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Title: Immunogenicity and efficacy of fowlpox-vectored and inactivated avian influenza vaccines alone or in a prime-boost schedule in chickens with maternal antibodies

Author
item RICHARD-MAZET, ALEXANDRA - Merial Sas Research & Development
item GOUTEBROZE, SYLVAIN - Merial Sas Research & Development
item LE GROS, FRANÇOIS-XAVIER - Merial Sas Research & Development
item Swayne, David
item BUBLOT, MICHEL - Merial Sas Research & Development

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2014
Publication Date: 10/30/2014
Citation: Richard-Mazet, A., Goutebroze, S., Le Gros, F., Swayne, D.E., Bublot, M. 2014. Immunogenicity and efficacy of fowlpox-vectored and inactivated avian influenza vaccines alone or in a prime-boost schedule in chickens with maternal antibodies. Veterinary Research. 45:107. DOI: 10.1186/s13567-014-0107-6.

Interpretive Summary: Killed and live vaccines have been used to control avian influenza (AI) in poultry. In AI endemic countries, meat chickens that produce chicks (breeder hens), are AI vaccinated and therefore, AI-antibodies are passed to the hatched chickens via the egg yolk. Killed AI vaccines do not always induce new protective immunity in chicks that received antibodies from vaccinated hens. This interference by the hen maternal antibodies was lower when hens received only 1 administration of the same vaccine, or the hatched chicks were vaccinated at 1 day with the live vaccine that was an advanced biotechnology vaccine (combining a fowlpox vaccine and an AI hemagglutinin gene) plus a killed vaccine 3 weeks later.

Technical Abstract: Inactivated and fowlpox (FP)-vectored vaccines have been used to control avian influenza (AI) in poultry. In endemic countries, breeder flocks are vaccinated and therefore, maternally-derived antibodies (MDA) are transferred to their progeny. Results of several immunogenicity and efficacy studies performed in birds with or without MDA indicated that the immunogenicity of an inactivated vaccine based on a H5N9 AI isolate (iH5N9-It) was severely impaired in chicks hatched from iH5N9-It-vaccinated breeders. This MDA interference was lower when breeders received only 1 administration of the same vaccine and could be overcome by priming the chicks at day-of-age with a live recombinant fowlpoxvirus vectored vaccine with H5 avian influenza gene insert (rFP-AI-H5). The interference of anti-FP MDA was of lower intensity than the interference of anti-H5 AI virus MDA. The highest interference observed on the prime-boost immunogenicity was in chicks hatched from breeders vaccinated with the same prime-boost scheme. In chicks hatched from hyperimmunized breeders, neither the prime-boost nor 2 administrations of iH5N9-It induced HI titers or H5N1 protection in severe challenge conditions. Thus, the immunogenicity of vaccines in young chicks with MDA depends on the vaccination scheme and the type of vaccine used in their parent flocks. The heterologous prime-boost in birds with MDA may at least partially overcome MDA interference on inactivated vaccine.