Analysis of the Streptococcus agalactiae exoproteome

International audienceThe two-component regulatory system CovRS is the main regulator of virulence gene expression in Group B Streptococcus (GBS), the leading cause of invasive infections in neonates. In this study we analyzed by mass spectrometry the GBS extracellular protein complex (i.e. the exoproteome) of NEM316 wild-type (WT) strain and its isogenic covRS deletion mutant (ΔcovRS). A total of 53 proteins, 49 of which had classical secretion signals, were identified: 12 were released by both strains while 21 and 20 were released exclusively by WT and ΔcovRS strains, respectively. In addition to known surface proteins, we detected here unstudied cell-wall associated proteins and/or orthologs of putative virulence factors present in other pathogenic streptococci. While the functional role of these proteins remains to be elucidated, our data suggest that the analysis of the exoproteome of bacterial pathogens under different gene expression conditions may be a powerful tool for the rapid identification of novel virulence factors and vaccine candidates

A Herbal Mixture from Propolis, Pomegranate, and Grape Pomace Endowed with Anti-Inflammatory Activity in an In Vivo Rheumatoid Arthritis Model

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized by the production of inflammatory factors. In order to overcome the side effects of currently used anti‐inflammatory drugs, several attempts have been made to identify natural products capable of relieving RA symptoms. In this work, a herbal preparation consisting of propolis, pomegranate peel, and Aglianico grape pomace (PPP) extracts (4:1:1) was designed and evaluated for its effect on a murine collagen‐induced arthritis (CIA) model. Firstly, the chemical contents of four different Italian propolis collected in the Campania region (Italy) were here reported for the first time. LC‐MS analyses showed the presence of 38 constituents, identified in all propolis extracts, belonging to flavonoids and phenolic acids classes. The Pietradefusi extract was the richest one and thus was selected to design the PPP preparation for the in vivo assay. Our results highlight the impact of PPP on RA onset and progression. By using in vivo CIA models, the treatment with PPP resulted in a delayed onset of the disease and alleviated the severity of the clinical symptoms. Furthermore, we demonstrated that early PPP treatment was associated with a reduction in serum levels of IL‐17, IL‐1b, and IL‐17–triggering cytokines

Activation of the NLRP3 Inflammasome by Group B Streptococci

International audienceGroup B Streptococcus (GBS) is a frequent agent of life-threatening sepsis and meningitis in neonates and adults with predisposing conditions. We tested the hypothesis that activation of the inflammasome, an inflammatory signaling complex, is involved in host defenses against this pathogen. We show in this study that murine bone marrow-derived conventional dendritic cells responded to GBS by secreting IL-1β and IL-18. IL-1β release required both pro–IL-1β transcription and caspase-1–dependent proteolytic cleavage of intracellular pro–IL-1β. Dendritic cells lacking the TLR adaptor MyD88, but not those lacking TLR2, were unable to produce pro–IL-1β mRNA in response to GBS. Pro–IL-1β cleavage and secretion of the mature IL-1β form depended on the NOD-like receptor family, pyrin domain containing 3 (NLRP3) sensor and the apoptosis-associated speck-like protein containing a caspase activation and recruitment domain adaptor. Moreover, activation of the NLRP3 inflammasome required GBS expression of β-hemolysin, an important virulence factor. We further found that mice lacking NLRP3, apoptosis-associated speck-like protein, or caspase-1 were considerably more susceptible to infection than wild-type mice. Our data link the production of a major virulence factor by GBS with the activation of a highly effective anti-GBS response triggered by the NLRP3 inflammasome

GMP-grade nanoparticle targeted to nucleolin downregulates tumor molecular signature, blocking growth and invasion, at low systemic exposure

Patients with breast or ovarian cancer have not benefited from improved efficacy with pegylated liposomal doxorubicin relative to free drug, likely due to the limited extent of the enhanced permeability and retention (EPR) effect, further compromising drug bioavailability in the tumor. Herein it is hypothesized that targeting nucleolin overexpressed in tumor endothelial cells (readily accessible from the vascular compartment), besides cancer cells, with PEGASEMP (doxorubicin hydrochloride in a lipid-based pegylated nanoparticle functionalized with a 31-aminoacid peptide targeting nucleolin), lessens the dependence on high systemic exposures and EPR effect for successful tumor targeting. This strategy has resulted in improved intracellular tumor bioavailability of doxorubicin, at low systemic exposure, associated with a safe toxicological profile. Levels of cell surface nucleolin dictated the antitumor activity of PEGASEMP against nucleolin-overexpressing solid tumors of diverse histological origin, evidencing a significant growth inhibition of malignant mesothelioma over the standard of care. Those observations were paralleled by an impairment of the nucleolin-positive vasculature and downregulation of typically overexpressed genes. Patient stratification based on nucleolin mRNA expression correlated with prognosis and enabled identification of breast and mesothelioma tumors that may potentially benefit from PEGASEMP. Overall, a novel principle of drug delivery is presented with potential therapeutic impact across nucleolin-overexpressing human cancers

Plasminogen- and Fibronectin-binding Protein B Is Involved in the Adherence of Streptococcus pneumoniae to Human Epithelial Cells*

Streptococcus pneumoniae is a major cause of morbidity and mortality worldwide. The ability of this bacterium to adhere to epithelial cells is considered as an essential early step in colonization and infection. By screening a whole genome phage display library with sera from infected patients, we previously identified three antigenic fragments matching open reading frame spr0075 of the strain R6 genome. This locus encodes for an ∼120-kDa protein, herein referred to as plasminogen- and fibronectin-binding protein B (PfbB), which displays an LPXTG cell wall anchoring motif and six repetitive domains. In this study, by using isogenic pfbB-deleted mutants of the encapsulated D39 and of the unencapsulated DP1004 type 2 pneumococcal strains, we show that PfbB is involved in S. pneumoniae adherence to various epithelial respiratory tract cell lines. Our data suggest that PfbB directly mediates bacterial adhesion, because fluorescent beads coated with the recombinant PfbB sp17 fragment (encompassing one of the six repetitive domains and the C-terminal region) efficiently bound to epithelial cells. Mutants lacking PfbB bound to fibronectin and plasminogen considerably less efficiently than wild type bacteria, whereas sp17-coated beads specifically bound to both of these substrates. Taken together, our data suggest that, by directly interacting with fibronectin, PfbB significantly increases the ability of S. pneumoniae to adhere to human epithelial cells

Effects of active immunoprotection with the 6pGST FbsA fragment in adult and neonatal mouse models of GBS sepsis.

<p><b>A</b>. Immunoprotection in adult mice. Five-week-old CD1 mice underwent three immunizations with the 6p FbsA fragment fused to GST (6pGST) or with GST alone. At 3 weeks after the last immunizations mice were challenged by the i.p. injection of GBS strain COH1 (5x10⁷ CFUs) and lethality was observed daily. *, p<0.05 relative to GST-immunized mice by Kaplan-Meier survival plots. Shown are the cumulative results of two independent experiments. <b>B</b>. Effect of maternal immunization on survival of experimentally infected pups. Female CD1 mice (5 wk old) were immunized three times with the 6p FbsA fragment fused to GST (6pGST) or with GST alone. Mice were then time-mated and two-day-old pups were infected s.c. with 250 CFUs of GBS strain 6313. *, p<0.05 relative to GST-immunized mice by Kaplan-Meier survival plots.</p