|Bertran, Kateri - Consultant|
|Lee, Dong-huh - Orise Fellow|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2017
Publication Date: 7/21/2017
Citation: Bertran, K., Balzli, C.L., Lee, D., Killmaster, L.F., Swayne, D.E. 2017. Influence of maternal immunity on vaccine efficacy and susceptibility of commercial broilers against highly pathogenic avian influenza virus. Convention Notes of Annual Meeting of The American Association of Avian Pathologists, July 21-25, 2017, Indianapolis, Indiana. 2017 CDROM.
Technical Abstract: Maternal antibodies provide early protection from disease, but may interfere with the vaccination efficacy in short-lived broilers. This study seeks to assess how maternal immunity can interfere with vaccine efficacy against clade 22.214.171.124 H5N2 highly pathogenic avian influenza virus (HPAIV) and how prime-boost protocols using recombinant live vaccines can overcome such interference. Commercial broilers with (AIV Ab+) and without (AIV Ab–) H5 AIV maternal antibodies were used. In Study 1, birds were spray-vaccinated with rNDV-H5 vector vaccine at 3 weeks of age to evaluate how a mass-applicable vector vaccine can overcome passive immunity. All birds were challenged at 5 weeks of age with 106.5 EID50/0.1ml dose of clade 126.96.36.199 H5N2 HPAIV. All sham birds died within 3 days; 20% (AIV Ab–) and 30% (AIV Ab+) of vaccinated birds died, with statistically different mean death times (MDT) of 9.5 and 5 days, respectively. Vaccinated birds had significantly reduced oral virus shedding titers compared to shams, but all vaccinated birds shed and the mean titers were 4 log10/ml. Vaccinated birds had mounted mean antibodies of log2 6.1 (NDV) and 3.9 (AIV) GMT at the time of challenge and log2 =6.0 GMT (NDV and AIV) at termination. In Study 2, birds were vaccinated with rHVT-H5 and rNDV-H5 in different combinations to evaluate how prime-boost can improve vaccine efficacy with and without maternal antibodies to H5 AIV. Our results suggest that mass-applied rNDV-H5 at the farm can partially control HPAIV in enzootic countries, but optimal efficacy might require a prime-boost strategy.