I cant imagine being a physician 60 years ago, with this picture being an every-day reality:
Row after row of kids with paralyzed diaphragms, locked in iron lungs. Polio.
Though I suppose I cant be too 'shocked and awed'-- I get this:
But with gymnasiums of iron lungs existing only as fading memories for some, and just pictures in history books for others, its easy to forget one tiny little fact-- Polio still exists, in the wild, on this planet. Unlike smallpox, which is confined to prison in a few research laboratories, we have not eradicated polio. And we might never get rid of it completely, unless we change our vaccine strategy.
You all might be aware of three different kinds of vaccines:
- Only a component or protein of a virus/bacteria, like a tetanus shot. No risk of infection at all.
- A dead virus/bacteria, like your annual flu shot. No risk of infection at all.
- An attenuated virus (has been passaged over and over in a different species so its crippled in humans, evolution, WHOOO!). Might actually get the disease from the vaccination.
So why isnt polio gone?
A problem with this attenuated vaccine is that you poop polio viruses. Crippled polio viruses, but you poop viruses. And because polio is an RNA virus, it might have mutated back to a wild type form.
What can we do? We dont want to keep giving the oral vaccine because it keeps polio 'alive'. We cant do the dead vaccine because its just not as good, and impractical in areas that need the most help. And we cant not give vaccines.
Vignuzzi et al think they have a good idea for how to keep the better live vaccine for RNA viruses, and lose the crappy wild-type polio pooping-- Controlling the attenuation process:
Engineering attenuated virus vaccines by controlling replication fidelity
Their idea is simple-- alter the viruses ability to mutate by making its RNA dependent RNA polymerase better! They tested lots of different amino acid positions and lots of different replacements to see what mutation they could make that would not hurt the overall fitness of the virus. If you start messing with an organisms fitness, you are putting it under pressure to mutate. So dont mess with it! Let it replicate nice and happy, no problems, no stress, let it replicate.
Why? So your immune system can launch a full on assault on the progeny virions, giving you that awesome attenuated vaccine response!
And those progeny viruses (you will still be pooping them, but not as much according to this paper), will be under no pressure to mutate away from the vaccine strain, and their ability to do so will be handicapped anyway (its hard to mutate when your polymerase is super accurate!), so you lose (or at least lessen) the chance of pooping a wild-type virus back into the environment.
Neato! This directed attenuation scheme could work on any RNA virus-- measles, mumps, rubella, rabies-- but they havent actually tried this yet. I mean, they tried it in mice, and got great results, but they havent tried it in people, much less an entire population.
Its nice to know that even though you and I can live blissfully ignorant, iron-lung-free lives, someone is out there making sure our kids can have the same luxury. And theyre using basic principles of the theory of evolution to do it. *gasp!*