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    Flu shot might also offer protection against H5N1

    Richard J. Webby, PhD

    The yearly influenza vaccine that health officials urge people to get each fall might also offer certain individuals some cross protection against the H5N1 virus commonly known as bird flu, according to St. Jude investigators.

    Scientists found that the virus protein N1, one of two or more proteins present in the annual flu shot, can act as a vaccine itself and trigger some cross protection against H5N1 in mice; and that some human volunteers already had antibodies directed against the same part of this virus.

    “The jury is still out on whether the seasonal flu vaccine is definitely a reliable way to offer people some protection from H5N1,” said Richard Webby, PhD, Infectious Diseases. “But our initial results suggest to us that this is a research trail worth following.”

    Webby is senior author of a report on this study that appears in the February issue of the online journal PLoS Medicine (

    The key to the apparent cross protection against H5N1 provided by the human flu vaccine appears to be the antibodies produced in response to N1, a variety of the protein neuraminidase (NA)—one of the two proteins on the virus’ surface, Webby explained. While the amount of the other protein in the vaccine, hemagluttinin (HA, or H), occurs in large amounts, the amount of N1 can vary widely depending on the company that produces the vaccine.

    If initial findings of the St. Jude study are confirmed in the future, there may be a greater interest in examining the amount of NA in yearly flu vaccines, according to former employee Matthew Sandbulte, PhD, the postdoctoral fellow who did much of the work on this project. “HA is more abundant than NA on viruses and is a better target for protective immunity, so current vaccines are designed to trigger immune responses mostly to HA,” Sandbulte said. “That’s why vaccines contain standard amounts of HA, but varying amounts of NA. But if further research confirms that the N1 part of the flu vaccine offers some cross-protection against H5N1, it will be desirable to have a better idea of the amount of N1 present in these vaccines.”

    The other St. Jude author of the paper is former employee Adrianus C. M. Boon.

    February 2007