Comparative Assessment of Seroconversion in Poultry Vaccinated with Two Avian Influenza Vaccines

FromAugust to December 2020, a new outbreak of H5 avian influenza caused anotherserious animal health emergency in Kazakhstan, leading to the deaths or cullingof more than 500 000 chickens. This outbreak renewed interest in developingprevention strategies for this re-emerging infection. In this study, weevaluated poultry seroconversion levels after two H5 vaccines.  Regardless of age, productivity, and schemeof vaccination Super Nick layers (a total of 368 heads) received a single doseof an inactivated whole H5 vaccine or a baculovirus-derived H5 vaccine,respectively.  We assessed theseroconversion by Hemagglutination Inhibition (HI) and Enzyme-LinkedImmunosorbent (ELISA) assays. Cloacal and tracheal swabs were tested forInfluenza A Virus (AIV) by real-time PCR to monitor the field AIV circulation.The analysis of 368 serum samples showed that the inactivated vaccine provideda significantly higher humoral immune response when compared to thebaculovirus-derived vaccine as evaluated by both ELISA and HI in 30, 60, and120 Days Post-Vaccination (DPV). Thus, our study demonstrates that under farmconditions classical Inactivated Avian Influenza (AIV) vaccine induces a higherseroconversion level against the H5N1 virus predicting better protectionagainst field infection, than a baculovirus-derived H5 vaccine.