Background The influence of diet on immune function and resistance to enteric infection and disease is becoming
ever more established. Highly processed, refined diets can lead to inflammation and gut microbiome dysbiosis,
whilst health-promoting dietary components such as phytonutrients and fermentable fibres are thought to promote
a healthy microbiome and balanced mucosal immunity. Chicory (Cichorium intybus) is a leafy green vegetable rich in
fibres and bioactive compounds that may promote gut health.
Results Unexpectedly, we here show that incorporation of chicory into semisynthetic AIN93G diets renders mice
susceptible to infection with enteric helminths. Mice fed a high level of chicory leaves (10% dry matter) had a more
diverse gut microbiota, but a diminished type-2 immune response to infection with the intestinal roundworm Heligmosomoides
polygyrus. Furthermore, the chicory-supplemented diet significantly increased burdens of the caecumdwelling
whipworm Trichuris muris, concomitant with a highly skewed type-1 immune environment in caecal tissue.
The chicory-supplemented diet was rich in non-starch polysaccharides, particularly uronic acids (the monomeric
constituents of pectin). In accordance, mice fed pectin-supplemented AIN93G diets had higher T. muris burdens and
reduced IgE production and expression of genes involved in type-2 immunity. Importantly, treatment of pectin-fed
mice with exogenous IL-25 restored type-2 responses and was sufficient to allow T. muris expulsion.
Conclusions Collectively, our data suggest that increasing levels of fermentable, non-starch polysaccharides in
refined diets compromises immunity to helminth infection in mice. This diet-infection interaction may inform new
strategies for manipulating the gut environment to promote resistance to enteric parasites.