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Short-Lived Immunity Helps Keep Mutant Flu Strains in Check

The flu virus is always changing. Its genetic material, prone to mutations, is forever trying out new combinations to outwit a person's antibodies. Yet with all the changes going on, why are there so few strains circulating from year to year?

"Short-lived immunity," says University of California at Irvine researcher Robin M. Bush, Ph.D.

Photo of Robin M. Bush, Ph.D.
Robin M. Bush, Ph.D.

Dr. Bush and her colleagues Neil Ferguson, Ph.D., a mathematical biologist at Imperial College in London, and Alison Galvani, Ph.D., now at the University of California, Berkeley, have created a mathematical model that simulates how Type A and B flu viruses evolve. The group has found that, on its own, cross-immunity—the ability of antibodies against one flu strain to fight off another strain—would actually increase the number of mutant strains persevering. Only when a new type of immunity is factored in does the model more accurately reflect actual flu tracking data collected in the field.

According to Dr. Bush, for a few weeks or months after a person is exposed to one strain of the flu, he or she may be immune to reinfection by virtually any new strain that comes along. Such short-lived immunity would force most new mutations to die out immediately, keeping the total number of flu strains in check.

"If immunologists can identify the basis of such a response, we may be able to develop a vaccine that offers a less strain-specific, and thus longer-lasting, immunity to the virus," says Dr. Bush.

This information is based on the article, "Ecological and Immunological Determinants of Influenza Evolution," in Nature.

References

Ecological and Immunological Determinants of Influenza Evolution

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Last Updated March 22, 2010