Recombinant Fusion Protein Vaccine Containing FliC and FliD Protects Mice Against Clostridioides Difficile Infection

Bacterial flagella are involved in infection through their roles in host-cell adhesion, cell invasion, auto-agglutination, colonization, and formation of biofilms, as well as in the regulation and secretion of non-flagellar bacterial proteins involved in the virulence process. In this study, we constructed a fusion protein vaccine (FliCD) containing Clostridiodes difficile flagellar proteins FliC and FliD. Immunization of mice with FliCD induce potent IgG antibody responses against FliCD and protected mice against C. difficile infection and decrease C. difficile spores and toxin levels in the feces after infection. Furthermore, we found anti-FliCD serum protected mice against CDI and decreased C. difficile spores and toxin levels in the feces after C. difficile infection. Finally, we found that anti-FliCD serum inhibited the binding of C. difficile vegetative cells to HCT8 cells. These results imply that FliCD fusion protein may represent an effective vaccine candidate for the prevention from C. difficile infection (CDI).