Streptococcal Pyrogenic Exotoxin Research Articles

Superantigen influence in conjunction with cytokine polymorphism potentiates autoimmunity in systemic lupus erythematosus patients.

Risk posed by microbial superantigens in triggering or exacerbating SLE in genetically predisposed individuals, thereby altering the response to its treatment strategies, has not been studied. Using streptococcal pyrogenic exotoxin A and staphylococcal enterotoxin B as prototype superantigens, we have demonstrated that they profoundly affect the magnitude of polyclonal T cell response, particularly CD4(+) T cells and expression of CD45RA and CD45RO, and cytokine secretion in vitro in SLE patient PBMCs. Also, reduced proportions of FoxP3 expressing CD4(+)CD25(+) T cells were detected in SLE as compared to healthy control PBMCs. Furthermore, polymorphism in IL-10 and TGF-β showed significant association with SLE in our study population. These results indicate that accumulation of superantigen-reactive T cells and cytokine polymorphism may cause disease exacerbation, relapse, or therapeutic resistance in SLE patients. Attempts to contain colonizing and/or superantigen-producing microbial agents in SLE patients in addition to careful monitoring of their therapy may be worthwhile in decreasing disease severity or preventing frequent relapses. The study suggests that superantigen interference in conjunction with cytokine polymorphism may play a role in immune dysregulation, thereby contributing to autoimmunity in SLE. Therefore, changes in T cell phenotypes and cytokine secretion might be good indicators of therapeutic efficacy in these patients.

Changes in Antibody Levels during and following an Episode of Acute Adenolymphangitis (ADL) among Lymphedema Patients in Léogâne, Haiti.

IntroductionEpisodes of acute adenolymphangitis (ADL) are often the first clinical sign of lymphatic filariasis (LF). They are often accompanied by swelling of the affected limb, inflammation, fever, and general malaise and lead to the progression of lymphedema. Although ADL episodes have been studied for a century or more, questions still remain as to their etiology. We quantified antibody levels to pathogens that potentially contribute to ADL episodes during and after an episode among lymphedema patients in Léogâne, Haiti. We estimated the proportion of ADL episodes hypothesized to be attributed to specific pathogens.MethodsWe measured antibody levels to specific pathogens during and following an ADL episode among 41 lymphedema patients enrolled in a cohort study in Léogâne, Haiti. We calculated the absolute and relative changes in antibody levels between the ADL and convalescent time points. We calculated the proportion of episodes that demonstrated a two-fold increase in antibody level for several bacterial, fungal, and filarial pathogens.ResultsOur results showed the greatest proportion of two-fold changes in antibody levels for the carbohydrate antigen Streptococcus group A, followed by IgG2 responses to a soluble filarial antigen (BpG2), Streptococcal Pyrogenic Exotoxin B, and an antigen for the fungal pathogen Candida. When comparing the median antibody level during the ADL episode to the median antibody level at the convalescent time point, only the antigens for Pseudomonas species (P-value = 0.0351) and Streptolysin O (P-value = 0.0074) showed a significant result.ConclusionAlthough our results are limited by the lack of a control group and few antibody responses, they provide some evidence for infection with Streptococcus A as a potential contributing factor to ADL episodes. Our results add to the current evidence and illustrate the importance of determining the causal role of bacterial and fungal pathogens and immunological antifilarial response in ADL episodes.

T-cell activation or tolerization: the Yin and Yang of bacterial superantigens.

Bacterial superantigens (SAg) are exotoxins from pathogens which interact with innate and adaptive immune cells. The paradox that SAgs cause activation and inactivation/anergy of T-cells was soon recognized. The structural and molecular events following SAg binding to antigen presenting cells (APCs) followed by crosslinking of T-cell receptors were characterized in detail. Activation, cytokine burst and T-cell anergy have been described in vitro and in vivo. Later it became clear that SAg-induced T-cell anergy is in part caused by SAg-dependent activation of T-regulatory cells (Tregs). Although the main focus of analyses was laid on T-cells, it was also shown that SAg binding to MHC class II molecules on APCs induces a signal, which leads to activation and secretion of pro-inflammatory cytokines. Accordingly APCs are mandatory for T-cell activation. So far it is not known, whether APCs play a role during SAg-triggered activation of Tregs. We therefore tested whether in SAg (Streptococcal pyrogenic exotoxin A) -treated APCs an anti-inflammatory program is triggered in addition. We show here that not only the anti-inflammatory cytokine IL-10 and the co-inhibitory surface molecule PD-L1 (CD274) but also inhibitory effector systems like indoleamine 2,3-dioxygenase (IDO) or intracellular negative feedback loops (suppressor of cytokine signaling molecules, SOCS) are induced by SAgs. Moreover, cyclosporine A completely prevented induction of this program. We therefore propose that APCs triggered by SAgs play a key role in T-cell activation as well as inactivation and induction of Treg cells.

Non-proteolytic functions of microbial proteases increase pathological complexity.

Proteases are enzymes that catalyse hydrolysis of peptide bonds thereby controlling the shape, size, function, composition, turnover and degradation of other proteins. In microbes, proteases are often identified as important virulence factors and as such have been targets for novel drug design. It is emerging that some proteases possess additional non‐proteolytic functions that play important roles in host epithelia adhesion, tissue invasion and in modulating immune responses. These additional “moonlighting” functions have the potential to obfuscate data interpretation and have implications for therapeutic design. Moonlighting enzymes comprise a subcategory of multifunctional proteins that possess at least two distinct biological functions on a single polypeptide chain. Presently, identifying moonlighting proteins relies heavily on serendipitous empirical data with clues arising from proteins lacking signal peptides that are localised to the cell surface. Here, we describe examples of microbial proteases with additional non‐proteolytic functions, including streptococcal pyrogenic exotoxin B, PepO and C5a peptidases, mycoplasmal aminopeptidases, mycobacterial chaperones and viral papain‐like proteases. We explore how these non‐proteolytic functions contribute to host cell adhesion, modulate the coagulation pathway, assist in non‐covalent folding of proteins, participate in cell signalling, and increase substrate repertoire. We conclude by describing how proteomics has aided in moonlighting protein discovery, focusing attention on potential moonlighters in microbial exoproteomes.

Application of the C3-binding motif of streptococcal pyrogenic exotoxin B to protect mice from invasive group a streptococcal infection.

Group A streptococcus (GAS) is an important human pathogen that produces several extracellular exotoxins to facilitate invasion and infection. Streptococcal pyrogenic exotoxin B (SPE B) has been demonstrated to be an important virulence factor of GAS. Our previous studies indicate that SPE B cleaves complement 3 (C3) and inhibits the activation of complement pathways. In this study, we constructed and expressed recombinant fragments of SPE B to examine the C3-binding site of SPE B. Using enzyme-linked immunosorbent assays and pull-down assays, we found that the C-terminal domain, containing amino-acid residues 345–398, of SPE B was the major binding site of human serum C3. We further identified a major, Ala376-Pro398, and a minor C3-binding motif, Gly346-Gly360, that both mediated the binding of C3 complement. Immunization with the C3-binding motifs protected mice against challenge with a lethal dose of non-invasive M49 strain GAS but not invasive M1 strains. To achieve higher efficiency against invasive M1 GAS infection, a combination of synthetic peptides derived from C-terminal epitope of streptolysin S (SLSpp) and from the major C3-binding motif of SPE B (PP6, Ala376-Pro398) was used to elicit specific immune response to those two important streptococcal exotoxins. Death rates and the severity of skin lesions decreased significantly in PP6/SLSpp-immunized mice that were infected with invasive M1 strains of GAS. These results indicate a combination of the C3-binding motif of SPE B and the protective epitope of SLS could be used as a subunit vaccine against invasive M1 strains group A streptococcal infection.

Acute Poststreptococcal Glomerulonephritis: The Most Common Acute Glomerulonephritis

Acute Poststreptococcal Glomerulonephritis: The Most Common Acute Glomerulonephritis

Unique genomic arrangements in an invasive serotype M23 strain of Streptococcus pyogenes identify genes that induce hypervirulence.

The first genome sequence of a group A Streptococcus pyogenes serotype M23 (emm23) strain (M23ND), isolated from an invasive human infection, has been completed. The genome of this opacity factor-negative (SOF(-)) strain is composed of a circular chromosome of 1,846,477 bp. Gene profiling showed that this strain contained six phage-encoded and 24 chromosomally inherited well-known virulence factors, as well as 11 pseudogenes. The bacterium has acquired four large prophage elements, ΦM23ND.1 to ΦM23ND.4, harboring genes encoding streptococcal superantigen (ssa), streptococcal pyrogenic exotoxins (speC, speH, and speI), and DNases (spd1 and spd3), with phage integrase genes being present at one flank of each phage insertion, suggesting that the phages were integrated by horizontal gene transfer. Comparative analyses revealed unique large-scale genomic rearrangements that result in genomic rearrangements that differ from those of previously sequenced GAS strains. These rearrangements resulted in an imbalanced genomic architecture and translocations of chromosomal virulence genes. The covS sensor in M23ND was identified as a pseudogene, resulting in the attenuation of speB function and increased expression of the genes for the chromosomal virulence factors multiple-gene activator (mga), M protein (emm23), C5a peptidase (scpA), fibronectin-binding proteins (sfbI and fbp54), streptolysin O (slo), hyaluronic acid capsule (hasA), streptokinase (ska), and DNases (spd and spd3), which were verified by PCR. These genes are responsible for facilitating host epithelial cell binding and and/or immune evasion, thus further contributing to the virulence of M23ND. In conclusion, strain M23ND has become highly pathogenic as the result of a combination of multiple genetic factors, particularly gene composition and mutations, prophage integrations, unique genomic rearrangements, and regulated expression of critical virulence factors.

Development of a recombinant fusion protein vaccine formulation to protect against Streptococcus pyogenes

Diseases resulting from infection by group A streptococcus (GAS) are an increasing burden on global health. A novel vaccine was developed targeting infection by Streptococcus pyogenes. The vaccine incorporates a recombinant fusion protein antigen (SpeAB) which was engineered by combining inactive mutant forms of streptococcal pyrogenic exotoxin A (SpeA) and streptococcal pyrogenic exotoxin B (SpeB) from S. pyogenes. A rational, scientific approach to vaccine development was utilized to determine optimal formulation conditions with aluminum adjuvants. Investigations of the pH stability profile of SpeAB concluded the antigen was most stable near pH 8. Incorporation of the stabilizers sucrose and mannitol significantly enhanced the stability of the antigen. Vaccines were formulated in which most of the SpeAB was adsorbed to the adjuvant or remained in solution. A SpeAB vaccine formulation, stabilized with sucrose, in which the antigen remains adsorbed to the aluminum adjuvant retained the greatest potency as determined by evaluation of neutralizing antibody responses in mice. This vaccine has great potential to provide a safe and effective method for prevention of GAS disease.

Control of established colon cancer xenografts using a novel humanized single chain antibody-streptococcal superantigen fusion protein targeting the 5T4 oncofetal antigen.

Superantigens (SAgs) are microbial toxins that cross-link T cell receptors with major histocompatibility class II (MHC-II) molecules leading to the activation of large numbers of T cells. Herein, we describe the development and preclinical testing of a novel tumor-targeted SAg (TTS) therapeutic built using the streptococcal pyrogenic exotoxin C (SpeC) SAg and targeting cancer cells expressing the 5T4 tumor-associated antigen (TAA). To inhibit potentially harmful widespread immune cell activation, a SpeC mutation within the high-affinity MHC-II binding interface was generated (SpeCD203A) that demonstrated a pronounced reduction in mitogenic activity, yet this mutant could still induce immune cell-mediated cancer cell death in vitro. To target 5T4+ cancer cells, we engineered a humanized single chain variable fragment (scFv) antibody to recognize 5T4 (scFv5T4). Specific targeting of scFv5T4 was verified. SpeCD203A fused to scFv5T4 maintained the ability to activate and induce immune cell-mediated cytotoxicity of colorectal cancer cells. Using a xenograft model of established human colon cancer, we demonstrated that the SpeC-based TTS was able to control the growth and spread of large tumors in vivo. This required both TAA targeting by scFv5T4 and functional SAg activity. These studies lay the foundation for the development of streptococcal SAgs as ‘next-generation’ TTSs for cancer immunotherapy.

Functional overexpression and purification of a codon optimized synthetic four superantigens in Escherichia coli: Production of superantigens with improved safety and efficacy for cancer immunotherapy (LB582)

Bacterial superantigens (SAGs) are potent T cell stimulatory molecules and comprise a large family of disease‐associated proteins. The best‐characterized members of the superantigen family are staphylococcal enterotoxins (SEs), which are secreted by Staphylococcus aureus, and streptococcal pyrogenic exotoxins (SPEs), which are secreted by Streptococcus pyogenes Unlike conventional antigens they are not processed internally by antigen presenting cells (APC), and are thus not displayed as peptide antigen in the peptide‐binding groove of the MHC class II molecule. Superantigens bind to APCs on the outside of the MHC class II molecule and to T cells via the external face of the T cell receptor (TCR). This enables them to activate up to 20% of resting T cells, whilst conventional antigen presentation results in the activation of 0.001‐ 0.0001% of the T cell population. These biological properties of superantigens make them very attractive for use in immunotherapy.In this study, four synthetic genes coding for four different superantigens, SEA, SEB, TSST‐1 and SPEA were codon‐optimised and synthesized for maximum expression in E. coli using the vector pET28a.Our work indicated that in all cases the recombinant superantigens were expressed to 40% of the total host protein. We managed to optimise the condition to obtain 20% of the recombinant superantigens in a soluble form. The purification of the soluble His‐tagged recombinant superantigens have been achieved in a single step by Ni2+ charged column chromatography.The superantigenicity of each synthetic recombinant SEA, SEB, TSST‐1 and SPEA was determined by 2 methods. First method includes 3H‐thymidine incorporation assay as a measure of T‐cell proliferation i.e. T‐cell stimulation by modified SAGs. The second part of the superantigenicity assays includes measurement of cytokines produced by peripheral blood cells.The successful cloning and expression of four codon optimised synthetic superantigens genes will provide the recombinant protein for production of safe superantigen for cancer immunotherapy.Grant Funding Source: Anti‐doping lab‐Qatar

スーパー抗原関与の検討を行った急性感染性電撃性紫斑病の1例

急性感染性電撃性紫斑病（acute infectious purpura fluminans: AIPF）は，感染を契機に敗血症性ショック，播種性血管内凝固症候群（disseminated intravascular coagulation: DIC）に至り，四肢顔面の限局性紫斑を呈する死亡率の高い稀な疾患であるが，その病態については十分に解明されていない。我々は文献的考察に加え，患者血清中のスーパー抗原を測定し，AIPFの病態について考察したので報告する。症例は生来健康な74歳の女性。意識障害を主訴に当院に搬送された。入院6時間後に敗血症性ショックに至り，同時に四肢顔面の限局性紫斑が出現した。第4病日には紫斑部が表皮剥離し，第9病日には紫斑部は乾性壊疽に至った。第5病日に血液培養で肺炎球菌が確認され，AIPFと診断し集中治療管理を行ったが，第14病日，消化管ないし尿路感染による敗血症性ショックに再度至り，第16病日に死の転帰に至った。我々は，紫斑，表皮剥離などの急激な皮膚症状を引き起こし，敗血症性ショックに至る臨床像からAIPFの病態にスーパー抗原の関与を疑い，その関連性を検討した。黄色ブドウ球菌性AIPFとスーパー抗原の関連性を示唆したKravitzらの報告を参考に患者血清中のブドウ球菌性スーパー抗原（Staphylococcal enterotoxin A, B, C: SEA, SEB, SEC），レンサ球菌性スーパー抗原（Streptococcal pyrogenic exotoxin A: SPEA，toxic shock syndrome toxin-1: TSST-1）を測定したが，いずれも検出することはできなかった。今回測定できていない他のスーパー抗原も含め，AIPFとスーパー抗原の関連性について今後も検討していく必要があると考えられる。

Outbreak of Streptococcus pyogenes emm type 58 in a high dependency unit of a level-1 trauma center of India

Background and Aims:Group A Streptococcus (GAS) can cause illnesses ranging from self-limited to severe, life-threatening, invasive infections. The objective of the following study was to investigate a suspected Streptococcus pyogenes outbreak in a high dependency unit (HDU) of our trauma center.Materials and Methods:All the isolates of beta hemolytic Streptococci were identified by standard microbiological methods, Vitek 2 system and latex agglutination tests. Antimicrobial susceptibility testing was performed as recommended by Clinical Laboratory Standards Institute. Exotoxin genes, including speA, speB, speC, speF, smeZ, ssa, speG, speH, speJ, speL, speM and speI were detected by polymerase chain reaction (PCR). The emm types of isolates of S. pyogenes were determined by sequencing the variable 5’ end of emm gene after amplification by PCR.Results:In a 28 bedded poly-trauma ward with a four bedded HDU three out of four patients developed S. pyogenes emm type 58 infection. The strain was macrolide and tetracycline resistant and produced the Streptococcal pyrogenic exotoxins speB, speC, speG, speF and smeZ. Surveillance sampling was done for investigation from patients, health-care workers and environmental samples.Conclusion:An outbreak of GAS infections was established caused by the uncommonly reported emm type 58. The outbreak was controlled by prompt treatment, intensive surveillance, feedback and training.

Streptococcal SpeB Cleaved PAR-1 Suppresses ERK Phosphorylation and Blunts Thrombin-Induced Platelet Aggregation

BackgroundThe family of 4 related protease-activated receptors (PAR-1, 2, 3 & 4) expressed by mammalian cells allow to sense for and react to extracellular proteolytic activity. Since major human bacterial pathogens secret a wide array of protease(-s) we investigated whether they interfere with human PAR function. Methodology/Principal FindingsSupernatants from cultures of major human bacterial pathogens were assayed for the presence of protease(-s) capable to cleave overexpressed human PAR-1, 2, 3 and 4 reporter constructs. Group A streptococcus (GAS) was found to secret a PAR-1-cleaving protease. Experiments involving genetical and pharmacological gain and loss of function identified streptococcal pyrogenic exotoxin B SpeB as the protease responsible. On the host’s side analysis of overexpressed PAR-1 carrying alanine substitutions and deletions showed the amino acid residue leucine44 on PAR-1’s extracellular N-terminus to be the only cleavage site. Complementary studies on endogenously expressed PAR-1 using PAR-1 blocking antibodies further supported our conclusion. Through PAR-1 cleavage SpeB efficiently blunted thrombin-induced induction of the ERK-pathway in endothelial cells and prevented platelets aggregation in response to thrombin. Conclusions/SignificanceOur results identify a novel function of the streptococcal virulence factor SpeB. By cleaving human PAR-1 at the N-terminal amino acid residue leucine44 SpeB rendered endothelial cells unresponsive to thrombin and prevented human platelets from thrombin-induced aggregation. These results suggest that by blunting PAR-1 signaling, SpeB modulates various innate host responses directed against invasive GAS potentially helping the invasive bacteria to escape. This may allow to tailor additional treatments in the future since upon invasion of the blood stream endothelial cells as well as platelets and mononuclear cells respond to PAR-1 agonists aiming to prevent further bacterial dissemination.

Staphylococcal and Streptococcal Superantigens: Basic Biology of Conserved Protein Toxins

Staphylococcus aureus and Streptococcus pyogenes are gram-positive bacteria that possess great pathogenic potential in humans, causing numerous maladies such as arthritis, cutaneous infections, endocarditis, enterocolitis, food poisoning, pharyngitis, pneumonia, rheumatic fever, surgical site infections, and toxic shock. These prevalent pathogens produce various virulence factors that include the staphylococcal enterotoxins (SEs), toxic shock syndrome toxin-1 (TSST-1), and streptococcal pyrogenic exotoxins (SPEs). Minute (picomolar) amounts of these structurally-similar superantigens (SAgs) elicit high levels of proinflammatory cytokines and chemokines that can induce fever, hypotension, and lethal shock. In vitro and in vivo models have provided important tools for studying the biological effects of, and potential vaccines plus therapeutics against, these related protein toxins. This review will delve into the known physical and biological properties of the SEs, TSST-1, and SPEs. The reader will hopefully derive a general appreciation of these wonderfully-complex, structurally-similar toxins produced by S. aureus and S. pyogenes.

P159 Invasive group A streptococcal disease in the UK, 2008–2012 and molecular characterisation of isolates during enhanced surveillance

A potent basic superantigen (designated streptococcal pyrogenic exotoxin X, SPEX/SMEZ3) was purified to homogeneity from culture supernatants of a Streptococcus pyogenes scarlatina strain of type 12 (genotype speA−, speC−) and characterized. Sequence alignments revealed SPEX to be an allele of the streptococcal mitogens type Z (SMEZ). The N-terminal amino acid sequence of SPEX was found with LEVDNNSLLR to be identical to the recently described acidic superantigen SMEZ. Although SPEX/SMEZ genes were present in all of the streptococcal strains tested, a toxin production could only be detected in a small number of strains. The produced toxin concentration in the culture supernatants of positive strains differed between 0 and 20 ng ml−1. The purified SPEX stimulated human T-lymphocytes with Vβ8 specificity at extremely low concentrations (lower than 100 pg ml−1).

Acute poststreptococcal glomerulonephritis with acute interstitial nephritis related to streptococcal pyrogenic exotoxin B.

A 20-year-old man presented with symptoms of edema. Three weeks prior to admission, he experienced an upper respiratory tract infection. On admission, blood pressure was 177/118 mmHg. Initial laboratory investigations revealed serum creatinine, 170 µmol/L; complement C3, 130 mg/L and antistreptolysin O titer, 538 IU/mL (reference, <239 IU/mL). Urinalysis showed nephrotic range proteinuria and hematuria. A percutaneous kidney biopsy was performed. Light microscopy contained 20 glomeruli, 4 of which were globally sclerotic and 1 of which showed cellular crescent formation. Diffuse endocapillary proliferative glomerulonephritis was identified (Figure 1A). Forty percent of the interstitium was infiltrated by inflammatory cells (Figure 1B). Immunofluorescent staining revealed complement C3, mainly on capillary walls. Fig. 1. (A and B) Findings of the kidney biopsy. Hematoxylin and eosin-stained section showing diffuse endocapillary proliferation with massive infiltration of neutrophils (A) and inflammatory cells infiltration in the cortical interstitium (B). (C–F ... Acute poststreptococcal glomerulonephritis (APSGN) with acute interstitial nephritis (AIN) was diagnosed. We administered methylprednisolone pulse therapy (1 g/day) for 3 days, followed by prednisolone at 80 mg/day. The serum creatinine level declined to 74 µmol/L and proteinuria decreased to <1 g/day. Transient type 4 renal tubular acidosis was observed during steroid treatment. AIN is found in the infectious diseases of children, particularly in streptococcal infection [1]. We investigated the localization of two streptococcal antigens, streptococcal pyrogenic exotoxin B (SPEB) and nephritis-associated plasmin receptor (NAPlr), using an anti-SPEB antibody (Abcam, Cambridge, MA) and a fluorescein isothiocyanate-conjugated anti-NAPlr antibody [1F10] (Abcam). Although NAPlr was not detected, SPEB was positive in the interstitium as well as glomeruli (Figure 1C–F). Chang et al. [2] reported a case of streptococcal infection-related AIN, in which SPEB was found in both tubular epithelial cells and interstitium. In the present case, negative results were obtained for SPEB in tubular epithelial cells. Similarly, SPEB and its precursors have been detected only in glomeruli and interstitium in the rat kidney [3]. SPEB has been reported in association with the pathogenesis of APSGN. The mechanisms of leukocyte infiltration could be mediated by chemotactic effects and the migration inhibitor factor-like activities of SPEB [3]. SPEB also induces proliferation of human mononuclear leukocytes [4]. SPEB may be one of the causes of streptococcal infection-related AIN.

Group A Streptococcal Cysteine Protease Cleaves Epithelial Junctions and Contributes to Bacterial Translocation

Group A Streptococcus (GAS) translocates across the host epithelial barrier. Streptococcal pyrogenic exotoxin B (SpeB) directly cleaves junctional proteins. The proteolytic efficacy of SpeB allows GAS to translocate across the epithelial barrier. SpeB-mediated dysfunction of the epithelial barrier may have important implications for not only bacterial invasion but also dissemination of other virulence factors throughout intercellular spaces. Group A Streptococcus (GAS) is an important human pathogen that possesses an ability to translocate across the epithelial barrier. In this study, culture supernatants of tested GAS strains showed proteolytic activity against human occludin and E-cadherin. Utilizing various types of protease inhibitors and amino acid sequence analysis, we identified SpeB (streptococcal pyrogenic exotoxin B) as the proteolytic factor that cleaves E-cadherin in the region neighboring the calcium-binding sites within the extracellular domain. The cleaving activities of culture supernatants from several GAS isolates were correlated with the amount of active SpeB, whereas culture supernatants from an speB mutant showed no such activities. Of note, the wild type strain efficiently translocated across the epithelial monolayer along with cleavage of occludin and E-cadherin, whereas deletion of the speB gene compromised those activities. Moreover, destabilization of the junctional proteins was apparently relieved in cells infected with the speB mutant, as compared with those infected with the wild type. Taken together, our findings indicate that the proteolytic efficacy of SpeB in junctional degradation allows GAS to invade deeper into tissues.

Percutaneous sclerotherapy of sialoceles after parotidectomy with fibrin glue, OK-432, and bleomycin

We evaluated the curative effect of fibrin glue combined with OK-432 (streptococcal pyrogenic exotoxin A, Picibanil™) and bleomycin on 9 patients with sialoceles after parotidectomy. The primary lesions included pleomorphic adenomas in 6 cases and Warthin's tumours in 3 cases. After a sialocele had been diagnosed each patient had repeated aspirations and pressure dressings for 3–4 weeks, but these treatments failed. The patients were then treated with percutaneous sclerotherapy with the injection of fibrin glue 8–10ml combined with OK-432 5mg and bleomycin 15mg. All the sialoceles disappeared completely after a single procedure in 2–3 weeks. The patients have been followed up for more than 6 months with no evidence of recurrent sialocele or injury to the facial nerve related to sclerotherapy. This simple, safe technique can be successfully used to treat sialoceles after parotidectomy.

Partial loss of CovS function in Streptococcus pyogenes causes severe invasive disease

BackgroundCovRS (or CsrRS) is a two-component regulatory system that regulates the production of multiple virulence factors in Streptococcus pyogenes. covS mutations are often found in isolates recovered from mice that have been experimentally infected with S. pyogenes and covS mutations enhance bacterial virulence in an invasive infection mouse model. In addition, covS mutations were detected more frequently in a panel of clinical isolates from severe invasive streptococcal infections than those from non-severe infections. Thus, covS mutations may be associated with the onset of severe invasive infections.ResultsKnown covS mutations were divided into two groups: (i) frameshift mutations that caused a deletion of functional regions and (ii) point mutations that caused single (or double) amino acid(s) substitutions. Frameshift mutations are frequent in mouse-passaged isolates, whereas point mutations are frequent in clinical isolates. The functions of CovS proteins with a single amino acid substitution in clinical isolates were estimated based on the streptococcal pyrogenic exotoxin B (SpeB) production and NAD+-glycohydrolase (NADase) activity, which are known to be regulated by the CovRS system. Point mutations partially, but not completely, impaired the function of the covS alleles. We also investigated some of the benefits that a partial loss of function in covS alleles with point mutations might confer on clinical isolates. We found that covS knockout mutants (ΔcovS strains) had an impaired growth ability in a normal atmosphere in Todd Hewitt broth compared with parental isolates having wild-type or point-mutated covS.ConclusionsThe loss of CovS proteins in S. pyogenes may confer greater virulence, but bacteria may also lose the ability to respond to certain external signals recognized by CovS. Therefore, point mutations that retain the function of CovS and confer hypervirulence may have natural selective advantages.

A Natural Inactivating Mutation in the CovS Component of the CovRS Regulatory Operon in a Pattern D Streptococcal pyogenes Strain Influences Virulence-associated Genes*

A skin-tropic invasive group A Streptococcus pyogenes (GAS) strain, AP53, contains a natural inactivating mutation in the covS gene (covS(M)) of the two-component responder (CovR)/sensor (CovS) gene regulatory system. The effects of this mutation on specific GAS virulence determinants have been assessed, with emphasis on expression of the extracellular protease, streptococcal pyrogenic exotoxin B (SpeB), capsular hyaluronic acid, and proteins that allow host plasmin assembly on the bacterial surface, viz. a high affinity plasminogen (Pg)/plasmin receptor, Pg-binding group A streptococcal M protein (PAM), and the human Pg activator streptokinase. To further illuminate mechanisms of the functioning of CovRS in the virulence of AP53, two AP53 isogenic strains were generated, one in which the natural covS(M) gene was mutated to WT-covS (AP53/covS(WT)) and a strain that contained an inactivated covR gene (AP53/ΔcovR). Two additional strains that do not contain PAM, viz. WT-NS931 and NS931/covS(M), were also employed. SpeB was not measurably expressed in strains containing covR(WT)/covS(M), whereas in strains with natural or engineered covR(WT)/covS(WT), SpeB expression was highly up-regulated. Alternatively, capsule synthesis via the hasABC operon was enhanced in strain AP53/covS(M), whereas streptokinase expression was only slightly affected by the covS inactivation. PAM expression was not substantially influenced by the covS mutation, suggesting that covRS had minimal effects on the mga regulon that controls PAM expression. These results demonstrate that a covS inactivation results in virulence gene alterations and also suggest that the CovR phosphorylation needed for gene up- or down-regulation can occur by alternative pathways to CovS kinase.