Come winter, and many countries are vulnerable to influenza. In the cold half of the year, flu outbreaks shoot up like anything. In the U.S. the flu season starts in October and peaks in February, while in Australia season is at its extreme in August. Influenza A, B, and C strains are behind the highly contagious respiratory infection.
Now, it is relevant and reassuring to learn that scientists from the Scripps Research Institute and Crucell Vaccine Institute in the Netherlands have managed to isolate and describe three human antibodies that offer protection against Influenza B virus. The same team had earlier reported broadly neutralizing antibodies against Influenza A strains.
The latest findings of antibodies will enable scientists to develop a universal antibody-based therapy for flu. Moreover, it will also provide clues for the development of vaccines for long-term protection against the disease.
When compared to Influenza A viruses, Influenza B is less dangerous and have less capacity to mutate into deadly pandemic strains. However, influenza B viruses account for a significant part of the annual flu illness burden in humans.
Ian Wilson, Professor of Structural Biology at Scripp Research and senior investigator for the new study said, "To develop a truly universal flu vaccine or therapy, one needs to be able to provide protection against influenza A and influenza B viruses, and with this report we now have broadly neutralizing antibodies against both."
To find protective antibodies against the Influenza B virus, scientists at Crucell generated flu antibodies from immune cells of volunteers who were given seasonal vaccinations. They screened this collection for antibodies that could bind with influenza B strains.
Three of these antibodies -CR 8033, CR8071 and CR9114 protected mice against lethal doses of two major strains of Influenza B. CR9114 also protected mice against Influenza A virus, including the H1N1 subtype that killed 17,000 people in a 2009.
As these antibodies protected against a variety of flu strains, it became clear to scientists that they bound themselves to functionally important portion of molecules or epitopes in the virus that were unchanging from one strain to another.
Using an electron microscope and from X-ray crystallography studies, scientists from Scripps Research found out that while the antibody CR 8033 bound to a highly conserved epitope on the head of the hemagglutinin protein found in the outer coat of the flu virus, antibody CR8071 bound to the base of the hemagglutinin protein. The antibodies prevented the virus particles from exiting infected cells and thus neutralized them.
Antibody CR9114 bound to a site on the stem of hemagglutinin protein. It prevented the the protein from undergoing the shape-change needed to fuse to the outer membrane of the host cell. The epitope was highly conserved among Influenza A subtypes and Influenza B.
In 2009, another Crucell antibody broadly neutralized Influenza A virus by binding to the same site at the hemagglutinin stem. But that antibody was not effective against the Influenza B virus. Scientists believe that with a bit of tweaking of the antibody's binding domains, they might be able to get a broader effect like CR9114.
Designing a new universal antibody would need more tests for antibodies such as CR9114, which may be highly effective but have novel mechanisms of neutralization.
The research was published in journal Science's advance online edition, Science Express in August.
by RTT Staff Writer
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