TORONTO - It appears humankind has a reason to be grateful for the 2009 H1N1 pandemic virus -- widescale exposure to it has lessened the threat posed by the virus that caused the 1918 Spanish flu, the worst known infectious disease outbreak ever.
New research suggests the antibodies many people around the world generated against the 2009 virus -- either through being ill or by getting vaccinated -- would protect them if a lab accident resulted in the release of the 1918 virus or if terrorists tried to use it as a bio weapon.
"Our results should ease concerns of accidental release of the 1918 virus from the laboratory, or its use as a bioterrorist agent, as a cross-protective vaccine is now available and a large proportion of the general population would already have cross-reactive antibodies," said the researchers, led by flu expert Adolfo Garcia-Sastre of Mount Sinai School of Medicine in New York City.
The work was done in mice and the team said in their paper -- published in the journal Nature Communications -- that they will need to replicate it in other animal models, including monkeys.
But they did test the blood of human volunteers who had received the 2009 pandemic flu shot, checking to see if the blood samples contained antibodies that reacted to the 1918 virus.
Not only did they find the antibodies, but when they transferred the human blood to the mice and then gave the mice what should have been a lethal dose of 1918 virus, they were protected.
Garcia-Sastre said the discovery should assuage concerns that were raised when a team of U.S. researchers reconstituted the 1918 virus from genetic sequences teased from virus fragments retrieved from people who died in the outbreak. That research, done in select labs with the highest level of biosecurity and biosafety ratings, has been criticized in some quarters as being too risky.
The 1918 virus is believed to have killed approximately 50 million people worldwide, many of them young and previously healthy adults. It is unclear what the release of that virus would do in the current immunological landscape, where most people alive have had multiple exposures over years to distant offspring of the 1918 virus.
But the 2009 pandemic showed that viruses that become genetically different enough from their ancestors are still capable of causing a pandemic. In fact, older people who were exposed to H1N1 viruses that circulated prior to 1957 fared better, as a group, than younger people who had only encountered more recent H1N1 viruses.
That pattern was explained by studies published earlier this year that found the 2009 virus more closely resembled its 1918 ancestor than its more contemporary cousins.
Imaging of the hemagglutinin -- the major protein on the surface of flu viruses -- showed both the Spanish flu virus and the pandemic H1N1 version lacked two sugar coats seen on more modern viruses from the same family, other U.S. scientists reported.
Garcia-Sastre's new study bookends one he published in January showing that an experimental vaccine made to protect against the 1918 virus also protects against the 2009 pandemic variant.
One might assume that if 1918 protects against 2009 that the reverse would automatically be true, but that isn't always the case, the virologist said from New York.
"This story I think finishes the cycle, complements what has been published before doing the opposite thing. And this isn't always the case," he said.
"So it's nice to see that that's the case. And I also think that makes things easier for people like my lab, working on 1918 or the CDC working on 1918 because now we have a vaccine that is working," Garcia-Sastre said.
"And that has been for a long time one of the concerns about working with 1918 (virus) ... the small possibility but always the possibility that this virus might infect one of the workers or be used as a bioterrorist weapon.
