Superantigens Subvert the Neutrophil Response To Promote Abscess Formation and Enhance Staphylococcus aureusSurvival In Vivo

ABSTRACTStaphylococcus aureusis a versatile bacterial pathogen that produces T cell-activating toxins known as superantigens (SAgs). Although excessive immune activation by SAgs can induce a dysregulated cytokine storm as a component of what is known as toxic shock syndrome (TSS), the contribution of SAgs to the staphylococcal infection process is not well defined. Here, we evaluated the role of the bacterial superantigen staphylococcal enterotoxin A (SEA) in a bacteremia model using humanized transgenic mice expressing SAg-responsive HLA-DR4 molecules. Infection with S. aureusNewman induced SEA-dependent Vß skewing of T cells and enhanced bacterial survival in the liver compared with infection by seaknockout strain. SEA-induced gamma interferon, interleukin-12, and chemokine responses resulted in increased infiltration of CD11b+Ly6G+neutrophils into the liver, promoting the formation of abscesses that contained large numbers of viable staphylococci. Hepatic abscesses occurred significantly more frequently in S. aureusNewman-infected livers than in livers infected with the Newman seaknockout strain, promoting the survival of S. aureusin vivo. This represents a novel mechanism during infection whereby S. aureusutilizes SAgs to form a specialized niche and manipulate the immune system.