Imma Perfetto
Cosmos science journalist
As global immunologists race to get ahead of bird flu there’s some good news from Australia where scientists have found that molecules on the inside of highly pathogenic influenza A H5N1 virus could be promising targets for human vaccines.
A new study found these proteins remain largely unchanged among different viruses, which suggests that vaccines could defend not only against H5N1, but other strains of influenza A too.
And, according to the paper’s lead author, Dr Emma Grant from Australia’s La Trobe University, people exposed to the current strains of influenza circulating in humans may already have some level of immunity against H5N1.
Since 2020, outbreaks of H5N1 have been occurring on every continent except Australia, causing outbreaks and deaths among wild birds, poultry, and mammals.
“Cases of H5N1 in humans are rare, but they do happen,” says Grant.
“If someone has been in close proximity for a long time with infected animals, such as farm workers, they can catch the infection from their livestock.”
There have been includes 70 human cases and one death in the current US outbreak in poultry and dairy cattle.
“T cells – our own immune cells that defend us against pathogens – can recognise viruses they’ve previously come into contact with,” says Grant.
“If we can use this knowledge to develop vaccines using the parts of the virus that T cells recognise, we might be able to protect ourselves from future flu mutations.”
Current flu vaccines present the immune system with haemagglutinin – a protein on the surface of influenza A viruses that denotes the “H” in the virus name.
There are 18 types of haemagglutinin. H1 and H3 most commonly bind with and infect human cells, while H5 typically binds with animal cells in birds, marine mammals and cattle.
Current vaccines are effective at defending humans against H1N1 and H3N2 influenza A viruses and influenza B viruses, which cause seasonal flu. However, influenza viruses mutate quickly, which makes it difficult to inoculate against all strains.
“With each vaccine, we mount an immune response to the haemagglutinin in the vaccine, but once the virus has significantly mutated these proteins, our immune system can no longer recognise it,” she says.
But the new research indicates that, of the molecules inside influenza A viruses that are recognised by T cells of the human immune system, 64% remain unchanged between different H5N1 viruses from clade 2.3.4.4b.
These “conserved” molecules must therefore play an important role in the virus life cycle and cannot mutate too much without interfering with it.
Because these conserved molecules can be recognised by human T cells, they could make a promising new vaccine target.
“If we could develop a new vaccine using these conserved molecules from inside the virus, we might be able to protect against lots of different flu viruses,” says Grant.
“That’s the long-term goal.”
The research appears in the journal Clinical & Translational Immunology.
