PERSONAL DE APOYO
GAROFALO Ailin Natalia
congresos y reuniones científicas
Título:
Role of Sbi in the inflammatory response induced by Staphylococcus aureus
Autor/es:
GOMEZ MARISA; FOSTER TIM; GONZALEZ CINTIA ; LEDO CAMILA; GIAI CONSTANZA; GAROFALO AILIN; MENDOZA ANDREA
Reunión:
Congreso; GORDON CONFERENCE; 2013
Institución organizadora:
2Department of Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin, Ireland.
Resumen:
staphylococcus aureus is an important human pathogen that causes infections with high morbidity and mortality. Among its many virulence factors protein A (SpA) and Staphylococcal binding immunoglobulin protein (Sbi) bind the Fc portion of IgG avoiding opsonophagocytosis. We have previously demonstrated that SpA interacts with the TNF receptor (TNFR) 1 through each of the IgG binding domains and induces the production of pro-inflammatory cytokines. The IgG binding domains of Sbi are homologous to those of SpA, which allow us to hypothesize that Sbi might also have a role in the inflammatory response induced by Staphylococcus aureus. This study was aimed at elucidating the contribution of Sbi in the induction of inflammatory cytokines and chemokines in immune cells. Peritoneal macrophages were stimulated with purified recombinant Sbi containing the four globular domains for different periods of time and cytokines were quantified in the culture supernatant by ELISA. A significant increase in TNF-α and IL-6 production was observed after 2 hours of stimulation (p < 0.01, p < 0.001, Student t Test). IL-1β induction was also observed although it required at least 4 hours of stimulation (p < 0.05 Student t Test). In order to assess the relevance of the inflammatory responses induced by Sbi in the context of whole S. aureus, peritoneal macrophages were stimulated with a sbi- mutant and the sbi+ complemented strain. A significant increase in IL-6 and TNF-α was observed at 2 and 4 hours after stimulation with the sbi+ strain compared to the sbi- mutant, highlighting the importance of Sbi in the induction of inflammatory mediators. We then characterized the intracellular signaling cascade induced by Sbi and determined that it activates Mitogen-activated protein kinases (MAPKs) in macrophages, inducing phosphorylation of p38 and erk1/2 upon 5 and 15 min of stimulation respectively. MAPKs activity was required for the production of IL-6 and TNF-α as demonstrated using specific chemical inhibitors. In order to demonstrate the biological relevance of the in vitro findings we then evaluated the role of Sbi in the induction of inflammatory cytokines and chemokines in vivo by using a model of intraperitoneal inflammation. Mice were inoculated with purified Sbi by intraperitoneal route and serum levels of IL-1β, IL-6 and TNF-α were determined by ELISA at 2 and 4 hours after inoculation. A significant increase in the circulating levels of IL-6 and TNF-α was observed at 2 hours after inoculation (p < 0.001; p