April 2, 2010

Elderly’s protection from H1N1 studied

Elderly’s protection from H1N1 studied

In two papers published in March, researchers at Vanderbilt University Medical Center and their colleagues explain why older people seem to be protected against the H1N1 “swine flu” virus.

Last year's outbreak of a novel influenza virus in Mexico developed into the first human influenza pandemic in 40 years. To date the virus, which disproportionately affects children and young adults, has contributed to at least 16,000 deaths worldwide.

Reporting in the March issue of the Journal of Virology, James Crowe Jr., M.D., Jens Krause, M.D., and their colleagues report that antibodies isolated from elderly survivors of the 1918 “Spanish flu” pandemic also bound to and inhibited the 2009 H1N1 virus in laboratory and animal experiments.

The envelope protein hemagglutinin is the principal surface antigen the influenza virus uses to infect its host and it is the major component of flu vaccines. The H1N1 virus is named for its specific surface antigen (H1) and for the enzyme neuraminidase (N1), which helps it spread from cell to cell.

The surface antigen mutates rapidly in most influenza viruses, enabling them to evade the body's immune system and requiring the development of a new flu shot every season.

But in this case, parts of the protein sequence were conserved from the 1918 H1N1 virus, which was responsible for nearly 50 million deaths worldwide.

In the second report, published last week in the journal Science, researchers at The Scripps Research Institute in La Jolla, Calif., collaborated with Crowe and Krause and a colleague at Mount Sinai School of Medicine to solve the structure of the conserved protein.

“One of the amazing and encouraging aspects of this study is that it shows that sometimes there are parts of the flu virus that are the same in major strains as far apart as 92 years,” said Crowe, professor of Pediatrics and Microbiology & Immunology and director of the Vanderbilt Vaccine Center.

“These studies suggest that sometimes flu may have a chink in its armor,” he continued. “The more we can understand about parts of the virus that are conserved, the more effectively we can design better vaccines that induce longer lasting immunity.”