The influenza pandemic of 1918 killed nearly 50 million people worldwide. With fears of another looming flu pandemic stoked by the emergence of “bird flu” in Asia, researchers have wanted to study the 1918 virus and the immune response to it.
In 2005, researchers resurrected the 1918 virus from the bodies of people killed in the outbreak. The bodies, and the virus, had been preserved in the permanently frozen soil of Alaska. The researchers collected blood samples from 32 survivors age 91 to 101 years and found that all reacted to the 1918 virus, suggesting that they still possessed antibodies to the virus.
The team was then able to isolate exceedingly rare B cells - the immune cells that produce antibodies - from eight of those samples and grow them in culture. Seven of those samples produced antibodies to a 1918 virus protein, suggesting that their immune systems were waiting on standby for a long-awaited second outbreak.
Aging typically causes immunity to weaken but: “The B cells have been waiting for at least 60 years - if not 90 years - for that flu to come around again,” James Crowe who led the study said.
The scientists then fused cells showing the highest levels of activity against the virus with “immortal” cells to create a cell line that secretes monoclonal (or identical) antibodies to the 1918 flu. The antibodies reacted strongly to the 1918 virus and cross-reacted with proteins from the related 1930 swine flu but not to more modern flu strains.
To test if these antibodies still work against 1918 flu in a living animal, the researchers infected mice with the 1918 flu and then administered the antibodies at varying doses. Mice receiving the lowest dose of 1918 antibody - and those receiving a non-reactive “control” antibody - died. All mice given the highest doses of 1918 antibodies survived.
The findings suggest that B cells responding to a viral infection - and the antibody-based immunity that results - may last a lifetime, even nine or more decades after exposure.
MEDICA.de; Source: Vanderbilt University Medical Center