Reassortment Incompetent Live Attenuated and Replicon Influenza Vaccines Provide Improved Protection Against Influenza in Piglets

Abstract Swine influenza A viruses (swIAV) cause an economically important respiratory disease in modern pig production. Continuous virus transmission and antigenic drift are difficult to control in enzootically infected pig herds. Here, antibody-positive piglets from a herd enzootically infected with swIAV H1N2 (clade 1 A.3.3.2) were immunized using a homologous prime-boost vaccination strategy with novel live attenuated influenza virus (LAIV) based on a reassortment-incompetent bat influenza-swIAV chimera or a vesicular stomatitis virus-based replicon vaccine. Challenge infection of vaccinated piglets by exposure to H1N2 swIAV-infected unvaccinated seeder pigs showed that both LAIV and replicon vaccine markedly reduced virus replication in the upper and lower respiratory tract, respectively, compared to piglets immunized with commercial heterologous or autologous adjuvanted whole-inactivated virus vaccines. Our novel vaccines may aid in interrupting continuous IAV transmission chains in large enzootically infected pig herds, improve the health status of the animals, and reduce the risk of zoonotic swIAV transmission.