Influenza A virus of the H9N2 subtype is enzootic in poultry in parts of Asia, the Middle East, Europe, and Africa and causes significant economic losses to the poultry industry. Inactivated whole virus vaccines are being used extensively, though they confer limited protection. Modified live virus (MLV) vaccines mimic a natural infection and, therefore, have the potential to induce broader immune responses. We aimed to generate efficacious and safe MLVs carrying molecular markers and immunomodulators. The stability and growth properties of the viruses were analyzed in vitro, whereas safety, immunogenicity, and efficacy were evaluated in two-week-old chickens. MLV candidates were stable and grew to similar levels compared to wild-type viruses in vitro. Because of the fear of reassortment with MLVs, we performed co-infection studies using our vaccine candidates and wild-type viruses. We demonstrated that, upon inclusion of unique molecular markers, our H9 vaccines do not reassort with wild-type strains in vivo. Studies in vivo showed that MLVs given intranasally are safe, immunogenic, and protective upon homologous challenge. To achieve mass vaccination, two-week-old chickens were vaccinated via drinking water with two different doses of our vaccine with the immunomodulator. We confirmed that vaccination via drinking water is immunogenic in chickens. Moreover, we also confirmed that animals vaccinated via drinking water are protected and do not shed virus after a homologous challenge. This work provides novel insight into the development of MLV vaccines against FLUAV-carrying molecular markers and immunomodulators and their mass vaccination application in the field.

Flavio Cargnin Faccin1, C. Joaquin Cáceres1, L. Claire Gay1, Brittany Seibert1, Ana Luiza Soares Fraiha1, Nick van Bentem1, Luis A. Rodriguez1, Ginger Geiger1, Matias Cardenas1, Daniela S. Rajao1, Silvia Carnaccini1, Darrell R. Kapczynski2 and Daniel R. Perez1 1 Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA. 2 Exotic and Emerging Avian Viral Disease Research Unit, Southeast Poultry Research Laboratory, U.S. National Poultry Research Center, Agricultural Research Service, USDA, Athens, Georgia, USA.

Diagnostics, vaccination, or other mitigation strategies for poultry and wildlife