Scientists at La Trobe University have identified a possible defence for humans against the influenza virus H5N1 – commonly known as 'bird flu' – which could open avenues of research for new vaccine development.
The research, published in Clinical & Translational Immunology, showed that target molecules inside the newly circulating H5N1 virus which can be recognised by human "killer" T cells do not change in 64 per cent of these T cell target molecules.
The paper's first author Dr Emma Grant, from the La Trobe Institute for Molecular Science (LIMS) and the School of Agriculture, Biomedicine and Environment (SABE), said the research suggests vaccines targeting these molecules could be developed to defend against different strains of flu – not just bird flu.
Dr Grant also said those exposed to the current strains of influenza circulating in humans may already have some level of immunity against H5N1.
"Cases of H5N1 in humans are rare, but they do happen. 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," she said.
"T cells - our own immune cells that defend us against pathogens – can recognise viruses they've previously come into contact with. 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."
Currently, human influenza vaccines use Hemagglutinin – a protein on the surface of the virus that is denoted by the "H" in the virus name – to train our immune system to recognise the flu.
There are 18 types of Hemagglutinin, with H1 and H3 most commonly binding with and infecting human cells, while H5 typically binds with cells in animals such as birds and, more recently, cattle.
Dr Grant said that although current vaccines are effective at defending humans against the 3-4 specific types of influenza they were created for, the virus mutates quickly which makes it difficult to inoculate against all strains.
"With each vaccine, we mount an immune response to the Hemagglutinin in the vaccine, but once the virus has significantly mutated these proteins, our immune system can no longer recognise it," she said.
However, Dr Grant's research showed that several molecules inside the virus were highly conserved in most cases – meaning, they were unchanged, or much less likely to change, even if the rest of the virus was quite different.
These conserved types of molecules can be recognised by T cells, which Dr Grant said means they could make a good 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. That's the long-term goal."
To date, there have been 67 human cases of H5N1 in the USA in the current outbreak, including one death.
Dr Grant said this could change if the virus mutates, but the research suggested those who have already had other influenza exposures or infections, might be protected.
"If human-to-human transmission or human infection of H5N1 becomes more common, these people may have some level of protection already, which may help prevent severe disease," she said.
Dr Grant and her group at LIMS and SABE focus on understanding the immune response to influenza.
The research was conducted by Dr Grant and Professor Stephanie Gras, and published in Clinical & Translational Immunology.
Dr Grant is
