Project description:Streptococcus pyogenes (Group A Streptococcus: GAS) is a major human pathogen that causes streptococcal pharyngitis, skin and soft-tissue infections, and life-threatening conditions such as streptococcal toxic shock syndrome (STSS). A large number of virulence-related genes are encoded on GAS genomes, which are involved in host-pathogen interaction, colonization, immune invasion, and long-term survival within hosts, causing the diverse symptoms. Here, we investigated the interaction between GAS-derived extracellular vesicles and host cells in order to reveal pathogenicity mechanisms induced by GAS infection.
Project description:The complex response of murine macrophages to infection with Streptococcus pyogenes was investigated at the level of gene expression using a high-density oligomer microarray. More than 400 genes were identified as being differentially regulated. Many of the up-regulated genes encoded molecules were involved in immune response and inflammation, transcription, signalling, apoptosis, cell cycle, electron transport and cell adhesion. Of particular interest was the up-regulation of proinflammatory cytokines, typical of the classically activated macrophages (M1 phenotype) such as TNF-?, IL-1 and IL-6, and also the up-regulation of anti-inflammatory mediators such as IL-1ra and IL-10 associated with macrophage alternative activation (M2 phenotype). Furthermore, the gene encoding inducible nitric oxide synthase (iNOS), an enzyme typically implicated in classical activation was not induced in infected macrophages. Instead, the gene encoding arginase, a competitor for the iNOS substrate arginine and involved in the alternative activation pathway was up-regulated in S. pyogenes-infected cells. Thus, the microarray-based gene expression analysis demonstrated that S. pyogenes induced an atypical activation program in macrophages with some but not all features of classically or alternatively activation phenotypes. The microarray data also suggested that the bactericidal activity of macrophages against S. pyogenes is mediated by phagocyte oxydase since p47phox was up-regulated in infected cells. Indeed, the in vivo and in vitro killing of S. pyogenes was markedly diminished in the absence of functional phagocyte (p47phox-/-) but not in the absence of iNOS (iNOS-/-). Understanding how macrophages respond to S. pyogenes at the molecular level may facilitate the development of new therapeutic paradigms. Keywords: infection response
Project description:Manuscript title: Zinc disrupts central carbon metabolism and capsule biosynthesis in Streptococcus pyogenes. Macrophages and neutrophils release free zinc to eliminate phagocytosed bacterial pathogens. The study investigates the effect of how zinc toxicity affects Streptococcus pyogenes. Therefore, a microarray analysis was performed in S. pyogenes cells to determine gene expression changes when exposed to high levels of zinc. We discovered that a pathway involved in tagatose-6-phosphate metabolism was upregulated when the cells are under zinc stress.
Project description:A total of 163 genes were found to be differentially expressed; 38 genes of them were up regulated and 125 genes were down regulated. Most notably the functional categories that were affected include Virulence genes (18 genes 11% of the total significantly differentiated genes), carbohydrate metabolism and cell envelop realted genes ( 31, 19.1% of the total), and aminoacid transport genes (21genes, 12.9%). Among the virulence-related genes, the most notable one were those belong to the production of capsule, the M protein, exotoxin, NAD glycohydrolase and Streptolysin S. Some of the capsule related genes were down regulated by more than 64 fold. These results indicate that CdhA (group A Streptococcal Cell division controlling and Chain-forming cell wall hydrolase) plays an important role in the regulation of virulence. S.pyogenes strain SF370 (wild-type) was procured from ATCC (ATCC 700294). M1-CdhA(-) mutant strain was obtained using pFW5 vector containing spectinomycin resistance marker (aad9). The mutant lacking CdhA is highly defective in cell division and growth, lacks antiphagocytic property and attenuated for virulence. Both strains (M1-Wild-type and M1-CdhA(-) were grown in Todd-Hewitt broth to their late log phase. Bacteria were harvested by centrifugation and washed twice with sterile PBS. Total RNA was isolated from these washed streptococci using Qiagen RNeasy Mini kit. For synthesis and labeling of cDNA, 20 ug of total RNA, 1.5 ug of random hexamer, 0.5mM dNTPs (except that 0.2mM of dTTP was replaced by the same amount of amino-allyl dUTP to incorporate dUTP into first-strand cDNA) were used in each reverse transcriptase reaction (Superscript II Reverse Transcriptase, Invitrogen). Purified cDNA preparations from the wild-type and M1CdhA(-) mutant strains were labeled with either Alexafluor-555 or Alexafluor-647 depending on the experimental design ( i.e. dye swap experiment). Differentially labeled probes were then combined and purified. Using three independently isolated RNA preparations (biological replicates), a total of 11 experiments (incorporating dye swaps) were performed. Accordingly eleven hybridization measurements for this mutant were performed. Thus Exp-1 to -4 (GSM388703, GSM388717, GSM388718 and GSM388719) are the technical replicates of the biological sample-1, Exp-5 to 8(GSM388732, GSM388733, GSM388734, and GSM388735) are technical replicates of biological sample-2 and Exp-9,-10, and -11 (GSM388736,GSM388737, and GSM388738) are technical replicates of the biological sample-3. Signals of the bound reagents on the microarray spots in terms of relative fluorescence values were measured and quantified by a laser scanner (GenePix 4100 ) at 10um/pixel resolution. The resulting images were processed using Gene Pix Pro software (version 4.0, Axon instruments). The raw data were obtained in the form of GenPix *.gpr output files. The web application CARMAweb (Comprehensive R based microarray analysis web service) was used for the normalization and analysis of microarray data. All raw data (in the form of *. GPR files) were uploaded to the web application in the data directory. Using appropriate navigation tree, background correction from the foreground signal was applied and within microarray normalization was achieved using the Lowess method. Genes flagged as bad spots by the scanning software were excluded from the analysis and all flagged spots were given a weight of zero. The normalized data were then subjected to fold-change analysis and t-statistics using Bioconductor multtest package. CARMAweb allows to set Log2 cut-off values for both the M (regulation) and the A (average expression) values. Differentially expressed genes (Log2 values of Mutant647-red vs. wild-type555-green or Log2 values Mutant-555(green) vs Wild-type 647-red) were defined based on cut-off value >1 Log2< i.e. all genes that show a two or more-fold up- or down-regulation. Bioconductors Multtest package provided suitable method to adjust P values according to multiple hypothesis testing problems.