Study: New vaccine to stop bovine TB developed
To do this, a collection of BCG strains that had each lost a single gene were injected into cows and survival rates measured. This allowed the team to identify genes that could be removed without compromising the BCG vaccine's effectiveness. These dispensable genes encoding immunogenic proteins were then deleted from the BCG chromosome to make a BCG-minus strain.
The deleted immunogenic proteins were then used to develop a new synthetic skin test that, like PPD, will be positive for animals that have been exposed to TB but, unlike PPD, will be negative for animals that have been vaccinated with the BCG-minus strain.The protective efficiency of the new strain was tested in guinea pigs.
It was found that TB-infected guinea pigs tested positive for the disease using the synthetic skin test whilst guinea pigs vaccinated with the BCG-minus strain did not. So, unlike PPD, the new skin test also works in animals that are protected from TB by BCG-minus vaccination. This potentially allows farmers and veterinarians to protect their animals with the new BCG vaccine, whilst still maintaining a diagnostic test that will detect TB.