Tetravalent antibody
The new antibody recognized four flu strains at once
Maxim Abdulaev, "The Attic"
Scientists have found an antibody that recognizes a conservative site in the most common strains of the influenza virus – swine, avian and Hong Kong. The authors of the study believe that this antibody can become the basis for new antiviral drugs and vaccines that will act against many strains.
The flu virus, like other viruses, is dangerous because it can mutate quickly. The main "hook" used by antibodies that neutralize the virus is hemagglutinin proteins, which it needs in order to sit on the surface of the cell. Without contact with the cell, the virus would not be dangerous.
The hemagglutinin of the influenza virus has a head by which antibodies recognize the infection, a "face" by which the immune system recognizes the aggressor. They are attached to it, thus neutralizing the dangerous particle. Unfortunately, this part of the viral protein is the most changeable, it looks different for different viruses. Mutating, the virus changes its face and sneaks past antibodies to defenseless cells.
Scientists from the USA and Australia decided to find an antibody that would be difficult to deceive with the help of machinations with the heads of hemagglutinin. They took blood from a patient who had been vaccinated against different strains of the flu virus for 20 years, including from such well-known ones as pork, poultry and Hong Kong.
The scientists found out which antibody recognized all the strains and bound to the viral protein, no matter how it looked. They isolated it, named it FluA-20 and sent it for further experiments.
First, they tested the isolated antibody in vitro, allowing it to bind to isolated proteins of different strains. It turned out that FluA-20 recognizes the same head, because it "pays attention" not to what is changing, but to what remains unchanged. The virus is able to change the protein, but it still needs some permanent parts so as not to lose the ability to bind to the cell membrane. It is these conservative parts that FluA-20 recognizes.
Next, the scientists got to in vivo, that is, mice. Rodents injected with FluA-20 antibodies were infected with non-fatal influenza (swine, Hong Kong and two strains of avian), and then watched as they lost weight. The control group was not injected with an antibody. After two weeks, all the patients recovered, but those protected by FluA-20 lost less weight. The animals with the antibody that were infected with H1N1 (swine flu) also gained weight.
At other stages, mice were infected with already deadly strains. Mice from the control group who were not treated at all died on the eighth day (in the case of the Hong Kong flu strain). Mice with an antibody injection survived all or almost all (Hong Kong flu still killed 20% of the animals). Experiments in which mice were treated in parallel with the drug oseltamivir (which is sold in Russia as nomides) showed that FluA-20 treats better – again by 20%.
Scientists believe that FluA-20 does not completely neutralize the virus, but does not allow it to attach to the cell membrane, making it harmless. In addition, the antibody interferes with the assembly of new viral particles by binding to the conservative part of proteins-hemagglutinins even before they assemble into a whole molecule.
Perhaps the results will allow us to create a vaccine against four strains of the virus at once – the most common, H1N1 (one of its strains became known as swine flu), H5N1 and H7N9 (both belong to avian flu), H3N2 (Hong Kong).
Article by Bangaru et al. A Site of Vulnerability on the Influenza Virus Hemagglutinin Head Domain Trimer Interface is published in the journal Cell.
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