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| 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.”
