3 March 2015 – Source: www.theguardian.com/science/2015/mar/02/mouse-gene-could-help-produce-tb-resistant-cattle-study-shows

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….

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.”…