Thermally-stable TB vaccine closer to reality

Thermally-stable TB vaccine closer to reality thanks to microscopic silica cages
Thermally-stable TB vaccine closer to reality thanks to microscopic silica cages

Scientists working on a new TB vaccine for both humans and cattle have achieved a major step forward.

This has been achieved by showing that a promising TB antigen and a novel vaccine adjuvant can be protected from heat damage.

Their method prevents these crucial vaccine components from spoiling outside of a fridge - meaning a thermally stable vaccine that can be reliably delivered to remote areas around the world is more likely.

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' - as up to 50% of vaccine doses are discarded before use due to exposure to suboptimal temperatures.

Thermostable vaccines have therefore been named a priority research area in the World Health Organisation (WHO).

Ensilication, a method developed at the University of Bath, '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 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 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 a thermally-stable TB vaccines, but in showing that ensilication could be used for many different kinds of vaccines.

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."