Researchers have potentially made the standard tuberculosis (TB) vaccine more effective at fighting the infection by causing it to burst open cells containing the bacterium that causes the disease.
The improved vaccine, which has so far been tested only in mice, was described in a paper published online last week by the Journal of Clinical Investigation.
The standard vaccine against TB — known as BCG — works in children but provides adults with little or no protection.
It works by stimulating the production of blood cells called 'CD4', which help the body's immune system fight infection. Another type of immune cell called 'CD8' could also help fight TB but the BCG vaccine does not trigger its production.
The immune system also makes cells called macrophages that engulf and kill harmful organisms that invade the body. But the tuberculosis bacterium has found a way to use these macrophages to its advantage. Once inside the body, it enters them and multiplies inside.
The researchers created their improved vaccine by making the existing BCG vaccine produce a protein that can 'punch holes' in the coating of infected macrophages. This makes the infected macrophages burst and send distress signals to both the CD4 and CD8 cells.
When the researchers injected mice with the modified vaccine and exposed them to the TB bacterium, they found that CD4 and CD8 cells together fight the infection more effectively than CD4 alone.
They also found that the potential new vaccine works against a drug-resistant strain of TB that is spreading around the world.
TB kills around two million people every year, most of whom live in the developing world.