Double-barreled live viral vectored vaccines target beef diseases

Posted June 15, 2001


"Double-barreled" live viral vectored vaccines target beef diseases

Saskatoon, Sask., June 14, 2001: Costly beef respiratory and intestinal
diseases may have a potent new enemy in the form of new live viral vectored
vaccines under development at the Veterinary Infectious Disease Organization
(VIDO) in Saskatoon, Sask.

Bovine respiratory and intestinal diseases cost North American cattle
producers approximately $1 billion and $300 million respectively each year.

"One of the most effective ways to fight these disease-causing viruses is to
use vaccines that directly target the appropriate site in the body and
induce an immune response," says Dr. Suresh Tikoo, VIDO Virology Program
Manager. "Live viral vectored vaccines are an excellent way to deliver the
antigens to the right area of the body for the most effective defensive
response to a particular disease."

Tikoo and his team are using the Bovine adenovirus-3 (BAV-3) as the delivery
vehicle for the antigens of diseases such as bovine viral diarrhea (BVD).
"BAV-3 is ideal because it infects the bovine respiratory tract. Also, we
have identified a number of regions within the virus that can be deleted to
cripple the virus so it will not cause disease." By replacing the deleted
genes with the protective antigens of respiratory disease-causing organisms,
we can produce a single-shot multivalent vaccine that induces immunity to a
variety of diseases in cattle - in other words "a double-barreled approach,"
says Tikoo.

A key to the effectiveness of live vaccines is their suitability for
intranasal delivery. "Intranasal delivery of live viral vectored vaccines
targets the respiratory tract, promoting a stronger and longer immune
response over conventional vaccines," explains Tikoo. "Intranasal delivery
also eliminates the needle injection site reaction that can reduce meat
quality."

Besides their potential disease-fighting and meat-quality guarding benefits,
live viral vectored vaccines delivered intranasally do not require the
strong oil-based adjuvants that the other vaccines require, making them
cheaper to produce, he says. "Economic viability of vaccine production is
always an important factor in effective vaccine development strategy. We can
certainly reach standard targets with these vaccines if everything goes
well."

Other VIDO researchers are also working on intranasal delivery systems that
would carry the vaccine antigens.

Considering the economic losses, a cost-effective live vaccine that reduces
respiratory and intestinal disease by 50 percent, should have a dramatic
impact for the producer bottom line. "The positive effects of this
intranasal vaccine will also flow over into the meat processing industry,
since injection site reactions would be avoided."

Support for this research has been received from Alberta Agriculture
Research Institute, Saskatchewan Agriculture Development Fund, Saskatchewan
Beef Development Fund, Saskatchewan Horned Cattle Trust Fund, Saskatchewan
Cattle Marketing Deductions Fund, Manitoba Cattle Producers Association,
Kamloops Stockmen's 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 not-for-profit research institute specializing in food animal and
poultry infectious diseases and is wholly owned by the University of
Saskatchewan. It operates with significant support from the Government of
Alberta and Government of Saskatchewan.

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For more information, contact:

Stuart Bond
Associate Director, Producer Relations
Veterinary Infectious Disease Organization
Phone: (306) 966-7474
Fax: (306) 966-7478
E-mail: bonds@sask.usask.ca