Group A streptococcal DNase Sda1 impairs plasmacytoid dendritic cell's type I interferon response.

Group A Streptococcus causes severe invasive infections, including necrotizing fasciitis. The expression of an array of virulence factors targeting specific host immune functions impedes successful bacterial clearance. The virulence factor streptococcal DNase Sda1 was previously shown to interfere with the entrapment of bacteria through neutrophil extracellular traps and TLR9 signaling. In this study, we showed that plasmacytoid dendritic cells are recruited to the infected tissue during group A streptococcal necrotizing fasciitis. We found that the streptococcal DNase Sda1 impairs plasmacytoid dendritic cells recruitment by reducing IFN-1 levels at the site of infection. We found that streptococcal DNase Sda1 interferes with stabilization of the DNA by the host molecule High Mobility Group Box1 protein, which may account for decreased IFN-1 levels at the site of infection.