Role of complement in mucosal protection against <i>N. meningitidis</i>.

<p>(A): (i): Cohorts of mice were either left untreated or PMN depleted using the antibody clone RB6-8C5 and were subsequently i.n. infected with inoculi of 10⁸ CFU MC58 or MC58Δ<i>siaD</i> (capsule-deficient mutant). Viable bacteria were recovered and enumerated at day 3 post infection. Bars in graph denote median. * denotes <i>P</i><0.05, using the Mann-Whitney nonparametric test. <i>CEACAM1</i>-humanized cohort infected with MC58 (encapsulated) is the same as in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003509#ppat-1003509-g001" target="_blank">Fig. 1D</a> (day3) and is shown here for comparison (not included in statistical test). (ii): Cohorts of mice were i.n. infected with 10⁸ CFU H44/76 or H44/76Δ<i>siaD</i> (capsule-deficient mutant) and viable bacteria recovered at day 3 post infection. Bars in graph denote median. (iii): Cohorts of mice were i.n. infected with 10⁸ CFU of MC58Δ<i>siaD</i>, H44/76Δ<i>siaD</i> or 2275, which is naturally non-capsulate because it harbors the capsule null locus 2 (<i>cnl-2</i>), grown in presence of 20 µM cytidine-5′-monophospho-N-acetylneuraminic acid (CMP-NANA). Viable bacteria were recovered and enumerated at day 3 post infection. Horizontal bars in graph represent median. (B) Cohorts of mice were i.n. infected with 10⁸ CFU of MC58 with or without receiving Cobra venom factor (CVF) 4 h prior to infection. Viable bacteria were recovered and enumerated at day 3 post infection. Data were pooled from at least two individual infections for each group, horizontal bars indicate median. Note that untreated control group is the same as in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003509#ppat-1003509-g001" target="_blank">Fig. 1D</a> (day3). (C): (i): <i>CEACAM1</i>-humanized mice were left untreated or received CVF alone, or anti-Gr-1 antibody clone RB6-8C5 alone, or both in combination at 30 h prior to infection with 10⁸ CFU of MC58. Viable bacteria were recovered and enumerated at day 3 post infection. Data were pooled from at least two individual infections for each group, horizontal bars indicate median. Significance levels are *, **, or *** denoting <i>P</i><0.05, <i>P</i><0.01, or <i>P</i><0.001, respectively, using Kruskal-Wallis test applying Dunn's multiple comparison <i>post hoc</i> test. Note that untreated control group is the same as in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003509#ppat-1003509-g001" target="_blank">Fig. 1D</a> (day 3) and shown here to facilitate comparison. (ii): Cohorts of WT or CEACAM1-humanized mice were injected with CVF or left untreated at 24 h prior to i.n. infection with 10⁸ CFU of strain H44/76. Viable bacteria were recovered at day 3 post infection, horizontal bars in graph represent median.