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

HtpG-A Major Virulence Factor and a Promising Vaccine Antigen against Mycobacterium tuberculosis

Tuberculosis (TB) is the leading global cause of death f rom an infectious bacterial agent. Therefore, limiting its epidemic spread is a pressing global health priority. The chaperone-like protein HtpG of M. tuberculosis (Mtb) is a large dimeric and multi-domain protein with a key role in Mtb pathogenesis and promising antigenic properties. This dual role, likely associated with the ability of Heat Shock proteins to act both intra- and extra-cellularly, makes HtpG highly exploitable both for drug and vaccine development. This review aims to gather the latest updates in HtpG structure and biological function, with HtpG operating in conjunction with a large number of chaperone molecules of Mtb. Altogether, these molecules help Mtb recovery after exposure to host-like stress by assisting the whole path of protein folding rescue, from the solubilisation of aggregated proteins to their refolding. Also, we highlight the role of structural biology in the development of safer and more effective subunit antigens. The larger availability of structural information on Mtb antigens and a better understanding of the host immune response to TB infection will aid the acceleration of TB vaccine development.

Targeting collagen damage for sustained in situ antimicrobial activities

Antimicrobial peptides (AMPs) are promising anti-infective drugs, but their use is restricted by their short-term retention at the infection site, non-targeted uptake, and adverse effects on normal tissues. Since infection often follows an injury (e.g., in a wound bed), directly immobilizing AMPs to the damaged collagenous matrix of the injured tissues may help overcome these limitations by transforming the extracellular matrix microenvironment of the infection site into a natural reservoir of AMPs for sustained in situ release. Here, we developed and demonstrated an AMP-delivery strategy by conjugating a dimeric construct of AMP Feleucin-K3 (Flc) and a collagen hybridizing peptide (CHP), which enabled selective and prolonged anchoring of the Flc-CHP conjugate to the damaged and denatured collagen in the infected wounds in vitro and in vivo. We found that the dimeric Flc and CHP conjugate design preserved the potent and broad-spectrum antimicrobial activities of Flc while significantly enhancing and extending its antimicrobial efficacy in vivo and facilitating tissue repair in a rat wound healing model. Because collagen damage is ubiquitous in almost all injuries and infections, our strategy of targeting collagen damage may open up new avenues for antimicrobial treatments in a range of infected tissues.

Amyloid deposition in granuloma of tuberculosis patients: A single-center pilot study

The formation of granuloma is one of the characteristic features of tuberculosis. Besides, elevated serum amyloid A (SAA) protein level is the indicator for chronic inflammation associated with tuberculosis. The linkage between tuberculosis and SAA-driven secondary amyloidosis is well documented. However, SAA-derived amyloid onset and deposition start sites are not well understood in tuberculosis. We hypothesized that granuloma could be a potential site for amyloid deposition because of the presence of SAA protein and proteases, cleaving SAA into aggregation-prone fragments. 150 tuberculosis patients were identified and biopsies were collected from the affected organs. Patients showing eosinophilic hyaline-rich deposits within granuloma and its periphery were further screened for the presence of amyloid deposits. Upon Congo red staining, these hyaline deposits exhibited characteristic apple-green birefringence under polarized light, confirming their amyloid nature in 20 patients. Further upon Immuno-histochemical staining with anti-SAA antibody, the amyloid enriched areas showed positive immunoreactivity. In this pilot study, we have shown granuloma as a potential site for serum amyloid A derived amyloid deposition in tuberculosis patients. This study would expand the clinical and fundamental research for understanding the mechanism of amyloid formation in granuloma underlying tuberculosis and other chronic inflammatory conditions.

Spatial localization of cathepsins: Implications in immune activation and resolution during infections

Cathepsins were first described, as endolysosomal proteolytic enzymes in reference to the organelles where they degrade the bulk of endogenous and exogenous substrates in a slightly acidic environment. These substrates include pathogens internalized via endocytosis and/or marked for destruction by autophagy. However, the role of cathepsins during infection far exceeds that of direct digestion of the pathogen. Cathepsins have been extensively investigated in the context of tumour associated immune cells and chronic inflammation. Several cathepsin-dependent immune responses develop in the endocytic pathway while others take place in the cytosol, the nucleus, or in the extracellular space. In this review we highlight the spatial localization of cathepsins and their implications in immune activation and resolution pathways during infection.

Clostridium, Bacteroides and Prevotella associates with increased fecal metabolites Trans-4-Hydroxy-L-proline and Genistein in active pulmonary tuberculosis patients during anti-tuberculosis chemotherapy with isoniazid-rifampin-pyrazinamide-ethambutol (HRZE)

Purpose

To investigated the changes of gut microbiome and fecal metabolome during anti-tuberculosis chemotherapy with isoniazid (H)-rifampin (R)-pyrazinamide (Z)-ethambutol (E).

Patients and methods

(1) In this study, we recruited 168 stool specimens from 49 healthy volunteers without M. tuberculosis (Mtb), 30 healthy volunteers with latently infected by Mtb, 41 patients with active tuberculosis (ATB), 28 patients with 2-month HRZE treatment and 20 patients with 2-month HRZE followed by 4-month HR treatment. (2) We used 16S rRNA sequencing and an untargeted Liquid Chromatograph Mass Spectrometer-based metabolomics to investigate the changes of gut microbiome and the alteration of fecal metabolome, respectively, during anti-TB chemotherapy.

Results

Mtb infection can reduce the diversity of intestinal flora of ATB patients and change their taxonomic composition, while the diversity of intestinal flora of ATB patients were restored during anti-TB chemotherapy. Especially, family Veillonellacea and Bateroidaceae and their genera Veillonella and Bacteroides significantly increased in the gut microbiota during anti-TB chemotherapy. Additionally, Mtb infection dynamically regulates fecal metabolism in ATB patients during anti-TB chemotherapy. Interestingly, the altered abundance of fecal metabolites correlated with the altered gut microbiota, especially the change of gut Clostridium, Bacteroides and Prevotella was closely related to the change of fecal metabolites such as Trans-4-Hydroxy-L-proline and Genistein caused by Mtb infection or anti-TB chemotherapy.

Conclusion

Anti-TB chemotherapy with HRZE can disrupt both gut microbiotas and metabolome in ATB patients. Some specific genera and metabolites are depleted or enriched during anti-TB chemotherapy. Therefore, revealing potential relevance between gut microbiota and anti-TB chemotherapy will provide potential biomarkers for evaluating the therapeutic efficacy in ATB patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-022-01003-2.

Multiplex proteomics as risk predictor of infection in patients treated with hemodialysis-A prospective multicenter study

INTRODUCTION

Severe infection is a major problem in hemodialysis patients. Multiplex proteomics might reveal novel insights into disease mechanisms increasing the risk of infection and might also be used as a risk prediction tool. The aims of this study were (1) to evaluate associations between 92 proteins assessed by a proximity extension assay and the development of severe infection in patients on hemodialysis and (2) to develop a risk prediction model for severe infection using prespecified clinical variables and proteomics.

METHODS

Prospective, observational multicenter cohort study with 5-year follow-up. Patients receiving in-center hemodialysis in five facilities in Denmark were included. The primary composite endpoint was death caused by infection, bacteremia, and infections requiring hospitalization of at least 2 days or prolonging a hospital stay.

FINDINGS

Of 331 patients included 210 patients reached the primary endpoint during follow-up. In adjusted Cox regression analyses, 14 plasma proteins were associated with severe infection. Correcting for multiple testing revealed only cathepsin-L1 and interleukin-6 significantly associated with the primary outcome. Cathepsin-L1-hazard ratio: 1.64 (95% confidence interval [CI] 1.24-2.17) and interleukin-6-hazard ratio: 1.16 (95% CI 1.05-1.29). Apparent C-statistics of the risk prediction model using clinical variables was 0.605, addition of cathepsin-L1 and interleukin-6 to the model improved discrimination slightly: C = 0.625.

DISCUSSION

Proteomic profiling identified cathepsin-L1 and interleukin-6 as markers for infectious risk in hemodialysis patients. Further studies are needed to replicate the results and to examine possible causality. The developed risk prediction models need considerable improvement before implementation in clinical practice is meaningful.

Biomaterials from the sea: Future building blocks for biomedical applications

Marine resources have tremendous potential for developing high-value biomaterials. The last decade has seen an increasing number of biomaterials that originate from marine organisms. This field is rapidly evolving. Marine biomaterials experience several periods of discovery and development ranging from coralline bone graft to polysaccharide-based biomaterials. The latter are represented by chitin and chitosan, marine-derived collagen, and composites of different organisms of marine origin. The diversity of marine natural products, their properties and applications are discussed thoroughly in the present review. These materials are easily available and possess excellent biocompatibility, biodegradability and potent bioactive characteristics. Important applications of marine biomaterials include medical applications, antimicrobial agents, drug delivery agents, anticoagulants, rehabilitation of diseases such as cardiovascular diseases, bone diseases and diabetes, as well as comestible, cosmetic and industrial applications.

Cathepsins and Their Endogenous Inhibitors in Host Defense During Mycobacterium tuberculosis and HIV Infection

The moment a very old bacterial pathogen met a young virus from the 80's defined the beginning of a tragic syndemic for humanity. Such is the case for the causative agent of tuberculosis and the human immunodeficiency virus (HIV). Syndemic is by definition a convergence of more than one disease resulting in magnification of their burden. Both pathogens work synergistically contributing to speed up the replication of each other. Mycobacterium tuberculosis (Mtb) and HIV infections are in the 21st century among the leaders of morbidity and mortality of humankind. There is an urgent need for development of new approaches for prevention, better diagnosis, and new therapies for both infections. Moreover, these approaches should consider Mtb and HIV as a co-infection, rather than just as separate problems, to prevent further aggravation of the HIV-TB syndemic. Both pathogens manipulate the host immune responses to establish chronic infections in intracellular niches of their host cells. This includes manipulation of host relevant antimicrobial proteases such as cathepsins or their endogenous inhibitors. Here we discuss recent understanding on how Mtb and HIV interact with cathepsins and their inhibitors in their multifactorial functions during the pathogenesis of both infections. Particularly we will address the role on pathogen transmission, during establishment of intracellular chronic niches and in granuloma clinical outcome and tuberculosis diagnosis. This area of research will open new avenues for the design of innovative therapies and diagnostic interventions so urgently needed to fight this threat to humanity.

Association of rs12722 COL5A1 with pulmonary tuberculosis: a preliminary case-control study in a Kazakhstani population

Lung cavitation is the classic hallmark of TB, which facilitates the disease development and transmission. It involves the degradation of lung parenchyma which is mainly made up of collagen fibers by metalloproteinases (MMPs) produced by activated monocyte-derived cells, neutrophils and stromal cells. The following population-based preliminary case-control study of adults with TB (50) and controls (112) without TB was used to investigate possible association between rs1800012 in COL1A1, rs12722 in COL5A1 genes and pulmonary TB in Kazakhstan. We examined 162 samples (50 cases and 112 controls) to study the associations between TB disease status and demographic variables along with single nucleotide polymorphisms related to COLA1 and COL5A1. The unadjusted χ2 and multivariable logistic regression was performed to find out relationships between SNP and other predictors. Preliminary findings suggest that there is a statistically significant association of age (AOR = 0.97, 95% CI:0.94-0.99, p value = 0.049), social status (AOR = 2.41, 95% CI:1.16-5.02, p value = 0.018), HIV status (AOR = 7.12, 95% CI:1.90-26.7, p value = 0.004) and heterozygous rs12722 SNP (AOR = 2.47, 95% CI:1.17-5.19, p value = 0.018) polymorphism of COL5A1 gene with TB susceptibility. The association of collagen genes with TB pathogenesis indicates that anti TB programs can include development of new drug regimens that include MMP inhibitors which has been found to be helpful in collagen remodeling and repair. Therapeutic targeting of MMPs will prevent extracellular matrix and collagen degradation and granuloma maturation.

Delay in diagnosis of pulmonary tuberculosis increases the risk of pulmonary cavitation in pastoralist setting of Ethiopia

BACKGROUND

Delay in diagnosis and treatment of pulmonary tuberculosis (PTB) leads to severe disease, adverse outcomes and increased transmission. Assessing the extent of delay and its effect on disease progression in TB affected settings has clinical and programmatic importance. Hence, the aim of this study was to investigate the possible effect of delay on infectiousness (cavitation and smear positivity) of patients at diagnosis in Somali pastoralist area, Ethiopia.

METHODS

A cross-sectional study was conducted between December 2017 and October 2018, and 434 newly coming and confirmed PTB patients aged ≥15 years were recruited in five facilities. Data were collected using interview, record-review, anthropometry, Acid-fast bacilli and chest radiography techniques. Log-binomial regression models were used to reveal the association of delay and other factors associated with cavitation and smear positivity, and ROC Curve was used to determine discriminative ability and threshold delays.

RESULTS

Median age of patients was 30 years. Of all, 62.9% were males, and 46.5% were pastoralists. Median diagnosis delay was 49 days (IQR = 33-70). Cavitation was significantly associated with diagnosis delay [P < 0.001]; 22.2% among patients diagnosed within 30 days of illness and 51.7% if delay was over 30 days. The threshold delay that optimizes cavitation was 43 days [AUC (95% CI) = 0.67(0.62-0.72)]. Smear positivity was significantly increased in patients delayed over 49 days [p = 0.02]. Other factors associated with cavitation were age ≤ 35 years [APR (95% CI) =1.3(1.01-1.6)], chronic diseases [APR (95% CI) = 1.8(1.2-2.6)] and low MUAC*female [APR (95% CI) = 1.8(1.2-2.8)]. Smear positivity was also associated with age ≤ 35 years [APR (95% CI) =1.4(1.1-1.8)], low BMI [APR (95% CI) =1.3(1.01-1.7)] and low MUAC [APR (95% CI) =1.5(1.2-1.9)].

CONCLUSION

This study highlights delay in diagnosis of pulmonary TB remained high and increased infectiousness of patients in pastoral settings of Ethiopia. Hence, delay should be targeted to improve patient outcomes and reduce transmission in such settings.

Cysteine Cathepsins and their Extracellular Roles: Shaping the Microenvironment

For a long time, cysteine cathepsins were considered primarily as proteases crucial for nonspecific bulk proteolysis in the endolysosomal system. However, this view has dramatically changed, and cathepsins are now considered key players in many important physiological processes, including in diseases like cancer, rheumatoid arthritis, and various inflammatory diseases. Cathepsins are emerging as important players in the extracellular space, and the paradigm is shifting from the degrading enzymes to the enzymes that can also specifically modify extracellular proteins. In pathological conditions, the activity of cathepsins is often dysregulated, resulting in their overexpression and secretion into the extracellular space. This is typically observed in cancer and inflammation, and cathepsins are therefore considered valuable diagnostic and therapeutic targets. In particular, the investigation of limited proteolysis by cathepsins in the extracellular space is opening numerous possibilities for future break-through discoveries. In this review, we highlight the most important findings that establish cysteine cathepsins as important players in the extracellular space and discuss their roles that reach beyond processing and degradation of extracellular matrix (ECM) components. In addition, we discuss the recent developments in cathepsin research and the new possibilities that are opening in translational medicine.