Exploration of compounds to inhibit the Panton-Valentine leukocidin of Staphylococcus aureus

Abstract

The Panton-Valentine leukocidin (PVL) of Staphylococcus aureus is associated with necrotizing infections. After binding to complement 5a receptor (C5aR/CD88) and CD45 it causes cytolysis in polymorphonuclear neutrophils (PMNs) as well as inflammasome activation in monocytes. The objective of this study was to test if (ant)agonists of C5aR and CD45 can attenuate the effect of PVL on PMNs and monocytes. We tested the effect of various concentrations of six C5aR (ant)agonists (avacopan, BM213, DF2593A, JPE-1375, PMX205 and W-54011) and one CD45 antagonist (NQ301) to attenuate the cytotoxic effect of PVL on human PMNs and monocytes in vitro. Shifts in the half-maximal effective concentration (EC₅₀) of PVL to achieve a cytotoxic effect on PMNs and modulation of inflammatory cytokine response from monocytes were determined by flow cytometry and IL-1β detection. Pre-treatment of PMNs with avacopan, PMX205 and W-54,011 resulted in 3.6- to 4.3-fold shifts in the EC₅₀ for PVL and were able to suppress IL-1β secretion by human monocytes in the presence of PVL. BM213, DF2593A and NQ301 were unable to change the susceptibility of PMNs towards PVL or reduce inflammasome activation in monocytes. Avacopan, PMX205 and W-54,011 showed protection against PVL-induced cytotoxicity and suppressed IL-1β secretion by monocytes. Clinical studies are needed to prove whether these substances can be used therapeutically as repurposed drugs.

Keywords: Staphylococcus aureus; Antagonist; CD45; CD88; Complement 5a receptor; Panton-Valentine leukocidin.

Fig. 1

Inhibitory effect of C5a or CD45 receptor (ant)agonists on Panton-Valentine leukocidin (PVL)-induced cytotoxicity in polymorphonuclear neutrophils (PMNs) Inhibitor concentrations ranged from 1 nM to 10 µM. C5a receptor antagonists avacopan (A), DF2593A (B), PMX2015 (C), W-54,011 (D), JPE-1375 (E), C5a receptor agonist BM213 (F), and CD45 antagonist NQ301 (G) were added to PMNs prior to incubation with PVL (0.125-4 nM). The cytotoxic effect of PVL is displayed as mean percentage ± SEM of propidium iodide (PI)-stained PMNs from three independent experiments quantified by flow cytometry

Fig. 2

Differential effects of C5a receptor (ant)agonists on PVL-induced cytotoxicity (A) and IL-1β secretion (B) in human monocytes. Percentage of damaged monocytes after treatment with PVL (0-0.5 nM) in absence (black bars) or presence (red bars) of 10 µM competitor is displayed as percentage of PI-stained cells quantified by flow cytometry. Levels of IL-1β (in pg/ml) in culture supernatant were quantified by ELISA. Data represent mean ± SEM of three independent experiments (Tables S2 and S3)