Streptococcal IdeS and Its Impact on Immune Response and Inflammation

Survival of the important bacterial pathogen Streptococcus pyogenes relies on its ability to circumvent the antimicrobial actions of innate and specific immune responses and to modulate the inflammatory responses induced during the course of an infection. Inflammatory processes play key roles during streptococcal pathogenesis and streptococcal infections are accompanied by an intense inflammatory state. As an exclusively human pathogen, S. pyogenes has adapted to the various countermeasures employed by its host to fight bacterial infections, in particular to interfere with the effector functions of immunoglobulin G (IgG). For this purpose, S. pyogenes has evolved an IgG-specific endopeptidase, IdeS, which is highly specific for the lower hinge region of IgG. This review summarizes the current knowledge about this intriguing enzyme as well as its role in inflammation and in the attenuation of human immune responses towards streptococcal infection.