An O Antigen Capsule Modulates Bacterial Pathogenesis in Shigella sonnei
Fig 5
Group 4 capsule affects the pattern of S. sonnei pathology in the rabbit intestine.
(A) Representative results of histopathological analysis of S. sonnei WT (Ss WT), S. sonnei Δg4c (Ss Δg4c), S. sonnei Δg4c(g4c) (Ss Δg4c(g4c)) and S. sonnei -pSS (Ss -pSS) infected loops after 8 h of single strain challenge. Control sample is the uninfected tissue. Upper row: Hematoxylin and Eosin (H&E) staining of 7 μm slices of rabbit ileal loops. Lower row: immunostaining of 7 μm slices of rabbit loops with a polyclonal S. sonnei GMMA antisera (anti-Ss GMMA) to demonstrate bacteria localization (red dots) and counterstaining with Hematoxylin. (B) Histological alteration observed in the rabbit model following 8 h infection by S. sonnei strains. Severity of villi atrophy is measured according to the ratio between the length and width (L/W) of 120 villi counted on each among at least 4 different loops in 2 different animals (****p<0.0001, Mann-Whitney test). (C) Severity of submucosal edema is measured according to the ratio between the length of the entire mucosal and submucosal layer and the length of the villi (Lvilli+submucosa/Lvilli). 120 measurements were performed on each among at least 4 different loops in 2 different animals (****p<0.0001, Mann-Whitney test). (D) Evaluation of the Shigella-induced pathology for each strain according to the Ameho histopathological grading scale was performed on at least 4 image fields of 4 different loops in 2 different animals (***p = 0.0001, Mann-Whitney test). (E) Induction of IL-8, IL-6 and IL-1β in rabbit loops by S. sonnei Δg4c (Ss Δg4c) relative to S. sonnei WT (Ss WT). Expression levels were measured by RT-qPCR in the set up experiment using an infectious dose of 5x109/loop (the other experiments used 3x109 bacteria/loop). Two loops per strain were inoculated in 2 different animals. The scatter plot shows induction of gene expression in S. sonnei Δg4c loops relative to the adjacent S. sonnei WT loop.