THE flu virus is a slippery customer, expert at escaping attack by our immune system. But there is a chink in its defences that could lead to a universal flu vaccine.
We can get flu repeatedly because the virus evolves: its surface proteins change, so the antibodies generated by one bout are not effective a second time. For the same reason, the vaccine for one year鈥檚 strain won鈥檛 work in later years. Now Wayne Marasco at Harvard University and his team may have found a way round this.
The flu virus鈥檚 main surface protein, haemagglutinin, is lollipop-shaped, and existing vaccines stimulate the production of antibodies that bind to its big round head 鈥� which changes every year. But in a library of human antibodies, Marasco鈥檚 team found a few that target proteins on the 鈥渟talk鈥�. These proteins barely change between flu strains, which suggests they don鈥檛 evolve quickly (Nature Structural and Molecular Biology, ).
Advertisement
Marasco鈥檚 team suspected that the prominent head of the lollipop normally attracts the attention of the immune system away from the stalk. If the immune system could be persuaded to target these unchanging proteins, they reasoned, it might be possible to provide protection year after year.
His team produced antibodies to these stalk proteins in bulk, and injected them into mice before and after they were infected with a range of flu viruses, including H5N1 bird flu, pandemic H1N1, and ordinary flu. The antibodies protected or cured the animals in each case.
In cell cultures, the viruses did not evolve to escape the stalk antibodies, so a vaccine based on them should, in theory, work for longer than a year. In a pandemic, the antibodies alone might offer useful protection. They last more than three weeks when injected into people, which could keep them alive long enough to make their own antibodies.
鈥淲hen injected into people, the antibodies lasted long enough to offer protection in a pandemic鈥�