New vaccine delivery system targets cattle respiratory diseases

Saskatoon, Sask., December 4, 2002

It could be called a Trojan-horse approach to vaccine delivery. Researchers at the Veterinary Infectious Disease Organization (VIDO) in Saskatoon have developed a virus to shepherd vaccine antigens into the respiratory tracts of cattle, immunizing the animal against diseases that cost producers $1 billion annually in North America.

The virus, a modified version of Bovine adenovirus-3 (BAV-3), is a live vaccine vector that offers several key advantages for cattle producers and commercial development, says Dr. Suresh Tikoo, Program Manager (Virology). The virus is harmless to the animal, targets the respiratory tract and is relatively inexpensive to produce.

"This vaccine delivery system is what we call a 'platform technology,' due to its broad potential for use against many pathogens," says Tikoo. "It works as a beacon, with a unique ability to carry vaccine antigens and inject them into cells in the respiratory tract."

VIDO researchers identified BAV-3's potential several years ago and since then have modified and tested the virus for use as a vaccine vector. VIDO has several patents on the technology and it has passed the crucial "proof of concept" testing stage, which is essentially a stamp of approval for effectiveness.

The vector's most immediate potential is for intranasal delivery against bovine respiratory disease pathogens, says Tikoo. VIDO is working with industry partners to fully explore its market potential.

"An important advantage from a commercial perspective is this virus is quick and easy to produce," he says. "That's important because production cost is often the main limiting factor in making a new vaccine economically feasible."

Modified-live vaccines induce much stronger and longer lasting immune responses than other traditional vaccines, but there are concerns about their safety and stability, says Tikoo. Because the modified BAV-3 adenovirus is non-pathogenic, it can be used without any danger of causing disease.

"Even if the virus were to mutate back to its non-modified form, it would still be harmless," he says. "It was isolated from normal, healthy cattle and poses no risk when introduced to other animals. That's a major reason why we chose to develop this particular adenovirus."

The development process revolved around two key stages of intensive science, says Tikoo. Researchers first performed a molecular characterization of the virus and identified sequences of genes that could be deleted without damaging the virus' effectiveness. They then tested the potential to replace these deleted genes with protective antigens of respiratory disease-causing organisms. The result is a well-honed vector system ready to be tailored for use with different antigens.

"We expect a lot of longevity out of this technology," he says. "We've developed a very good system for modifying the virus, to the point that we can construct a new virus in less than 20 days. In time, we hope to develop the system for many viral antigens."

The BAV-3 vaccine vector research has received broad industry and government support. Supporters have included: Alberta Agriculture Research Institute, Saskatchewan Agriculture Development Fund, Saskatchewan Beef Development Fund, Saskatchewan Horned Cattle Trust Fund, Saskatchewan Cattle Marketing Deductions Fund, B.C. Cattlemen's Association, Manitoba Cattle Producers Association, Kamloops Stockmen's Association, Ontario Cattleman Association, Natural Science and Engineering Research Council of Canada, Canadian Institute of Health Research, Saskatchewan Health Services Utilization and Research Council, Governments of Manitoba and British Columbia and private sector partners.

VIDO is a world leader in vaccine research for the control of infectious diseases in food animals and poultry and is a wholly owned University of Saskatchewan not-for-profit institute. It operates with substantial support from the Government of Alberta and the Government of Saskatchewan as well as Government of Canada competitive grants.

For more information, contact:

Stuart Bond
Associate Director, Producer Relations
Veterinary Infectious Disease Organization
Phone: (306) 966-7465
Fax: (306) 966-7478