Scientists work on TB vaccine that does not need refrigeration

Scientists are a major step closer to cracking the code for a tuberculosis (TB) vaccine that does not need to be kept cold.

Researchers have been able to show that a promising TB antigen (toxin) and a vaccine adjuvant can be protected from heat damage with a technique developed at the University of Bath.

An adjuvant is a substance which enhances the body’s immune response to an antigen.

The method prevents these crucial vaccine components from spoiling when not in a fridge.

It means a thermally stable vaccine that can be reliably delivered to remote areas around the world is more likely.

Researchers say there is an urgent need not only for a new TB vaccine, but also for methods to keep vaccines stable outside of the refrigeration “cold chain”.

This is because up to 50% of vaccine doses are discarded before use due to exposure to suboptimal temperatures.

Lead author Professor Jean van den Elsen said: “A new TB vaccine is really urgently needed to supplement or replace the existing BCG vaccine and reduce the number of TB cases and deaths – particularly as drug-resistant TB infections remain high.”

Thermostable vaccines have been named a priority research area in the World Health Organisation’s Global Vaccine Action Plan 2011-2020.

The method, ensilication, “shrink-wraps” vaccine proteins using layers of silica that build up into a cage around the molecules – so they do not unravel when exposed to temperatures that would usually break them down.

The proteins are held in place until ready to be removed from the silica cage and delivered.

First the team from the Departments of Biology & Biochemistry and Chemistry demonstrated that the TB antigen ag85b and a vaccine fused with the adjuvant protein Sbi are sensitive to breaking down outside of refrigerated temperatures.

They then showed the components were protected from heat damage when ensilicated and kept on a shelf at room temperature for long periods of time.

The components maintained structure and function.

Scientists say this is the first time ensilication has been used to improve the thermal stability of proteins in a vaccine setting, after proof-of-principle work using model proteins.

The results are a big step forward not only in developing thermally-stable TB vaccines, but in showing that ensilication could be used for many different kinds of vaccines.

First author Ayla Wahid, said: “To make the vaccine as effective as possible it needs to be thermally-stable, or in other words not spoil outside of a fridge, which is why we’re really encouraged by these results.

“Cold-chain storage leads to a lot of wastage and expense which could be avoided by ensilication.”

Dr Asel Sartbaeva, who invented ensilication, added: “Our results reveal the potential of ensilication in storing and transporting life-saving vaccines at ambient temperatures globally – in particular to remote areas of developing countries where disease rates are often highest.”

The study is published in Scientific Reports.