antigen ESAT6, it becomes highly effective in boosting BCG immunization and it adopts low cytotoxicity compared to ESAT6. We here characterize these proteins by coupling various biophysical techniques to cytofluorimetry and computational studies. Altogether, our data provide an experimental evidence of the role of Rv2299c as a dimeric and highly thermostable molecular chaperone, here denoted as HtpGMtb. Molecular dynamics simulations show that ATP rigidly anchors the ATP-binding loop in a conformation incompatible with the structure of the free enzyme. We also show that HtpGMtb dimeric state is an important molecular feature for the improved antigenic and cytotoxic properties of HtpG-ESAT6Mtb. Indeed, structural features of HtpG-ESAT6Mtb show that not only does this molecule combine the antigenic properties of HtpGMtb and ESAT6, but HtpGMtb locks ESAT6 in a dimeric state, thus improving its cytotoxicity properties. The data presented here provide solid basis for the rational design of upgraded antigens.

Mechanical Forces between Mycobacterial Antigen 85 Complex and Fibronectin

Adhesion to extracellular matrix proteins is an important first step in host invasion, employed by many bacterial pathogens. In mycobacteria, the secreted Ag85 complex proteins, involved in the synthesis of the cell envelope, are known to bind to fibronectin (Fn) through molecular forces that are currently unknown. In this study, single-molecule force spectroscopy is used to study the strength, kinetics and thermodynamics of the Ag85-Fn interaction, focusing on the multidrug-resistant Mycobacterium abscessus species. Single Ag85 proteins bind Fn with a strength of ~75 pN under moderate tensile loading, which compares well with the forces reported for other Fn-binding proteins. The binding specificity is demonstrated by using free Ag85 and Fn peptides with active binding sequences. The Ag85-Fn rupture force increases with mechanical stress (i.e., loading rate) according to the Friddle–Noy–de Yoreo theory. From this model, we extract thermodynamic parameters that are in good agreement with previous affinity determinations by surface plasmon resonance. Strong bonds (up to ~500 pN) are observed under high tensile loading, which may favor strong mycobacterial attachment in the lung where cells are exposed to high shear stress or during hematogenous spread which leads to a disseminated infection. Our results provide new insight into the pleiotropic functions of an important mycobacterial virulence factor that acts as a stress-sensitive adhesin.

Diagnostic Value of Recombinant Heparin-binding Hemagglutinin Adhesin Protein in Spinal Tuberculosis

Background and aim

To explore the diagnostic value of recombinant heparin-binding hemagglutinin adhesin (HBHA) protein antigen in spinal tuberculosis.

Materials and methods

Forty patients with spinal tuberculosis were included in the experimental group and 40 healthy people were included in the control group. Serum IgG antibody expression level was detected with recombinant HBHA protein as the antigen, using enzyme-linked immunosorbent assay (ELISA) detection.

Results

Patients with spinal tuberculosis and healthy volunteers were included in this study. A total of 40 eligible patients with spinal tuberculosis were included (24 males and 16 females, aged 18-72 years, with an average age of 41.24 ± 15.74 years). Forty healthy people were included (21 males and 19 females, aged 18-70 years, with an average age of 41.33 ± 12.36 years). On comparing the groups, no significant difference was found in the general data (P >0.05). IgG antibody level in the experimental group was higher than that in the control group, and the difference was significant (P < 0.00001).

Conclusions

Detection of serum HBHA protein antibody is of great value in the auxiliary diagnosis of spinal tuberculosis, and high HBHA expression can be used as an indicator for diagnosis of spinal tuberculosis.

Granzyme B Attenuates Bacterial Virulence by Targeting Secreted Factors

Pathogenic bacteria secrete virulence factors that interact with the human host to establish infections. The human immune system evolved multiple mechanisms to fight bacterial invaders, including immune proteases that were demonstrated to contribute crucially to antibacterial defense. Here we show that granzyme B degrades multiple secreted virulence mediators from Listeria monocytogenes, Salmonella typhimurium, and Mycobacteria tuberculosis. Pathogenic bacteria, when infected in the presence of granzyme B or granzyme-secreting killer cells, fail to grow in human macrophages and epithelial cells owing to their crippled virulence. A granzyme B-uncleavable mutant form of the major Listeria virulence factor, listeriolysin O, rescued the virulence defect in response to granzyme treatment. Hence, we link the degradation of a single factor with the observed decrease in virulent bacteria growth. Overall, we reveal here an innate immune barrier function of granzyme B by disrupting bacterial virulence to facilitate bacteria clearance by bystander immune and non-immune cells.

Identification of antigens presented by MHC for vaccines against tuberculosis

Mycobacterium tuberculosis (M.tb) is responsible for more deaths globally than any other pathogen. The only available vaccine, bacillus Calmette-Guérin (BCG), has variable efficacy throughout the world. A more effective vaccine is urgently needed. The immune response against tuberculosis relies, at least in part, on CD4⁺ T cells. Protective vaccines require the induction of antigen-specific CD4⁺ T cells via mycobacterial peptides presented by MHC class-II in infected macrophages. In order to identify mycobacterial antigens bound to MHC, we have immunoprecipitated MHC class-I and class-II complexes from THP-1 macrophages infected with BCG, purified MHC class-I and MHC class-II peptides and analysed them by liquid chromatography tandem mass spectrometry. We have successfully identified 94 mycobacterial peptides presented by MHC-II and 43 presented by MHC-I, from 76 and 41 antigens, respectively. These antigens were found to be highly expressed in infected macrophages. Gene ontology analysis suggests most of these antigens are associated with membranes and involved in lipid biosynthesis and transport. The sequences of selected peptides were confirmed by spectral match validation and immunogenicity evaluated by IFN-gamma ELISpot against peripheral blood mononuclear cell from volunteers vaccinated with BCG, M.tb latently infected subjects or patients with tuberculosis disease. Three antigens were expressed in viral vectors, and evaluated as vaccine candidates alone or in combination in a murine aerosol M.tb challenge model. When delivered in combination, the three candidate vaccines conferred significant protection in the lungs and spleen compared with BCG alone, demonstrating proof-of-concept for this unbiased approach to identifying new candidate antigens.

Protective vaccines against Mycobacterium tuberculosis (M.tb), such as bacillus Calmette-Guérin (BCG), trigger strong CD4 T-cell responses specific to mycobacterium peptides, but their efficacy is variable. Paulo Bettencourt and colleagues now identify a set of mycobacterium peptides presented by BCG-infected macrophages via major compatibility complexes (MHC), and show that three of these antigens can be combined to formulate a vaccine that confers improved protection to Mtb infection in mice. After identifying 94 MHC-II-associated and 43 MHC-I-associated mycobacterium peptides, the researchers performed immunogenicity assays with peripheral blood mononuclear cells from BCG-vaccinated donors, latent Mtb-infected patients and patients with tuberculosis, and show that a set of these peptides was recognised by the immune cells, validating their potential as possible components for new Mtb vaccine formulations. These findings further support the value of immunopeptidomics for the identification of new antigens for effective vaccine alternatives.

Theranostic Application of a Novel G-Quadruplex-Forming DNA Aptamer Targeting Malate Synthase of Mycobacterium tuberculosis

The successful management of tuberculosis (TB) requires efficient diagnosis and treatment. Further, the increasing prevalence of drug-resistant TB highlights the urgent need to develop novel inhibitors against both drug-susceptible and drug-resistant forms of disease. Malate synthase (MS), an enzyme of the glyoxylate pathway, plays a vital role in mycobacterial persistence, and therefore it is considered as an attractive target for novel anti-TB drug development. Recent studies have also ascribed an adhesin function to MS and established it as a potent diagnostic biomarker. In this study, a panel of Mycobacterium tuberculosis (Mtb) MS-specific single-stranded DNA aptamers was identified by Systematic Evolution of Ligands by EXponential enrichment (SELEX). The best-performing G-quadruplex-forming 44-mer aptamer, MS10, was optimized post-SELEX to generate an 11-mer aptamer, MS10-Trunc. This aptamer was characterized by various biochemical, biophysical, and in silico techniques. Its theranostic activity toward Mtb was established using enzyme inhibition, host cell binding, and invasion assays. MS10-Trunc aptamer exhibited high affinity for MS (equilibrium dissociation constant [K_D] ∼19 pM) and displayed robust inhibition of MS enzyme activity with IC₅₀ of 251.1 nM and inhibitor constant (K_i) of 230 nM. This aptamer blocked mycobacterial entry into host cells by binding to surface-associated MS. In addition, we have also demonstrated its application in the detection of tuberculous meningitis (TBM) in patients with sensitivity and specificity each of >97%.

Streptococcal Collagen-like Protein 1 Binds Wound Fibronectin: Implications in Pathogen Targeting

Group A Streptococcus (GAS) infections are responsible for significant morbidity and mortality worldwide. The outlook for an effective global vaccine is reduced because of significant antigenic variation among GAS strains worldwide. Other challenges in GAS therapy include the lack of common access to antibiotics in developing countries, as well as allergy to and treatment failures with penicillin and increasing erythromycin resistance in the industrialized world. At the portal of entry, GAS binds to newly deposited extracellular matrix, which is rich in cellular fibronectin isoforms with extra domain A (EDA, also termed EIIIA) via the surface adhesin, the streptococcal collagen-like protein 1 (Scl1). Recombinant Scl1 constructs, derived from diverse GAS strains, bind the EDA loop segment situated between the C and C' β-strands. Despite the sequence diversity in Scl1 proteins, multiple sequence alignments and secondary structure predictions of Scl1 variants, as well as crystallography and homology modeling studies, point to a conserved mechanism of Scl1-EDA binding. We propose that targeting this interaction may prevent the progression of infection. A synthetic cyclic peptide, derived from the EDA C-C' loop, binds to recombinant Scl1 with a micromolar dissociation constant. This review highlights the current concept of EDA binding to Scl1 and provides incentives to exploit this binding to treat GAS infections and wound colonization.

The Cell Wall Hydrolytic NlpC/P60 Endopeptidases in Mycobacterial Cytokinesis: A Structural Perspective

In preparation for division, bacteria replicate their DNA and segregate the newly formed chromosomes. A division septum then assembles between the chromosomes, and the mother cell splits into two identical daughters due to septum degradation. A major constituent of bacterial septa and of the whole cell wall is peptidoglycan (PGN), an essential cell wall polymer, formed by glycan chains of β−(1-4)-linked-N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), cross-linked by short peptide stems. Depending on the amino acid located at the third position of the peptide stem, PGN is classified as either Lys-type or meso-diaminopimelic acid (DAP)-type. Hydrolytic enzymes play a crucial role in the degradation of bacterial septa to split the cell wall material shared by adjacent daughter cells to promote their separation. In mycobacteria, a key PGN hydrolase, belonging to the NlpC/P60 endopeptidase family and denoted as RipA, is responsible for the degradation of septa, as the deletion of the gene encoding for this enzyme generates abnormal bacteria with multiple septa. This review provides an update of structural and functional data highlighting the central role of RipA in mycobacterial cytokinesis and the fine regulation of its catalytic activity, which involves multiple molecular partners.

Lectins of Mycobacterium tuberculosis - rarely studied proteins

The importance of bacterial lectins for adhesion, pathogenicity, and biofilm formation is well established for many Gram-positive and Gram-negative bacteria. However, there is very little information available about lectins of the tuberculosis-causing bacterium, Mycobacterium tuberculosis (Mtb). In this paper we review previous studies on the carbohydrate-binding characteristics of mycobacteria and related Mtb proteins, discussing their potential relevance to Mtb infection and pathogenesis.

Collagen degradation in tuberculosis pathogenesis: the biochemical consequences of hosting an undesired guest

The scenario of chemical reactions prompted by the infection by Mycobacterium tuberculosis is huge. The infection generates a localized inflammatory response, with the recruitment of neutrophils, monocytes, and T-lymphocytes. Consequences of this immune reaction can be the eradication or containment of the infection, but these events can be deleterious to the host inasmuch as lung tissue can be destroyed. Indeed, a hallmark of tuberculosis (TB) is the formation of lung cavities, which increase disease development and transmission, as they are sites of high mycobacterial burden. Pulmonary cavitation is associated with antibiotic failure and the emergence of antibiotic resistance. For cavities to form, M. tuberculosis induces the overexpression of host proteases, like matrix metalloproteinases and cathepsin, which are secreted from monocyte-derived cells, neutrophils, and stromal cells. These proteases destroy the lung parenchyma, in particular the collagen constituent of the extracellular matrix (ECM). Namely, in an attempt to destroy infected cells, the immune reactions prompted by mycobacterial infections induce the destruction of vital regions of the lung, in a process that can become fatal. Here, we review structure and function of the main molecular actors of ECM degradation due to M. tuberculosis infection and the proposed mechanisms of tissue destruction, mainly attacking fibrillar collagen. Importantly, enzymes responsible for collagen destruction are emerging as key targets for adjunctive therapies to limit immunopathology in TB.