Group A Streptococcus Prevents NOX‐2 Complex Formation to Limit Oxidative Burst in Macrophages

Abstract

Group A Streptococcus (GAS) is a Gram positive bacterial pathogen responsible for about 500,000 deaths a year, causing diseases ranging from superficial pharyngitis to acute rheumatic fever. Immune cells such as macrophages and neutrophils generate reactive oxygen species (ROS) to aid in bacterial destruction. Unlike other bacterial species, GAS lacks enzymes that can detoxify ROS. We thus sought to determine whether GAS can prevent ROS production altogether. We found that THP‐1 macrophages infected with GAS indeed produce less ROS as measured by DCF‐DA assays. We next sought to determine whether GAS affect the formation of the NOX‐2 enzyme complex that produces ROS. The NOX‐2 complex is made up of cytosolic and membrane bound subunits that come together when activated by the phagocytosis of a pathogen. Analysis of whole cell lysates by Western blot indicate decreased NOX‐2 complex formation in GAS‐infected cells compared with controls. Furthermore, we analyzed recruitment of the cytosolic components to the phagosome membrane by analyzing crude cell fractions. These results confirmed that GAS infection prevents NOX‐2 complex assembly. Interestingly, our data indicates that GAS can not only prevent the formation of the NOX‐2 complex, but can disassemble the complex in stimulated cells. Our findings suggest that one way GAS evades defenses of our immune system is by preventing the formation of toxic ROS. Inducing ROS production in GAS‐infected cells would therefore provide an alternative to antibiotic treatment for GAS infections.Support or Funding InformationAmerican Heart Association (17GRNT3410851), Occidental College Undergraduate Research Center