Fig. 1.

Differential adhesion of PilE- and PilV-defective strains of N. meningitidis. (A) HDMECs, hCMEC/D3, and EA.Hy926 human endothelial cells were incubated 30 min with meningococci. Following infection, unbound bacteria were removed, and adherent bacteria were quantified by plating serial dilution on GCB agar plates and counting CFUs after overnight growth. Adhesion is expressed as the mean ± 95% CI of CFUs normalized to the control infection (WT). Data were analyzed using the Brown–Forsythe test and Welch’s ANOVA. (B) Human skin–grafted SCID mice were infected intravenously with 5 × 10⁶ N. meningitidis (WT; ΔE; ΔV). Graft bacterial loads were quantified at 4 h after infection by serial dilutions on GCB agar plates. Two independent experiments performed with a skin batch from a different donor. Each dot represents a single mouse; data are expressed as log10 of the mean ± 95% CI of CFU/g (B). Data were analyzed using Bonferroni's multiple comparisons. (C) Piliation index. Pili of WT, ΔV, and ΔpilV-complemented strain (ΔV + V) were sheared from the bacterial cells by vortexing and then precipitated with ammonium sulfate. To determine the piliation index, the sheared pilus fraction and the bacterial fraction were analyzed by SDS-PAGE and immunoblotting with anti-PilE antibodies. Piliation indices were normalized to that of the WT. Data are expressed as the mean ± 95% CI and were analyzed using the Brown–Forsythe test and Welch’s ANOVA.