BLACKSBURG, Virginia, January 8, 2004 (ENS):
The scientist who cloned Dolly, the world's first cloned
sheep, is now working to clone cattle that are genetically
incapable of developing mad cow disease.
As government officials try to limit the economic and
health risks related to the nation's first case of bovine
spongiform encephalopathy (BSE), or mad cow disease,
found in December 2003, researchers in the Virginia-Maryland
Regional College of Veterinary Medicine (VMRCVM) at
Virginia Tech are attempting to genetically engineer
their way to a BSE free cow.
Associate professor Will Eyestone, who heads the VMRCVM's
transgenic animal research program, is the molecular
reproductive biologist who was senior research scientist
for PPL Therapeutics, the organization that cloned Dolly.
Together with Bill Huckle, associate professor of biomedical
science, Eyestone is using the same somatic cell transfer
technology that PPL used to create Dolly and Mr. Jefferson,
the first cloned calf to to clone a cow without normal
Transmissible spongiform encephalopathies such as mad
cow disease and its human counterpart, variant Creutzfeldt-Jakob
disease, are not caused by bacteria or viruses. The
causative agent is prions, proteins that are a normal
part of the animal's nervous system. But prions can
mutate to abnormal forms, and these fatal brain-wasting
diseases are the result.
If efforts to produce a normally functioning cow that
lacks the genetic ability to code for the production
of prions are successful, the researchers may have found
a strategy for eliminating mad cow and related diseases.
"In order to be susceptible to prion disease,
the individual has to be able to express the prion,"
says Eyestone. "We know that this prion does not
appear to be required for normal functions of life."
We know that if you knock out these prion proteins
in laboratory mice that there is no apparent negative
effect, Eyestone explained. "But the mouse has
not been that informative to us and we are hoping that
the cow will be more so."
This research is funded by the National Institutes
of Health. The goal of the NIH grant is to engineer
a cow that is genetically incapable of producing prions,
and then determine whether the animal is impaired by
the lack of the prion.
Eyestone expects the cow to be cloned later this year.
While the prospects of "cloning" prion free
cattle on the scale of America's 100 million head cattle
herd may seen daunting, Eyestone points out that with
the widespread use of artificial insemination in modern
agriculture, great strides could be made in as few as
On a smaller scale, Eyestone envisions sub-populations
of prion free cattle that are produced to make pharmaceutical
compounds for human use, eliminating the risk that a
drug produced to promote human health might in fact
cause a fatal transmissible spongiform disease.