FIG 6.

Upregulation of IL-33 occurs early and is necessary for AXPN-mediated protection. (A) qRT-PCR analysis of Il33 mRNA in the ceca of antibiotic-pretreated mice infected with C. difficile spores and treated with AXPN or the vehicle control PBS. Data are shown relative to those for untreated, naive mice as the mean ± SE (n = 4 or 5 mice/group). *, P < 0.05, between PBS- and AXPN-treated groups. (B) Levels of IL-33 protein assessed by ELISA (mean ± SEM, n = 4 or 5 mice/group). *, P < 0.05; **, P < 0.01, compared to results for naive or indicated groups. (C to G) Mice were treated with anti-IL-33 or Ig control antibodies 1 day prior to infection with C. difficile spores and drug treatment and every 48 h thereafter for up to 4 days. (C) Survival was monitored over the course of infection. (D) Bacterial burden in the cecal contents was determined at the time of necropsy by qPCR analysis of the quantities of 16S rRNA gene copies of C. difficile relative to the total number of 16S rRNA gene copies in the cecal contents. Expression levels are shown relative to that of the AXPN + Ig group on a log₁₀ scale. (E and F) Toxin levels in cecal contents were determined by ELISA at 30 h postinfection. (G) Neutrophils in the lamina propria were quantified morphometrically. Data are the mean ± SE (n = 4 or 5 mice/group from two or three independent experiments). *, P < 0.05; **, P < 0.01; ***, P < 0.001, compared to results for the AXPN + Ig or indicated groups.