Development of intimin-enriched outer membrane vesicles (OMVs) as a vaccine to control intestinal carriage of Enterohemorrhagic Escherichia coli

Enterohemorrhagic Escherichia coli (EHEC) are foodborne pathogens causing severe human infections including hemorrhagic colitis and hemolytic uremic syndrome (HUS), particularly in children. Ruminants are the main reservoir of EHEC which colonize their intestinal tract through a mechanism involving the bacterial outer membrane adhesin intimin. Vaccination of cattle has shown efficacy in reducing EHEC O157:H7 shedding in feces. However, most of these vaccines are based on purified proteins and/or require the addition of adjuvants, resulting in expensive vaccines that are not used by breeders. This study introduces the development of a new type of vaccine based on Outer Membrane Vesicles (OMVs) carrying the C-terminal domain of intimin (Int280). A vaccine which combines OMVs carrying luminal Int280 and OMVs displaying surface-exposed Int280 was produced using two addressing systems based on PelB peptide signal and Lpp-OmpA hybrid protein, respectively. This mixed vaccine was tested in a mouse model as a proof of concept using the murine host-specific intestinal pathogen Citrobacter rodentium which shares a similar intimin-based adhesion mechanism with EHEC. Vaccination of mice with OMV-Int280 elicited a strong anti-intimin IgG response. Interestingly, we observed a shortened C. rodentium fecal shedding duration in immunized mice compared to the control group. This OMVs-intimin vaccine therefore represents a promising candidate for the control of EHEC intestinal carriage and fecal shedding in ruminants. IMPORTANCEEnterohemorrhagic Escherichia coli (EHEC) are foodborne pathogenic bacteria causing intestinal infection that may lead to hemorrhagic colitis and hemolytic uremic syndrome (HUS) particularly in young children. There is no effective treatment, and antibiotics are contraindicated because they promote the development of HUS. Vaccination of ruminants, the main reservoir of EHEC, has been proposed as an important strategy to reduce the fecal shedding of EHEC to reduce transmission to humans. Outer Membrane Vesicles (OMVs) derived from E. coli are a highly attractive vaccine platform. Here, we produced OMVs enriched with the C-terminal part of the intimin (Int280). As a proof of concept, we used a mice model of Citrobacter rodentium colonization as a surrogate for EHEC intestinal colonization. Vaccination elicited antibodies against intimin and decreased the duration of fecal shedding of C. rodentium. Therefore, this OMV-Int280 vaccine is a promising candidate to control EHEC intestinal carriage and fecal shedding in ruminants.