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Study Explains Immunity to H1N1 in Older People
Reuters
Steenhuysen, Julie
10/15/2009
Parts of the pandemic H1N1 virus have been found in earlier flu strains by Carol Cardona of the University of California Davis School of Veterinary Medicine and colleague Zheng Xing. The researchers say some people over the age of 60 years who have been infected with or vaccinated against seasonal flu may have some latent immune cells that protect them from the swine flu virus. "These findings indicate that human populations may have some level of existing immunity to the pandemic H1N1 influenza and may explain why the 2009 H1N1-related symptoms have been generally mild," says Cardona. Older people may have been exposed to similar viruses in their youth. The cytotoxic T-cells, which secrete antiviral chemicals, may be weakening the effects of the swine flu. Cardona analyzed data from previous H1N1 virus studies and discovered that more than a dozen of the proteins known as epitopes were also in seasonal flu viruses that have been circulating for years. She says that "not every single person can process these stretches of the protein," which may explain why some cases are mild and others are severe.
