Safer production of polio vaccines

British researchers have found a way to produce a stable fragment of poliovirus, which could enable safer production of vaccines.

Polio vaccines are required to protect against the virus’s re-emergence; however, existing vaccine production methods require growing live viruses, which poses safety risks. While previous research had suggested that the empty protein shell of poliovirus had the potential to serve as an effective vaccine, these shell particles proved too unstable to be practical.

Now, researchers at the UK’s National Institute for Biological Standards and Control (NIBSC) have developed a method to produce polio protein shells that are stable enough to consider using as vaccines. Their study, published in the journal PLOS Pathogens, shows that these shells can be produced without growing live viruses.

The researchers first identified mutations in the three types of poliovirus which increased shell stability without altering the structures of the shells. By systematically introducing these new mutations into viruses and growing them, the scientists narrowed down the genetic characteristics that allow for extra shell stability.

The team then combined the stabilising genes into a single genome sequence and placed it into a mammalian cell line in the lab. The cells were able to use the genetic code to produce an empty, stable poliovirus protein shell.

When tested in mice and rats, the particles caused the animals to generate high levels of protective antibodies, suggesting that they could function effectively as vaccines. Additionally, the particles can be stored without refrigeration for many months without significant loss of activity.

“The approach we developed was remarkably effective and worked for all three types of polio, so may have applications in the design of vaccines against other virus diseases,” said Dr Andrew Macadam, lead scientist at NIBSC. “The challenge now is to transfer these designs to production systems that can deliver large quantities cheaply so that a vaccine for global use is feasible.”

Pictured: An image of the cryo-EM density at 3.75A resolution for a stabilised poliovirus empty shell. Image credit: M Bahar, A Kotecha, C Porta, E Fry and D Stuart, Division of Structural Biology, University of Oxford.