Caractérisation de la zinc métalloprotéase de Streptococcus suis sérotype 2

S. suis est un important pathogène du porc et un agent zoonotique causant méningites, morts soudaines et chocs septiques. Bien que plusieurs facteurs ont été décrits comme étant impliqués dans la virulence de S. suis, les premières étapes de sa pathogénèse restent peu connues. Parmi ces facteurs, il y a la zinc métalloprotéase de S. suis sérotype 2, qui a été décrite comme une IgA1 protéase ayant un rôle critique dans la virulence de S. suis sérotype 2. De plus, cette protéine a été démontrée comme étant un antigène protecteur dans un modèle murin. Cependant des résultats contradictoires ont été obtenus et l’activité IgA protéase de S. suis sérotype 2 est remise en question. De plus, des études phylogénétiques ont permis de démontrer que la zinc métalloprotéase de S. suis est plutôt homologue à la protéine ZmpC de S. pneumoniae, protéine n’ayant pas d’activité IgA protéase. L’objectif général de ce projet a donc été de caractériser la zinc métalloprotéase de S. suis sérotype 2, afin de déterminer son rôle dans la pathogénèse. Pour ce faire, différentes expériences de clivage et d’activation ont été réalisées avec les cibles de l’IgA protéase et de la protéine ZmpC de S. pneumoniae, soit les IgA1 humaines, la matrice métalloprotéase-9 (MMP-9), la glycoprotéine de liaison à la P-sélectine (PSGL-1) et la mucine 16 (MUC16). Les résultats ont démontré que S. suis sérotype 2 n’a pas la capacité de cliver les IgA1 humaines, confirmant l’absence d’activité IgA protéase de ce pathogène. De plus, S. suis n’est pas capable d’activer MMP-9 et de cliver les ectodomaines de PSGL-1. Cependant, la protéine Zmp de S. suis clive partiellement les ectodomaines de MUC16. Malgré cette fonction, Zmp n’est pas un facteur critique pour la colonisation des voies respiratoires ou pour la virulence de S. suis sérotype 2 dans des modèles murins et porcins d’infection. Comme il a été décrit auparavant, la protéine Zmp est un antigène protecteur et la protection obtenue est fortement influencée par l’adjuvant utilisé.   En somme, cette étude a permis de démontrer que S. suis sérotype 2 ne possède pas d’activité IgA protéase et que sa zinc métalloprotéase n’est pas un facteur de virulence critique. Ceci permet donc à nouveau de souligner l’importance de confirmer les rôles associés à des facteurs de virulence critique de S. suis par différentes équipes de recherche mondialement.Streptococcus suis is an important swine pathogen and zoonotic agent responsible for sudden death, septic shock, and meningitis. Although several putative factors have been described to be involved in the S. suis virulence, the first steps of the S. suis pathogenesis remain misunderstood. Among these factors is the S. suis serotype 2 zinc metalloprotease, which has been described as an IgA1 protease and it was demonstrated to be a critical virulence factor for S. suis serotype 2. Moreover, this protein was a protective antigen in a mouse model of infection. However, contradictory results have been obtained regarding the role of the S. suis serotype 2 zinc metalloprotease and its IgA protease function has been question. More recently, phylogenetic analyses suggested that this protein would be homologous to the ZmpC of Streptococcus pneumoniae, which does not possess an IgA protease activity. Consequently, the main objective of this project was to characterize the S. suis serotype 2 zinc metalloprotease and to determine its role in the pathogenesis. To do this effect, different cleavage and activation experiments have been carried out with the different targets of the IgA protease and the ZmpC protein of S. pneumoniae, whether the human IgA1, matrix metalloprotease-9 (MMP-9), P-selectin glycoprotein ligand (PSGL-1), and mucin 16 (MUC16). Results showed that S. suis was unable to cleave human IgA1, thus confirming the lack of IgA protease activity by this pathogen. In addition, S. suis was unable to activate MMP-9 and to cleave PSGL-1 ectodomains. By contrast, Zmp partially cleaves MUC16 ectodomains. However, Zmp was not a required for colonization of the respiratory tract by S. suis nor for its virulence in both pig and mouse models of infection. Yet, and as previously described, the Zmp protein is a protective antigen with protection strongly influenced by the adjuvant used. Overall, this study showed that S. suis serotype 2 does not possess an IgA protease activity and that its zinc metalloprotease is not a critical virulence factor. Taken together, these results emphasize, once again, the importance of confirming the functions associated with critical S. suis virulence factors by different research teams worldwide

Interleukin-1 signaling induced by Streptococcus suis serotype 2 is strain-dependent and contributes to bacterial clearance and inflammation during systemic disease in a mouse model of infection

International audienceAbstractStreptococcus suis serotype 2 is an important porcine pathogen and zoonotic agent causing sudden death, septic shock and meningitis, with exacerbated inflammation being a hallmark of the infection. A rapid, effective and balanced innate immune response against S. suis is critical to control bacterial growth without causing excessive inflammation. Even though interleukin (IL)-1 is one of the most potent and earliest pro-inflammatory mediators produced, its role in the S. suis pathogenesis has not been studied. We demonstrated that a classical virulent European sequence type (ST) 1 strain and the highly virulent ST7 strain induce important levels of IL-1 in systemic organs. Moreover, bone marrow-derived dendritic cells and macrophages contribute to its production, with the ST7 strain inducing higher levels. To better understand the underlying mechanisms involved, different cellular pathways were studied. Independently of the strain, IL-1β production required MyD88 and involved recognition via TLR2 and possibly TLR7 and TLR9. This suggests that the recognized bacterial components are similar and conserved between strains. However, very high levels of the pore-forming toxin suilysin, produced only by the ST7 strain, are required for efficient maturation of pro-IL-1β via activation of different inflammasomes resulting from pore formation and ion efflux. Using IL-1R−/− mice, we demonstrated that IL-1 signaling plays a beneficial role during S. suis systemic infection by modulating the inflammation required to control and clear bacterial burden, thus promoting host survival. Beyond a certain threshold, however, S. suis-induced inflammation cannot be counterbalanced by this signaling, making it difficult to discriminate its role

Paradoxical low-flow, low-gradient aortic stenosis despite preserved left ventricular ejection fraction : new insights from weights of operatively excised aortic valves

Aims : We reported that patients with small aortic valve area (AVA) and low flow despite preserved left ventricular ejection fraction (LVEF), i.e. ‘paradoxical’ low flow (PLF), have worse outcomes compared with patients with normal flow (NF), although they generally have a lower mean gradient (MG). The aortic valve weight (AVW) excised at the time of valve replacement is a flow-independent marker of stenosis severity. The objective of this study was to compare the AVW of patients with PLF and MG,40 mmHg with the AVW of patients with NF and MG=40 mmHg. Methods and results : We recruited 250 consecutive patients undergoing valve replacement (Cohort A) for severe stenosis. Among them, 33 (13%) were in PLF [LVEF > 50% but stroke volume index (SVi) = 35 mL/m2] with MG 50% and SVi > 35 mL/m2) with MG = 40 mmHg (NF-HG group). Despite a much lower MG (29 ± 7 vs. 53 ± 10 mmHg; P < 0.0001), patients in the PLF-LG group had a similar AVA (0.73 ± 0.12 vs. 0.69 ± 0.13; P = 0.19) compared with those in the NF-HG group. The AVW [median (interquartile): 1.90 (1.63–2.50) vs. 2.60 (1.66–3.32)] and prevalence of bicuspid phenotype (15 vs. 42%) were lower in the PLF-LG group than in the NF-HG group. However, AVWs analysed separately in the tricuspid and bicuspid valves were similar in both groups [tricuspid valves: 1.80 (1.63–2.50) vs. 2.30 (1.58–3.00) g; P = 0.26 and bicuspid valves: 2.72 (1.73–3.61) vs. 2.60 (2.10–3.55) g; P = 0.93]. When using cut-point values of AVW established in another series of non-consecutive patients (n = 150, Cohort B) with NF and concordant Doppler-echocardiographic findings, we found that the percentage of patients with evidence of severe stenosis in Cohort A was 70% in patients with PLF-LG and 86% in patients with NF-HG. Conclusion : The aortic valve weight data reported in this study provide evidence that a large proportion of patients with PLF and low-gradient have a severe stenosis and that the gradient may substantially underestimate stenosis severity in these patients. A multi-parametric approach including all Doppler-echocardiographic parameters of valve function as well as other complementary diagnostic tests may help correctly identify these patients

HISA big data in biomedicine and healthcare 2013 conference

Additional file 5. Biofilm formation by the S. suis serotype 2 (S2) and serotype 9 (S9) wild-type and agI/II -deficient mutant strains in the absence of porcine fibrinogen. Biofilm formation capacity was quantified after 24 h of incubation at 37 °C in the absence of porcine fibrinogen. Data represent the mean ± SEM from at least three independent experiments

Pubertal development of transfusion-dependent thalassemia patients in the era of oral chelation with deferasirox: results from the French registry

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Interactions of Streptococcus suis serotype 9 with host cells and role of the capsular polysaccharide: Comparison with serotypes 2 and 14.

Streptococcus suis is an important porcine bacterial pathogen and a zoonotic agent responsible for sudden death, septic shock and meningitis, of which serotype 2 is the most widespread, with serotype 14 also causing infections in humans in South-East Asia. Knowledge of its pathogenesis and virulence are almost exclusively based on these two serotypes. Though serotype 9 is responsible for the greatest number of porcine cases in Spain, the Netherlands and Germany, very little information is currently available regarding this serotype. Of the different virulence factors, the capsular polysaccharide (CPS) is required for S. suis virulence as it promotes resistance to phagocytosis and killing and masks surface components responsible for host cell activation. However, these roles have been described for serotypes 2 and 14, whose CPSs are structurally and compositionally similar, both containing sialic acid. Consequently, we evaluated herein the interactions of serotype 9 with host cells and the role of its CPS, which greatly differs from those of serotypes 2 and 14. Results demonstrated that serotype 9 adhesion to but not invasion of respiratory epithelial cells was greater than that of serotypes 2 and 14. Furthermore serotype 9 was more internalized by macrophages but equally resistant to whole blood killing. Though recognition of serotypes 2, 9 and 14 by DCs required MyD88-dependent signaling, in vitro pro-inflammatory mediator production induced by serotype 9 was much lower. In vivo, however, serotype 9 causes an exacerbated inflammatory response, which combined with persistent bacterial presence, is probably responsible for host death during the systemic infection. Though presence of the serotype 9 CPS masks surface components less efficiently than those of serotypes 2 and 14, the serotype 9 CPS remains critical for virulence as it is required for survival in blood and development of clinical disease, and this regardless of its unique composition and structure

Complex Population Structure and Virulence Differences among Serotype 2 Streptococcus suis Strains Belonging to Sequence Type 28

Streptococcus suis is a major swine pathogen and a zoonotic agent. Serotype 2 strains are the most frequently associated with disease. However, not all serotype 2 lineages are considered virulent. Indeed, sequence type (ST) 28 serotype 2 S. suis strains have been described as a homogeneous group of low virulence. However, ST28 strains are often isolated from diseased swine in some countries, and at least four human ST28 cases have been reported. Here, we used whole-genome sequencing and animal infection models to test the hypothesis that the ST28 lineage comprises strains of different genetic backgrounds and different virulence. We used 50 S. suis ST28 strains isolated in Canada, the United States and Japan from diseased pigs, and one ST28 strain from a human case isolated in Thailand. We report a complex population structure among the 51 ST28 strains. Diversity resulted from variable gene content, recombination events and numerous genome-wide polymorphisms not attributable to recombination. Phylogenetic analysis using core genome single-nucleotide polymorphisms revealed four discrete clades with strong geographic structure, and a fifth clade formed by US, Thai and Japanese strains. When tested in experimental animal models, strains from this latter clade were significantly more virulent than a Canadian ST28 reference strain, and a closely related Canadian strain. Our results highlight the limitations of MLST for both phylogenetic analysis and virulence prediction and raise concerns about the possible emergence of ST28 strains in human clinical cases

Characterization of the zinc metalloprotease of Streptococcus suis serotype 2

Abstract Streptococcus suis is a swine pathogen and zoonotic agent responsible for meningitis and septic shock. Although several putative virulence factors have been described, the initial steps of the S. suis pathogenesis remain poorly understood. While controversial results have been reported for a S. suis serotype 2 zinc metalloprotease (Zmp) regarding its IgA protease activity, recent phylogenetic analyses suggested that this protein is homologous to the ZmpC of Streptococcus pneumoniae, which is not an IgA protease. Based on the previously described functions of metalloproteases (including IgA protease and ZmpC), different experiments were carried out to study the activities of that of S. suis serotype 2. First, results showed that S. suis, as well as the recombinant Zmp, were unable to cleave human IgA1, confirming lack of IgA protease activity. Similarly, S. suis was unable to cleave P-selectin glycoprotein ligand-1 and to activate matrix metalloprotease 9, at least under the conditions tested. However, S. suis was able to partially cleave mucin 16 and syndecan-1 ectodomains. Experiments carried out with an isogenic Δzmp mutant showed that the Zmp protein was partially involved in such activities. The absence of a functional Zmp protein did not affect the ability of S. suis to adhere to porcine bronchial epithelial cells in vitro, or to colonize the upper respiratory tract of pigs in vivo. Taken together, our results show that S. suis serotype 2 Zmp is not a critical virulence factor and highlight the importance of independently confirming results on S. suis virulence by different teams

Capsular Sialyltransferase Specificity Mediates Different Phenotypes in Streptococcus suis and Group B Streptococcus

The capsular polysaccharide (CPS) represents a key virulence factor for most encapsulated streptococci. Streptococcus suis and Group B Streptococcus (GBS) are both well-encapsulated pathogens of clinical importance in veterinary and/or human medicine and responsible for invasive systemic diseases. S. suis and GBS are the only Gram-positive bacteria which express a sialylated CPS at their surface. An important difference between these two sialylated CPSs is the linkage between the side-chain terminal galactose and sialic acid, being α-2,6 for S. suis but α-2,3 for GBS. It is still unclear how sialic acid may affect CPS production and, consequently, the pathogenesis of the disease caused by these two bacterial pathogens. Here, we investigated the role of sialic acid and the putative effect of sialic acid linkage modification in CPS synthesis using inter-species allelic exchange mutagenesis. To this aim, a new molecular biogenetic approach to express CPS with modified sialic acid linkage was developed. We showed that sialic acid (and its α-2,6 linkage) is crucial for S. suis CPS synthesis, whereas for GBS, CPS synthesis may occur in presence of an α-2,6 sialyltransferase or in absence of sialic acid moiety. To evaluate the effect of the CPS composition/structure on sialyltransferase activity, two distinct capsular serotypes within each bacterial species were compared (S. suis serotypes 2 and 14 and GBS serotypes III and V). It was demonstrated that the observed differences in sialyltransferase activity and specificity between S. suis and GBS were serotype unrestricted. This is the first time that a study investigates the interspecies exchange of capsular sialyltransferase genes in Gram-positive bacteria. The obtained mutants represent novel tools that could be used to further investigate the immunomodulatory properties of sialylated CPSs. Finally, in spite of common CPS structural characteristics and similarities in the cps loci, sialic acid exerts differential control of CPS expression by S. suis and GBS