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Neutrophils Directly Recognize Group B Streptococci and Contribute to Interleukin-1? Production during Infection.

ABSTRACT: Previous studies have shown that the pro-inflammatory cytokine IL-1? has a crucial role in host defenses against group B streptococcus (GBS), a frequent human pathogen, by recruiting neutrophils to infection sites. We examined here the cell types and mechanisms involved in IL-1? production during infection. Using a GBS-induced peritonitis model in mice, we first found that a large proportion of exudate cells contain intracellular IL-1? by immunofluorescence. Of the IL-1? positive cells, 82 and 7% were neutrophils and macrophages, respectively, suggesting that the former cell type might significantly contribute to IL-1? production. Accordingly, depletion of neutrophils with anti-Ly6G antibodies resulted in a significant reduction in the levels of IL-1?, but not of TNF-? or IL-6. We next found that neutrophils are capable of releasing mature IL-1? and TNF-? directly in response to in vitro stimulation with GBS. The production of pro-IL-1? and TNF-? in these cells required the Toll-like receptor (TLR) adaptor MyD88 and the chaperone protein UNC93B1, which is involved in mobilization of a subfamily of TLRs to the endosomes. Moreover, pro-IL-1? processing and IL-1? release was triggered by GBS hemolysin and required components of the canonical inflammasome, including caspase-1, ASC and NLRP3. Collectively our findings indicate that neutrophils make a significant contribution to IL-1? production during GBS infection, thereby amplifying their own recruitment. These cells directly recognize GBS by means of endosomal TLRs and cytosolic sensors, leading to activation of the caspase-1 inflammasome.

SUBMITTER: Mohammadi N

PROVIDER: S-EPMC4980021 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Neutrophils Directly Recognize Group B Streptococci and Contribute to Interleukin-1β Production during Infection.

Mohammadi Nastaran N Midiri Angelina A Mancuso Giuseppe G Patanè Francesco F Venza Mario M Venza Isabella I Passantino Annamaria A Galbo Roberta R Teti Giuseppe G Beninati Concetta C Biondo Carmelo C

PloS one 20160810 8

Previous studies have shown that the pro-inflammatory cytokine IL-1β has a crucial role in host defenses against group B streptococcus (GBS), a frequent human pathogen, by recruiting neutrophils to infection sites. We examined here the cell types and mechanisms involved in IL-1β production during infection. Using a GBS-induced peritonitis model in mice, we first found that a large proportion of exudate cells contain intracellular IL-1β by immunofluorescence. Of the IL-1β positive cells, 82 and 7 ...[more]

PMID: 27509078

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Project description:Streptococcus dysgalactiae subsp. equeisimilis (SDSE) has Lancefield group G or C antigens. Recent epidemiological studies reveal that invasive SDSE infections have been increasing in Asia, Europe and US. Although SDSE possesses similar virulence factors to S. pyogenes including streptolysin S (SLS) and streptolysin O (SLO), some important S. pyogenes virulence factors including active superantigens, SpeB and a hyarulonic acids capsule are missing in SDSE genome. The mechanisms and the key virulence factors for causing invasive diseases by SDSE are poorly understood. Here, we analyzed the transcriptome of SDSE in vivo using the murine sepsis model, revealing the strategy of SDSE to destruct host tissues with the virulence factors and to scavenge depleted nutrients. The expression of SLO operon increased at relatively early stage of infection while the SLS and hyaluronidases upregulated after 4h post infection. Microarray data suggested that SDSE degraded host tissue polysaccharides by streptococcal-secreting poly/oligosaccharide lyases and simultaneously used the Entner-Doudoroff pathway to metabolize acquired carbohydrates. A global negative virulence gene regulator CsrRS of SDSE modulated the expressions of genes encoding SLS and the carbohydrate metabolism enzymes. Moreover, csrS deficient mutant induced sever systemic hemolysis in mice. The most frequently isolated stG6792 strains from invasive disease secreted abundant SLS and SLO rather than other SDSE emm types, indicating the relationship between the SLS and SLO productions and poor outcome by the stG6792 strain infection. Our findings suggest that the concomitant regulation of virulence factors destructing the host tissues and metabolic enzymes play an important role to produce invasive diseases by SDSE. To analyze gene expressions in group G streptococci with the murine infection model, we developed a custom microarray for Streptococcus dysgalactiae subsp. equisimilis (SDSE) based on the genome sequences of three SDSE strains; GGS_124, ATCC12923 and RE378. We intraperitoneally inoculated 10^8 CFU of GGS_124 stain and the csrS deficient mutant into ddY mice. Bacterial cells were collected from the abdominal cavity at 0, 2, 4 and 8 h post infection. GGS_124 cells were also collected from OD600=0.6 culture in brain heart infusion broth as a control.

Dataset Information

Neutrophils Directly Recognize Group B Streptococci and Contribute to Interleukin-1? Production during Infection.

Publications

Neutrophils Directly Recognize Group B Streptococci and Contribute to Interleukin-1β Production during Infection.

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