Secretory Protease Research Articles

FRI0343 Acidification Enhances Acid Sensing Protein and Matrix Metalloproteinase Expression in Human Rheumatoid Fibroblast like Synoviocytes

BackgroundIn rheumatoid arthritis (RA), fibroblast-like synoviocytes (RAFLS) develop an aggressive phenotype, promoting cartilage damage and bone destruction through the secretion of proteolytic enzymes and cytokines. We have recently shown that...

Knocking Out Bcsas1 in Botrytis cinerea Impacts Growth, Development, and Secretion of Extracellular Proteins, Which Decreases Virulence

Pathogenic fungi usually secrete a series of virulence factors to the extracellular environment to facilitate infection. Rab GTPases play a central role in the secretory pathway. To explore the function of Rab/GTPase in filamentous fungi, we knocked out a Rab/GTPase family gene, Bcsas1, in Botrytis cinerea, an aggressive fungal pathogen that infects more than 200 plant species. A detailed analysis was conducted on the virulence and the secretory capability of the mutants. The results indicated that knockout of Bcsas1 inhibited hyphal development and reduced sporulation of B. cinerea on potato dextrose agar plates resulting in reduced virulence on various fruit hosts. Knocking out the Bcsas1 gene led to an accumulation of transport vesicles at the hyphal tip, significantly reduced extracellular protein content, and lowered the activity of polygalacturonase and xylanase in the extracellular medium. However, mutation of Bcsas1 did not affect the expression of genes encoding polygalacturonase and xylanase, suggesting the secretion of these two family enzymes was suppressed in the mutant. Moreover, a comparative analysis of the secretome provided further evidence that the disruption of Bcsas1 in mutant strains significantly depressed the secretion of polysaccharide hydrolases and proteases. The results indicate that Bcsas1, the Rab8/SEC4-like gene, plays a crucial role in development, protein secretion, and virulence of B. cinerea.

Complex 3D Models to Study Drug Targeting of Invadopodia

Metastasis is the main cause of death in cancer patients, and in spite of its significance, it is still incompletely understood. In order for cancer to be metastatic, it must undergo a sequence of events, termed as the metastatic cascade. The ability of cancer cells to migrate and invade surrounding tissue is a critical step in the metastasis and is often associated with the formation of specific cellular structures called invadopodia. Invadopodia are actin-based protrusions of tumour cells or transformed cells critically involved in protease secretion and targeting, and cytoskeletal rearrangements enabling cellular invasion. Anti-invadopodia therapy is a possible new field in anti-metastatic treatment. We propose here a novel model for drug discovery of anti-invadopodial compounds based on large scale screening of invadopodia formation in 2D setting followed by validation of the results in complex 3D matrices such as dermis-based matrix.

Effect of bovine apo-lactoferrin on the growth and virulence of Actinobacillus pleuropneumoniae.

Actinobacillus pleuropneumoniae (App) is a Gram-negative bacterium that causes porcine pleuropneumonia, leading to economic losses in the swine industry. Due to bacterial resistance to antibiotics, new treatments for this disease are currently being sought. Lactoferrin (Lf) is an innate immune system glycoprotein of mammals that is microbiostatic and microbicidal and affects several bacterial virulence factors. The aim of this study was to investigate whether bovine iron-free Lf (BapoLf) has an effect on the growth and virulence of App. Two serotype 1 strains (reference strain S4074 and the isolateBC52) and a serotype 7 reference strain (WF83) were analyzed. First, the ability of App to grow in iron-charged BLf was discarded because in vivo, BapoLf sequesters iron and could be a potential source of this element favoring the infection. The minimum inhibitory concentration of BapoLf was 14.62, 11.78 and 10.56µM for the strain BC52, S4074 and WF83, respectively. A subinhibitory concentration (0.8µM) was tested by assessing App adhesion to porcine buccal epithelial cells, biofilm production, and the secretion and function of toxins and proteases. Decrease in adhesion (24-42%) was found in the serotype 1 strains. Biofilm production decreased (27%) for only the strain 4074 of serotype 1. Interestingly, biofilm was decreased (60-70%) in the three strains by BholoLf. Hemolysis of erythrocytes and toxicity towards HeLa cells were not affected by BapoLf. In contrast, proteolytic activity in all strains was suppressed in the presence of BapoLf. Finally, oxytetracycline produced synergistic effect with BapoLf against App. Our results suggest that BapoLf affects the growth and several of the virulence factors in App.

Aliphatic fatty acids and esters: Inhibition of growth and exoenzyme production of Candida, and their cytotoxicity in vitro: Anti-Candida effect and cytotoxicity of fatty acids and esters

The secretion of extracellular phospholipases and proteinases of Candida has been described as a relevant virulence factor in human infections. Aliphatic fatty acids have antimicrobial properties, but the mechanism by which they affect the virulence factors of microorganisms, such as Candida, is still unclear, and there are a few reports about their toxicity. The current study investigated the in vitro antifungal activity, exoenzyme production and cytotoxicity of some aliphatic fatty acids and their ester derivatives against the Candida species. The minimum inhibitory concentration and minimum fungicidal concentrations of aliphatic medium-chain fatty acids, methyl and ethyl esters were performed using the CLSI M27-A3 method and the cytotoxicity assay was performed according to ISO 10993-5. The influence of these compounds in the inhibition of the production of hydrolytic enzymes, phospholipases and proteinases by Candida was also investigated. Data analysis was performed using the one-way ANOVA method (p≤0.05). In relation to the MIC against Candida species, the fatty acid with the best result was Lauric acid, although its ester derivatives showed no activity. The inhibition of phospholipase production was more significant than the inhibition of proteinase production by Candida. Tested fatty acids revealed more than 80% cell viability in their MIC concentrations. Additionally, a cell viability of 100% was reported at concentrations of anti-enzymatic effect. Therefore, the potential use of these fatty acids could be the basis for more antimicrobial tests.

Control of morphogenesis, protease secretion and gene expression in Candida albicans by the preferred nitrogen source ammonium.

Micro-organisms sense the availability of nutrients in their environment to control cellular behaviour and the expression of transporters and enzymes that are required for the utilization of these nutrients. In the pathogenic yeast Candida albicans, the preferred nitrogen source ammonium suppresses the switch from yeast to filamentous growth in response to certain stimuli, and it also represses the secretion of proteases, which are required for the utilization of proteins as an alternative nitrogen source. To investigate whether C. albicans senses the availability of ammonium in the extracellular environment or if ammonium uptake into the cell is required to regulate morphogenesis and gene expression, we compared the behaviour of wild-type cells and ammonium uptake-deficient mutants in the presence and absence of extracellular ammonium. Arginine-induced filamentous growth was suppressed by ammonium in the wild-type, but not in mutants lacking the ammonium permeases Mep1 and Mep2. Similarly, ammonium suppressed protease secretion and extracellular protein degradation in the wild-type, but not in mutants lacking the ammonium transporters. By comparing the gene expression profiles of C. albicans grown in the presence of low or high ammonium concentrations, we identified a set of genes whose expression is controlled by nitrogen availability. The repression of genes involved in the utilization of alternative nitrogen sources, which occurred under ammonium-replete conditions in the wild-type, was abrogated in mep1Δ mep2Δ mutants. These results demonstrate that C. albicans does not respond to the presence of sufficient amounts of the preferred nitrogen source ammonium by sensing its availability in the environment. Instead, ammonium has to be taken up into the cell to control morphogenesis, protease secretion and gene expression.

Improving biomass resource recycling capacity of Rubrivivax gelatinosus cultivated in wastewater through regulating the generation and use of energy

This paper investigated Mg2+ enhancement of biomass production through regulating the generation and use of energy in Rubrivivax gelatinosus wastewater treatment. Results showed that proper Mg2+ dosage range was 1.5–15 mg/L. With optimal Mg2+ dosage (10 mg/L), biomass production (5010 mg/L) was improved by 60%. Both protein and chemical oxygen demand (COD) removals reached above 90%. Biomass yield improved by 38%. Hydraulic retention time was shortened by 25%. Mechanism analysis indicated that as activator, Mg2+ promoted specifically isocitrate dehydrogenase (IDH) and Ca2+/Mg2+-ATPase activities in energy metabolism, and then improved the generation of adenosine triphosphate (ATP) and the use of ATP. This enhanced the secretion and activity of protease, protein and COD removals, and then led to more biomass production. With 10 mg/L Mg2+, IDH and Ca2+/Mg2+-ATPase activities, ATP production, protease activity were improved by 43.8%, 40.6%, 39.4% and 46.5%, respectively.

Sinomenine inhibits microglia activation and attenuates brain injury in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) causes morbidity and mortality and commonly follows the reperfusion after an ischemic event. Microglial activation mediated cytokine and protease secretion contributes to brain injury in ICH. Previous studies have shown that sinomenine possesses potent immunoregulatory properties. However, little is known about its exact role in ICH. In the present study, to investigate the effect of sinomenine on microglial cells inflammation, we treated ICH-challenged BV2 microglial cells with sinomenine in vitro, and explored its neuroprotection role in intracerebral hemorrhage in vivo. Changes in inflammatory cytokines, such as TNF-α, IL-1β and IL-6, reactive oxygen species (ROS) and NF-κB activation NF-κB were observed. In addition, the neurological deficit and cerebral water content of ICH mice were studied. The results demonstrated that sinomenine could inhibit the release of these cytokines and attenuate ROS production in a dose-dependent manner, and reduce NF-κB activation. Furthermore, sinomenine markedly inhibited cerebral water content and neurological deficit. In conclusion, our findings suggest that sinomenine played the protective effects through inhibition of microglial inflammation, and the findings also provided a novel therapy to treat ICH induced brain injury.

Anti-biofilm activity of Marula – A study with the standardized bark extract

Ethnopharmacological relevanceMarula (Sclerocarya birrea; family – Anacardiaceae) is an African plant, which enjoys wide socio-economic importance particularly in southern part of Africa. The fruits are consumed as food and also as alcoholic beverage (cream liquor). In different parts of Africa, the decoction of the bark is traditionally used for the treatment of dysentery, diarrhoea, and various other infectious conditions. The aim of the study was to investigate the anti-biofilm properties of the methanol extract of Marula bark (stem bark of Sclerocarya birrea), with a view towards combating the emergence of antimicrobial resistance often associated with bacterial biofilms. Materials and methodsThe standardized methanol extract was initially tested for its antimicrobial property. The crystal violet assay was used for evaluating anti-biofilm (biofilm formation by Pseudomonas aeuginosa) activity. Further in order to study the mechanism of anti-biofilm activity, the same was evaluated for understanding its role on various quorums sensing mediated phenomenon (swarming motility assay, protease and pyoverdin assay) that are known to be associated with the formation of biofilms and pathogenicity. ResultsThe methanol extract showed no inhibition of bacterial growth up to a concentration of 200µg/ml. Interestingly, the sample produced anti-biofilm activity (around 75% decrease; 100µg/ml) at sub-lethal concentration. Further it also significantly reduced the QS mediated swarming motility. The release of various virulent factors (protease and pyoverdin) was found to be lowered when pre-treated with the extract. ConclusionThe present study illustrates the anti-biofilm property Sclerocarya birrea. The standardized extract significantly disrupted the quorum sensing mediated production of biofilm formation and also inhibited swarming ability of the cells. The extract displayed a regulatory role on the secretion of protease and pyoverdin, two QS dependent pathogenic factors found in Pseudomonas aeruginosa. This study also validates the ethnobotanical use of Marula.

Mechanisms of buffer therapy resistance

Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.

Identification and characterization of novel granzyme in fish (971.1)

Granzymes are serine proteases released by cytoplasmic granules within cytotoxic T lymphocytes and natural killer (NK) cells. Granzymes induce apoptosis within virus‐infected and transformed cells. Information on the function of fish granzymes is limited, although granzyme‐like genes have been reported in several fishes. Here, we report the identification and characterization of a granzyme in ginbuna crucian carp, Carassius auratus langsdorfii, focusing on substrate specificity and gene expression after allo‐sensitization and bacterial infection.A full‐length granzyme cDNA, termed gcGranzyme was identified from ginbuna crucian carp. gcGranzyme molecule has trypsin‐like catalytic triad: His66, Asp109, and Ser201 residues, and active center: Ser201 residue. Phylogenetic analysis of deduced amino acids sequence revealed that gcGranzyme formed a cluster with human and mouse granzyme B (separate from the other members of the granzyme). gcGranzyme was secreted from the HeLa cells transfected with gcGranzyme as in mammals. Enzyme assay using recombinant gcGranzyme indicated that the enzyme hydrolyzed Bz‐Arg‐4Methyl‐Coumaryl‐7‐amide, suggesting that the gcGranzyme was different from mammalian granzyme B in substrate specificity.To investigate the role of gcGranzyme in cell‐mediated immunity in fish, we analyzed the gcGranzyme mRNA expression in allo‐sensitized fish. Expression level of gcGranzyme mRNA from CD8+ T cells was greatly elevated by allo‐sensitization. Furthermore, gcGranzyme mRNA expression in CD8+ T cells was also enhanced by the in vivo infection with intracellular bacteria, Edwardsiella tarda.These results suggest that newly found gcGranzyme is a novel secretory serine protease involved in cell‐mediated immunity in fish with similar structure to human granzyme B but different substrate specificity.

Environmental pH influences Candida albicans biofilms regarding its structure, virulence and susceptibility to fluconazole

Candida albicans colonizes sites with different environmental pH. However, it is unclear how these conditions can interfere on biofilms. This study aimed to evaluate the influence of environmental pH on behavior of C. albicans regarding its structure, virulence and susceptibility to fluconazole (FLZ). Minimal inhibitory concentration, minimal fungicidal concentration and time kill were used to evaluate the susceptibility to FLZ in planktonic cells under three pH values (4.0, 5.5, 7.0). These pH values were used for biofilms analysis. C. albicans ATCC 90028 was developed on poly(methlymethacrylate) resin for 48 h. Then, 2.56 μg/mL of FLZ was added to experimental groups for 24 h, and biofilms were analyzed by cell quantification, bioactivity, secretion of proteinases and phospholipases and structure. All data were analyzed by two-way ANOVA, followed by Tukey's test (α = 0.05). For planktonic cells, changes in environmental pH decreased the susceptibility to FLZ. C. albicans biofilms developed at pH 5.5 showed higher cell counts, bioactivity, bio-volume, average thickness and roughness coefficient (p < 0.05). In contrast, the presence of FLZ at pH 4.0 did not influence the structural parameters (p > 0.05), but increased secretion of proteinase and phospholipase (p < 0.05). Within the conditions studied, it was shown that environmental pH modulates the structure, virulence and susceptibility of C. albicans to FLZ.

A culture-based method for determining the production of secreted protease inhibitors

We have developed a culture-based method for determining the production of secreted protease inhibitors. The assay utilizes standard proteolysis detection plates to support microbial growth followed by infiltrating the plate with a protease and subsequently detecting the remaining protein by trichloroacetic acid (TCA) precipitation, or by bromocreosol green (BCG) or Ponseau S (PS) staining. The presence of a protease inhibitor can be observed in the form of a protected zone of protein around the protease inhibitor-producing strain. Using the protease inhibitors α-2-macroglobulin, aprotinin, leupeptin, and bestatin and the primary and secondary forms of Photorhabdus luminescens in combination with the protease trypsin, we were able to demonstrate that the assay is specific for the cognate inhibitor of the protease and for bacteria secreting protease inhibitors. In addition, when casein-containing plates were used, the size of the diffusion zone was inversely correlated with the molecular weight of the inhibitor allowing a relative estimation of the protease inhibitor molecular weight. This assay is useful for detecting the presence of microbial secreted protease inhibitors and may reveal their production by microorganisms that were not previously recognized to produce them.

A secretory multifunctional serine protease, DegP of Plasmodium falciparum, plays an important role in thermo‐oxidative stress, parasite growth and development

Plasmodium falciparum heat shock proteins and proteases are known for their indispensable roles in parasite virulence and survival in the host cell. They neutralize various host-derived stress responses that are deleterious for parasite growth and invasion. We report identification and functional characterization of the first DegP from an apicomplexan (P. falciparum). To determine the molecular identity and functions of the parasite-encoded DegP, we complemented the Escherichia coli degP null mutant with a putative PfdegP gene, and the results showed that PfDegP complements the growth defect of the temperature sensitive DegP-deficient mutant and imparts resistance to non-permissive temperatures and oxidative stress. Molecular interaction studies showed that PfDegP exists as a complex with parasite-encoded heat shock protein 70, iron superoxide dismutase and enolase. DegP expression is significantly induced in parasite culture upon heat shock/oxidative stress. Our data suggest that the PfDegP protein may play a role in the growth and development of P. falciparum through its ability to confer protection against thermal/oxidative stress. Antibody against DegP showed anti-plasmodial activity against blood-stage parasites in vitro, suggesting that PfDegP and its associated complex may be a potential focus for new anti-malarial therapies. ●PfDegP physically interacts with PfHsp70 and PfEno by anti-bait co-immunoprecipitation (View interaction) ●PfDegP physically interacts with PfEno, PfSod, PfOat, PfHsp70, PfLDH and PfGpi by anti-bait co-immunoprecipitation (View interaction) ●PfHsp-70 and PfDegP co-localize by fluorescence microscopy (View interaction) ●PfDegP physically interacts with PfOat, PfHsp70, PfEno, PfSod, PfGpi and PfLDH by surface plasmon resonance (View interaction) ●PfEno and PfDegP co-localize by fluorescence microscopy (View interaction) ●PfDegP and PfHsp70 co-localize by co-sedimentation through density gradient (View interaction).

When neutrophils meet T cells: Beginnings of a tumultuous relationship with underappreciated potential

Neutrophils play a key role in the innate immune system's response to infection. They eliminate microbes through phagocytosis, the production of ROS, and the secretion of various proteases and antimicrobial peptides. In addition, they influence adaptive immune responses by modulating B-cell antibody production, dendritic cell activation and anti-microbial CD4(+) and CD8(+) T-cell responses. Here we discuss the current knowledge of the reciprocal interactions between neutrophils and T cells. A special emphasis is put on their interaction with γδ T cells, which respond in the early stages of infection to produce a pivotal source of neutrophil-recruiting IL-17. Human peripheral blood γδ T cells are activated by microbe-derived and endogenous isoprenoid pyrophosphate antigens, the levels of which can be enhanced by the therapeutic application of aminobisphosphonates. We specifically discuss intriguing new evidence showing how pyrophosphates and aminobisphosphonates modulate the interplay between neutrophils and human γδ T cells.

Supporting a Role for the GTPase Rab7 in Prostate Cancer Progression

Invasion and subsequent metastasis is the major cause of death from most cancers including prostate cancer. Herein we report on the potential tumor suppressive properties of Rab7, a GTPase that regulates trafficking of lysosomes. The movement of lysosomes to the cell surface in response to environmental cues increases the secretion of proteinases and cell invasion. We determined that Troglitazone and other members of the Thiazolidinedione family inhibit cell-surface directed lysosome trafficking and cathepsin B secretion through a Rab7-dependent mechanism. Moreover, Rab7 shRNA expressing cells were found to be more invasive in vitro and in vivo. Increased invasiveness was accompanied by elevated expression of the c-Met receptor and prolonged downstream signaling, thereby supporting a role for Rab7 as a mediator of signaling down-regulation. Taken together, these results suggested that Rab7 acts as a negative regulator of prostate tumor growth and invasion, providing further evidence for its potential as a tumor suppressor.

Granule maturation in mast cells: Histamine in control

Mast cells are derived from committed progenitors that originate in the BM. They mature into histochemically distinguishable, metachromatic mast cells containing numerous cytoplasmic secretory granules. Accumulating evidence demonstrates that mast cell granule maturation is very tightly regulated by many factors including different granule components such as proteoglycans. In this issue of the European Journal of Immunology, Nakazawa et al. [Eur. J. Immunol. 2014. 44: 204-214] highlight a role for mast cell derived histamine as another factor critical for mast cell maturation. Using histidine decarboxylase (HDC) deficient mice that are unable to make histamine, they show poorly formed secretory granules and decreased secretory granule protease expression in peritoneal mast cells. Co-culturing BM-derived mast cells with fibroblasts normally drives granule maturation, but HDC-deficient BM-derived mast cells fail to do so. Exogenously provided histamine partly restores granule differentiation as evidenced by increased tryptase and chymase activity, and this is histamine receptor type H4 -dependent. However, H4 -deficient mice have intact granule formation in peritoneal mast cells, suggesting that when HDC is functional, the intrinsic histamine production is sufficient for most granule maturation processes and H4 is dispensable. This study highlights the role of histamine in the regulation of mast cell maturation, although the cytosolic target remains unknown.

TheAspergillus nidulansATM Kinase Regulates Mitochondrial Function, Glucose Uptake and the Carbon Starvation Response

Mitochondria supply cellular energy and also perform a role in the adaptation to metabolic stress. In mammals, the ataxia-telangiectasia mutated (ATM) kinase acts as a redox sensor controlling mitochondrial function. Subsequently, transcriptomic and genetic studies were utilized to elucidate the role played by a fungal ATM homolog during carbon starvation. In Aspergillus nidulans, AtmA was shown to control mitochondrial function and glucose uptake. Carbon starvation responses that are regulated by target of rapamycin (TOR) were shown to be AtmA-dependent, including autophagy and hydrolytic enzyme secretion. AtmA also regulated a p53-like transcription factor, XprG, inhibiting starvation-induced XprG-dependent protease secretion and cell death. Thus, AtmA possibly represents a direct or indirect link between mitochondrial stress, metabolism, and growth through the influence of TOR and XprG function. The coordination of cell growth and division with nutrient availability is crucial for all microorganisms to successfully proliferate in a heterogeneous environment. Mitochondria supply cellular energy but also perform a role in the adaptation to metabolic stress and the cross-talk between prosurvival and prodeath pathways. The present study of Aspergillus nidulans demonstrated that AtmA also controlled mitochondrial mass, function, and oxidative phosphorylation, which directly or indirectly influenced glucose uptake. Carbon starvation responses, including autophagy, shifting metabolism to the glyoxylate cycle, and the secretion of carbon scavenging enzymes were AtmA-dependent. Transcriptomic profiling of the carbon starvation response demonstrated how TOR signaling and the retrograde response, which signals mitochondrial dysfunction, were directly or indirectly influenced by AtmA. The AtmA kinase was also shown to influence a p53-like transcription factor, inhibiting starvation-induced XprG-dependent protease secretion and cell death. Therefore, in response to metabolic stress, AtmA appears to perform a role in the regulation of TOR signaling, involving the retrograde and SnfA pathways. Thus, AtmA may represent a link between mitochondrial function and cell cycle or growth, possibly through the influence of the TOR and XprG function.

Screening of Compounds from an FDA-Approved Drug Library for the Ability to Inhibit Aspartic Protease Secretion from the Pathogenic Yeast Candida albicans

The pathogenic fungus Candida albicans causes disseminated candidiasis with a poor prognosis in immunocompromised hosts. Secreted aspartyl protease (Sap) from the microorganism acts as a hydrolase to facilitate invasion into host tissues. Inhibition of Candida Sap activity could be a new treatment strategy for candidiasis. In the present study, we screened compounds from an FDA-approved drug library, Screen-Well, for their ability to inhibit Candida Sap activity. Sixteen compounds (piroxicam, carbidopa, nisoldipine, cerivastatin, fluvastatin, mycophenolic acid, rapamycin, bleomycin, bortezomib, 5-fluorouracil, floxuridine, fumagillin, pentamidine, albendazole, fenbendazole, and amprenavir) inhibited Sap activity in a dose-dependent manner in vitro, although strain differences in the activity of the compounds were observed. Our study shows that existing drug compounds have the potential to inhibit Sap activity.

Aggregatibacter actinomycetemcomitans - a tooth killer?

Strong evidence is available on Aggregatibacter actinomycetemcomitans (A.a) on its role as the causative agent of localised juvenile periodontitis (LJP), a disease characterised by rapid destruction of the tooth-supporting tissues. This organism possesses a large number of virulence factors with a wide range of activities which enable it to colonise the oral cavity, invade periodontal tissues, evade host defences, initiate connective tissue destruction and interfere with tissue repair. Adhesion to epithelial and tooth surfaces is dependent on the presence of surface proteins and structures such as microvesicles and fimbriae. Invasion has been demonstrated in vivo and in vitro. The organism has a number of means of evading host defences which include: (i) production of leukotoxin; (ii) producing immunosuppressive factors; (iv) secreting proteases capable of cleaving IgG; and (v) producing Fc-binding.