Oral vaccines strike infections where they hurt

Saskatoon, Sask., August 10, 2001

New oral cattle vaccines in development at the Veterinary Infectious Disease Organization (VIDO) in Saskatoon, Sask., could increase vaccine effectiveness, decrease producer workloads and reduce the risk of meat damage due to needle injections.

“Conventional vaccines injected either into the muscle or under the skin induce a strong, specific response in the blood,” says Dr. Phillip Griebel, Immunology Program Co-ordinator. “But they are inefficient at producing a protective response in mucosal surfaces such as the lungs and intestinal tract, where disease agents actually enter the body.”

To improve the response at those sites, vaccines need to be delivered directly to those surfaces and oral vaccines have the ability to do that, he says.

For producers, oral vaccines formulated for feed or mineral blocks could mean less work. “Both needle injection and intranasal delivery can be labour-intensive, even when administering to young calves. Oral vaccines would also be less stressful on the animals,” he adds.

Meat quality is another driving force behind research on oral vaccine delivery, says Griebel. “This research is one of many projects underway at VIDO to find alternatives to needle injection, which would address meat quality and safety issues associated with needle use.”

Oral vaccines offer an impressive package of advantages, but Griebel, Dr. George Mutwiri, a VIDO immunologist also working on the project, and their team still face a few obstacles.

How to move the vaccine through the rumen without damaging or inactivating it is one of the major hurdles, he says. To do that, Griebel and Mutwiri are using alginate microspheres to carry the vaccine. These alginate microspheres are tiny enough to be absorbed by the Peyer’s patches, the specialized lymphoid tissue in the gut that acts as a quick portal for the vaccine. Alginate, an extract of seaweed, is used in human food products.

“This food product, which is used as a thickener in ice cream, is ideal for oral vaccines because it gels into little droplets when sprayed through a specialized spray nozzle and if mixed into salt solution. Formulating a vaccine in alginate microspheres requires no harsh chemicals and no high temperatures, making vaccines easy to produce.”

Alginate has great potential as a platform technology that could be used for a variety of vaccines and even to reformulate existing vaccines, he says. “We have found that defensive responses to oral vaccines in the small intestine can also spread to other mucosal surfaces, meaning oral vaccines have additional potential to protect those other surfaces from infections.”

Most of the respiratory diseases in cattle, diarrheas in newborn calves and venereal diseases are potential targets for oral vaccines. A key to protecting cattle against many of these diseases is to vaccinate in the first 28 days of life. Young calves, therefore, are presently the main targets of the research, says Griebel.

Currently, the focus is on finding the right formulation of the test vaccines to ensure the proper uptake by the intestinal tract and to produce a strong immune response.

“While we are still a few years away from seeing oral vaccines as a commonplace alternative to conventional vaccines, we believe we have found the technology to make these vaccines work. Their strong potential means oral vaccines will become an important disease management option for the industry in the future,” says Griebel.

VIDO is a non-profit research institute wholly owned by the University of Saskatchewan. It is a global leader in food animal vaccine research for the control of infectious diseases and operates with significant support from the Province of Alberta and the Province of Saskatchewan. This research is currently funded by Saskatchewan Horned Cattle Trust Fund, Saskatchewan Cattle Marketing Deductions Fund, Kamloops Stockmen’s Association, Manitoba Cattle Producers, Alberta Agriculture Research Institute, Beef Cattle Industry Development Fund, Health Services Utilization and Research Commission, National Science and Engineering Research Council, Ontario Cattleman’s Association, Saskatchewan Agriculture Development Fund and Beef Development Fund and Western Canadian Adaptation and Rural Development.

For more information, contact:

Stuart Bond
Associate Director, (Marketing and Business Development)
Veterinary Infectious Disease Organization
Phone: (306) 966-7474
Fax: (306) 966-7478