Fig. 4.

SPIN is important for evasion of MPO-dependent neutrophil killing. (A) S. aureus strains Newman (Left) and USA300 (Right) were killed in a dose-dependent manner by adding 0.7–7.0 nM MPO in a coupled glucose oxidase-MPO system. Addition of 120 nM SPIN prevented ROS killing. Statistical significance was determined by two-way ANOVA with Bonferroni posttest correction for multiple comparison. (B) SPIN provides dose-dependent protection from HOCl-mediated killing for strains Newman and USA300 relative to 0 nM SPIN. Statistical significance was determined by one-way ANOVA with Bonferroni posttest correction for multiple comparison. (C) Differential bacterial survival of Newman WT from neutrophils with active or membrane-permeable AZM198-inactivated MPO. (D) Supernatants of overnight culture of strains WT PlukM-spn, Δspn PlukM-spn, Δspn PlukM-gfp were diluted, tested for MPO activity, and compared with Newman WT. Bars express SD with n = 3 (A–D). (E) Effect of S. aureus survival from isolated neutrophils after 60 min of phagocytosis. Statistical analysis determined by paired Student t test for C and E. Bars express SEM with n = 6. *P ≤ 0.05, **P ≤ 0.01, ****P ≤ 0.0001; ns, not significant.