Panton-Valentine leukocidin-induced neutrophil extracellular traps lack antimicrobial activity and are readily induced in patients with recurrent PVL+-Staphylococcus aureus infections

Staphylococcus aureus (S. aureus) strains that produce the toxin Panton-Valentine leukocidin (PVL; PVL-SA) frequently cause recurrent skin and soft tissue infections (SSTI). PVL binds to and kills human neutrophils, resulting in the formation of neutrophil extracellular traps, but the pathomechanism has not been extensively studied. Furthermore, it is unclear why some individuals colonized with PVL-SA suffer from recurring infections whereas others are asymptomatic. We thus aimed to (a) investigate how PVL exerts its pathogenicity on neutrophils and (b) identify factors that could help to explain the predisposition of patients with recurring infections. We provide genetic and pharmacological evidence that PVL-induced NET formation is independent of NADPH-oxidase and reactive oxygen species (ROS) production. Moreover, through NET proteome analysis we identified that the protein content of PVL-induced NETs is different from NETs induced by mitogen or the microbial toxin nigericin. The abundance of the proteins cathelicidin (CAMP), elastase (NE), and proteinase 3 (PRTN3) was lower on PVL-induced NETs, and as such they were unable to kill S. aureus. Furthermore, we found that neutrophils from affected patients express higher levels of CD45, one of the PVL receptors, and are more susceptible to be killed at a low PVL concentration than control neutrophils. Neutrophils from patients that suffer from recurring PVL-positive infections may thus be more sensitive to PVL-induced NET formation, which might impair their ability to combat the infection. Importance Individuals colonized by Staphylococcus aureus strains that produce Panton-Valentine leukocidin (PVL-SA) often present with recurrent skin and soft-tissue infections, whilst other individuals remain asymptomatic. PVL is a toxin that kills neutrophils, which results in the formation of neutrophil extracellular traps. Traps induced by other stimuli are known to be toxic to S. aureus. We found however that NETs specifically induced by PVL are not toxic to S. aureus. Furthermore, we show that neutrophils from individuals that suffer from recurring PVL-SA infections are more sensitive to PVL-induced NET formation compared to healthy individuals. The significance of our work is in identifying a mechanism through which PVL-SA may actively counter the engagement of neutrophils. Moreover, we identified that patients with recuring PVL-SA infections may be more sensitive to this mechanism, which may help to explain their clinical condition and might provide avenues for future treatment development.