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Title: Avian influenza in ovo vaccination with replication defective recombinant adenovirus in chickens: Vaccine potency, antibody persistence, and maternal antibody transfer

item MESONERO, ALEXANDER - Auburn University
item Suarez, David
item VAN SANTEN, EDZARD - Auburn University
item TANG, DE-CHU - Vaxin, Inc
item TORO, HAROLDO - Auburn University

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2011
Publication Date: 11/1/2011
Citation: Mesonero, A., Suarez, D.L., Van Santen, E., Tang, D., Toro, H. 2011. Avian influenza in ovo vaccination with replication defective recombinant adenovirus in chickens: Vaccine potency, antibody persistence, and maternal antibody transfer. Avian Diseases. 55:285-292.

Interpretive Summary: Avian influenza virus can infect chickens and other poultry species resulting in mild to severe disease. Vaccination is often used to prevent clinical disease in countries where the virus is widely spread. Unfortunately the costs of the vaccine and the administration costs make it difficult to vaccinate for avian influenza in the U.S. A new vaccine was recently developed using an adenovirus to carry an influenza gene that results in protection for both viruses. Previous work has shown that the vaccine can work well, but the administration costs are still high. However, chickens are often vaccinated inside the egg before they hatch, because this process can be performed cost effectively at the hatchery. This study examined the adenovirus vectored vaccine given by the in egg route of vaccination. This method was effective under some circumstances. Further work to see if it is practical for poultry needs to be done.

Technical Abstract: Protective immunity against avian influenza (AI) can be elicited in chickens in a single-dose regimen by in ovo vaccination with a replication-competent adenovirus (RCA)-free human adenovirus serotype 5 (Ad)-vector encoding the AI virus (AIV) hemagglutinin (HA). We evaluated vaccine potency, antibody persistence, transfer of maternal antibodies (MtAb), and interference between MtAb and active in ovo or mucosal immunization with RCA-free recombinant Ad expressing a codon optimized AIV H5 HA gene from A/turkey/WI/68 (AdTW68.H5ck). Vaccine coverage and intrapotency test repeatability were based on anti-H5 hemagglutination inhibition (HI) antibody levels detected in in ovo vaccinated chickens. Even though egg inoculation of each replicate was performed by individuals with varying expertise and with different vaccine batches, the average vaccine coverage of three replicates was 85%. The intrapotency test repeatability, which considers both positive as well as negative values, varied between 0.69 and 0.71, indicating effective vaccination. Highly pathogenic (HP) AIV challenge of chicken groups vaccinated with increasing vaccine doses showed ,90% protection in chickens receiving 10^8 ifu (infectious units)/bird. The protective dose 50% (PD50) was determined to be 10^6.5 ifu. Even vaccinated chickens that did not develop detectable antibody levels were effectively protected against HP AIV challenge. Intramuscular (IM) booster vaccination with the same vaccine at 16 wk of age significantly increased the antibody responses in breeder hens, and these responses were maintained at high levels throughout the experimental period (34 wk of age). Chickens with high maternal antibody levels that were vaccinated either in ovo or via mucosal routes (ocular or spray) did not seroconvert. In contrast, chickens without MtAb successfully developed specific antibody levels after either in ovo or mucosal vaccination. These results indicate that high levels of MtAb interfered with active Advectored vaccination.