GMO chickens and herd immunity

Posted by ERV on January 19, 2011
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HA!

You remember a while ago, I wrote about how GMO papaya creates a population of ‘papaya’ that has herd immunity against papaya ringspot virus, thus is able to protect non-GMO papaya from the virus?

Theyre trying to do a similar thing with chickens (any commercial bird, really– ducks, geese, turkeys, etc) and avian flu!

Suppression of Avian Influenza Transmission in Genetically Modified Chickens

Fundamentally this is the same idea as the GMO papaya, but the way they are accomplishing it is different. With the papaya, the GMO plants themselves were resistant to the virus, thus stopped the spread to non-GMO papaya.

With the chickens, the GMO chickens are still susceptible to infection and death from a highly pathogenic bird flu variant… but they dont pass on the virus to surrounding chickens, GMO or no. So again, the GMO variant protects everything, even the ‘organic’ variants!

Yes, this is neat, but what makes it even more neatier is that the researchers arent really sure how this is working (cue: OH MA GAH GMO CHICKEN GIVIN MEH CANKER!). They set up their experiments thinking that they knew how it would work: They inserted an RNA expression cassette (fake gene where what you want is RNA, not a protein) that encodes a short-hairpin RNA that looks like this bit on the influenza RNA segments. You know how HIV-1 is a ‘sheet cake’ virus? One big genome that makes one big RNA that gets chopped up into smaller RNAs and proteins? Influenza is a cup-cake virus. It has 8 segments of its genome, each coding for a protein (well, 11 genes/8 segments, some cupcakes get cut in half, lol).

Each of those segments has to have a region on it that tells influenza polymerase to make its gene(s).

The introduced RNA hair-pin is that region. The viral genomes form the same RNA structure as the ‘fake’ RNA. So when its present in a cell that is infected with influenza, the ‘fake’ RNA binds up all the polymerase, so its not binding to the viral genome–>replicating, thus tripping up the viruses life-cycle.

YAY!

Even better? You know how influenza mutates/drifts all the time, so thats why we have to make different vaccines every year? This ‘fake’ RNA is totally conserved in influenza. ‘Fake’ RNA will work on any influenza– no matter what year it is or how the proteins targeted by antibodies change.

DOUBLE YAY!

Well, they screened for modified chickens where what they did worked… but when they went to investigate why it worked, it didnt work the way they thought it would (IT MUST CAUSE CAAAAANKER! GMO=CANKER!!!!).

The question is hanging there– Why does this approach work in these chickens? What is really going on?

This means regardless of whether these chickens ever become a normal part of our commercial chicken populations– we now have a new tool for maybe figuring out a new target/new therapies for influenza! Maybe something is going on here that could help humans, short of GMO humans– something that can be turned into a drug that works on any influenza variant. Its always nice to have a few extra tricks up your sleeve with viruses, but especially highly contagious, fast moving, potentially very deadly influenza.

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Comments

  1. #1 Caudoviral
    January 19, 2011

    Influenza. Ick. It’s always nice to snag another arrow in our quiver against that omnipresent threat. While it is my hope that the environmental factors that let the 1918 flu pandemic be what it was will never occur again…there is no guarantee of that.

    So always nice to see new protection against influenza and I hope they identify the mechanism soon. Thanks for sharing this.

  2. #2 Douglas Watts
    January 19, 2011

    The problem with your argument is that industrial scale agriculturual monocultures, in and of themselves, are not good for native biota, simply due to the size of their footprint and the amount of habitat (and habitat complexity) that must be destroyed to create these monocultures in the first place.

  3. #3 ERV
    January 19, 2011

    What the hell? That has absolutely nothing to do with anything I wrote about. We get it, Dougie. You dont like GMOs. But you could at least attempt to read/understand what post is about.

    Or are you just trolling for site hits and dont really give a rats ass about anything?

  4. #4 daedalus2u
    January 19, 2011

    Wouldn’t that be flock immunity and not herd immunity?

  5. #5 Ankur Chakravarthy
    January 20, 2011

    Good stuff, I think the biggest advantage in combining sequence analysis from an evolutionary POV with what I call silenceomics (I know it sounds dopey) is that the spectrum of any gene silencing therapy can be rendered very broad, nullifying variation.

    Now yes, arguably there are concerns over GMO, but gene therapy delivering dsiRNA et cetera using VLPs to serve as therapy rather than prophylaxis could be a very attractive strategy in the future.

  6. #6 Ankur Chakravarthy
    January 20, 2011

    I have one nitpick regarding your explanation of shRNA action here,as far as I know, the process involved is not conformational disassociation of the enzyme and blockage of enzyme function as a consequence, but RNA interference, only that in cases of shRNA usage dicer cleaves the hairpin on the transcript from the Cassette to produce dsRNA that then leads to the breakdown of complementary mRNA through the action of the RNA Induced Silencing Complex.

    Please see http://www.scbt.com/images/en/gene_silencers/shrna_plasmids.png for an illustration.

  7. #7 Ankur Chakravarthy
    January 20, 2011

    No access to the full paper, drat, but it is quite strange that they opted for the decoy strategy looking at the abstract, I wonder if they managed to use it as a decoy without RNAi taking place at all. The birds succumbing to the initial challenge with the pathogen makes it even more bizarre.

    I think deciphering the mechanism of action could perhaps involve knocking out dicer or argonaute and then seeing if the effect is still present, that would rule out RNAi.

  8. #8 WLU
    January 20, 2011

    The problem with your argument is that industrial scale agriculturual monocultures, in and of themselves, are not good for native biota, simply due to the size of their footprint and the amount of habitat (and habitat complexity) that must be destroyed to create these monocultures in the first place.

    A counter-argument is that intensive, industrial agricultural monocultures actually means less land needs to be cultivated overall because the land that is used is used much more intensively and efficiently (in terms of food production). This has the effect of allowing more land to be left uncultivated, thus preserving more of the native biota. Seriously, do you realize how much land we would need in order to feed the populace if we didn’t have intensive agriculture? There’s a reason why hunter-gatherers had extremely low population densities – you can’t get enough food otherwise. If you want an argument, argue that it is the high prestige and flavour of meat that is the problem, since land needs to be cultivated to feed the animals. There at least you’ve got something reasonable to talk about. I’m hoping they get around to producing vat-meat in commercial quantities soon, eating bacon makes me feel guilty.

    Also, what the haych does this have to do with the actual blog post? And the technique could probably be used in any chicken population, and would actually increase the biological diversity by expanding the genome. Not to mention preserving any wildlife by preventing the transmission of potentially deadly viruses. Fail on three levels.

  9. #9 Mary
    February 1, 2011

    Yeah, I keep seeing *monoculture is teh devil and source of all evil* all the time now. I’m actually thinking that’s progress–some of them have realized that blaming teh GMOz for everything actually turns out not to be what they really meant.

    But when their 3 different backyard egg layers all die from the next bout of bird flu they’ll have to come up with something else.