A LITTLE protein that pops up on flu viruses the world over could be the key
to creating a universal flu vaccine that can tackle new strains as they
emerge.
Several flu vaccines are already available. They contain some of the proteins
found in abundance on the surfaces of the viruses, thus priming our immune
systems to attack the real thing. But the vaccines become useless within a year
or two as new flu strains evolve, sporting mutated proteins that the immune
system does not recognise. Experts fear a repeat of the flu pandemic of 1918 to
1920, in which 25 million people died.
So scientists are trying to home in on a protein that doesn鈥檛 change rapidly
as the virus evolves. Now Walter Fiers and his colleagues at the University of
Ghent in Belgium say they have found one鈥攁 tiny protein called M2. They
have showed that of the dozen or so flu strains that have been sequenced, almost
all have the same M2 protein dotting their surfaces.
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Fiers鈥檚 team has also found a way to make M2 provoke a strong immune
response. To present large numbers of M2 molecules to the immune systems of
mice, they engineered Escherichia coli bacteria to make a protein
complex that has many copies of the M2 protein sticking out of it.
After purifying this vaccine, they gave mice three doses, either by injection
or as nose drops. All immunised animals survived doses of flu virus that killed
half of their untreated littermates (Nature Medicine, vol 5, p 1157).
鈥淲e got protective, long-term immunity,鈥� says Fiers.
Edwin Kilbourne, a virologist at New York Medical College in Valhalla, New
York state, cautions that the team have not proved that the M2 vaccine works
against many strains of flu. 鈥淭he work is promising, but I think they鈥檙e making
a big jump,鈥� he says. Kilbourne thinks a truly universal flu vaccine might need
several lines of attack.