REUTERS: Researchers have discovered human antibodies that neutralize not only H5N1 bird flu but other strains of influenza as well and say they hope to develop them into lifesaving treatments.
The antibodies -- immune system proteins that attach to invaders such as viruses -- also might be used to protect front-line workers and others at high risk in case a pandemic of flu broke out, the researchers said.
In tests on mice the viruses neutralized several types of influenza A viruses, including the H5N1 avian influenza virus, the researchers reported in Sunday's issue of the journal Nature Structural & Molecular Biology.
"We were surprised and actually delighted to find that these antibodies neutralized a majority of other influenza viruses, including the regular seasonal (H1N1 strain of) flu," Robert Liddington of the Burnham Institute for Medical Research in La Jolla, California, told reporters in a telephone briefing.
The researchers found the antibodies in a "library" of such immune system proteins generated from 57 volunteers at the Dana-Farber Cancer Institute affiliated with Harvard Medical School in Boston. They said it is not clear how common they are in the general population.
Influenza is especially difficult to fight because it cloaks itself in lollipop-shaped proteins called hemagglutinin and neuraminidase, which mutate regularly and give influenza A strains the "H" and "N" designations in their names.
Vaccines target hemagglutinin, while drugs called neuraminidase inhibitors, including Roche AG's Tamiflu and GlaxoSmithKline's Relenza, attack neuraminidase.
Because of the mutations, vaccines have to be reformulated every year and the viruses can develop resistance to the neuraminidase inhibitors, as they have to older antivirals.
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