National Geographic

Vaccine against 2009 pandemic flu also protects mice against 1918 strain

1918_fluIn 2005, a group of American scientists resurrected one of history’s deadliest killer – the H1N1 flu virus of 1918 that killed approximately 50 million people worldwide. Using samples from a patient buried in Alaskan permafrost, they deciphered the virus’s genome and structure, rebuilt it from scratch and infected mice with it.

The move was understandably a controversial one. It has led to a greater understanding of the 1918 pandemic, and other important flu strains, but scientists have cited the possibility that this infamous killer could be accidentally released from a lab (as has happened before with other H1N1 strains). Worse still, it could be developed into a bioterror weapon. But according to Rafael Medina from the Mount Sinai School of Medicine, these worries may be unfounded. He has shown that since 1918, the world has gained an ally that will protect people against the deadly strain should it ever reemerge. That ally is a most unexpected one – the H1N1 swine flu virus from 2009.

The virus that went pandemic last year is actually a fourth-generation descendant of the 1918 virus. It’s part of a ‘pandemic era’ that was kicked off by the original strain and that has lasted for almost a century. Despite the 91-year gulf between them, the 1918 and 2009 viruses have some important similarities that set them apart from seasonal strains. This likeness means that antibodies that target one strain should work against the other. Indeed, elderly people who survived the 1918 pandemic still carry such defensive antibodies, and these can neutralise the 2009 virus too. This probably explains why elderly people, who are usually most at risk from flu viruses, were largely spared the brunt of the recent pandemic.

Now, Medina has found that the protection works the other way too, at least in mice. He gave mice the vaccine against the 2009 pandemic or antibody transfusions from humans who had themselves been vaccinated. Either way, the rodents produced antibodies that completely protected them against extremely lethal doses of the 1918 virus. Without the vaccine, all of the mice were dead within 8 days. With it, they barely showed any signs of illness and lost trivial amounts of weight. By contrast, vaccines against other strains of seasonal flu failed to provide any sort of protection against the 1918 monster.

Of course, this study has only looked at mice and Medina acknowledges that the next step will be to see if the 2009 vaccine will protect against 1918 flu in other animal models, such as guinea pigs, monkeys and ferrets. But for now, the results are encouraging

The 2009 pandemic spread worldwide and it is still the dominant strain of seasonal flu. Huge numbers of people were vaccinated when the pandemic hit, and the World Health Organisation has recommended that the standard annual flu vaccine should also target the pandemic strain. This means that large swathes of the population should now be immune to the 1918 virus should it ever rear its proteins again. It’s good news for scientist too; as Medina says, the current vaccine “should also serve as an additional layer of safety for researchers working with the 1918 influenza virus”.

Reference: Nature Communications http://dx.doi.org/10.1038/ncomms1026

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There are 10 Comments. Add Yours.

  1. PalMD
    June 15, 2010

    Ed, this is so cool…

  2. Nathan Myers
    June 15, 2010

    This seems to suggest that the space of variations practically available to flu viruses isn’t nearly as large as has been thought.

  3. Szwagier
    June 16, 2010

    Hmmm, the reference link at the end doesn’t seem to work. Very interesting post, though!

  4. Lilian Nattel
    June 16, 2010

    A bit scary (the possibility of release) and reassuring as well.

  5. pinsolomons
    June 16, 2010

    Can’t figure out why scientists went to all the trouble to dig out a deadly strain of flu from frozen corpses that had burned itself out (along with a large percentage of this planet’s population) , revived it and are now keeping it in labs to test vaccines developed for something else on. I’m not a rocket scientist either but I can’t figure the logic in that. Nor for keeping strains of smallpox in labs when it’s supposed to have been wiped off the planetary population by WHO.

  6. Ed Yong
    June 16, 2010

    Because it’s very, very important to work out why the 1918 strain that one was so deadly. That will inform monitoring initiatives and drug/vaccine design.

    This is one of the deadliest infections in human history; if it was a historical curiosity, we might be content to leave it well enough alone, but the fact is that flu is a continuing problem and pandemics have cropped up from time to time since 1918, all of which (including last year’s) are direct descendants of the original 1918 strain. You say that it burned itself out – that’s one way of looking at it, but you could equally argue that it set off a pandemic era that has been going strong for 91 years and shows no sign of abating. See here: http://blogs.discovermagazine.com/notrocketscience/2009/06/29/from-spanish-to-swine-how-h1n1-kicked-off-a-91-year-pandemic-era/

  7. Gentle Tiger
    June 16, 2010

    Whose to say that the 2009 flu wasn’t concocted from the 1918 strain?
    Maybe that’s why the number of generations apart is so small…
    Who watches the watchers?

    [Sometimes it's very hard to tell which comments are satire - Ed]

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