Intracellularly survived Staphylococcus aureus after phagocytosis are more virulent in inducing cytotoxicity in fresh murine peritoneal macrophages utilizing TLR-2 as a possible target

- SOD, catalase and TLR-2 receptor was blocked in isolated peritoneal macrophages.
- More bacteria were escaped killing in presence of host SOD and catalase inhibitor.
- Blocking host anti-oxidants modulated TLR-2 in macrophages after infection.
- Increased catalase and decreased SOD expression were found in bacterial lysate.
- This virulence-based strategy may be useful adjuncts to traditional therapeutics.

Staphylococcus aureus with high virulence potential is contributing to a current public health crisis in both hospital and community settings. TLR-2 and generation of reactive oxygen species (ROS) by phagocytic cells is thought to be an important component of the host's immunity against S. aureus infection. However, response of S. aureus against modulation of host-derived ROS in absence of TLR-2 during acute staphylococcal infection is still remains unclear. Peritoneal macrophages were pretreated with either inhibitors of superoxide dismutase (SOD) or catalase in presence or absence of anti TLR-2 antibody and were infected with S. aureus strain AG-789. Bacteria were recovered after time dependent phagocytosis; intracellular killing, level and expression of SOD and catalase were measured. Phagocytosed bacteria from respective groups were further used for infection to fresh peritoneal macrophages as well as for in vivo infection. Levels of ROS, cytokine, lysozyme, antioxidant enzymes activity and TLR-2 expression were measured. Results revealed that more bacteria were escaped killing in SOD and catalase inhibitor pretreated TLR-2 neutralized macrophages, found to express more catalase and are antibiotic resistant. Infection of fresh macrophages with S. aureus, recovered from SOD and catalase inhibited TLR-2 neutralized macrophages induced lower ROS, lysozyme and cytokine production and caused increased bacterial count. Furthermore, bacterial antioxidants by modulating host-derived ROS could regulate the cell surface TLR-2 expression in murine peritoneal macrophages. So, in the early phase of infection, TLR-2 participates in the innate immune response and targeting bacterial antioxidants might be useful in the alleviation of Staphylococcus aureus infection.