Latest mRNA vaccines mark a new dawn in global fight against viruses4th December 2020
Many had been sceptical of mRNA, worried that it was too fragile and difficult to deliver.
With those limitations now seemingly overcome, researchers who work in the field are already imagining what else the technology could cure: future pandemics, HIV, cystic fibrosis, even cancer.
“People said you’d never be able to deliver it into cells. We now know that’s not a problem. People said you could never get it stable. We now know that can be done,” said Associate Professor Archa Fox, an mRNA researcher at the University of Western Australia.
“For future pandemics, and for other viruses, we now should be able to act much quicker.”
MRNA stands for messenger ribonucleic acid. It is a cut-down sheet of instructions for making proteins.
When a cell needs to make something, it copies the instructions from your DNA onto mRNA – like copying a page from a book onto a sheet of paper.
That sheet is then sent to the cell’s protein factory, which reads the instructions and makes a protein.
An mRNA vaccine quietly slips a new piece of paper into your cells and says “hey, make this instead”.
These instructions are single-use only and get deleted after a protein is made. As they are mRNA, not DNA, scientists think there is no risk the vaccine could affect our DNA.
In the case of COVID-19, Moderna and Pfizer’s vaccines carry the genetic blueprint for SARS-CoV-2’s spike protein, the harpoon it uses to infect human cells.
Their vaccines pack that code into tiny bubbles of fat. After injection, the bubbles enter our cells, where our protein factories read the code and pump out exact replicas of the coronavirus spike protein.
Our immune system then recognises and learns to make antibodies to the spike protein, offering us immunity to the virus.
The technology was pioneered in animals in 1990 but scientists doubted that it would have any bigger applications.
The key problems the virus faced were stability and delivery.
If you inject mRNA directly into our blood, our immune cells will destroy it. It took researchers many years to perfect the delivery system: lipid nanoparticles, which get absorbed by our cells.
Another problem remains: both inside and outside the body, mRNA breaks down quickly at room temperature. Pfizer’s jab needs to be stored at minus 70 degrees.
“That’s a benefit in terms of safety but a downside in terms of distribution,” said Dr Adam Taylor, a virologist at Griffith University.
To beat that challenge, Pfizer and Moderna have invested in giant cold storage chains. Millions of doses of vaccine will be whisked around the world in eskies packed with dry ice.
These challenges were not easy, nor cheap, to overcome. But the intoxicating potential of mRNA is easy to see.
“This technology is hailed as the next generation of vaccines,” said Dr Taylor.
The single biggest advantage of an mRNA vaccine is speed; they can be built almost as soon as the genetic sequence of a new virus is isolated.
That makes them powerful weapons against newly-emerging pandemics, as COVID-19 demonstrates. Some groups hope to build platform mRNA vaccines: a fully-built and tested vaccine that genetic code from a new virus can be bolted on to.
They can be made quickly, cheaply and in huge quantities simply by combining chemicals in a vial. Compare that with a flu vaccine which often needs to be grown inside a chicken egg, which is expensive, difficult and gives the virus a chance to mutate before it is extracted.
But it’s not just speed. MRNA could deliver nearly any kind of protein into the body.
For example, you could use mRNA to deliver instructions to make a protein into the cells of people whose own cellular instructions are corrupted – such as people with cystic fibrosis.
You could deliver instructions for a protein that looks similar to something found in a cancerous tumour, prompting the immune system to attack the cancer (Moderna has such technology in clinical trials right now).
“We’re just at the starting point,” said Dr Fox. “Now we know the concept works. We know it’s tolerable in humans, we know it can be delivered. We can see this future potential.”
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Liam is The Age and Sydney Morning Herald’s science reporter