Project description:Streptococcus pneumoniae (the pneumococcus) account for significant morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteremia and meningitis. In this study, we used microarray analysis to compare gene expression patterns of either serotype 4 or serotype 6A pneumococci in the nasopharynx and blood of mice, as a model to identify genes involved in invasion of blood in the context of occult bacteremia in humans.
Project description:Streptococcus pneumoniae (the pneumococcus) account for significant morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteremia and meningitis. In this study, we used microarray analysis to compare gene expression patterns of either serotype 4 or serotype 6A pneumococci in the nasopharynx and blood of mice, as a model to identify genes involved in invasion of blood in the context of occult bacteremia in humans. Microarray experiments were performed on whole genome S. pneumoniae PCR arrays obtained from the Bacterial Microarray Group at St George's Hospital Medical School, London (http://bugs.sghms.ac.uk/). The array was designed using TIGR4 base strain annotation and extra target genes from strain R6. Pair-wise comparisons were made between the nasopharynx and blood RNA samples labeled with either Alexa Fluor 546 or Alexa Fluor 647 dye from the 48, 72 and 96 h time points.
Project description:The primary mechanism by which pneumococcal capsular polysaccharide-based vaccines are believed to mediate protection is by induction of serotype-specific opsonic antibodies that facilitate bacterial killing by phagocytes (opsonophagocytosis). However, antibodies that are protective against experimental pneumococcal pneumonia in mice but do not promote opsonophagocytic killing in vitro have also been identified 1-3. Such non-opsonic antibodies are associated with bacterial clearance in vivo, but the mechanism by which this occurs is unknown. In this letter, we demonstrate that a protective, non-opsonic serotype 3 pneumococcal capsular polysaccharide-specific monoclonal antibody (MAb) enhances quorum sensing, which results in competence induction and fratricide of serotype 3 pneumococcus. Gene expression profile analysis revealed that the MAb together with the pneumococcal autoinducer, competence stimulating peptide 2 (CSP2), augments differential expression of competence (com) related bacteriocin-like peptide (blp) genes that are known to be involved in pneumococcal fratricide. Taken together, these findings reveal a previously unsuspected mechanism of antibody action, namely, enhancement of quorum sensing and bacterial fratricide. Given that this activity does not require phagocytes, antibodies that function accordingly may hold promise as adjuncts to current vaccines or as desired products of next generation pneumococcal vaccines. 6 samples
Project description:The primary mechanism by which pneumococcal capsular polysaccharide-based vaccines are believed to mediate protection is by induction of serotype-specific opsonic antibodies that facilitate bacterial killing by phagocytes (opsonophagocytosis). However, antibodies that are protective against experimental pneumococcal pneumonia in mice but do not promote opsonophagocytic killing in vitro have also been identified 1-3. Such non-opsonic antibodies are associated with bacterial clearance in vivo, but the mechanism by which this occurs is unknown. In this letter, we demonstrate that a protective, non-opsonic serotype 3 pneumococcal capsular polysaccharide-specific monoclonal antibody (MAb) enhances quorum sensing, which results in competence induction and fratricide of serotype 3 pneumococcus. Gene expression profile analysis revealed that the MAb together with the pneumococcal autoinducer, competence stimulating peptide 2 (CSP2), augments differential expression of competence (com) related bacteriocin-like peptide (blp) genes that are known to be involved in pneumococcal fratricide. Taken together, these findings reveal a previously unsuspected mechanism of antibody action, namely, enhancement of quorum sensing and bacterial fratricide. Given that this activity does not require phagocytes, antibodies that function accordingly may hold promise as adjuncts to current vaccines or as desired products of next generation pneumococcal vaccines.
Project description:Our understanding of the synergism between S. pneumoniae and influenza virus remains incomplete. The classic dogma has been that influenza attenuates the host innate immunity and increase the susceptibility to subsequent bacterial infection. Therefore, the majority of current studies have been focusing on the interaction of S. pneumoniae and influenza in the context of host cells. By contrast, in this study, we set out to investigate the response of pneumococcus alone to virus infection. Our hypothesis was that prior to causing any damages to host cells, influenza may have induced (lethal) changes to pneumococcus cell itself. Indeed, a very recent evidence has shown that direct viral treatment to pneumococcus will increase its adhesion to macrophage cells. Here, using quantitative shotgun approach, we attempt to investigate the proteomic alterations of S. pneumoniae by influenza virus challenge, and provide a landscape of interactions between the IAV and pneumococcus.
Project description:Our understanding of the synergism between S. pneumoniae and influenza virus remains incomplete. The classic dogma has been that influenza attenuates the host innate immunity and increase the susceptibility to subsequent bacterial infection. Therefore, the majority of current studies have been focusing on the interaction of S. pneumoniae and influenza in the context of host cells. By contrast, in this study, we set out to investigate the response of pneumococcus alone to virus infection. Our hypothesis was that prior to causing any damages to host cells, influenza may have induced (lethal) changes to pneumococcus cell itself. Indeed, a very recent evidence has shown that direct viral treatment to pneumococcus will increase its adhesion to macrophage cells. Here, using quantitative phosphoproteomic approach, we attempt to investigate the global alterations of S. pneumoniae phosphorylation by influenza virus challenge, and provide a landscape of synergism between the IAV and pneumococcus.
Project description:Streptococcus pneumoniae (pneumococcus) is a leading human respiratory pathogen that causes a variety of serious mucosal and invasive diseases. D39 is an historically important serotype 2 strain that was used in experiments by Avery and coworkers to demonstrate that DNA is the genetic material. Although isolated nearly a century ago, D39 remains extremely virulent in murine infection models and is perhaps the strain used most frequently in current studies of pneumococcal pathogenicity. To date, the complete genome sequences have been reported for only two S. pneumoniae strains; TIGR4, a recent serotype 4 clinical isolate, and laboratory strain R6, an avirulent, unencapsulated derivative of strain D39. We report herein the genome sequences of two different isolates of strain D39 and the corrected sequence and updated annotation of strain R6. Comparisons of these three related sequences allowed deduction of the likely sequence of the D39 progenitor and mutations that arose in each isolate. Despite its numerous repeated sequences and IS elements, the serotype 2 genome has remained remarkably stable during cultivation, and one of the D39 isolates contains only 5 relatively minor mutations compared to the deduced D39 progenitor. In contrast, laboratory strain R6 contains 71 single base pair changes, 6 deletions, 4 insertions, and has lost the cryptic pDP1 plasmid compared to the D39 progenitor strain. Many of these mutations are in or affect the expression of genes that play important roles in regulation, metabolism, and virulence. The nature of the mutations that arose spontaneously in these three strains, relative global transcription patterns determined by microarray analyses, and the implications of the D39 genome sequences to studies of pneumococcal physiology and pathogenesis are presented and discussed. Keywords: bacterial strain comparison, bacterial isolate comparison
Project description:To study the effects of secondary bacterial infection during 1918 pandemic H1N1 influenza virus infection, BALB/c mice were inoculated with the fully reconstructed 1918 influenza virus followed by inoculation with pneumococcus 72h later. To study the effects of secondary bacterial infection during 1918 pandemic H1N1 influenza virus infection, BALB/c mice were inoculated with the fully reconstructed 1918 influenza virus followed by inoculation with pneumococcus 72h later.