Influence of transcription regulator SAUSA300_1968 on the virulence protein secretion and immune evasion by Staphylococcus aureus

Abstract

Staphylococcus aureus employs an arsenal of secreted virulence factors to evade host immune responses, such as inducing host cell death pathways or hiding within phagocytes. A previous study indicated that the transcription regulator SA1804 is a novel virulence repressor of S. aureus, and is regulated by SaeRS. However, the function of this regulator in S. aureus pathogenesis remains unclear. In this study, we created a SA1804 homologue, SAUSA300_1968, deletion mutant in the S. aureus USA300 strain LAC, and found that culture supernatant proteins of the mutant exhibit higher cytotoxicity and greater ability to induce the expression of inflammatory cytokines in mouse primary peritoneal macrophages as compared with that of its parent strain. Comparative proteome analysis of secreted protein expression profiles between the two strains was determined through tandem mass tags (TMT). Among the 18 well-known extracellular virulence-related factors that showed significantly different expressions, 17 proteins were up-regulated in the SAUSA300_1968 deletion mutant, including various pore-forming toxins and extracellular proteases. Accordingly, we also found that inactivation of SAUSA300_1968 enhanced S. aureus survival in mouse macrophages. Our data provide novel insights into the role of the SAUSA300_1968 regulator in host immune evasion and S. aureus pathogenesis.