SpxA1 and SpxA2 act coordinately to fine-tune stress responses and virulence in Streptococcus pyogenes

SpxA is a unique transcriptional regulator highly conserved among members of the phylum Firmicutes that binds RNA polymerase and can act as an antiactivator. Why some Firmicutes members have two highly similar SpxA paralogs is not understood. Here, we show that the SpxA paralogs of the pathogen Streptococcus pyogenes, SpxA1 and SpxA2, act coordinately to regulate virulence by fine-tuning toxin expression and stress resistance. Construction and analysis of mutants revealed that SpxA1− mutants were defective for growth under aerobic conditions, while SpxA2− mutants had severely attenuated responses to multiple stresses, including thermal and oxidative stresses. SpxA1− mutants had enhanced resistance to the cationic antimicrobial molecule polymyxin B, while SpxA2− mutants were more sensitive. In a murine model of soft tissue infection, a SpxA1− mutant was highly attenuated. In contrast, the highly stress-sensitive SpxA2− mutant was hypervirulent, exhibiting more extensive tissue damage and a greater bacterial burden than the wild-type strain. SpxA1− attenuation was associated with reduced expression of several toxins, including the SpeB cysteine protease. In contrast, SpxA2− hypervirulence correlated with toxin overexpression and could be suppressed to wild-type levels by deletion of speB. These data show that SpxA1 and SpxA2 have opposing roles in virulence and stress resistance, suggesting that they act coordinately to fine-tune toxin expression in response to stress. SpxA2− hypervirulence also shows that stress resistance is not always essential for S. pyogenes pathogenesis in soft tissue

Mucosal Infections and Invasive Potential of Nonencapsulated <i>Streptococcus pneumoniae</i> Are Enhanced by Oligopeptide Binding Proteins AliC and AliD.

Nonencapsulated &lt;i&gt;Streptococcus pneumoniae&lt;/i&gt; (NESp) is an emerging human pathogen that colonizes the nasopharynx and is associated with noninvasive diseases such as otitis media (OM), conjunctivitis, and nonbacteremic pneumonia. Since capsule expression was previously thought to be necessary for establishment of invasive pneumococcal disease (IPD), serotype-specific polysaccharide capsules are targeted by currently licensed pneumococcal vaccines. Yet, NESp expressing oligopeptide binding proteins AliC and AliD have been isolated during IPD. Thus, we hypothesize AliC and AliD are major NESp virulence determinants that facilitate persistence and development of IPD. Our study reveals that NESp expressing AliC and AliD have intensified virulence compared to isogenic mutants. Specifically, we demonstrate AliC and AliD enhance murine nasopharyngeal colonization and pulmonary infection and are required for OM in a chinchilla model. Furthermore, AliC and AliD increase pneumococcal survival in chinchilla whole blood and aid in resistance to killing by human leukocytes. Comparative proteome analysis revealed significant alterations in protein levels when AliC and AliD were absent. Virulence-associated proteins, including a pneumococcal surface protein C variant (CbpAC), were significantly downregulated, while starvation response indicators were upregulated in the double mutant relative to wild-type levels. We also reveal that differentially expressed CbpAC was essential for NESp adherence to epithelial cells, virulence during OM, reduction of C3b deposition on the NESp surface, and binding to nonspecific IgA. Altogether, the rise in NESp prevalence urges the need to understand how NESp establishes disease and persists in a host. This study highlights the roles of AliC, AliD, and CbpAC in the pathogenesis of NESp. &lt;b&gt;IMPORTANCE&lt;/b&gt; Despite the effective, widespread use of licensed pneumococcal vaccines over many decades, pneumococcal infections remain a worldwide burden resulting in high morbidity and mortality. NESp subpopulations are rapidly rising in the wake of capsule-targeted vaccine strategies, yet there is very little knowledge on NESp pathogenic potential and virulence mechanisms. Although NESp lacks a protective capsule, NESp lineages expressing AliC and AliD have been associated with systemic infections. Furthermore, higher antibiotic resistance rates and transformation efficiencies associated with emerging NESp threaten treatment strategies needed to control pneumococcal infections and transmission. Elucidating how NESp survives within a host and establishes disease is necessary for development of broadened pneumococcal prevention methods. Our study identifies virulence determinants and host survival mechanisms employed by NESp with a high pathogenic potential. Moreover, our study also identifies virulence determinants shared by NESp and encapsulated strains that may serve as broad prevention and therapeutic targets

Surface proteins and pneumolysin of encapsulated and nonencapsulated Streptococcus pneumoniae mediate virulence in a chinchilla model of otitis media

Streptococcus pneumoniae infections result in a range of human diseases and are responsible for almost one million deaths annually. Pneumococcal disease is mediated in part through surface structures and an anti-phagocytic capsule. Recent studies have shown that nonencapsulated Streptococcus pneumoniae (NESp) make up a significant portion of the pneumococcal population and are able to cause disease. NESp lack some common surface proteins expressed by encapsulated pneumococci, but express surface proteins unique to NESp. A chinchilla model of otitis media (OM) was used to determine the effect various pneumococcal mutations have on pathogenesis in both NESp and encapsulated pneumococci. Epithelial cell adhesion and invasion assays were used to examine the effects in relation to deletion of intrinsic genes or expression of novel genes. A mouse model of colonization was also utilized for comparison of various pneumococcal mutants. It was determined that pneumococcal surface protein K (PspK) and pneumolysin (Ply) affect NESp middle ear pathogenesis, but only PspK affected epithelial cell adhesion. Experiments in an OM model were done with encapsulated strains testing the importance of native virulence factors and treatment of OM. First, a triple deletion of the common virulence factors PspA, PspC, and Ply, (ΔPAC), from an encapsulated background abolished virulence in an OM model while a PspC mutant had detectable, but reduced amounts of recoverable bacteria compared to wildtype. Next, treatment of OM was effective when starting antibiotic treatment within 24 hrs with resolution by 48 hrs post treatment. Expression of NESp-specific virulence factor PspK in an encapsulated strain has not been previously studied, and we showed significantly increased adhesion and invasion of human epithelial cells by pneumococci. Murine colonization was not significantly increased when an encapsulated strain expressed PspK, but colonization was increased when a capsule mutant expressed PspK. The ability of PspK expression to increase colonization in a capsule mutant despite no increase in adhesion can be attributed to other functions of PspK, such as sIgA binding or immune modulation. OM is a substantial economic burden, thus a better understanding of both encapsulated pneumococcal pathogenesis and the emerging pathogen NESp is necessary for effective prevention and treatment

Pyruvate Oxidase of \u3ci\u3eStreptococcus pneumoniae\u3c/i\u3e Contributes to Penumolysin Release

Background Streptococcus pneumoniae is one of the leading causes of community acquired pneumonia and acute otitis media. Certain aspects of S. pneumoniae’s virulence are dependent upon expression and release of the protein toxin pneumolysin (PLY) and upon the activity of the peroxide-producing enzyme, pyruvate oxidase (SpxB). We investigated the possible synergy of these two proteins and identified that release of PLY is enhanced by expression of SpxB prior to stationary phase growth. Results Mutants lacking the \u3c\u3espxB gene were defective in PLY release and complementation of spxB restored PLY release. This was demonstrated by cytotoxic effects of sterile filtered supernatants upon epithelial cells and red blood cells. Additionally, peroxide production appeared to contribute to the mechanism of PLY release since a significant correlation was found between peroxide production and PLY release among a panel of clinical isolates. Exogenous addition of H2O2 failed to induce PLY release and catalase supplementation prevented PLY release in some strains, indicating peroxide may exert its effect intracellularly or in a strain-dependent manner. SpxB expression did not trigger bacterial cell death or LytA-dependent autolysis, but did predispose cells to deoxycholate lysis. Conclusions Here we demonstrate a novel link between spxB expression and PLY release. These findings link liberation of PLY toxin to oxygen availability and pneumococcal metabolism

EIN ALTKROATISCHES GRABERFELD AUF DEM BERGE SPAS BEI KNIN

Autor objavljuje rezultate istraživanja starohrvatske nekropole na brdu Spasu kod Knina (otkriveno ukupno 228 grobova). Na temelju prikupljenih podataka tijekom višegodišnjih arheoloških istraživanja i sprovedene analize grobne arhitekture, pogrebnih običaja i grobnih nalaza utvrđeno je vrijeme ukopavanja na toj nekropoli i uputilo na mogući prostorni smještaj naselja kojemu je to groblje pripadalo. Završna razmatranja objelodanjenih grobnih nalaza otkrivaju niz novih spoznaja o gospoda.stvenim mogućnostima stanovništva, njihov kulturni i duhovni život u 9, 10. i 11. stoljeću. Osim starohrvatskih grobova na Spasu su otkopani i temeljni ostaci arhitekture, za koje se utvrdilo da pripadaju rimskom naselju, vjerojatno ostacima stare Ninie, odnosno Curcuma. Sve to popraćeno je obilnom dokumentacijskom građom i katalogom grobova.Westlich der Stadt Knin erstreckt sich der Berg Spas. Auf seinem siidlichen Teil erhebt sich die mittelalterliche Festung Knin, und an den nord lichen Teil schlieBt sich das Hochplateau des Berges Spas an, das im horizontalen Querschnitt cinE\u27 birnentormige Form hat. Spas ist anfangs des 18. lahrhunderts durch einen kiinstlichen Durchstich von der Festung getrennt worden. Im nordlichen, breitesten Teil des Plateaus wurde ein altkroatisches Graberfeld entdeckt, mit insgesamt 228 Grabern. Das erforsci1te Gebiet umfaBt etwa 1200 m2 Oberflache. Es wurden neben Grabern auch Fundamente von Bauwerken aus vorktoatischer Zeit gefunden, was bezeugt, daB es sich hier um eine komplexe archaologische Fundstatte handelt. Im ersten Teil seiner Abhandlung beschreibt. der Verfasser die Lage des Fundortes, seine strategische Bedeutung, und den geschichtlichen Ablauf der Forschungen an diesem Ort. AuBerdem erwahnt er unter anderen bedeutenden Funden auch die Entdeckung von Fundamenten von Bauwerken , fUr die er aufgrund von Fragmenten steinernen Skulpturen, Ziegeln und Fragmenten von KeramikgefaBen festelIen konnte, daB sie einer romisehen Ansiedlung angehorten. Durch Suchgrabung wurde festgestelIt, daB die Reste dieser Bauwerke sich auch auf den iibrigen Teil des Plateaus erstrecken, der bis jetzt nicht erforscht worden ist. Diese Entdeckungen, zusammen mit einem groBen, schon friiher untersuchten Graberfeld am ostlichen FuBe dieses Berges, genannt »Greblje«, sind ein starkes Argumentfi.ir die Annahme jener Forscher, die der Meinung sind, daB die alte, antike Stadtsiedlung Ninia, die von der Schriftstellern der Antike erwahnt wird , sich an der SteIle der heutigen Stadt Knin befunden hatte, beziehungsweise an der Stelle ihrer Festung und der Wallburg Spas. Im siidostlichen Teil des ausgegrabenen Graberfeldes hat man ziemlich groBe Schuttablagerungen gefunden, unter denen sich auch Stiicke von Mortel mit Farbresten befanden. An dieser Stelle und in ihrer unmittelbaren Nahe wurden einige steinerne Fragmente mit vorromanischer F1echtwerkplastik gefunden , die zu Kircheneinrichtungsgegenstanden aus dem 9. oder 10. lh. gehorten. Die erwahnten Funde weisen mjt Sicherheit darauf hin, daB sich an eben dieser Stelle, wo man den Schutt gefunden hat, eine altkroatische Kirche befunden hatte, der die gefundenen Fragmente angehorten. Da sich von diesem Kirchenbau auch nicht der allergeringste Rest einer Mauer erhalten hat, kann man nur schlieBen, daB die Kirche bis zu den Grundmauern zerstort worden war, und daB ihre Steine als Baurnaterial fUr die Mauern der nahegelegenen Festung verwendet wurden. Der zwei te Teil dieser Abhandlung enthalt den Katalog der Grabarchitektur und ihres lnventars. Hier findet man kurz gefaBt die wichtigsten Angaben i.iber jedes cinzeIne Grab und die osteologischen Funde, sowie eine genaue Beschreibung der Grabbeigaben. Der dritte Teil behandelt die allgemeinen Merkmale des Graberfeldes. Wegen der ungi.instigen Bodenstruktur, sowie der Fundamente der Bauwerke, besitzt das Graberfeld nicht die Merkmale von Reihengrabern, Die Graber sind sehr verschiedenartig orientiert, und liegen in allen Richtungen; der groBte Teil der Graber war trotzdem richtjg orientiert, in der Richtung Osten-Westen (103 Graber) . In den meisten Grabern befand sich nur ein Verstorbener, manchmal jedoch auch mehrere. Die gefundenen osteologischen Reste bestatigen, daB das Graberfeld einer Siedlung zugehorig; mit einer gleich groBen Anzahl von bestatteten Mannern , Frauern und Kindern. Die Graber waren meistens aus behauener Rauhwacke , aus unregelmaBigen Steinplatten oder aus Bruchsteinen gebaut. Die behauene Rauhwacke ftir die Graber stammte wahrscheinlich von den eingesttirzten Bauwerken in der nahen Umgebung. Weiterhin analysiert der Verfasser die Grabfunde, meistens Schmuck, und zwar Ohrringe und Ringe. Indem er die typologischen Besonderheiten der einzelnen Gegenstande genau beurteilt, und sie mit analogem Material aus den tibrigen altkroatischen und anderen Graberfeldern vergleicht, kommt er zu Schltissen ber die Herkunft und\u27 Datierung der Funde. Mehr Aufmerksamkeit schenkt der Verfasser den Ohrringen vom Typ mit drei Beeren und zwar deshalb, weil in letzter Zeit versucht wurde, fast alle entwickelteren Varianten dieses Typs, die in Grabern auf dem Gebiet des altkroatisches Staates gefunden worden waren, von allen tibrigen Ohrringen die ebenfalls auf diesem Gebiet gefunden wurden, zu trennen. [ndem er auf das Problem der Datierung und Herkunft der Ohrringe mit drei Beeren eingeht, versuchte der Verfasser aufgrund einer Reihe sicherer Tatsachen und Hinweise darauf hinzuweisen, daB dieser Typ von Ohrringen, beziehungsweise die starker entwickelten Varianten , nicht von den tibrigen Typenvarianten altkroatischer Ohrringe isoliert werden dtirfen, die auf dem Gebiet des dalmatinischen Kroatiens gefunden worden waren , und die meistens in die Zeit vom Beginn des 9. bis zum Ende des 11. lahrhunderts datiert werden. Er machte ebenfalls darauf aufmerksam, daB samtliche Typen von altkroatischen Ohrringen, und so auch die entwickelteren Varianten von Ohrringen mit drei Beeren, die aus Grabern des Mutterlandes stammen, aus einheimischen Goldschmiedewerkstatten stammen , und daB sie als Ganzes eine altkroatische Kulturgruppe bilden. AuBer seinen Vermutungen tiber die Lage und GroBe der Ansiedlung, zu der das Graberfeld auf dem Berge Spas gehorte, ist der Verfasser im Ganzen der Meinun~, daB das Graberfeld auf Spas dem Zeitraum des frtihfeudalen kroatischen Staates angehorte, d. h., daB das Graberfeld sei t dem Anfang des 9. Jahrhunderts bestanden hatte und kontinuierlich bis zum Ende des ll. Jahrhunderts fortdauerte

Association of IL4R single-nucleotide polymorphisms with rheumatoid nodules in African Americans with rheumatoid arthritis

Abstract Introduction To determine whether IL4R single-nucleotide polymorphisms (SNPs) rs1805010 (I50V) and rs1801275 (Q551R), which have been associated with disease severity in rheumatoid arthritis (RA) patients of European ancestry, relate to the presence of rheumatoid nodules and radiographic erosions in African Americans. Methods Two IL4R SNPs, rs1805010 and rs1801275, were genotyped in 749 patients from the Consortium for Longitudinal Evaluation of African-Americans with Early Rheumatoid Arthritis (CLEAR) registries. End points were rheumatoid nodules defined as present either by physical examination or by chest radiography and radiographic erosions (radiographs of hands/wrists and feet were scored using the modified Sharp/van der Heijde system). Statistical analyses were performed by using logistic regression modeling adjusted for confounding factors. Results Of the 749 patients with RA, 156 (20.8%) had rheumatoid nodules, with a mean age of 47.0 years, 84.6% female gender, and median disease duration of 1.9 years. Of the 461 patients with available radiographic data, 185 (40.1%) had erosions (score >0); their mean age was 46.7 years; 83.3% were women; and median disease duration was 1.5 years. Patients positive for HLA-DRB1 shared epitope (SE) and autoantibodies (rheumatoid factor (RF) or anti-cyclic citrullinated peptide (CCP)) had a higher risk of developing rheumatoid nodules in the presence of the AA and AG alleles of rs1801275 (odds ratio (OR)adj = 8.08 (95% confidence interval (CI): 1.60-40.89), P = 0.01 and ORadj = 2.97 (95% CI, 1.08 to 8.17), P = 0.04, respectively). Likewise, patients positive for the HLA-DRB1 SE and RF alone had a higher risk of developing rheumatoid nodules in presence of the AA and AG alleles of rs1801275 (ORadj = 8.45 (95% CI, 1.57 to 45.44), P = 0.01, and ORadj = 3.57 (95% CI, 1.18 to 10.76), P = 0.02, respectively) and in the presence of AA allele of rs1805010 (ORadj = 4.52 (95% CI, 1.20 to 17.03), P = 0.03). No significant association was found between IL4R and radiographic erosions or disease susceptibility, although our statistical power was limited by relatively small numbers of cases and controls. Conclusions We found that IL4R SNPs, rs1801275 and rs1805010, are associated with rheumatoid nodules in autoantibody-positive African-American RA patients with at least one HLA-DRB1 allele encoding the SE. These findings highlight the need for analysis of genetic factors associated with clinical RA phenotypes in different racial/ethnic populations

THP-1 Monocytes Up-Regulate Intercellular Adhesion Molecule 1 in Response to Pneumolysin from Streptococcus pneumoniae

Pneumolysin (PLY) is a major virulence factor of Streptococcus pneumoniae that elicits a variety of proinflammatory responses from cells of the host immune system. Intercellular adhesion molecule 1 (ICAM-1) is a cell adhesion molecule involved in leukocyte trafficking toward inflammatory stimuli in extravascular sites. In this study, we evaluated the effect of PLY on expression of ICAM-1 in THP-1 monocytic cells exposed to S. pneumoniae. Exposure of cells to PLY-expressing S. pneumoniae strain WU2 for 6 h led to significantly higher levels of ICAM-1 message than those in cells exposed to either medium alone or ΔPLY1, a PLY-negative isogenic mutant of WU2. Cells exposed to purified recombinant PLY also showed a dose-dependent increase in ICAM-1 mRNA compared to cells exposed to medium alone. Exposure to recombinant PLY containing a single amino acid substitution (Trp433→Phe) that decreases cytolytic activity did not increase ICAM-1 mRNA to levels seen with wild-type PLY. In addition, THP-1 cells exposed to wild-type strain WU2 or D39 had increased ICAM-1 on their surface compared to cells exposed to medium alone or their PLY-negative isogenic mutants ΔPLY1 and ΔPLY2, respectively. These data indicate that PLY induces transcription and production of a cell adhesion molecule involved in the inflammatory response that may play a role in pneumococcal infection