Scientists have
identified new ways to provide vaccines against polio, which do not
require the growth of live virus for their manufacture.
Despite the success of vaccines produced
from ‘virus-like particles’ (VLPs) for hepatitis B and human papilloma
viruses, poliovirus VLPs have proved to be too unstable to make
practical vaccines.
Now, a research team at the University
of Leeds has found a new way to modify these VLPs, also known as “empty
capsids” by identifying mutations which make their structures
sufficiently stable to act as vaccines.
The empty capsids change shape when
warmed and become unusable as vaccines, but the mutations identified in
this research prevent these damaging changes.
Polio is on the verge of being
eradicated worldwide, but even when it has been officially declared as
extinct as a disease, governments will need to continue to vaccinate to
ensure against it recurring.
Using current technology, the production
of vaccine requires the growth of enormous quantities of live virus,
which is then chemically killed, thus presenting a dangerous security
risk of virus escaping into the environment.
These new stabilised VLPs are suitable
as replacements for the current killed poliovirus vaccines and can be
produced in ways that do not require the growth of live virus.
The Leeds team and collaborators say
this form of vaccine, using the newly developed stabilised VLPs, would
be best used after the virus has been eradicated.
David Rowlands, Professor of Molecular
Virology and co-leader of the study at the university, said: “Continuing
to vaccinate after polio has been eradicated is essential to ensure
against the disease recurring, but there are significant biosafety
concerns about current production methods.
“Our new method of creating the vaccine
has been proven to work in lab conditions and on top of that, we’ve
proved it’s actually more stable than existing vaccines.
“The improved stability of these
modified VLPs means that they can be produced using bioengineering
techniques without involving the growth of live virus”.
This study was a lab experiment, which
shows stabilised VLPs to be effective in a controlled environment.
Further research using animals (rats and mice) is planned, as part of
the essential process of making sure the new VLPs are safe and effective
for use in humans.
Professor Nicola Stonehouse, co-leader
of the study, from the University of Leeds said: “The international
drive to eradicate polio using existing vaccines continues, but methods
need to be found to maintain vaccination safely as insurance after it
appears to have been eradicated. This is when our approach will come
into its own.
“Further research is needed to refine
them more but we are confident they will work for all three forms of
polio. After that we need to find a way to manufacture them cost
effectively on a large scale.”
The research has been funded through a
$1.5 million World Health Organisation grant to a consortium led by
Leeds and including the National Institute for Biological Standards and
Control (NIBSC), John Innes Centre (JIC) in Norwich, the University of
Oxford, University of Reading, and the Pirbright Institute.
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