Mouse gene could help produce TB- resistant cattle, study shows
Breakthrough as scientists in China
produce genetically modified animals that
are more difficult to infect with
tuberculosis
More news Topics Agriculture
Animals Genetics
Medical research
Genetic engineering technique could
reduce need for culls of infected cattle and
the blanket use of antibiotic drugs.
Photograph: Eduard Korniyenko/Reuters
Hannah Devlin, science correspondent
Monday 2 March 2015 15.00 EST
Scientists have created the first
tuberculosis-resistant cattle using genetic
engineering techniques. The advance
could pave the way for genetically
modified farm animals that would be
automatically protected against disease,
reducing the need for culls of infected
herds and the blanket use of antibiotic
drugs.
The study is the first to show that when
cattle are genetically modified to carry a
protective mouse gene, they become more
difficult to infect and are largely shielded
from the damaging symptoms of the
disease.
Professor Bruce Whitelaw, of the Roslin
Institute at the University of Edinburgh,
said: “The world faces unprecedented
population growth on a backdrop of
competing pressure on agricultural land
and resources. Society needs to embrace
many strategies to address this global
challenge, both traditional and new, with
many seeing genetic engineering as
contributing to the much needed
solutions.”
Bovine TB is endemic to many countries
and the traditional approach to controlling
the disease has been to cull infected herds.
Badgers, which are thought to transmit the
disease to cattle, have also been culled in
field trials in Britain. However, the trials
have been fiercely opposed by
conservation groups and and some experts
concluded that too few badgers had been
killed to make the strategy an effective way
of reducing the prevalence of the disease
on farms. In 2010-2011, bovine TB cost the
government £152m, according to the
Department for Environment, Food and
Rural Affairs (Defra).
In the latest study, published in the
journal Proceedings of the National
Academy of Sciences, scientists from the
Chinese agriculture ministry created 23
genetically modified calves, 13 of which
survived into adulthood. The team used a
gene editing tool, known as TALEN, which
allows scientists to delete naturally
occurring genes and insert new ones with a
high degree of precision.
In laboratory tests, they showed that the
Mycobacterium bovis bacterium, which
causes TB, multiplied far less effectively in
the presence of immune cells taken from
the GM cattle, which had been given a
mouse gene that was known to be
protective against TB.
The scientists deliberately introduced the
TB bacteria into the lungs of three of the
GM cattle and three control cattle and
compared the effects. One of the GM cattle
showed no sign of the illness and the other
two showed far fewer lesions than the
control cattle in their lungs, spleen and
liver, when they were dissected several
weeks later.
In a second transmission test, nine GM
cattle and nine control cows were housed
with infected animals. Six of the GM cattle
were not infected and the other three
again showed minimal symptoms
compared with all nine of the control
animals, whose lungs showed extensive
damage.
Professor Mike Coffey, a livestock expert at
Scotland’s Rural College, said: “This
doesn’t produce completely TB-resistant
cows, but the aim is to raise the general
resistance. This would slow down any
spread of the disease and slowly reduce
the national level in herds.”
Scientists in Britain have been working
towards the same goal using traditional
breeding methods, but that requires
breeding programmes spanning many
generations. “The GM approach cuts out
the middle man,” Coffey said.
The scientists found that the introduction
of the mouse gene, called SP110, did not
appear to have any “spillover” effects on
the activity of the cattle’s natural genes.
The mouse gene was also passed on to the
offspring of the transgenic cattle,
suggesting that it could be introduced in
one generation without the need for
constant genetic manipulation of livestock.
Professor Heiner Niemann, head of the
Institute of Farm Animal Genetics at
Friedrich-Loeffler-Institut, Germany, said:
“These findings are another step towards
the creation of disease-resistant livestock
animals based on advanced genetic tools.
Whether this approach protects cows
against TB infection when exposed to high
doses of the pathogen remains to be
determined.”
Currently, the only genetically modified
animals in Britain are laboratory animals,
but there are a growing number of
practical applications on the horizon. A US
company, Aquabounty, has developed a
hybrid salmon species designed to grow
quicker than traditional fish. Scientists in
New Zealand have genetically modified
cows to produce milk that is less likely to
cause allergic reactions, while another
group in China has engineered cows to
produce milk with similar properties to
human breast milk.
