Science and Health

People have broader immunity to H1N1 flu: study

(Xinhua)
Updated: 2009-11-18 02:58

LOS ANGELES: People's immunity to A/H1N1 flu virus is greater than previously thought, a new study suggests.

This may explain why the disease hasn't posed more problems, according to the study conducted by researchers at the La Jolla Institute for Allergy and Immunology in La Jolla, California.

By using a major flu database funded by the US National Institutes of Health, the researchers analyzed the reaction of immune system cells to the H1N1 virus. They found that 17 percent of the B cells that attack viruses in the bloodstream recognized H1N1 because of exposure to other flu viruses.

"They (B cells) produce antibodies in the bloodstream and try to find the virus before it ends up in cells, so they are what prevents the disease," said study lead author Bjoern Peters, an assistant member of the division of vaccine discovery at the institute.

The study also found that 69 percent of T cells, which attack the virus in infected cells, were alerted by those previous infections.

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"They recognize the virus inside cells, so they are responsible for clearing the infection once you have it," Peters said. "Nobody knows what level of immunity is sufficient for protection. But if infected, our data suggest that T cells in those who have previously been exposed to influenza may make the infection less severe."

"What has been widely reported in the general press is that the swine flu is totally new, so there is no immunity to it," said Peter. "But the severity of infections that have been seen is not greater than usually seen in seasonal flu."

The reason why the H1N1 flu virus isn't the killer it was feared seems to be that the various protective mechanisms of the immune system have been primed by exposure to previous flu viruses, said study co-author Alessandro Sette, director of the institute's Center for Infectious Disease.

The research, published in this week's Proceedings of the National Academy of Sciences, helps understand why the H1N1 flu pandemic is not as deadly as was originally feared, Sette said. " We provide an explanation for observations that the disease severity is not greater," he said. "Maybe it is even less than ordinary seasonal flu."

The research, however, doesn't negate advice to get vaccinated against the H1N1 virus, Peters said. "From our findings, we see that it is necessary to get a shot," he said. "Yet it provides an explanation why you do not have to be absolutely concerned if you have not been able to get a shot yet."