Those who eat beef do not have to be at higher risk of contracting mad cow disease. Researchers have genetically engineered healthy cattle that may resist mad cow disease although further testing continues, according to
new research published in the journal
Mad cow disease or bovine spongiform encephalopathy (BSE) in
cattle is believed to be caused "by propagation of misfolded forms of the
normal cellular prion protein PrPC, such as PrPBSE in bovine spongiform
encephalopathy (BSE) in cattle and PrPCJD in Creutzfeldt-Jakob disease (CJD) in
humans," according to the researchers.
People may contract variant CJD or vCJD, a deadly brain wasting disease in humans, by eating beef from
cattle with mad cow disease.
UK, hundreds of
people have already died from the disease and thousands of
people might have contracted the disease without knowing it, according to early
Using a gene targeting system that was originally developed
to produce drugs such as antibodies in cattle, researchers from Hematech, Inc (a
subsidiary of the Kirin Brewery Company, Ltd), a pharmaceutical research
company based in Sioux Falls, S.D., knocked out the gene that is responsible for
production of prion protein known as PrPC in the studied cattle, making the
|These cows, on a farm in South Dakota, were genetically engineered by scientists to be prion-free, which likely makes them resistant to mad cow disease. (courtesy of Hematech, Inc)|
"By knocking out the prion protein gene and producing
healthy calves, our team has successfully demonstrated that normal cellular
prion protein is not necessary for the normal development and survival of
cattle. The cows are now nearly two years old and are completely healthy,"
stated James M. Robl, Ph.D., President and Chief Scientific Officer of
already successfully produced knockout cattle using the sequential gene
targeting system. We anticipate that prion protein-free cows will be useful
models to study prion disease processes in both animals and humans."
In the current research, researchers from the Agriculture
Research Service or ARS-USDA's chief intramural scientific research agency with
assistance from researchers at Hematech and the
meant to evaluate the prion-free cattle to see if there are any developmental
abnormalities in the GM cattle and if the cattle resist prion diseases.
"The cattle were monitored for growth and general
health status from birth up to 19 months of age. Mean birth and daily gain were
both within the normal range for
General physical examinations, done at monthly intervals by licensed
veterinarians, revealed no unusual health problems," said Juergen Richt,
lead author of the report, from ARS' National Animal Disease Center (NADC) in
"At over 20 months of age, the cattle are clinically,
physiologically, histopathologically, immunologically and reproductively
normal. Brain tissue homogenates are resistant to prion propagation in vitro as
assessed by protein misfolding cyclic amplification," the authors write in
The researchers said, "the PrPC-deficient cattle may be a
useful model for prion research and could provide industrial bovine products
free of prion proteins."
"These cattle can help in the exploration and improved
understanding of how prions function and cause disease, especially with
relation to bovine spongiform encephalopathy, or BSE," said Edward B.
Knipling, administrator of ARS.
The prion theory is just one of a few theories to explain
the mad cow disease, according to a scientist affiliated with foodconsumer.org.
Not all types of vCJD or brain wasting
diseases seem to be equally fetal.
indicated that there may be various forms of brain wasting diseases in humans.
Further testing on the GM cattle will be completed in three
years, according to the ARS. It remains to be seen if the prion-free animals resist mad cow disease.
et al. Production of cattle lacking prion
Nature Biotechnology Published Online December 31, 2006; DOI: