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Each flu season, a large segment of older adults will become seriously ill with the flu—flu shot or not. How come?
"As a person ages, her immune system will gradually weaken," says Yuping Deng, Ph.D., assistant professor of internal medicine at Eastern Virginia Medical School, Norfolk. Why this decline occurs is not entirely understood, but one theory is that the cells of the immune system that cause B cells to secrete protective antibodies—known as type 1 helper T cells (Th1 cells)—don't function as well in older people as they do in younger people. As a result, older adults produce fewer antibodies in response to a flu shot than will a younger person.
Earlier, Dr. Deng had found a potential relationship between Th1 cell function and the generation of antibodies in older people. Now, in a two-year study sponsored by NIAID, she is trying to understand the process a little better—and then give it a little nudge.
In 2004, Dr. Deng’s team vaccinated healthy older adults and young people against the flu. Then the researchers monitored the activity of each group's Th1 cells by measuring how much interferon-gamma they secrete. Interferon-gamma is a chemical that causes B cells to produce flu-fighting antibodies, especially IgG1. The investigators then compared Th1 activity to antibody levels to see if the two factors are directly linked.
"We predicted that we would see a decline in Th1 cell activity in healthy older individuals. Our prediction was accurate; compared to the healthy young volunteers, older people in our study had a diminished Th1 response to vaccination," says Dr. Deng.
In the 2005-06 flu season, the researchers are conducting Phase I clinical trials to test whether either of two vaccination strategies can improve the immune response to flu vaccine in both healthy older adults and young people. In one strategy, Dr. Deng and her colleagues will follow up the usual flu vaccine with an injection of a molecule found in bacteria that helps stimulate the Th1 response. In the second strategy, they will administer a booster vaccine when Th1 cells are at their peak (7 days after vaccination), or when Th1 cell activity dies down (28 days after vaccination), to determine if immunity is enhanced.
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Last Updated August 13, 2010