Thermostable TB vaccine on the horizon

Dr. Aswin Doekhie with a vial of ensilicated protein

A promising TB vaccine can be protected from heat damage with Ensilication - a technique developed at the University of Bath. The method prevents crucial vaccine components from going bad outside of refrigeration, giving hope for the development of a thermally stable vaccine that can be reliably delivered to remote areas around the world.

A new TB vaccine is urgently needed to withstand ‘cold chain’ challenges, especially as up to 50 percent of vaccine doses are discarded before use due to exposure to suboptimal temperatures. Thermostable vaccines are priority research to the World Health Organisation’s Global Vaccine Action Plan 2011-2020.

Ensilication

Ensilication “shrink-wraps” vaccine proteins in position using layers of silica that build up into a cage around the molecules – so 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.

The 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.

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.

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.

“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,” said Lead author Prof Jean van Den Elsen.

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 Sarbaeva, 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.

“With up to 50 percent of vaccines being thrown away, and refrigeration raising vaccine costs by up to 80 percent, this is a major global health challenge that we need to overcome. By demonstrating for the first time that ensilication works to protect vaccine-relevant proteins from breaking down outside a fridge, we’re a big step closer to achieving this goal.”