Oral administration of engineered recombinant outer membrane vesicles-based nano-vaccine formulation triggers robust mucosal and systemic humoral immunity against poultry pathogens

Vaccination plays a crucial role in maintaining poultry health. Yet, there is an urgent need for affordable, scalable, and easily administered platforms to develop new-generation vaccines to tackle emerging and re-emerging infectious diseases. Oral vaccines present an alternative to injectable ones due to their simplicity of administration; however, current platforms do not effectively stimulate strong protective systemic and mucosal immunity. In this research, we utilized engineered outer membrane vesicles (rOMVs) that display the desired vaccine antigens from hypervesiculating probiotic E. coli Nissle 1917 (EcN) [36], which, when given orally, trigger both mucosal and systemic immunity. We aimed to create an rOMV-based single oral vaccine targeting NDV and IBDV, which are significant threats to the poultry industry. We engineered rOMVs to display immunodominant HN and VP2 of NDV and IBDV, respectively, on their surface, with sizes below 150 nm and notable polydispersity. Oral delivery induced a strong immune response, marked by high-titer antigen-specific sIgA and IgG, effectively neutralizing the virus in an in vitro infection model. While NDV and IBDV serve as models for poultry pathogens, rOMV-based platforms have considerable potential for developing multivalent oral biotherapeutic agents, including vaccines against a wide range of emerging human and animal pathogens.