Immune Response to Staphylococcus aureus

Although Staphylococcus aureus is not a high virulent pathogen in healthy persons, this bacterium often persists in various tissues and mucosa and attacks immunocompromised hosts. S. aureus produces various virulence factors containing adhesion molecules and exotoxins. S. aureus tries to colonize using microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) such as fibrinogen binding proteins and clumping factors located on the surface of this bacterium. The proliferating S. aureus cells produce exotoxins containing staphylococcal enterotoxins (SEs), toxic shock syndrome toxin-1 (TSST-1), Panton-Valentine leucocidin, hemolysins, and phenol-soluble modulins. These virulence factors and bacterial constituents containing cell wall components can stimulate host immune system. Typically, SEs and TSST-1 act as “superantigen” and induce massive proinflammatory cytokines. Thus, staphylococcal virulence factors set up active stimulation of host immune system. On the other hand, some factors interrupt performance of immune responses: destruction of leukocytes and trap of IgG by protein A. Although S. aureus seems not to be an aggressive pathogen, vigorous and continuous offense and defense must be executed between S. aureus and host.