Hydrostatic Filtration Enables Large-Scale Production of Outer Membrane Vesicles That Effectively Protect Chickens against .

is a Gram-negative opportunistic avian pathogen representing an emerging threat to poultry meat and egg production worldwide. To date, no vaccine able to effectively prevent the morbidity associated with infections has been developed yet. Our group previously reported that inoculation of different combinations of outer membrane vesicles (OMVs), FlfA and GtxA-N proteins is effective in preventing lesions caused by infections in layer chickens. Here we report the testing of the efficacy as vaccine prototypes of OMVs isolated by hydrostatic filtration, a simple technique that allows the cost-effective isolation of high yields of OMVs. Layer chickens were immunized with OMVs alone or in combination with FlfA and/or GtxA-N proteins. Subsequent challenge with a heterologous strain showed that immunization with OMVs alone could significantly reduce the lesions following a infection. A second study was carried out to characterize the dose-response (0.25, 2.5 and 25 µg) relationship of OMVs as immunogens, showing that 2.5 μg of OMVs represent the optimal dose to elicit protection in the immunized animals after a similar challenge. Additionally, administration of ≥2.5 μg of OMVs induced specific IgY titers and possibly vertical transfer of immunity.