Streptococcus mutans surface alpha-enolase binds salivary mucin MG2 and human plasminogen

Transient bacteremia following the removal of four different types of rapid palatal expanders

PURPOSE

General health related recommendations for prophylactic measures in connection with orthodontic treatments are limited due to the lack of evidence-based data. This study aimed to investigate the development of transient bacteremia following the removal of four types of rapid palatal expanders (RPE).

METHODS

Seventy-five individuals aged 10-18 years undergoing rapid palatal expansion with four types of RPE were categorized according to the type of RPE used in their treatment: banded tooth-borne (group A (1), n = 17), banded tooth- and tissue-borne (group A (2), n = 17), bonded tooth-borne (group B (1), n = 18), and bonded tooth- and tissue-borne (group B (2), n = 23). Gingival inflammation was assessed using the gingival index one day before RPE removal. Furthermore, samples of blood (5 ml each) were collected before and 3 min after RPE removal. The groups were statistically evaluated for comparability with respect to sex, age, or wear time of the RPE and to the gingival index. In addition, the prevalence of bacteremia in the different groups was evaluated and statistically compared.

RESULTS

No significant difference was found among the groups (p > 0.05) for sex, age, and RPE wear time. Mean gingival index was higher in group B (2) than in group A (1) (p < 0.05). The prevalence of bacteremia did not differ significantly between groups. Streptococcus species were identified in all bacteremia cases. The bacteremia prevalence of the groups was as follows: group A (1), 11.8%; group A (2), 23.5%; group B (1), 16.7%; and group B (2), 30.4%.

CONCLUSION

This investigation demonstrated that removal of a RPE could cause bacteremia, but the RPE design did not affect the prevalence of bacteremia. The results of this study support the necessity of prophylaxis measures before RPE removal in indicated patients.

Unveiling the functional significance of the 14.3.3 protein: A key player in Paracoccidioides brasiliensis biofilm formation

Paracoccidioidomycosis (PCM) is a systemic mycosis caused by Paracoccidioides spp. The interaction mediated by the presence of adhesins on the fungal surface and receptors in the extracellular matrix of the host, as well as the biofilm formation, is essential in its pathogenesis. Adhesins such as gp43, enolase, GAPDH (glyceraldehyde-3-phosphate dehydrogenase), and 14-3-3 have been demonstrated in the Paracoccidioides brasiliensis (Pb18) strain and recognized as necessary in the fungus-host interaction. The Pb 18 strain silenced to 14-3-3 showed changes in morphology, virulence, and adhesion capacity. The study aimed to evaluate the role of adhesin 14-3-3 in P. brasiliensis biofilm formation and the differential expression of genes related to adhesins, comparing planktonic and biofilm forms. The presence of biofilm was also verified in sutures in vitro and in vivo. The silenced strain (Pb14-3-3 aRNA) was compared with the wild type Pb18, determining the differential metabolic activity between the strains by the XTT reduction assay; the biomass by violet crystal and the polysaccharides by safranin, even as morphological differences by microscopic techniques. Differential gene expression for adhesins was also analyzed, comparing the relative expression of these in planktonic and biofilm forms at different times. The results suggested that the silencing of 14-3-3 protein altered the ability to form biofilm and its metabolism. The quantity of biomass was similar in both strains; however, the formation of exopolymeric substances and polysaccharide material was lower in the silenced strain. Our results showed increased expression of enolase, GAPDH, and 14-3-3 genes in the first periods of biofilm formation in the Pb18 strain. In contrast, the silenced strain showed a lower expression of these genes, indicating that gene silencing can influence the expression of other genes and be involved in the biofilm formation of P. brasiliensis. In vitro and in vivo assays using sutures confirmed this yeast's ability to form biofilm and may be implicated in the pathogenesis of paracoccidioidomycosis.

Mycobacterium tuberculosis H37Rv enolase (Rv1023)- expression, characterization and effect of host dependent modifications on protein functionality

Mycobacterium tuberculosis enolase is an essential glycolytic enzyme that catalyzes the conversion of 2, phosphoglycerate (PGA) to phosphoenol pyruvate (PEP). It is also a crucial link between glycolysis and the tricarboxylic acid (TCA) pathway. The depletion of PEP has recently been associated with the emergence of non-replicating drug resistant bacteria. Enolase is also known to exhibit multiple alternate functions, such as promoting tissue invasion via its role as a plasminogen (Plg) receptor. In addition, proteomic studies have identified the presence of enolase in the Mtb degradosome and in biofilms. However, the precise role in these processes has not been elaborated. The enzyme was recently identified as a target for 2-amino thiazoles - a novel class of anti-mycobacterials. In vitro assays and characterization of this enzyme were unsuccessful due to the inability to obtain functional recombinant protein. In the present study, we report the expression and characterization of enolase using Mtb H37Ra as a host strain. Our study demonstrates that the enzyme activity and alternate functions of this protein are significantly impacted by the choice of expression host (Mtb H37Ra or E. coli). Detailed analysis of the protein from each source revealed subtle differences in the post-translational modifications. Lastly, our study confirms the role of enolase in Mtb biofilm formation and describes the potential for inhibiting this process.

Moonlighting proteins [ML proteins]: The pandora's box of insidious oro-dental diseases

Oral pathogens survive in the harsh niche of the oral microbiome on account of a plethora of moonlighting [ML] proteins that can multitask in the oro-mucosal layers. ML proteins are considered as the complex protein hyperspace expressed in many oral bacterial pathogens and encompass many hypothetical and experimentally evidenced proteins that can efficiently assist in the initiation and progression of various oro-dental infections. With the propensity of multi-drug resistance and biofilm formation, unravelling the mysterious functions associated with the oral ML proteins could be essential in targeting the vital oral bacteria and their associated infections. This commentary thus throws insights onto the key clues on various ML proteins that can be considered for the development of therapeutic versatility to curtail the complications caused by various oral bacterial species.

Virulence factors of Streptococcus anginosus - a molecular perspective

Streptococcus anginosus together with S. constellatus and S. intermedius constitute the Streptococcus anginosus group (SAG), until recently considered to be benign commensals of the human mucosa isolated predominantly from oral cavity, but also from upper respiratory, intestinal, and urogenital tracts. For years the virulence potential of SAG was underestimated, mainly due to complications in correct species identification and their assignment to the physiological microbiota. Still, SAG representatives have been associated with purulent infections at oral and non-oral sites resulting in abscesses formation and empyema. Also, life threatening blood infections caused by SAG have been reported. However, the understanding of SAG as potential pathogen is only fragmentary, albeit certain aspects of SAG infection seem sufficiently well described to deserve a systematic overview. In this review we summarize the current state of knowledge of the S. anginosus pathogenicity factors and their mechanisms of action.

Enolase of Staphylococcus lugdunensis Is a Surface-Exposed Moonlighting Protein That Binds to Extracellular Matrix and the Plasminogen/Plasmin System

The coagulase-negative staphylococcal (CoNS) species Staphylococcus lugdunensis is unique in causing serious infections in humans that resemble those of Staphylococcus aureus rather than those of other CoNS species. The colonization and invasion of host tissue presupposes the presence of adherence factors, but only a few proteins mediating adhesion of S. lugdunensis to biotic surfaces are known yet. Here, we report on the functionality of the S. lugdunensis enolase (SlEno), which performs two distinct roles, first, as the metabolic enzyme of the glycolysis, and second, as an adherence factor to the extracellular matrix (ECM) of cells. Phylogenetic analyses of the SlEno confirmed their high conservation to enolases of other species and revealed a closer relationship to Staphylococcus epidermidis than to S. aureus. Using matrix-assisted laser desorption/ionization time of flight mass spectrometry and Western blot experiments, we identified SlEno to be located in the cytoplasm as well as on the cell surface of S. lugdunensis. Recombinantly generated and surface-associated SlEno showed the usual enolase activity by catalyzing the conversion of 2-phosphoglycerate to phosphoenolpyruvate but, in addition, also displayed strong binding to immobilized laminin, fibronectin, fibrinogen, and collagen type IV in a dose-dependent manner. We also showed a strong binding of SlEno to plasminogen (Plg) and observed a tissue plasminogen activator (tPA)-dependent conversion of Plg to plasmin (Pln) whereby the Plg activation significantly increased in the presence of SlEno. This interaction might be dependent on lysines of the SlEno protein as binding to Plg was inhibited by ε-aminocaproic acid. Furthermore, the enhanced activation of the Plg/Pln system by SlEno enabled S. lugdunensis to migrate through a fibrin matrix. This migration was about 10-fold higher than without exogenously added SlEno. Finally, we observed a significantly higher clearance of S. lugdunensis by freshly prepared granulocytes and in the presence of anti-SlEno antibodies. In conclusion, these data demonstrate for the first time a moonlighting function of the S. lugdunensis enolase, which is an underrated virulence factor for colonization and invasion of tissues. Hence, SlEno might be a potential vaccine candidate to prevent severe infections caused by this pathogen.

Immunogenic Proteins of Group B Streptococcus-Potential Antigens in Immunodiagnostic Assay for GBS Detection

Streptococcus agalactiae (Group B Streptococcus, GBS) is an opportunistic pathogen, which asymptomatically colonizes the gastrointestinal and genitourinary tract of up to one third of healthy adults. Nevertheless, GBS carriage in pregnant women may lead to several health issues in newborns causing life threatening infection, such as sepsis, pneumonia or meningitis. Recommended GBS screening in pregnant women significantly reduced morbidity and mortality in infants. Nevertheless, intrapartum antibiotic prophylaxis, recommended following the detection of carriage or in case of lack of a carriage test result for pregnant women who demonstrate certain risk factors, led to the expansion of the adverse phenomenon of bacterial resistance to antibiotics. In our paper, we reviewed some immunogenic GBS proteins, i.e., Alp family proteins, β protein, Lmb, Sip, BibA, FsbA, ScpB, enolase, elongation factor Tu, IMPDH, and GroEL, which possess features characteristic of good candidates for immunodiagnostic assays for GBS carriage detection, such as immunoreactivity and specificity. We assume that they can be used as an alternative diagnostic method to the presently recommended bacteriological cultivation and MALDI.

Klebsiella pneumoniae enolase-like membrane protein interacts with human plasminogen

Many models assessing the risk of sepsis utilize the knowledge of the constituents of the plasminogen system, as it is proven that some species of bacteria can activate plasminogen, as a result of interactions with bacterial outer membrane proteins. However, much is yet to be discovered about this interaction since there is little information regarding some bacterial species. This study is aimed to check if Klebsiella pneumoniae, one of the major factors of nosocomial pneumonia and a factor for severe sepsis, has the ability to bind to human plasminogen. The strain used in this study, PCM 2713, acted as a typical representative of the species. With use of various methods, including: electron microscopy, 2-dimensional electrophoresis, immunoblotting and peptide fragmentation fingerprinting, it is shown that Klebsiella pneumoniae binds to human plasminogen, among others, due to plasminogen-bacterial enolase-like protein interaction, occurring on the outer membrane of the bacterium. Moreover, the study reveals, that other proteins, such as: phosphoglucomutase, and phosphoenolpyruvate carboxykinase act as putative plasminogen-binding factors. These information may virtually act as a foundation for future studies investigating: the: pathogenicity of Klebsiella pneumoniae and means for prevention from the outcomes of Klebsiella-derived sepsis.

Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), Photoluminescence analysis and immersion tests were performed to assess structural and long-term corrosion properties of the new coating. Biocompatibility and antibacterial potential of the new coating were evaluated using U2OS cell culture and the gram-positive Staphylococcus aureus (S. aureus, strain B 918). PEO provided the formation of a porous oxide layer with relatively high roughness. It was shown that Ca(OH)₂ was a crucial compound for oxidation and surface modification of Mg implants, treated with the PEO method. The addition of Ca²⁺ ions resulted in more intense oxidation of the Mg surface and growth of the oxide layer with a higher active surface area. Cell culture experiments demonstrated appropriate cell adhesion to all investigated coatings with a significantly better proliferation rate for the samples treated in Ca(OH)₂-containing electrolyte. In contrast, NaOH-based electrolyte provided more relevant antibacterial effects but did not support cell proliferation. In conclusion, it should be noted that PEO of Mg alloy in silicate baths containing Ca(OH)₂ provided the formation of stable biocompatible oxide coatings that could be used in the development of commercial degradable implants.

Susceptibility to biofilm formation on 3D-printed titanium fixation plates used in the mandible: a preliminary study

Background: In the oral and maxillofacial surgery, fixation plates are commonly used for the stabilization of bone fragments. Additive manufacturing has enabled us to design and create personalized fixation devices that would ideally fit any given fracture. Aim: The aim of the present preliminary study was to assess the susceptibility of 3D-printed titanium fixation plates to biofilm formation. Methods: Plates were manufactured using selective laser melting (SLM) from Ti-6Al-4 V. Reference strains of Streptococcus mutans, Staphyloccocus epidermidis, Staphylococcus aureus, Lactobacillus rhamnosus, and Candida albicans, were tested to evaluate the material's susceptibility to biofilm formation over 48 hours. Biofilm formations were quantified by a colorimetric method and colony-forming units (CFU) quantification. Scanning electron microscopy (SEM) visualized the structure of the biofilm. Results: Surface analysis revealed the average roughness of 102.75 nm and irregular topography of the tested plates. They were susceptible to biofilm formation by all tested strains. The average CFUs were as follows: S. mutans (11.91 x 107) > S.epidermidis (4.45 x 107) > S. aureus (2.3 x 107) > C.albicans (1.22 x 107) > L. rhamnosus (0.78 x 107). Conclusions: The present preliminary study showed that rough surfaces of additively manufactured titanium plates are susceptible to microbial adhesion. The research should be continued in order to compare additively manufactured plates with other commercially available osteotomy plates. Therefore, we suggest caution when using this type of material.

Moonlighting Proteins

The single gene, single protein, single function hypothesis is increasingly becoming obsolete. Numerous studies have demonstrated that individual proteins can moonlight, meaning they can have multiple functions based on their cellular or developmental context. In this review, we discuss moonlighting proteins, highlighting the biological pathways where this phenomenon may be particularly relevant. In addition, we combine genetic, cell biological, and evolutionary perspectives so that we can better understand how, when, and why moonlighting proteins may take on multiple roles.

From Normal Flora to Brain Abscesses: A Review of Streptococcus intermedius

Streptococcus intermedius is a β-hemolytic Gram-positive member of the Streptococcus anginosus group (SAG). Despite being a part of the normal microbiota, it is one of the most common pathogens associated with brain and liver abscesses and thoracic empyema, increasing as a result the morbidity and mortality rates in affected patients. Though there are numerous published case reports on S. intermedius infections, it is still understudied compared to other SAG members. Our knowledge of the genomic factors contributing to its dissemination to the brain and abscess development is also limited to few characterized genes. In this review, we summarize our current knowledge on S. intermedius identification methods, virulence factors, and insight provided by the whole-genome and correlate patients’ metadata, symptoms, and disease outcome with S. intermedius infections in 101 recent case reports obtained from PubMed. This combined information highlights the gaps in our understanding of S. intermedius pathogenesis, suggesting future research directions to unveil the factors contributing to abscess development.

MnmE, a Central tRNA-Modifying GTPase, Is Essential for the Growth, Pathogenicity, and Arginine Metabolism of Streptococcus suis Serotype 2

Streptococcus suis is an important pathogen in pigs and can also cause severe infections in humans. However, little is known about proteins associated with cell growth and pathogenicity of S. suis. In this study, a guanosine triphosphatase (GTPase) MnmE homolog was identified in a Chinese isolate (SC19) that drives a tRNA modification reaction. A mnmE deletion strain (ΔmnmE) and a complementation strain (CΔmnmE) were constructed to systematically decode the characteristics and functions of MnmE both in vitro and in vivo studies via proteomic analysis. Phenotypic analysis revealed that the ΔmnmE strain displayed deficient growth, attenuated pathogenicity, and perturbation of the arginine metabolic pathway mediated by the arginine deiminase system (ADS). Consistently, tandem mass tag -based quantitative proteomics analysis confirmed that 365 proteins were differentially expressed (174 up- and 191 down-regulated) between strains ΔmnmE and SC19. Many proteins associated with DNA replication, cell division, and virulence were down-regulated. Particularly, the core enzymes of the ADS were significantly down-regulated in strain ΔmnmE. These data also provide putative molecular mechanisms for MnmE in cell growth and survival in an acidic environment. Therefore, we propose that MnmE, by its function as a central tRNA-modifying GTPase, is essential for cell growth, pathogenicity, as well as arginine metabolism of S. suis.

MUC7 Level As A New Saliva Risk Factor For Dental Caries In Adult Patients

Purpose: Data currently available indicate the significance of salivary mucins MUC5B and MUC7 in the protection of teeth against caries. Our study aimed to determine the relationship between dental caries in adults and levels of MUC5B and MUC7. Methods: The studies were conducted on 45 adult subjects selected on the basis of dental examination and calculation of the DMFT (Decayed, Missing, and Filled Teeth) index. Among these patients, two research groups were distinguished: group 1 included 19 caries-free subjects (DMFT = 0); and group 2 included 26 patients with severe caries (DMFT > 13.9). Samples of whole unstimulated saliva were collected and centrifuged. MUC5B and MUC7 content in saliva supernatant were estimated using an enzyme-linked immunosorbent sandwich assay (ELISA). Analysis of the obtained data receiver operating characteristic (ROC) curves was employed to define relationships between the contents of the studied mucins and the detected dental caries. Results: In subjects from group 1, the mean level of MUC5B amounted to 0.63 ± 0.35 ng/ml and this was significantly higher than the concentration of mucin in patients of group 2, which amounted to 0.38 ± 0.32 ng/ml (p = 0.023). The mean level of MUC7 amounted to 5.47 ± 1.18 ng/ml and this was significantly higher than the level of the mucin in group 2, which was 1.39 ± 0.86 ng/ml (p< 0.0001). In parallel, a relationship was detected between levels of the examined mucins and manifestation of dental caries. For MUC7, the optimal cut-off value was obtained (i.e. corresponding to 100% sensitivity and specificity), amounting to 2.5 ng/ml for the detection of dental caries risk. Conclusions: Development of dental caries is linked to reduced concentrations of MUC5B and MUC7. The level of MUC7 may represent a significant parameter clinically suitable for evaluation of disease risk.

In Vitro Comparison of the Efficacy of Peri-Implantitis Treatments on the Removal and Recolonization of Streptococcus gordonii Biofilm on Titanium Disks

Objective: To compare the efficacy of four commonly used clinical procedures in removing Streptococcus gordonii biofilms from titanium disks, and the recolonization of the treated surfaces. Background: Successful peri-implantitis treatment depends on the removal of the dental biofilm. Biofilm that forms after implant debridement may threaten the success of the treatment and the long-term stability of the implants. Methods:S. gordonii biofilms were grown on titanium disks for 48 h and removed using a plastic curette, air-abrasive device (Perio-Flow®), titanium brush (TiBrush®), or implantoplasty. The remaining biofilm and the recolonization of the treated disks were observed using scanning electron microscopy and quantified after staining with crystal violet. Surface roughness (Ra and Rz) was measured using a profilometer. Results:S. gordonii biofilm biomass was reduced after treatment with Perio-Flow®, TiBrush®, and implantoplasty (all p < 0.05), but not plastic curette (p > 0.05), compared to the control group. Recolonization of S. gordonii after treatment was lowest after Perio-Flow®, TiBrush®, and implantoplasty (all p < 0.05 vs. control), but there was no difference between the plastic curette and the control group (p > 0.05). Ra and Rz values ranged from 1–6 µm to 1–2 µm and did not differ statistically between the control, plastic curette, Perio-Flow, and TiBrush groups. However, the implantoplasty group showed a Ra value below 1 µm (p < 0.01, ANOVA, Tukey). Conclusions: Perio-Flow^®, TiBrush^®, and implantoplasty were more effective than the plastic curette at removing the S. gordonii biofilm and preventing recolonization. These results should influence the surgical management of peri-implantitis.

Serodiagnostic Potential of Alpha-Enolase From Sarcoptes scabiei and Its Possible Role in Host-Mite Interactions

Infestation of the epidermis with the highly contagious ectoparasite, Sarcoptes scabiei, causes scabies, which is characterized by intense itching, pruritus, and secondary infection. This condition affects humans, livestock, and wildlife worldwide, incurring large economic losses and reducing the quality of human life. In the present study, we cloned the alpha-enolase, a key enzyme in the glycolytic and gluconeogenesis pathways, from S. scabiei var. cuniculi, characterized it and produced soluble recombinant enolase protein (rSsc-eno). We determined the localization of Ssc-eno in isolated mites and mites in lesioned skin. The results showed that native enolase was intensely localized in the tegument of the mouthparts, the entire legs, and the whole mites' body, as well as in the gut and reproduction system. Interestingly, we found that native enolase was widely distributed in mites in lesioned skin, with obvious high protein intensity compared with isolated mites. Building on good immunoreactivity, an indirect enzyme-linked immunosorbent assay (ELISA) based on rSsc-eno showed 92% sensitivity and 95.8% specificity, compared with other indirect ELISA in this study, rSsc-eno based ELISA is better in detecting scabies in rabbits. Besides, this method can detect S. scabiei infection as early as 1 week post infection. Compared with other detection methods, such as traditional microscopic examination and recently published universal conventional PCR, rSsc-eno ELISA was more effective to detect early infection in rabbits. Additionally, in vitro incubation experiments demonstrated the concentration-dependent acaricidal activity of rabbit anti-rSsc-eno sera against larval mites, suggested its potential as a vaccine candidate.

Antidiabetic "gliptins" affect biofilm formation by Streptococcus mutans

Streptococcus mutans, a dental caries causing odontopathogen, produces X-prolyl dipeptidyl peptidase (Sm-XPDAP, encoded by pepX), a serine protease known to have a nutritional role. Considering the potential of proteases as therapeutic targets in pathogens, this study was primarily aimed at investigating the role of Sm-XPDAP in contributing to virulence-related traits. Dipeptidyl peptidase (DPP IV), an XPDAP analogous enzyme found in mammalian tissues,is a well known therapeutic target in Type II diabetes. Based on the hypothesis that gliptins, commonly used as anti-human-DPP IV drugs, may affect bacterial growth upon inhibition of Sm-XPDAP, we have determined their ex vivo antimicrobial and anti-biofilm activity towards S. mutans. All three DPP IV drugs tested reduced biofilm formation as determined by crystal violet staining. To link the observed biofilm inhibition to the human-DPP IV analogue present in S. mutans UA159, a pepX isogenic mutant was generated. In addition to reduced biofilm formation, CLSM studies of the biofilm formed by the pepX isogenic mutant showed these were comparable to those formed in the presence of saxagliptin, suggesting a probable role of this enzyme in biofilm formation by S. mutans UA159. The effects of both pepX deletion and DPP IV drugs on the proteome were studied using LC-MS/MS. Overall, this study highlights the potential of Sm-XPDAP as a novel anti-biofilm target and suggests a template molecule to synthesize lead compounds effective against this enzyme.

Comparative salivary proteomics analysis of children with and without dental caries using the iTRAQ/MRM approach

BACKGROUND

Dental caries is a major worldwide oral disease afflicting a large proportion of children. As an important host factor of caries susceptibility, saliva plays a significant role in the occurrence and development of caries. The aim of the present study was to characterize the healthy and cariogenic salivary proteome and determine the changes in salivary protein expression of children with varying degrees of active caries, also to establish salivary proteome profiles with a potential therapeutic use against dental caries.

METHODS

In this study, unstimulated saliva samples were collected from 30 children (age 10-12 years) with no dental caries (NDC, n = 10), low dental caries (LDC, n = 10), and high dental caries (HDC, n = 10). Salivary proteins were extracted, reduced, alkylated, trypsin digested and labeled with isobaric tags for relative and absolute quantitation, and then they were analyzed with GO annotation, biological pathway analysis, hierarchical clustering analysis, and protein-protein interaction analysis. Targeted verifications were then performed using multiple reaction monitoring mass spectrometry.

RESULTS

A total of 244 differentially expressed proteins annotated with GO annotation in biological processes, cellular component and molecular function were identified in comparisons among children with varying degrees of active caries. A number of caries-related proteins as well as pathways were identified in this study. As compared with caries-free children, the most significantly enriched pathways involved by the up-regulated proteins in LDC and HDC were the ubiquitin mediated proteolysis pathway and African trypanosomiasis pathway, respectively. Subsequently, we selected 53 target proteins with differential expression in different comparisons, including mucin 7, mucin 5B, histatin 1, cystatin S and cystatin SN, basic salivary proline rich protein 2, for further verification using MRM assays. Protein-protein interaction analysis of these proteins revealed complex protein interaction networks, indicating synergistic action of salivary proteins in caries resistance or cariogenicity.

CONCLUSIONS

Overall, our results afford new insight into the salivary proteome of children with dental caries. These findings might have bright prospect in future in developing novel biomimetic peptides with preventive and therapeutic benefits for childhood caries.

Homology Modeling of Leishmania donovani Enolase and its Molecular Interaction with Novel Inhibitors

Introduction:

The treatment of Indian tropical disease such as kala-azar is likely to be troublesome to the clinicians as AmpB- and miltefosine-resistant Leishmania donovani has been reported. The rationale behind designed a novel inhibitors of model of L. donovani enolase and performing a binding study with its inhibitors to gain details of the interaction between protein residues and ligand molecules.

Methods and Materials:

The L. donovani enolase model consists of two typical domains. The N-terminal one contains three-stranded antiparallel β-sheets, followed by six α-helices. The C-terminal domain composes of eleven-stranded mixed α/β-barrel with connectivity. The first α-helix within the C-terminal domain, H7, and the second β-strand, S7, of the barrel domain was arranged in an antiparallel fashion compared to all other α-helices and β-strands. The root-mean-square deviation between predicted model and template is 0.4 Å. The overall conformation of L. donovani enolase model is similar to those of Trypanosoma cruzi enolase and Streptococcus pneumoniae enolase crystal structures.

Result:

The key amino acid residues within the docking complex model involved in the interaction between model enolase structure and ligand molecule are Lys70, Asn165, Ala168, Asp17, and Asn213.

Conclusion:

Our theoretical prediction may lead to the establishment of prophylactic and therapeutic approaches for the treatment of kala-azar. This biomedical informatics analysis will help us to combat future kala-azar.

The two-component system VicRK regulates functions associated with Streptococcus mutans resistance to complement immunity

Streptococcus mutans, a dental caries pathogen, can promote systemic infections upon reaching the bloodstream. The two-component system (TCS) VicRK_Sm of S. mutans regulates the synthesis of and interaction with sucrose-derived exopolysaccharides (EPS), processes associated with oral and systemic virulence. In this study, we investigated the mechanisms by which VicRK_Sm affects S. mutans susceptibility to blood-mediated immunity. Compared with parent strain UA159, the vicK_Sm isogenic mutant (UAvic) showed reduced susceptibility to deposition of C3b of complement, low binding to serum immunoglobulin G (IgG), and low frequency of C3b/IgG-mediated opsonophagocytosis by polymorphonuclear cells in a sucrose-independent way (P<.05). Reverse transcriptase quantitative polymerase chain reaction analysis comparing gene expression in UA159 and UAvic revealed that genes encoding putative peptidases of the complement (pepO and smu.399) were upregulated in UAvic in the presence of serum, although genes encoding murein hydrolases (SmaA and Smu.2146c) or metabolic/surface proteins involved in bacterial interactions with host components (enolase, GAPDH) were mostly affected in a serum-independent way. Among vicK_Sm -downstream genes (smaA, smu.2146c, lysM, atlA, pepO, smu.399), only pepO and smu.399 were associated with UAvic phenotypes; deletion of both genes in UA159 significantly enhanced levels of C3b deposition and opsonophagocytosis (P<.05). Moreover, consistent with the fibronectin-binding function of PepO orthologues, UAvic showed increased binding to fibronectin. Reduced susceptibility to opsonophagocytosis was insufficient to enhance ex vivo persistence of UAvic in blood, which was associated with growth defects of this mutant under limited nutrient conditions. Our findings revealed that S. mutans employs mechanisms of complement evasion through peptidases, which are controlled by VicRK_Sm.

Pseudomonas aeruginosa Enolase Influences Bacterial Tolerance to Oxidative Stresses and Virulence

Pseudomonas aeruginosa is a Gram negative opportunistic pathogenic bacterium, which causes acute and chronic infections. Upon entering the host, bacteria alter global gene expression to adapt to host environment and avoid clearance by the host. Enolase is a glycolytic enzyme involved in carbon metabolism. It is also a component of RNA degradosome, which is involved in RNA processing and gene regulation. Here, we report that enolase is required for the virulence of P. aeruginosa in a murine acute pneumonia model. Mutation of enolase coding gene (eno) increased bacterial susceptibility to neutrophil mediated killing, which is due to reduced tolerance to oxidative stress. Catalases and alkyl hydroperoxide reductases play a major role in protecting the cell from oxidative damages. In the eno mutant, the expression levels of catalases (KatA and KatB) were similar as those in the wild type strain in the presence of H₂O₂, however, the expression levels of alkyl hydroperoxide reductases (AhpB and AhpC) were significantly reduced. Overexpression of ahpB but not ahpC in the eno mutant fully restored the bacterial resistance to H₂O₂ as well as neutrophil mediated killing, and partially restored bacterial virulence in the murine acute pneumonia model. Therefore, we have identified a novel role of enolase in the virulence of P. aeruginosa.

Molecular and biochemical characterisation and recognition by the immune host of the enolase of the abomasal nematode parasite Teladorsagia circumcincta

A 1299 bp full length cDNA encoding Teladorsagia circumcincta enolase (TeciENO) was cloned, expressed in Escherichia coli and the recombinant protein purified and its kinetic properties determined. Helminth enolase sequences were used to construct a phylogenetic tree. The predicted protein consisted of 433 amino acids and was present as a single band of about 50 kDa on SDS-PAGE. Multiple alignments of the protein sequence of TeciENO with homologues from other helminths showed 98% similarity with Haemonchus contortus enolase, 78-95% similarity to other nematode sequences and 72-75% similarity to cestode and trematode enolases. Substrate binding sites and conserved regions were identified and were completely conserved in other homologues. The optimum pH for TeciENO activity at 25 °C was pH 7, the K_m for 2-phophoglycerate 0.09 ± 0.04 mM and the V_max was 604 ± 6 nmol min^-1 mg^-1 protein (both mean ± SD, n = 2). TeciENO activity was inhibited by 11.5% by 1 mM citrate (p < 0.001). Antibodies in both serum and saliva from field-immune, but not nematode-naïve, sheep recognised recombinant TeciENO in enzyme-linked immunosorbent assays. The recognition of the recombinant protein by antibodies generated by exposure of sheep to native enolase indicates similar antigenicity of the two proteins.

Influence of Surface Properties on Adhesion Forces and Attachment of Streptococcus mutans to Zirconia In Vitro

Zirconia is becoming a prevalent material in dentistry. However, any foreign bodies inserted may provide new niches for the bacteria in oral cavity. The object of this study was to explore the effect of surface properties including surface roughness and hydrophobicity on the adhesion and biofilm formation of Streptococcus mutans (S. mutans) to zirconia. Atomic force microscopy was employed to determine the zirconia surface morphology and the adhesion forces between the S. mutans and zirconia. The results showed that the surface roughness was nanoscale and significantly different among tested groups (P < 0.05): Coarse (23.94 ± 2.52 nm) > Medium (17.00 ± 3.81 nm) > Fine (11.89 ± 1.68 nm). The contact angles of the Coarse group were the highest, followed by the Medium and the Fine groups. Increasing the surface roughness and hydrophobicity resulted in an increase of adhesion forces and early attachment (2 h and 4 h) of S. mutans on the zirconia but no influence on the further development of biofilm (6 h~24 h). Our findings suggest that the surface roughness in nanoscale and hydrophobicity of zirconia had influence on the S. mutans initial adhesion force and early attachment instead of whole stages of biofilm formation.

GidA, a tRNA Modification Enzyme, Contributes to the Growth, and Virulence of Streptococcus suis Serotype 2

Glucose-inhibited division protein (GidA), is a tRNA modification enzyme functioning together with MnmE in the addition of a carboxymethylaminomethyl group to position 5 of the anticodon wobble uridine of tRNA. Here, we report a GidA homolog from a Chinese isolate SC-19 of the zoonotic Streptococcus suis serotype 2 (SS2). gidA disruption led to a defective growth, increased capsule thickness, and reduced hemolytic activity. Moreover, the gidA deletion mutant (ΔgidA) displayed reduced mortality and bacterial loads in mice, reduced ability of adhesion to and invasion in epithelial cells, and increased sensitivity to phagocytosis. The iTRAQ analysis identified 372 differentially expressed (182 up- and 190 down-regulated) proteins in ΔgidA and SC-19. Numerous DNA replication, cell division, and virulence associated proteins were downregulated, whereas many capsule synthesis enzymes were upregulated by gidA disruption. This is consistent with the phenotypes of the mutant. Thus, GidA is a translational regulator that plays an important role in the growth, cell division, capsule biosynthesis, and virulence of SS2. Our findings provide new insight into the regulatory function of GidA in bacterial pathogens.

Salivary mucins in host defense and disease prevention

Mucus forms a protective coating on wet epithelial surfaces throughout the body that houses the microbiota and plays a key role in host defense. Mucins, the primary structural components of mucus that creates its viscoelastic properties, are critical components of the gel layer that protect against invading pathogens. Altered mucin production has been implicated in diseases such as ulcerative colitis, asthma, and cystic fibrosis, which highlights the importance of mucins in maintaining homeostasis. Different types of mucins exist throughout the body in various locations such as the gastrointestinal tract, lungs, and female genital tract, but this review will focus on mucins in the oral cavity. Salivary mucin structure, localization within the oral cavity, and defense mechanisms will be discussed. These concepts will then be applied to present what is known about the protective function of mucins in oral diseases such as HIV/AIDS, oral candidiasis, and dental caries.

Borrelia burgdorferi elongation factor EF-Tu is an immunogenic protein during Lyme borreliosis

Borrelia burgdorferi, the etiological agent of Lyme disease, does not produce lipopolysaccharide but expresses a large number of lipoproteins on its cell surface. These outer membrane lipoproteins are highly immunogenic and have been used for serodiagnosis of Lyme disease. Recent studies have shown that highly conserved cytosolic proteins such as enolase and elongation factor Tu (EF-Tu) unexpectedly localized on the surface of bacteria including B. burgdorferi, and surface-localized enolase has shown to contribute to the enzootic cycle of B. burgdorferi. In this study, we studied the immunogenicity, surface localization, and function of B. burgdorferi EF-Tu. We found that EF-Tu is highly immunogenic in mice, and EF-Tu antibodies were readily detected in Lyme disease patients. On the other hand, active immunization studies showed that EF-Tu antibodies did not protect mice from infection when challenged with B. burgdorferi via either needle inoculation or tick bites. Borrelial mouse-tick cycle studies showed that EF-Tu antibodies also did not block B. burgdorferi migration and survival in ticks. Consistent with these findings, we found that EF-Tu primarily localizes in the protoplasmic cylinder of spirochetes and is not on the surface of B. burgdorferi. Taken together, our studies suggest that B. burgdorferi EF-Tu is not surfaced exposed, but it is highly immunogenic and is a potential serodiagnostic marker for Lyme borreliosis.

An overview of protein moonlighting in bacterial infection

We are rapidly returning to a world in which bacterial infections are a major health issue. Pathogenic bacteria are able to colonize and cause pathology due to the possession of virulence factors such as adhesins, invasins, evasins and toxins. These are generally specifically evolved proteins with selective actions. It is, therefore, surprising that most human bacterial pathogens employ moonlighting proteins as virulence factors. Currently, >90 bacterial species employ one or more moonlighting protein families to aid colonization and induce disease. These organisms employ 90 moonlighting bacterial protein families and these include enzymes of the glycolytic pathway, tricarboxylic acid (TCA) cycle, hexosemonophosphate shunt, glyoxylate cycle and a range of other metabolic enzymes, proteases, transporters and, also, molecular chaperones and protein-folding catalysts. These proteins have homologues in eukaryotes and only a proportion of the moonlighting proteins employed are solely bacterial in origin. Bacterial moonlighting proteins can be divided into those with single moonlighting functions and those with multiple additional biological actions. These proteins contribute significantly to the population of virulence factors employed by bacteria and some are obvious therapeutic targets. Where examined, bacterial moonlighting proteins bind to target ligands with high affinity. A major puzzle is the evolutionary mechanism(s) responsible for bacterial protein moonlighting and a growing number of highly homologous bacterial moonlighting proteins exhibit widely different moonlighting actions, suggesting a lack in our understanding of the mechanism of evolution of protein active sites.

Effect of daily drinking of Aloe vera gel extract on plasma total antioxidant capacity and oral pathogenic bacteria in healthy volunteer: a short-term study

BACKGROUND

The aim of this study was to investigate the effect of Aloe vera gel extract on plasma total antioxidant capacity (TAC) and oral pathogenic bacteria in healthy volunteer.

METHODS

Fifty-three healthy volunteers were participated and interviewed for history of allergy, current systemic diseases and medications. Participants were received 250 mL of A. vera gel extract daily for 14 consecutive days. At days 0 and 15 of the experiment, blood samples were collected and analyzed for biochemical markers. The plasma TAC was evaluated by ferric reducing ability of plasma technique. The biochemical markers, including aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), total protein (TP), serum albumin (ALB), serum globulin (GLB), total bilirubin (TB), blood urea nitrogen (BUN), serum creatinine (Cr) and creatinine clearance (CrCl) were measured. The antibacterial effect of A. vera gel extract against Lactobacillus spp. and Streptococcus mutans was also investigated. Statistical analysis was performed using paired t-test to compare between baseline and 14 days post-intervention.

RESULTS

Neither allergy nor side effects of A. vera gel extract was detected. After 14 days of A. vera gel extract consumption, plasma TAC was significantly greater than that of baseline (p = 0.001). ALP, TB, TP and GLB were significantly increased (p < 0.05) which were still within normal range. AST, ALT, ALB, BUN, Cr and CrCl were not significantly different. A. vera gel extract significantly reduced the number of Lactobacillus spp. (p < 0.05), not S. mutans.

CONCLUSIONS

Our data revealed that A. vera gel extract significantly increased plasma TAC, and decreased the number of Lactobacillus spp. without any clinical side effects.

Extracellular enolase of Candida albicans is involved in colonization of mammalian intestinal epithelium

Enolase is secreted by Candida albicans and is present in its biofilms although its extracellular function is unknown. Here we show that extracellular enolase mediates the colonization of small intestine mucosa by C. albicans. Assays using intestinal mucosa disks show that C. albicans adhesion is inhibited, in a dose dependent mode, either by pretreatment of intestinal epithelium mucosa disks with recombinant C. albicans enolase (70% at 0.5 mg/ml enolase) or by pretreatment of C. albicans yeasts with anti-enolase antibodies (48% with 20 μg antiserum). Also using flow cytometry, immunoblots of conditioned media and confocal microscopy we demonstrate that enolase is present in biofilms and that the extracellular enolase is not an artifact due to cell lysis, but must represent functional secretion of a stable form. This is the first direct evidence that C. albicans' extracellular enolase mediates colonization on its primary translocation site. Also, because enolase is encoded by a single locus in C. albicans, its dual role peptide, as glycolytic enzyme and extracellular peptide, is a remarkable example of gene sharing in fungi.

Enolase-like protein present on the outer membrane of Pseudomonas aeruginosa binds plasminogen

Pseudomonas aeruginosa is one of the pathogenic bacteria which utilize binding of the host plasminogen (Plg) to promote their invasion throughout the host tissues. In the present study, we confirmed that P. aeruginosa exhibits binding affinity for human plasminogen. Furthermore, we showed that the protein detected on the cell wall of P. aeruginosa and binding human plasminogen is an enolase-like protein. The hypothesis that alpha-enolase, a cytoplasmatic glycolytic enzyme, resides also on the cell surface of the bacterium was supported by electron microscopy analysis. The plasminogen-binding activity of bacterial cell wall outer membrane enolase-like protein was examined by immunoblotting assay.

Dancing to another tune-adhesive moonlighting proteins in bacteria

Biological moonlighting refers to proteins which express more than one function. Moonlighting proteins occur in pathogenic and commensal as well as in Gram-positive and Gram-negative bacteria. The canonical functions of moonlighting proteins are in essential cellular processes, i.e., glycolysis, protein synthesis, chaperone activity, and nucleic acid stability, and their moonlighting functions include binding to host epithelial and phagocytic cells, subepithelia, cytoskeleton as well as to mucins and circulating proteins of the immune and hemostatic systems. Sequences of the moonlighting proteins do not contain known motifs for surface export or anchoring, and it has remained open whether bacterial moonlighting proteins are actively secreted to the cell wall or whether they are released from traumatized cells and then rebind onto the bacteria. In lactobacilli, ionic interactions with lipoteichoic acids and with cell division sites are important for surface localization of the proteins. Moonlighting proteins represent an abundant class of bacterial adhesins that are part of bacterial interactions with the environment and in responses to environmental changes. Multifunctionality in bacterial surface proteins appears common: the canonical adhesion proteins fimbriae express also nonadhesive functions, whereas the mobility organelles flagella as well as surface proteases express adhesive functions.

EndoE from Enterococcus faecalis hydrolyzes the glycans of the biofilm inhibiting protein lactoferrin and mediates growth

Glycosidases are widespread among bacteria. The opportunistic human pathogen Enterococcus faecalis encodes several putative glycosidases but little is known about their functions. The identified endo-β-N-acetylglucosaminidase EndoE has activity on the N-linked glycans of the human immunoglobulin G (IgG). In this report we identified the human glycoprotein lactoferrin (hLF) as a new substrate for EndoE. Hydrolysis of the N-glycans from hLF was investigated using lectin blot, UHPLC and mass spectrometry, showing that EndoE releases major glycoforms from this protein. hLF was shown to inhibit biofilm formation of E. faecalis in vitro. Glycans of hLF influence the binding to E. faecalis, and EndoE-hydrolyzed hLF inhibits biofilm formation to lesser extent than intact hLF indicating that EndoE prevents the inhibition of biofilm. In addition, hLF binds to a surface-associated enolase of E. faecalis. Culture experiments showed that the activity of EndoE enables E. faecalis to use the glycans derived from lactoferrin as a carbon source indicating that they could be used as nutrients in vivo when no other preferred carbon source is available. This report adds important information about the enzymatic activity of EndoE from the commensal and opportunist E. faecalis. The activity on the human glycoprotein hLF, and the functional consequences with reduced inhibition of biofilm formation highlights both innate immunity functions of hLF and a bacterial mechanism to evade this innate immunity function. Taken together, our results underline the importance of glycans in the interplay between bacteria and the human host, with possible implications for both commensalism and opportunism.

In vivo study of the initial bacterial adhesion on different implant materials

OBJECTIVE

Biofilm formation on implant materials plays a major role in the aetiology of periimplantitis. The aim of this study was to examine in vivo the initial bacterial adhesion on six different implant materials.

METHODS

The implant materials Ti-m, TiUnite®, ZiUnite®, ATZ-m, ATZ-s, TZP-A-m were tested using bovine enamel slabs as controls. All materials, fixed on splint systems, were examined after 30 min and 120 min of oral exposure. DAPI staining was used for quantitative analysis of the initially adherent microorganisms. Initial adherent microorganisms were visualised by fluorescence In situ-hybridisation (FISH) and quantified by confocal laser scanning microscopy (CLSM). The targets of the oligonucleotide probes were Eubacteria, Veillonella spp., Fusobacterium nucleatum, Actinomyces naeslundii and Streptococcus spp.

RESULTS

DAPI analysis showed that increasing the time of oral exposure resulted in an increasing amount of initial adherent bacteria. The highest level of colonisation was on ZiUnite®, with the lowest occurring on the bovine enamel, followed by Ti-m. This early colonisation correlated significantly with the surface roughnesses of the materials. FISH and CLSM showed no significant differences relating to total bacterial composition. However, Streptococcus spp. was shown to be the main colonisers on each of the investigated materials.

CONCLUSION

it could be shown that within an oral exposure time of 30 min and 120 min, despite the salivary acquired pellicle initial biofilm formation is mainly influenced directly or indirect by the material surface topography. Highly polished surfaces should minimise the risk of biofilm formation, plaque accumulation and possibly periimplantitis.

Corrosion behaviour of titanium in the presence of Streptococcus mutans

OBJECTIVE

The main aim of this in vitro study was to evaluate the influence of Streptococcus mutans on the corrosion of titanium.

METHODS

S. mutans biofilms were formed on commercially pure titanium (CP-Ti) square samples (10mm×10mm×1mm) using a culture medium enriched with sucrose. Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements were used to evaluate the corrosion behaviour of CP-Ti in the presence of S. mutans in Fusayama's artificial saliva. The corrosion of biofilm-free CP-Ti samples was also evaluated in artificial saliva. Biofilms biomass was measured by spectrophotometry, using crystal violet staining, after 1, 2 and 7 days.

RESULTS

The OCP values recorded on CP-Ti in the presence of S. mutans (-0.3±0.02V vs. SCE) was lower than those on biofilm-free CP-Ti (-0.1±0.01V vs. SCE) after 2h of immersion in artificial saliva (p<0.05). That reveals a high reactivity of titanium in presence of S. mutans. Impedance spectra revealed the formation of a compact passive film on titanium in artificial saliva or in the presence of a 2 days old S. mutans biofilm even though the corrosion resistance of CP-Ti has decreased in presence of a S. mutans biofilm.

CONCLUSION

The presence of bacterial colonies, such as S. mutans, negatively affected the corrosion resistance of the titanium.

Enolase of Streptococcus pneumoniae binds human complement inhibitor C4b-binding protein and contributes to complement evasion

Streptococcus pneumoniae (pneumococcus) is a pathogen that causes severe local and life-threatening invasive diseases, which are associated with high mortality rates. Pneumococci have evolved several strategies to evade the host immune system, including complement to disseminate and to survive in various host niches. Thus, pneumococci bind complement inhibitors such as C4b-binding protein (C4BP) and factor H via pneumococcal surface protein C, thereby inhibiting the classical and alternative complement pathways. In this study, we identified the pneumococcal glycolytic enzyme enolase, a nonclassical cell surface and plasminogen-binding protein, as an additional pneumococcal C4BP-binding protein. Furthermore, we demonstrated that human, but not mouse, C4BP bound pneumococci. Recombinant enolase bound in a dose-dependent manner C4BP purified from plasma, and the interaction was reduced by increasing ionic strength. Enolase recruited C4BP and plasminogen, but not factor H, from human serum. Moreover, C4BP and plasminogen bound to different domains of enolase as they did not compete for the interaction with enolase. In direct binding assays with recombinant C4BP mutants lacking individual domains, two binding sites for enolase were identified on the complement control protein (CCP) domain 1/CCP2 and CCP8 of the C4BP α-chains. C4BP bound to the enolase retained its cofactor activity as determined by C4b degradation. Furthermore, in the presence of exogenously added enolase, an increased C4BP binding to and subsequently decreased C3b deposition on pneumococci was observed. Taken together, pneumococci specifically interact with human C4BP via enolase, which represents an additional mechanism of human complement control by this versatile pathogen.

Identification of the actin and plasminogen binding regions of group B streptococcal phosphoglycerate kinase

Phosphoglycerate kinase (PGK), present on the surface of group B streptococcus (GBS), has previously been demonstrated to bind the host proteins actin and plasminogen. The actin and plasminogen binding sites of GBS-PGK were identified using truncated GBS-PGK molecules, followed by peptide mapping. These experiments identified two actin and plasminogen binding sites located between amino acids 126-134 and 204-208 of the 398-amino acid-long GBS-PGK molecule. Substitution of the lysine residues within these regions with alanine resulted in significantly reduced binding to both actin and plasminogen. In addition, conversion of the glutamic acid residue at amino acid 133 to proline, the amino acid found at this position for the PGK protein of Streptococcus pneumoniae, also resulted in significantly reduced binding to actin and plasminogen. These results demonstrate that the lysine residues at amino acid positions 126, 127, 130, 204, and 208 along with the glutamic acid residue at amino acid position 133 are necessary for actin and plasminogen binding by GBS-PGK.

α-Enolase of Streptococcus pneumoniae induces formation of neutrophil extracellular traps

Streptococcus pneumoniae is the most common causative agent of community-acquired pneumonia throughout the world, with high morbidity and mortality rates. A major feature of pneumococcal pneumonia is abundant neutrophil infiltration. In this study, we identified S. pneumoniae α-enolase as a neutrophil binding protein in ligand blot assay and mass spectrometry findings. Scanning electron microscopic and fluorescence microscopic analyses also revealed that S. pneumoniae α-enolase induces formation of neutrophil extracellular traps, which have been reported to bind and kill microbes. In addition, cytotoxic assay results showed that α-enolase dose-dependently increased the release of extracellular lactate dehydrogenase from human neutrophils as compared with untreated neutrophils. Furthermore, an in vitro cell migration assay using Chemotaxicell culture chambers demonstrated that α-enolase possesses neutrophil migrating activity. Interestingly, bactericidal assay findings showed that α-enolase increased neutrophil extracellular trap-dependent killing of S. pneumoniae in human blood. Moreover, pulldown assay and mass spectrometry results identified myoblast antigen 24.1D5 as an α-enolase-binding protein on human neutrophils, whereas flow cytometric analysis revealed that 24.1D5 was expressed on human neutrophils, but not on human monocytes or T cells. Together, our results indicate that α-enolase from S. pneumoniae increases neutrophil migrating activity and induces cell death of human neutrophils by releasing neutrophil extracellular traps. Furthermore, we found that myoblast antigen 24.1D5, which expressed on the surface of neutrophils, bound to α-enolase of S. pneumoniae.

The interaction of canine plasminogen with Streptococcus pyogenes enolase: they bind to one another but what is the nature of the structures involved?

For years it has been clear that plasminogen from different sources and enolase from different sources interact strongly. What is less clear is the nature of the structures required for them to interact. This work examines the interaction between canine plasminogen (dPgn) and Streptococcus pyogenes enolase (Str enolase) using analytical ultracentrifugation (AUC), surface plasmon resonance (SPR), fluorescence polarization, dynamic light scattering (DLS), isothermal titration calorimetry (ITC), and simple pull-down reactions. Overall, our data indicate that a non-native structure of the octameric Str enolase (monomers or multimers) is an important determinant of its surface-mediated interaction with host plasminogen. Interestingly, a non-native structure of plasminogen is capable of interacting with native enolase. As far as we can tell, the native structures resist forming stable mixed complexes.

Antibiotic modulation of the plasminogen binding ability of viridans group streptococci

The ability of viridans group streptococci to bind human plasminogen and its subsequent activation into plasmin may contribute to the pathogenesis of infective endocarditis (IE) by leading to a decreased stability of the streptococcal vegetation and facilitating dehiscence of emboli. At levels greater than or equal to their MICs, penicillin, vancomycin, and linezolid are efficacious in the treatment of streptococcal endocarditis. However, at sub-MICs, antibiotics can modulate the expression of bacterial genes, including virulence-associated genes, which can have counterproductive effects on the treatment of endocarditis. The effects of 1/8× and 1/4× MICs of penicillin, vancomycin, and linezolid on the plasminogen binding ability of IE isolates Streptococcus mitis 881/956, Streptococcus oralis 12601, and Streptococcus sanguinis 12403 were assessed phenotypically and the expression of plasminogen receptors α-enolase and glyceraldehyde 3-phosphate dehydrogenase of S. oralis 12601 when exposed to 1/4× MIC of penicillin, was analyzed through quantitative reverse transcription (qRT)-PCR. The plasminogen binding ability of S. mitis 881/956 and S. sanguinis 12403 remained unaffected by exposure to sub-MICs of all of the antibiotics tested, while that of S. oralis 12601 was significantly enhanced by all of the antibiotics tested at sub-MICs. qRT-PCR analysis of S. oralis 12601 demonstrated an upregulation of the eno and gapdh genes, indicating an overexpression of plasminogen receptors. These findings suggest that for some endocarditis isolates, the effect of antibiotic sub-MICs, in addition to a reduced antibacterial effect, may influence the clinical response to nonsurgical therapy. It remains difficult to accurately predict isolate responses to sub-MIC antimicrobials since there appears to be interspecies variation.

A surface enolase participates in Borrelia burgdorferi-plasminogen interaction and contributes to pathogen survival within feeding ticks

Borrelia burgdorferi, a tick-borne bacterial pathogen, causes a disseminated infection involving multiple organs known as Lyme disease. Surface proteins can directly participate in microbial virulence by facilitating pathogen dissemination via interaction with host factors. We show here that a fraction of the B. burgdorferi chromosomal gene product BB0337, annotated as enolase or phosphopyruvate dehydratase, is associated with spirochete outer membrane and is surface exposed. B. burgdorferi enolase, either in a recombinant form or as a membrane-bound native antigen, displays enzymatic activities intrinsic to the glycolytic pathway. However, the protein also interacts with host plasminogen, potentially leading to its activation and resulting in B. burgdorferi-induced fibrinolysis. As expected, enolase displayed consistent expression in vivo, however, with a variable temporal and spatial expression during spirochete infection in mice and ticks. Despite an extracellular exposure of the antigen and a potential role in host-pathogen interaction, active immunization of mice with recombinant enolase failed to evoke protective immunity against subsequent B. burgdorferi infection. In contrast, enolase immunization of murine hosts significantly reduced the acquisition of spirochetes by feeding ticks, suggesting that the protein could have a stage-specific role in B. burgdorferi survival in the feeding vector. Strategies to interfere with the function of surface enolase could contribute to the development of novel preventive measures to interrupt the spirochete infection cycle and reduce the incidences of Lyme disease.

Bacterial virulence in the moonlight: multitasking bacterial moonlighting proteins are virulence determinants in infectious disease

Men may not be able to multitask, but it is emerging that proteins can. This capacity of proteins to exhibit more than one function is termed protein moonlighting, and, surprisingly, many highly conserved proteins involved in metabolic regulation or the cell stress response have a range of additional biological actions which are involved in bacterial virulence. This review highlights the multiple roles exhibited by a range of bacterial proteins, such as glycolytic and other metabolic enzymes and molecular chaperones, and the role that such moonlighting activity plays in the virulence characteristics of a number of important human pathogens, including Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Helicobacter pylori, and Mycobacterium tuberculosis.

rEnolase maternal immunization confers caries protection on offspring

Therapeutic vaccination with Streptococcus sobrinus recombinant enolase (rEnolase) protects rats from dental caries. Here, we investigated the effect that maternal rEnolase vaccination before pregnancy had on the offspring's immune response to S. sobrinus oral infection and dental caries progression. Female Wistar rats were immunized by intranasal and subcutaneous routes with rEnolase adsorbed onto aluminum hydroxide as adjuvant or similarly treated with the adjuvant alone (sham-immunized). Ten days after the last administration, the immunized females were paired with a male rat. The oral immune responses to S. sobrinus infection and dental caries in the offspring were evaluated. The results showed that pups born from rEnolase-immunized mothers had higher levels of rEnolase-specific salivary IgA and IgG antibodies (indicating a placental antibody transfer) and lower sulcal and proximal enamel caries scores than rats born from sham-immunized mothers. In conclusion, rEnolase maternal immunization before pregnancy provides offspring with protection against S. sobrinus-induced dental caries.

Clonorchis sinensis enolase: identification and biochemical characterization of a glycolytic enzyme from excretory/secretory products

Enolase plays a key role in energy metabolism and development of most organisms. We isolated a gene encoding enolase from Clonorchis sinensis (C. sinensis) adult cDNA library and expressed the recombinant protein in Escherichia coli. C. sinensis enolase (Csenolase) was identified as both an excretory/secretory product and a tegumental component of C. sinensis by western blot analysis. The transcriptional level of Csenolase was examined at adult worm, metacercaria, cercaria and egg of C. sinensis, and results showed that Csenolase is transcribed at the four life stages of C. sinensis while showing a significant higher expression level at the stage of adult worm. Immunohistochemical localization indicated that Csenolase was specifically deposited on the tegument of adult worm and cyst wall of metacercaria. Ligand blot assay revealed a specific characteristic of dose-dependent plasminogen-binding activity of Csenolase and kinetic parameters were explored using 2-phospho-D-glycerate (2-PGA) as the primary substrate by monitoring the conversion of nicotinamide-adenine dinucleotide (NADH) into nicotinamide adenine dinucleotide (NAD). In addition, Csenolase exhibited active enzyme activity in catalytic reactions while the anti-Csenolase serum inhibited the enzyme activity. In vitro incubation experiments revealed that Csenolase might play key roles in the growth of the parasites. In conclusion, Csenolase is an important glycolytic enzyme required for the development of C. sinensis, and may be a potential vaccine candidate and drug target against C. sinensis infection.

Elongation factor 1-alpha is released into the culture medium during growth of Giardia intestinalis trophozoites

The molecular pathogenesis of the intestinal parasite Giardia intestinalis is still not fully understood but excretory-secretory products have been suggested to be important during host-parasite interactions. Here we used SDS-PAGE gels and MALDI-TOF analysis to identify proteins released by Giardia trophozoites during in vitro growth. Serum proteins (mainly bovine serum albumin) in the growth medium, bind to the parasite surface and they are continuously released, which interfere with parasite secretome characterization. However, we identified two released Giardia proteins: elongation factor-1 alpha (EF-1α) and a 58 kDa protein, identified as arginine deiminase (ADI). This is the first description of EF-1α as a released/secreted Giardia protein, whereas ADI has been identified in an earlier secretome study. Two genes encoding EF-1α were detected in the Giardia WB genome 35 kbp apart with almost identical coding sequences but with different promoter and 3' regions. Promoter luciferase-fusions showed that both genes are transcribed in trophozoites. The EF-1α protein localizes to the nuclear region in trophozoites but it relocalizes to the cytoplasm during host-cell interaction. Recombinant EF-1α is recognized by serum from giardiasis patients. Our results suggest that released EF-1α protein can be important during Giardia infections.