Tuberculosis vaccine strengthened

Although more than three billion doses of the BCG (bacillus calmette-guerin) vaccine have been administered to fight tuberculosis, the ability of the vaccine to protect adults is very limited. The vaccine’s efficacy against newly emerging isolates is also very poor.

It is hoped that this new study will strengthen the protective abilities of BCG to fight a disease which still remains a major global threat against health.

The researchers from Max Planck found that by engineering a BCG strain that secretes the listeriolysin protein that punches holes in the membranes of phagosomes, the area where the bacteria responsible for tuberculosis is located, this gives better T cell-mediated immunity.

Because listeriolysin works optimally at a pH of 5.8, the researchers also deleted the urease C gene of BCG, which normally plays a role in pH neutralization of the phagosome. The lack of urease C allows phagosomal acidification and provides an ideal pH environment for listeriolysin.

The new BCG vaccine strain protects mice against tuberculosis significantly better than the parental BCG. Superior protection is not only induced against the laboratory strain of mycobacterium tuberculosis (the bacteria responsible for the disease), but also against a clinical isolate of the Beijing/W family, a strain of tuberculosis that is spreading all over the world, is drug-resistant, and is responsible for the most threatening disease outbreaks.

Recent investigation into the age of the disease, led by the Pasteur Institute in Paris, has led to the re-evaluation of theories describing the origination of tuberculosis. Rather than being 35,000 years old as previously believed, evidence points to its origination nearly three million years ago in an ancient species of bacteria related to the modern bacterial strain. In the light of this discovery it is perhaps even more surprising that scientists have yet to develop a vaccine that offers full immunity to adults.