Fig. 6

Protective efficacy and histopathological analysis of experimental mice challenged with C. jejuni. A Data showed a significant reduction in the cecal load of C. jejuni in mice that received rL. lactis express either cell wall-anchored or secretory form of Hcp compared to the control groups (PBS or NZ9000 only). For each experiment, total of six mice were sacrificed from three independent experiments performed under similar conditions. Data represent mean log₁₀ CFU/gm ± SE of three independent experiments (n = 18). Asterisks indicate a statistically significant difference compared to PBS control group (**P ≤ 0.01) (a). In vitro blocking of C. jejuni adhesion and invasion to human INT407 cells by antigen-specific neutralizing antibody (sIgA) present in the fecal soups of the immunized group (Sec-Hcp) of mice (*P ≤ 0.05; immunized vs. control). Data represent mean log₁₀ CFU/mL ± SE of three mice (n = 6) from two independent experiments (b). A pairwise statistical comparison among the groups was presented using a “P-value matrix” (a, b). The darker boxes represent the P- value closer to 0.01 (significant), while the lighter boxes represent P-value closer to 1 (non-significant). B Histological examination of formalin-fixed paraffin-embedded sections of the cecal tissue collected from unimmunized mice (PBS only) at day 7 post-infection with C. jejuni. Section of cecal tissue showed significant mucosal hyperplasia exhibited by extensive luminal erosion of the epithelial lining, loss of villi, and infiltration of polymorphonuclear cells (black arrow). C. jejuni characterized by spiral morphology was detected in the enterocyte of superficial mucosa (yellow arrowhead). Inset: Magnified image (a). Section of cecal tissue from mice that received empty L. lactis (NZ9000) cells showing focal necrosis in the lining epithelial and glandular cells (black arrow) (b). In case mice that received mucosal administration of rL. lactis expressing Hcp, show evenly organized epithelial cells in a single layer (black arrow). The epithelial cell population in the gland shows a tightly arranged cell structure (yellow arrow). Focal accumulation of eosinophilic proteinaceous material in submucosa in both immunized groups indicates the possible presence of secretory antibodies (arrowhead) (c). Presence of eosinophilic non-inflammatory material beneath the superficial enterocyte lining (arrowhead). The number of goblet cells was more in the Sec-Hcp group of mice (black arrow) (d)