Prevention of enteric disease by peritoneal cells from Bacillus subtilis exopolysaccharide (EPS)-treated mice (MUC4P.840)

Abstract

Abstract Beneficial microbes modulate host immune responses and prevent pathogen-induced inflammation; the molecular mechanisms involved in this process are only recently being elucidated. The enteric pathogen Citrobacter rodentium shares genetic and phenotypic similarities to the human pathogen enteropathogenic E. coli. We previously demonstrated that probiotic B. subtilis, but not an exopolysaccharide (EPS) null mutant, protected mice from C. rodentium-associated disease. We also showed that purified EPS were sufficient to prevent disease when administered i.p. 24 hr prior to pathogen infection. In addition, we found that B. subtilis and EPS failed to protect TLR2 KO and TLR4 KO mice, suggesting that EPS-mediated protection utilizes both of these pathways. Since EPS bind peritoneal macrophages and because EPS are administered i.p., we hypothesized that peritoneal cells may contribute to protection. To test this idea, we adoptively transferred peritoneal cells from EPS-treated mice to naïve mice and found that these cells could prevent disease. We also show that TLR4 and TLR2 are required by peritoneal cells and non-peritoneal cells, respectively. We hypothesize that B. subtilis EPS mediate their protective effects through TLR4-expressing macrophages. Adoptive transfer studies with sorted cells from wt and TLR4 KO mice will be performed to test this idea.