Streptococcal erythrogenic toxin B abrogates fibronectin-dependent internalization of Streptococcus pyogenes by cultured mammalian cells

Streptococcus pyogenes secretes several proteins that influence host-pathog en interactions. A tissue-culture model was used to study the influence of the secreted cysteine protease streptococcal erythrogenic toxin B (SPE B) o n the interaction between S. pyogenes strain NZ131 (serotype M49) and mamma lian cells. Inactivation of the speB gene enhanced fibronectin-dependent up take of the pathogen by Chinese hamster ovary (CHO-K1) cells compared to th at in the isogenic wild-type strain. Preincubation of the NZ131 speB mutant with purified SPE B protease significantly inhibited fibronectin-dependent uptake by bath CHO-K1 and CHO-pgs745 cells. The effect was attributed to a n abrogation of fibronectin binding to the surface of the bacteria that did not involve either the M49 protein or the streptococcal fibronectin-bindin g protein SfbI. In contrast, pretreatment of the NZ131 speB mutant with SPE B did not influence sulfated polysaccharide-mediated uptake by CHO-pgs745 cells. The results indicate that the SPE B protease specifically alters bac terial cell surface proteins and thereby influences pathogen uptake.