9th ISAI-Athens, GA, USA


Experimental and field results on the immunity induced by a rHVT-HAHemagglutinin vector vaccine against H5N1 and other H5 type Highly Pathogenic Avian Influenza Viruses.

Yannick Gardin1, Vilmos Palya2, Kristi Moore Dorsey3, Francesco Bonfante4, Darrell Kapczynski5, Walid Hamdy Kilany6, Fabienne Rauw7, Retno D. Soejoedono8.

  1. Ceva Animal Health, Libourne, France.
  2. Ceva Animal Health, Budapest, Hungary.
  3. Ceva Animal Health, Lenexa, KS, USA.
  4. Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (Padova), Italy.
  5. Southeast Poultry Research Laboratory, United States Department of Agriculture, Athens, GA, USA.
  6. National Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Giza, Egypt.
  7. Avian Virology and Immunology Unit, Veterinary and Agrochemical Research Centre (VAR), Ukkel (Brussels), Belgium.
  8. Faculty of Veterinary Medicine, Bogor Agricultural University, Bogor, Indonesia.

Vaccination against H5N1 Highly Pathogenic Avian Influenza Virus (HPAIV) is one of the possible means available for affected countries to control the disease once it has become endemic. Efficacy of vaccination against AIAvian Influenza relies essentially, but not exclusively, on the capacity of the vaccine to induce immunity against the targeted virus (which is prone to undergo antigenic variations) as well as its capacity to overcome interference with maternal immunity transmitted by immunized dams to their progeny. This property of the vaccine is a prerequisite for its administration at the hatchery, which assures higher and more reliable vaccine coverage of the chicken populations than vaccination on the farm.
A vector vaccine (Vectormune AI) based on HVTHerpes Virus of Turkey carrying the haemagglutinin gene of an H5N1 HPAIV as an insert, has been used in several experiments conducted in various research laboratories as well as in controlled field studies. The results have demonstrated high degree of cross protection against various genetic clades of the H5N1 HPAIV and high degree of efficacy was even observed against challenge with the 1994 Mexican H5N2 HPAIV as well as the more recent 2014 Germany H5N8. Furthermore, active immunity induced by this vaccine was not impaired by the presence of passive immunity, but on the contrary, cumulated with it for improved early protection.
The recorded levels of protection against the different challenge viruses showed some variations in terms of post-challenge mortality as well as challenge virus shedding. Although this should be further investigated, it is believed that this was probably more attributable to the variability in trials conditions, materials, methods and results, rather than variations in immunizing capability of the vaccine against various H5 strains of HPAIVs.
The data highlight the possibilities offered by this vaccine to be used as a useful and reliable tool to complement biosecurity and sanitary policies for better controlling the disease due to H5 type AI.

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