CPRC Update – May 2013

The February 2011 issue of the CPRC update introduced a new avian influenza (AI) research program, initiated as part of the Poultry Science Cluster.* Since that time, scientists from across the country have been working collaboratively to answer the following questions about AI:

How does AI virus adapt?

Certain subtypes of AI virus have moved beyond their natural reservoir of wild birds and have developed the ability to infect domestic poultry, sometimes with devastating results. To better understand the biological basis for this adaptation, Dr. Yohannes Berhane and his team at the Canadian Food Inspection Agency (CFIA) are using modern molecular biology techniques to, in essence, tear apart and reassemble the viral genomes in different configurations in order to mimic mutations observed in the field. Many so-called “re-assortment” AI viruses have been developed and characterized. These studies are revealing how the virus induces immune responses and causes disease in chickens.

How is it transmitted?

Avian influenza viruses are mainly transmitted by direct bird-to-bird contact and by contact with virus-contaminated materials; however, indirect contact or airborne transmission has been implicated in a number of AI outbreaks. By studying aerosolized viruses in carefully controlled experiments in the lab, as well as under commercial conditions, Dr. Jiewen Guan’s lab, also at CFIA, has confirmed that infectious viruses can be transmitted to chickens from the air and from other chickens through indirect contact. The amount of virus required to cause infection through indirect contact is surprisingly small. The results of this research have important implications for how AI is spread.

How does the chicken react?

Dr. Shayan Sharif at the University of Guelph is the lead on research that continues to produce new information on chicken immune responses to AI virus infection and to a commercial vaccine (not approved for use in Canada). Dr. Sharif’s team has identified components of the virus that elicit the greatest immune responses and may, therefore, be suitable components to include in vaccines. A number of molecules that act as adjuvants (immune system boosters) have also been identified that could improve the efficacy of these vaccines.

Is vaccination a viable  strategy?

One of the main goals of the overall research program is to develop a rational strategy to control AI infection in commercial poultry. Such a strategy may include vaccination. Dr. Éva Nagy and her team at the University of Guelph have developed a vaccine system, based on fowl adenovirus (FAdV), that can deliver AI virus antigens to the bird, and that can be administered via injection in the egg pre-hatch, or given orally in feed or water. Dr. Sharif’s group developed a different type of vaccine, based on what is known as a virosome, which can elicit protective immune responses against AI virus.

Dr. Dele Ogunremi and his team of researchers at CFIA have been working with Drs. Nagy and Sharif to assess various administration routes for candidate vaccine systems. The plan is to build upon the foundation laid by this research and to develop a strategy that combines virosome and FAdV-based vaccines. These two vaccines should complement and synergize each other, leading to enhanced protection against infection.

Furthermore, several adjuvants will be screened for their ability to further enhance vaccine efficacy. Candidate vaccine formulations will be tested against a range of low pathogenicity or highly pathogenic AI viruses using various routes of administration to determine which is most protective and practically feasible for the purpose of mass vaccination. It is expected that this research will lead to the creation of vaccine formulations that can mitigate the negative health effects of AI and control spread of the virus from vaccinated and infected birds.

*This research is part of the 2010-13 Poultry Science Cluster, which is supported by Agriculture and Agri-Food Canada as part of Growing Forward, a federal-provincial-territorial initiative. CPRC and a number of industry and government organizations also provided funding for this work.

For more details on these or any other CPRC activities, please contact The Canadian Poultry Research Council, 350 Sparks Street, Suite 1007, Ottawa, Ont., K1R 7S8. Phone: 613-566-5916, Fax: 613-241-5999, e-mail: info@cp-rc.ca, or visit us at www.cp-rc.ca.