A new vaccine designed to boost flagging immunity against TB in adults has been developed by scientists in the US.
As many as one in four people worldwide are thought to be infected with TB, which claims thousands of lives every day, partly because whilst the BCG vaccine can protect young children from developing severe disease and TB meningitis, the beneficial effects tend to wear off in adults, leaving them vulnerable again. When this happens, further BCG boosters are ineffective, meaning that a new vaccine is needed, especially since the advent of multi-drug resistant strains of the bug.
Now scientists think they may have the answer. Writing in the journal Science Translation Medicine, a team led by Seattle-based scientist Steve Reed, from the Infectious Disease Research Institute, explain how they have built an effective "super-vaccine" called ID93 that can rekindle the immune response and provide protection. The team developed the vaccine from four TB bacterial protein antigens known to play a role in the bug's virulence and ability to persist in the body long term. The researchers produce large amounts of the proteins by adding the genes encoding them to E. coli bacteria.
The resulting antigens were then combined with an immune-stimulating chemical called an adjuvant and injected into guinea pigs. Some of the guinea pigs had already also received a previous BCG vaccine, to mimic the situation of a human adult.
When the guinea pigs were challenged with TB infection, those given the new vaccine all remained healthy; however, more than two thirds of the animals that had received only the BCG vaccine shows signs of TB infection and had to be euthanased.
The team also tested the vaccine on non-human primates as a prelude to initiating clinical trials in humans and found that it triggered the production of TB-targeted white blood cells and antibodies, suggesting that it would be well tolerated and effective in humans and provide a novel way to tackle TB resurgence amongst adults.