Modified vaccine gives hope in battle against bovine TB

Scientists have developed a modified version of the BCG (Bacille Calmette-Guérin) vaccine and a complementary skin test which they believe could protect cattle against TB.

Researchers from the University of Surrey have revealed they have for the first time created a vaccine that is compatible with a synthetic form of the tuberculin skin test, a legally-required test used for the surveillance of TB in cattle throughout the UK.

The variant of the BCG vaccine strain will potentially allow farmers and veterinarians to protect their animals, whilst still maintaining a diagnostic test that can detect TB. 

See also: New test available to aid early detection of Bovine TB

Team leader Johnjoe McFadden told Farmers Weekly that researchers created a “BCG-minus” vaccine by knocking out some genes, without compromising the effectiveness of the live vaccine.

The deleted proteins were then used to develop a new synthetic skin test, which, when injected into the skin of infected cattle with the new strain, will show a response.

However, if the proteins are injected in the skin of vaccinated cattle, there will be no response.

“We have engineered a variant of the BCG vaccine to make it compatible with a synthetic skin test,” said Prof McFadden. “We are hopeful that the new BCG vaccine can be used to protect cows against TB, without interfering with the skin test.” 

Currently, the standard BCG vaccine which is used to protect people against TB and is effective in cattle, is incompatible with the skin test. This is because it can’t distinguish between infected cattle and those that have been vaccinated.

So far, the modified, BCG-minus vaccine has only been tested in guinea pigs and mice, but the team says it is showing good results and they are confident it will also be effective in cattle.

Cattle tests ‘next stage’

The next stage of the work will be to demonstrate that both the synthetic skin test and the BCG-minus vaccine work in cattle herds, which will require funding. 

The latest work was done in partnership with the Animal and Plant Health Agency, Public Health England, and research organisations in India, with funding from the Biotechnology and Biological Sciences Research Council (BBSRC) and the Department of Biotechnology, India.