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Pneumococcal BgaA promotes host organ bleeding and coagulation in mouse sepsis model

ABSTRACT: Streptococcus pneumoniae is a major cause of invasive diseases, such as pneumoniae, meningitis and sepsis resulting in high mortality. The molecular mechanisms and disease developing mechanism underlying pneumococcal infection remain unknown. Previously, we reported that S. pneumoniae β-galactosidase (BgaA) is evolutionarily conserved and contributes to pneumococcal pathogenesis in mouse sepsis model. BgaA is also known to play a role in pneumococcal growth, resistance to human neutrophil opsonophagocytic killing, bacterial adherence to human epithelial cells. In this study, since the detailed role that BgaA plays in sepsis remain unknown, we focused on the role of BgaA in pneumococcal sepsis. Our in vitro assays showed that BgaA promoted bacterial association with human lung epithelial and vascular endothelium cells. BgaA also contributes to pneumococcal survival with human blood by suppressing neutrophils killing, whereas BgaA did not affect pneumococcal survival in mouse blood. In a mouse sepsis model, mice infected with S. pneumoniae bgaA deletion mutant strain exhibited up-regulated host innate immunity pathways, and suppressed tissue damages and blood coagulation as compared to mice infected with the wild-type strain. These results suggest that BgaA works as a multifunctional virulence factor for inducing host tissue damages and blood coagulation. BgaA could be an attractive target for drug and vaccine development.

ORGANISM(S): Mus musculus

PROVIDER: GSE190418 | GEO | 2022/07/18

REPOSITORIES: GEO

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Project description:Background Mortality from bacterial meningitis, predominately caused by Streptococcus pneumoniae, exceeds 50% in low and middle income countries in sub-Saharan Africa with high HIV prevalence. Underlying causes of high mortality are poorly understood. We examined the host and pathogen proteome in adults with proven pneumococcal meningitis (PM), testing if differentially expressed proteins in CSF were implicated in outcome. Materials/methods CSF proteomes were analysed by quantitative Mass-Spectrometry. Spectra were identified using the Swissprot human and TIGR4 pneumococcal protein libraries. Proteins were quantitated and analysed against clinical outcome. Unique proteins in PM were identified against published normal CSF proteome. Random-Forest models were used to test for protein signatures discriminating outcome. Proteins of interest were tested for their effects on growth and opsonophagocytic killing of S. pneumoniae. Results CSF proteomes were available for 57 Adults with PM (median age 32 years, 60% male, 70% HIV-1 co-infected, mortality 63%). 360 individual human and 23 pneumococcal proteins were identified. Of the human protein hits, 30% were not expressed in normal CSF, and these were strongly associated with inflammation and primarily related to neutrophil activity. No human protein signature predicted outcome. However, expression of the essential S. pneumoniae protein Elongation Factor Tu (EF-Tu) was significantly increased in CSF of non-survivors (False Discovery Rate (q) <0.001). Expression of EF-Tu was negatively co-correlated against expression of Neutrophil defensin (r 0.4 p p<0.002), but not against complement proteins C3 or Factor H. In vitro, addition of EF-Tu protein impaired S. pneumoniae neutrophil killing when osponised with CSF. Conclusions Excessive CSF levels of S. pneumoniae EF-Tu protein was associated with reduced survival in human meningitis. Preliminary studies show EF-Tu inhibits neutrophil mediated killing of S. pneumoniae in CSF. Further functional studies are required to better understand the mechanistic role of EF-Tu during PM.

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Pneumococcal BgaA promotes host organ bleeding and coagulation in mouse sepsis model

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