RESUMO
Salmonella Paratyphi A (SPtA) remains one of the leading causes of enteric (typhoid) fever. Yet, despite the recent increased rate of isolation from patients in Asia, our understanding of its pathogenesis is incomplete. Here we investigated inflammasome activation in human macrophages infected with SPtA. We found that SPtA induces GSDMD-mediated pyroptosis via activation of caspase-1, caspase-4 and caspase-8. Although we observed no cell death in the absence of a functional Salmonella pathogenicity island-1 (SPI-1) injectisome, HilA-mediated overexpression of the SPI-1 regulon enhances pyroptosis. SPtA expresses FepE, an LPS O-antigen length regulator, which induces the production of very long O-antigen chains. Using a ΔfepE mutant we established that the very long O-antigen chains interfere with bacterial interactions with epithelial cells and impair inflammasome-mediated macrophage cell death. Salmonella Typhimurium (STm) serovar has a lower FepE expression than SPtA, and triggers higher pyroptosis, conversely, increasing FepE expression in STm reduced pyroptosis. These results suggest that differential expression of FepE results in serovar-specific inflammasome modulation, which mirrors the pro- and anti-inflammatory strategies employed by STm and SPtA, respectively. Our studies point towards distinct mechanisms of virulence of SPtA, whereby it attenuates inflammasome-mediated detection through the elaboration of very long LPS O-polysaccharides.
Assuntos
Inflamassomos/metabolismo , Macrófagos/microbiologia , Macrófagos/fisiologia , Antígenos O/fisiologia , Febre Paratifoide/microbiologia , Piroptose , Salmonella paratyphi A/patogenicidade , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Caspases/metabolismo , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Macrófagos/imunologia , Antígenos O/química , Proteínas de Ligação a Fosfato/metabolismo , Salmonella paratyphi A/imunologia , Células THP-1 , Sistemas de Secreção Tipo III/metabolismo , Virulência , Fatores de Virulência/metabolismoRESUMO
Non-typhoidal Salmonella (NTS) serovars, sequences types and antimicrobial susceptibility profiles have specific associations with animal and human infections in Vietnam. Antimicrobial resistance may have an effect on the manifestation of human NTS infections, with isolates from asymptomatic individuals being more susceptible to antimicrobials than those associated with animals and human diarrhoea.
