Protection of chickens against avian influenza with nonreplicating adenovirus-vectored vaccine

Abstract

Protective immunity against avian influenza (AI) virus has been elicited in chickens by single-dose in ovo or i.m. vaccination with a replication-competent adenovirus (Ad)-free human Ad vector encoding the AI virus A/Turkey/Wisconsin/68 H5 (AdTW68. H5) or the A/Chicken/New York/94 H7 (AdChNY94. H7) hemagglutinin (HA). The AdTW68.H5-vaccinated chickens were protected against both H5N1 and H5N2 highly pathogenic AI virus challenges. The AdChNY94. H7-vaccinated chickens were protected against an H7N3 highly pathogenic avian influenza virus challenge. Chickens vaccinated in ovo with AdTW68.H5 followed by posthatch i.m. vaccination with AdChNY94.H7 responded to both vaccinations, with robust antibody titers against both the H5 and H7 AI proteins. The use of a synthetic AI H5 HA gene codon optimized to match the tRNA pool found in chicken cells is more potent than the cognate H5 HA gene. Mass administration of this AI vaccine can be streamlined with available robotic in ovo injectors. In addition, Ad5-vectored vaccines can be produced rapidly and the safety margin of the nonreplicating vector is superior to that of a replicating counterpart. Furthermore, this mode of vaccination will not interfere with epidemiological surveys of natural AI infections. Finally, the demonstration that Ad-vectored vaccines can be administered repeatedly without appreciably losing potency highlights the commercial potential of this new class of vaccine in poultry.