Tuberculosis Vaccine Can Be Protected From Heat Damage

UK scientists working on a new tuberculosis (TB) vaccine have achieved a major step forward by showing that a promising TB antigen and a novel vaccine adjuvant can be protected from heat damage.

‘Ensilication’ is an innovative method developed at the University of Bath (UB), which “shrink-wraps” vaccine proteins in position using layers of silica that build up into a cage around the molecules.

This means they don’t 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.

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

According to a UB press release on August 8, 2019, their method means a thermally stable vaccine that can be reliably delivered to remote areas around the world.

This is important news since 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’. 

Previous research indicates that up to 50 percent of vaccines are discarded before use due to exposure to suboptimal temperatures. 

The UB research team from the Departments of Biology & Biochemistry and Chemistry first 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 that these vaccine components were protected from heat damage when ensilicated and kept on a shelf at room temperature for long periods of time without loss of structure and function.

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

Lead author Professor Jean van den Elsen, said in a press release, “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.”

First author Ayla Wahid, added: “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 research was funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and two Ph.D. studentships were sponsored by the Annette Trust, and Raoul and Catherine Hughes with the University of Bath alumni fund respectively.