<i>Salmonella</i> -derived OMVs as a vaccine platform for <i>Riemerella anatipestifer</i> outer membrane proteins to prevent infection in ducks

ABSTRACT Riemerella anatipestifer (RA) is a major pathogen in waterfowl, responsible for severe septicemia and serositis, leading to significant economic losses. As antibiotic resistance becomes more widespread, there is an urgent need for effective, novel vaccine strategies. In this study, we engineered three recombinant RA antigens, PorQ, YaeT, and YiaD, onto the surface of outer membrane vesicles (OMVs) derived from a Salmonella Typhimurium mutant strain using the lipoprotein signal peptide (Lpp). The engineered OMVs were shown to induce robust humoral and cellular immune responses in ducks. Immunization with these OMVs resulted in 80% survival for ducks immunized with OMVs displaying YaeT and YiaD antigens and 70% survival for ducks immunized with OMVs displaying PorQ, following challenge with RA-SD-1 (serotype 2). Furthermore, ducks immunized with OMVs displaying YaeT and YiaD exhibited reduced pathological damage and lower bacterial loads in key organs. These findings demonstrate that OMVs displaying YaeT and YiaD provide strong protection against RA infections, suggesting the potential of OMVs as an effective vaccine platform for waterfowl across various RA serotypes. IMPORTANCE The study addresses a growing challenge in poultry health, as Riemerella anatipestifer (RA) infections continue to cause substantial losses in waterfowl farming. The development of novel vaccines is crucial due to the rise in antibiotic resistance. This study highlights the potential of using outer membrane vesicles (OMVs) as a versatile vaccine platform to display multiple RA antigens. The promising results, including high survival rates and reduced organ damage, indicate that OMVs could provide an effective means to prevent RA infection in waterfowl, paving the way for future vaccine development targeting various serotypes of RA.