A universal flu vaccine, capable of working against all strains, would save lives and money by eliminating the need for the annual jab.
Researchers in California and the Netherlands believe they are now a “step closer” to meeting this objective.
By putting the new antibody together with one they discovered two years ago, they hope to make a vaccine that protects against the vast majority of strains.
It would not only stop people catching a virus, they say, but also neutralise it in those already infected – extremely useful in a situation like the swine flu pandemic of 2009.
The NHS spends about £100 million on vaccinating people against flu every year, so a one-off jab that provided good protection could save it a lot of money.
It would also save numerous lives: while official estimates put the annual death toll in the UK at about 500, many virologists think that is a gross underestimate.
Ian Wilson, professor of structural biology at the Scripps Research Institute in La Jolla, California, said a vaccine containing the two antibodies had “the potential to protect people against most influenza viruses”.
Both work by binding to small, unchanging sites on the “envelopes” that cover flu viruses.
These protective layers are studded with mushroom-shaped proteins that attract the attention of the body’s immune system.
This leaves the virus to spread relatively unimpeded, to start with at least.
What makes flu viruses particularly tricky is that these proteins evolve rapidly, so a vaccine that works one year might be redundant the next.
However, scientists from Scripps and Crucell, a Dutch pharmaceutical company, have found that viruses also contain common elements which vary much less.
Antibodies that lock on to these “binding sites” – technically called epitopes – should therefore be able to work year in, year out.
Damian Ekiert, a graduate student at Scripps who has been working with Prof Wilson, explained: “The major goal of this research has been to find and attack relatively unvarying and functionally important structures on flu viruses.”
Two years ago the team identified the antibody CR6261, which in mice has been proven to work against about half of flu viruses, including those from the H1 family.
Such strains were responsible both for the Spanish flu of 1918-19, estimated to have killed up to 50 million people worldwide, and the recent swine flu pandemic.
Now they have found another antibody, CR8020, which appears to work against H3 and H7 strains.
Their work has been published in the journal Science Express.
Human trials of a vaccine based on the former are due to start soon; those on the latter are being planned.
Prof Wilson said that if they both worked separately they could be put into a combined vaccine that not only acted as a prophylactic but also a “fast-acting therapy” against epidemic or pandemic strains.
He said: “The ultimate goal is an active vaccine that elicits a robust, long-term antibody response against those vulnerable epitopes; but developing that is going to be a challenging task.”
Using antibodies is only one approach to developing a universal flu vaccine.
Other groups are looking at alternatives, such as “priming” the body’s immune system with a “base” of influenza DNA.