Also, when study participants' blood samples were tested in the lab and exposed to a flu virus 11 months after vaccination, about 75 percent of healthy weight people's CD8+ T cells still expressed interferon-γ, an infection-fighting protein. However, only about 25 percent of obese patients' cells responded by producing the protein.
When vaccination fails to prevent flu infection, people must rely in part on their CD8+ T cells to limit the spread and severity of infection, said Patricia Sheridan, Ph.D., research assistant professor of nutrition and an author on the paper.
"If antibody titers are not maintained over time in the obese individuals and memory CD+ T cell function is impaired, they may be greater risk of becoming ill from influenza," Sheridan said.
Heather Paich, a doctoral student in Beck's lab, added: "The findings also suggest overweight and obese people are more likely to become sicker and have more complications. That's because influenza-specific CD8+ T cells do not protect against infection, but instead act to limit the disease's progression and severity of disease."
In 2005, Beck and her colleagues reported that obesity in mice impaired the animals' ability to fight influenza infections and increased the percent dying from influenza, compared to lean mice with the same infections. In 2010, her team showed that obesity seemed to limit the mice's ability to develop immunity to influenza, suggesting vaccines may not be as effective in obese and overweight as in healthy weight humans. Also, the fatality rate was higher in obese mice none of the lean mice died, but 25 percent of the obese mice died.
"This latest study shows that obese people may have a similar impaired response to influenza vaccines as our mouse models did to influenza virus,
|Contact: Ramona Dubose|
University of North Carolina School of Medicine