EndoS expression and activity, and neutrophil killing assays. (A) Western immunoblot showing EndoS expression in bacterial supernatants. SpeB is shown as a loading control. (B) Lectin blot analysis of murine IgG incubated with bacterial supernatants or rEndoS as a positive control. Opsonized bacterial survival in the presence of human neutrophils: (C) M1T1 GAS strain 5448 and isogenic ndoS knockout, 5448ΔndoS. (D) Exogenous treatment of plasma with rEndoS prior to opsonization of GAS. (E) Heterologous expression of EndoS in NZ131 (serotype M49). Error bars indicate standard deviation from the mean. Experiments were performed in triplicate. * indicates P < 0.05, *** indicates P < 0.001, ns indicates no significant difference.