AP updated 12:36 p.m. CT, Sun., Aug. 17, 2008
WASHINGTON - Nearly a century after history's most lethal flu faded away, survivors' bloodstreams still carry super-potent protection against the 1918 virus, demonstrating the remarkable durability of the human immune system.

Scientists tested the blood of 32 people aged 92 to 102 who were exposed to the 1918 pandemic flu and found antibodies that still roam the body looking to strangle the old flu strain. Researchers manipulated those antibodies into a vaccine and found that it kept alive all the mice they had injected with the killer flu, according to a study published online Sunday in the journal Nature.

There's no pressing need for a 1918 flu vaccine because the virus has long since mutated out of its deadly form and is extremely unlikely to be a threat anymore, experts said. What's more important in this research, they said, is that it confirms theories that our immune system has a steel-trap memory.

"It's incredible. The Lord has blessed us with antibodies our whole lifetime," said study co-author Dr. Eric Altschuler at the University of Medicine and Dentistry in New Jersey. "What doesn't kill you, makes you stronger."

This is the longest that specific disease-fighting cells have lasted in people, said study lead author Dr. James Crowe, a professor of microbiology and immunology at Vanderbilt University Medical Center in Nashville, Tenn.

But these antibodies don't just survive; they have mutated tremendously and now bind tighter to disease cells than other antibodies. That makes them more potent, he said.

Crowe said he hopes to use similar techniques to boost the potencies of vaccines that would be more useful now against newer bird flu strains that could become epidemics.

The 1918 flu killed about 50 million people worldwide and nearly everybody else was exposed to the virus, Crowe said. The specific 1918 virus was lost to the world for decades, until it was reconstructed about three years ago using genetic material from victims. When scientists tested the antibodies from survivors on infected mice, they did so in a high level biosecurity lab at the Centers for Disease Control and Prevention in Atlanta.

The idea for the new study came from an old TV show, said Altschuler. In an episode of the since-cancelled TV series "Medical Investigation," a town improbably gets infected with the 1918 flu and the doctors treat everyone with the reluctantly donated blood of an old butler who survived the original pandemic, he said.

That prompted Altschuler, a professor of rehabilitation medicine who doesn't normally study flu, to look into the idea of testing people more than 90 years old for antibodies. The National Institutes of Health, which paid for much of the study, connected Altschuler with experts in the field and he found the elderly antibody donors.

The findings make sense, said Dr. Anthony Fauci, director of the National Institute for Allergies and Infectious Diseases in Bethesda, Md., who wasn't involved with the study. Recent studies have estimated that the human immune system should last many decades, but this gives real proof, he said.

"This is the mother of all immunological memory here," Fauci said.

Copyright 2008 The Associated Press. All rights reserved.

Source: http://www.msnbc.msn.com/id/26254075/wid/11915773?GT1=31037