Background: Chitin contributes to a healthy gut microbial population, modulates the immune response, and attenuates virulence gene expression in Listeria monocytogenes. However, little research is available on the effects of chitin in host-pathogen interactions. Here, we explored the polymer in the context of L. monocytogenes infection.
Objectives: Our studies investigated the modulatory properties of chitin in both host and pathogen and suggest that chitin is an excellent candidate for dietary inhibition of Listeria infection.
Methods: Different chitin concentrations were tested to assess their impact on Listeria infection in HT29-MTX-E12 and C2BBe1 cells. Adhesion/invasion and TEER assays were performed under the influence of chitin and a lux-reporter strain was used to assess virulence gene expression upon infection. ELISA assays were performed to measure cytokine expression in macrophages induced by LPS and Listeria monocytogenes following chitin treatment. For in vivo Listeria infection, dietary chitin was introduced via dietary intervention or incorporation into Listeria growth media. Organ CFU counts, and ileum gene expression were analyzed to study host immunity and Listeria pathogenicity.
Results: Biologically relevant chitin concentrations effectively downregulate L. monocytogenes virulence genes, impacting the ability to adhere to and invade epithelial cells. In macrophages chitin exerted immunomodulatory properties, reducing LPS-activated IL-6 but inducing a TNF-α response. Chitin intervention in Listeria infection resulted in reduced CFU counts. Moreover, gut barrier genes are expressed strongly in groups receiving chitin, indicating a protective local effect. The data suggest that chitin may provide a potential dietary intervention to inhibit L. monocytogenes infection in the gut, reducing the spread of the pathogen in primary and secondary organs.
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