The outcome of Cryptococcus neoformans intracellular pathogenesis in human monocytes

<p>Abstract</p> <p>Background</p> <p><it>Cryptococcus neoformans </it>is an encapsulated yeast that is a facultative intracellular pathogen. The interaction between macrophages and <it>C. neoformans </it>is critical for extrapulmonary dissemination of this pathogenic yeast. <it>C. neoformans </it>can either lyse macrophages or escape from within them through a process known as phagosomal extrusion. However, most studies of intracellular pathogenesis have been made with mouse cells and their relevance to human infection is uncertain. In this study we extended studies of <it>C. neoformans</it>-macrophage cellular interaction/s to human peripheral blood monocytes.</p> <p>Results</p> <p>This study demonstrated that <it>C. neoformans </it>can shed polysaccharide within human monocytes, spread from cell to cell, and be extruded from them. Furthermore, human monocytes responded to ingestion of <it>C. neoformans </it>with cell cycle progression from G1 to S.</p> <p>Conclusion</p> <p>Similarities between mouse and human cells support the suitability of mouse cells for the study of intracellular pathogenesis mechanisms. Given that these hosts diverged over 70 million years ago, the similar pathogenic strategies for <it>C. neoformans </it>in murine and human cells supports the hypothesis that the mechanism that underlies the mammalian intracellular pathogenesis of <it>C. neoformans </it>originated from interactions with a third host, possibly soil amoeboid predators, before the mammalian radiation.</p

Antibodies to Streptococcus pneumoniae Capsular Polysaccharide Enhance Pneumococcal Quorum Sensing

The use of pneumococcal capsular polysaccharide (PPS)-based vaccines has resulted in a substantial reduction in invasive pneumococcal disease. However, much remains to be learned about vaccine-mediated immunity, as seven-valent PPS-protein conjugate vaccine use in children has been associated with nonvaccine serotype replacement and 23-valent vaccine use in adults has not prevented pneumococcal pneumonia. In this report, we demonstrate that certain PPS-specific monoclonal antibodies (MAbs) enhance the transformation frequency of two different Streptococcus pneumoniae serotypes. This phenomenon was mediated by PPS-specific MAbs that agglutinate but do not promote opsonic effector cell killing of the homologous serotype in vitro. Compared to the autoinducer, competence-stimulating peptide (CSP) alone, transcriptional profiling of pneumococcal gene expression after incubation with CSP and one such MAb to the PPS of serotype 3 revealed changes in the expression of competence (com)-related and bacteriocin-like peptide (blp) genes involved in pneumococcal quorum sensing. This MAb was also found to induce a nearly 2-fold increase in CSP2-mediated bacterial killing or fratricide. These observations reveal a novel, direct effect of PPS-binding MAbs on pneumococcal biology that has important implications for antibody immunity to pneumococcus in the pneumococcal vaccine era. Taken together, our data suggest heretofore unsuspected mechanisms by which PPS-specific antibodies could affect genetic exchange and bacterial viability in the absence of host cells

Extracellular Vesicles from Different Pneumococcal Serotypes Are Internalized by Macrophages and Induce Host Immune Responses

Bacterial extracellular vesicles are membranous ultrastructures released from the cell surface. They play important roles in the interaction between the host and the bacteria. In this work, we show how extracellular vesicles produced by four different serotypes of the important human pathogen, Streptococcus pneumoniae, are internalized by murine J774A.1 macrophages via fusion with the membrane of the host cells. We also evaluated the capacity of pneumococcal extracellular vesicles to elicit an immune response by macrophages. Macrophages treated with the vesicles underwent a serotype-dependent transient loss of viability, which was further reverted. The vesicles induced the production of proinflammatory cytokines, which was higher for serotype 1 and serotype 8-derived vesicles. These results demonstrate the biological activity of extracellular vesicles of clinically important pneumococcal serotypes

The identification of Staphylococcus aureus factors required for pathogenicity and growth in human blood

Staphylococcus aureus is a human commensal but also has devastating potential as an opportunist pathogen. S. aureus bacteraemia is often associated with an adverse outcome. To identify potential targets for novel control approaches we have identified S. aureus components that are required for growth on human blood. An ordered transposon mutant library was screened, identifying 9 genes involved specifically in haemolysis or growth on human blood agar compared to the parental strain. Three genes (purA, purB and pabA) were subsequently found to be required for pathogenesis in the zebrafish embryo infection model. The pabA growth defect was specific to the red blood cell component of human blood, showing no growth difference compared to the parental strain on human serum, human plasma, sheep or horse blood. PabA is required in the tetrahydrofolate (THF) biosynthesis pathway. The pabA growth defect was found to be due to a combination of loss of THF-dependent dTMP production by the enzyme ThyA and an increased demand for pyrimidines in human blood. Our work highlights pabA and the pyrimidine salvage pathway as potential targets for novel therapeutics and suggests a previously undefined role for a human blood factor in the activity of sulphonamide antibiotics

Differential effects of IL-17 pathway in disseminated candidiasis and zymosan-induced multiple organ failure

Contains fulltext : 88879.pdf (publisher's version ) (Closed access)The role of the IL-17 pathway in antifungal host defense is controversial. Several studies suggested that IL-17 is crucial for the protection against Candida infection, whereas other studies reported that IL-17 may contribute to inflammatory pathology and worsening of fungal disease. To address these discrepancies, we assessed the differential role of IL-17 pathway in two models of fungal sepsis: intravenous infection with live Candida albicans, in which fungal growth is the main cause of mortality, and zymosan-induced multiple organ failure, in which the inflammatory pathology drives the mortality. First, IL-17 receptor-deficient (IL-17RA) mice showed increased mortality and higher fungal loads in the kidneys in the model of disseminated candidiasis, partly caused by lower neutrophil recruitment in the IL-17RA mice. Second, IL-17RA mice were not protected against the multiorgan failure induced by zymosan. These data demonstrate that IL-17 does not have a major contribution to the inflammatory pathology leading to organ failure in fungal sepsis and support the concept that the IL-17 pathway is protective in antifungal host defense.01 oktober 201

A semi-synthetic oligosaccharide conjugate vaccine candidate confers protection against Streptococcus pneumoniae serotype 3 infection

The identification of immunogenic glycotopes that render glycoconjugate vaccines protective is key to improving vaccine efficacy. Synthetic oligosaccharides are an attractive alternative to the heterogeneous preparations of purified polysaccharides that most marketed glycoconjugate vaccines are based on. To investigate the potency of semi-synthetic glycoconjugates, we chose the least-efficient serotype in the current pneumococcal conjugate vaccine Prevnar 13, Streptococcus pneumoniae serotype 3 (ST3). Glycan arrays containing synthetic ST3 repeating unit oligosaccharides were used to screen a human reference serum for antibodies and to define the recognition site of two ST3-specific protective monoclonal antibodies. The glycan array screens identified a tetrasaccharide that was selected for in-depth immunological evaluation. The tetrasaccharide-CRM197 carrier protein conjugate elicited protective immunity as evidenced by opsonophagocytosis assays and protection against pneumonia caused by ST3 in mice. Formulation of the defined protective lead candidate glycotope has to be further evaluated to elicit optimal long-term immunity