An experimental vaccine has generated antibody responses against all 20 known strains of influenza A and B in animal tests, raising hopes for developing a universal flu vaccine.
Influenza viruses are constantly evolving, making them a moving target for vaccine developers. The annual flu vaccines available now are tailored to give immunity against specific strains predicted to circulate each year. However, researchers sometimes get the prediction wrong, meaning the vaccine is less effective than it could be in those years.
Some researchers think annual flu jabs could be replaced by a universal flu vaccine that is effective against all flu strains. Researchers have tried to achieve this by making vaccines containing protein fragments that are common to several influenza strains, but no universal vaccine has yet gained approval for wider use.
Now, Scott Hensley at the University of Pennsylvania and his colleagues have created a vaccine based on mRNA molecules – the same approach that was pioneered by the Pfizer/BioNTech and Moderna covid-19 vaccines.
mRNA contains genetic codes for making proteins, just like DNA. The vaccine contains mRNA molecules encoding fragments of proteins found in all 20 known strains of influenza A and B – the viruses that cause seasonal outbreaks each year.
The strains have different versions of two proteins on their surface, haemagglutinin (H) and neuraminidase (N), which are targeted by immune responses. But even within one strain, such as H1N1, there can be slight variations in these proteins, so the version in the universal vaccine will not exactly match every possible variant.
In tests in mice, the team found that the animals generated antibodies specific to all 20 strains of the flu virus, and these antibodies remained at a stable level for up to four months.
In another test, the team gave mice the universal flu vaccine or a dummy vaccine containing code for a non-flu protein. A month later, they infected them with either one of two variants of the H1N1 flu virus, one with an H1 protein that was very similar to the version of the protein in the vaccine, and one with a more distinct version. (SOURCE)
