Fibronectin binding protein and Ca2+ play an access key role to mediate pathogenesis in Mycobacterium tuberculosis: An overview

The Assessment of Serum Fibronectin Levels as a Potential Biomarker for the Severity of Drug-Sensitive Pulmonary Tuberculosis: A Pilot Study

BACKGROUND

Tuberculosis (TB) is a global health burden caused by Mycobacterium tuberculosis (Mtb) infection. Fibronectin (Fn) facilitates Mtb attachment to host cells. We studied the Fn levels in smear-positive TB patients to assess its correlation with disease severity based on sputum smears and chest X-rays.

METHODS

Newly detected consecutive sputum AFB-positive pulmonary TB patients (n = 78) and healthy control subjects (n = 11) were included. The mycobacterial load in the sputum smear was assessed by IUATLD classification, ranging from 0 to 3. The severity of pulmonary involvement was assessed radiologically in terms of both the number of zones involved (0-6) and as localized (up to 2 zones), moderate (3-4 zones), or extensive (5-6 zones). The serum human fibronectin levels were measured by using a commercially available enzyme-linked immunosorbent assay (ELISA) kit (Catalogue No: CK-bio-11486, Shanghai Coon Koon Biotech Co., Ltd., Shanghai, China).

RESULTS

The PTB patients showed lower Fn levels (102.4 ± 26.7) compared with the controls (108.8 ± 6.8), but they were not statistically significant. Higher AFB smear grades had lower Fn levels. The chest X-ray zones involved were inversely correlated with Fn levels. The Fn levels, adjusted for age and gender, decreased with increased mycobacterial load and the number of chest radiograph zones affected. A Fn level <109.39 g/mL predicted greater TB severity (sensitivity of 67.57% and specificity of 90.38%), while a level <99.32 pg/mL predicted severity based on the chest radiology (sensitivity of 84.21% and specificity of 100%).

CONCLUSIONS

The Fn levels are lower in tuberculosis patients and are negatively correlated with severity based on sputum mycobacterial load and chest radiographs. The Fn levels may serve as a potential biomarker for assessing TB severity, which could have implications for early diagnosis and treatment monitoring.

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.

Flunarizine suppresses Mycobacterium tuberculosis growth via calmodulin-dependent phagosome maturation

Tuberculosis (TB), an infectious bacterial disease caused by Mycobacterium tuberculosis (Mtb), is a major cause of death worldwide. Multidrug-resistant TB remains a public health crisis and thus novel effective treatments, such as host-directed therapies (HDTs), are urgently required to overcome the challenges of TB infection. In this study, we evaluated 4 calcium modulators for their effects on Mtb growth in macrophages. Only flunarizine enhanced the bactericidal ability of macrophages against Mtb, which was induced by an increase in phosphorylated calcium/calmodulin (CaM)-dependent protein kinase II (pCaMKII) levels. We further discovered that the expression of CaM was decreased in Mtb-infected macrophages and restored following flunarizine treatment; this was associated with phagolysosome maturation and acidification. Consistent with these findings, the anti-TB ability of macrophages was reduced following the silencing of CaM or inhibition of CAMKII activity. In conclusion, our results demonstrated that flunarizine enhanced the bactericidal ability of macrophages and clarified its CaM-pCAMKII-dependent mechanism. Therefore, our findings strongly support further studies of this currently approved drug as an HDT candidate for TB therapy.

Computational evaluation of anticipated PE_PGRS39 protein involvement in host-pathogen interplay and its integration into vaccine development

Mycobacterium tuberculosis causes more than 1 million deaths every year, which is higher than any other bacterial pathogen. Its success depends on its interaction with the host and its ability to regulate the host's immune system for its own survival. Mycobacterium tuberculosis H37Rv (Mtb) proteome consists of unique PE_PGRS family proteins, which present a significant role in bacterial pathogenesis over the past years. Earlier evidence suggests that some PE_PGRS proteins display fibronectin-binding activity. In this manuscript, computational characterization of the PE_PGRS39 protein has indicated something peculiar about this protein. Investigation showed that PE_PGRS39 is an extracellular protein that, instead of acting as fibronectin-binding protein, might mimic fibronectin which binds to alpha-5 beta-1 (α5β1) integrin. PE_PGRS39 protein additionally turned into proven pieces of evidence to have motifs such as DXXG and GGXGXD and PXXP that bind with guanosine triphosphate (GTP), calcium, and host Src homology 3 (SH3) domains, respectively, in conjunction with RGD-integrin binding. These interactions designate the direct role of PE_PGRS39 in bacterial pathogenesis via cell adhesion and signaling. Additionally, the analysis showed that PE_PGRS39 is an antigenic protein and epitope prediction provided functional regions of the protein that trigger a cellular immune response facilitated by T or B cells. Further, an experimental analysis could also open up new avenues for developing novel drugs by targeting signaling motifs or novel vaccines using functional epitopes that could evoke an immune response in the host.

Adhesion molecules facilitate host-pathogen interaction & mediate Mycobacterium tuberculosis pathogenesis

Most of the microorganisms display adhesion molecules on their surface which help them to bind and interact with the host cell during infection. Adhesion molecules help mycobacteria to colonize and invade immune system of the host, and also trigger immune response explicated by the host against the infection. Hence, understanding the signalling pathways illustrated by these molecules to enhance our knowledge on mycobacterial survival and persistence inside the host cell is required. Hence, this review was focussed on the role of adhesion molecules and their receptor molecules. The various mechanisms adopted by adhesion molecules to bind with the specific receptors on the host cell and their role in invasion and persistence of mycobacterium inside the host cell are explained.

The genetic variants in calcium signaling related genes influence anti-tuberculosis drug induced liver injury: A prospective study

Although many genetic variants related to anti-tuberculosis drug induced liver injury (ATDILI) have been identified, the prediction and personalized treatment of ATDILI have failed to achieve, indicating there remains an area for further exploration. This study aimed to explore the influence of single nucleotide polymorphisms (SNPs) in Bradykinin receptor B2 (BDKRB2), Teneurin transmembrane protein 2 (TENM2), transforming growth factor beta 2 (TGFB2), and solute carrier family 2 member 13 (SLC2A13) on the risk of ATDILI.The subjects comprised 746 Chinese tuberculosis (TB) patients. Custom-by-design 2x48-Plex SNPscanTM kit was employed to genotype 28 selected SNPs. The associations of SNPs with ATDILI risk and clinical phenotypes were analyzed according to the distributions of allelic and genotypic frequencies and different genetic models. The odds ratio (OR) with corresponding 95% confidence interval (CI) was calculated.Among subjects with successfully genotyped, 107 participants suffered from ATDILI during follow-up. In BDKRB2, patients with rs79280755 G allele or rs117806152 C allele were more vulnerable to ATDILI (PBonferronicorrection = .002 and .03, respectively). Rs79280755 increased the risk of ATDILI significantly whether in additive (OR = 3.218, 95% CI: 1.686-6.139, PBonferroni correction = .003) or dominant model (PBonferroni correction = .003), as well as rs117806152 (Additive model: PBonferroni correction = .05; dominant model: PBonferroni correction = .03). For TENM2, rs80003210 G allele contributed to the decreased risk of ATDILI (PBonferroni correction = .02), while rs2617972 A allele conferred susceptibility to ATDILI (PBonferroni correction = .01). Regarding rs2617972, significant findings were also observed in both additive (OR = 3.203, 95% CI: 1.487-6.896, PBonferroni correction = .02) and dominant model (PBonferroni correction = .02). Moreover, rs79280755 and rs117806152 in BDKRB2 significantly affected some laboratory indicators. However, no meaningful SNPs were observed in TGFB2 and SLC2A13.Our study revealed that both BDKRB2 and TENM2 genetic polymorphisms were interrogated in relation to ATDILI susceptibility and some laboratory indicators in the Western Chinese Han population, shedding a new light on exploring novel biomarkers and targets for ATDILI.

Potential of Ca2+ in Mycobacterium tuberculosis H37Rv Pathogenesis and Survival

The host-pathogen interaction and involvement of calcium (Ca²⁺) signaling in tuberculosis infection is crucial and plays a significant role in pathogenesis. Ca²⁺ is known as a ubiquitous second messenger that could control multiple processes and is included in cellular activities like division, motility, stress response, and signaling. However, Ca²⁺ is thought to be a regulative molecule in terms of TB infection but its binding relation with proteins/substrates molecules which are influenced with Ca²⁺ concentrations in host-pathogen interaction requires attention. So, in this review, our primary goal is to focus on some Ca²⁺ substrates/proteins and their imperative involvement in pathogenesis, which is unclear. We have discussed several Ca²⁺-binding substrate and protein that affect intracellular mechanism of infected host cell. The major involvement of these proteins/substrates including calmodulin (CaM), calpain, annexin, surfactant protein A (SP-A), surfactant protein D (SP-D), calprotectin (MRP8/14), and PE_PGRS family protein are considered to be significant; however, their detailed understanding in mycobacterium infection is limited. In this aspect, this study will help in adding up our understanding in TB biology and additionally in the development of new therapeutic approach to reduce TB pandemic worldwide.