Where West Nile Meets Influenza!

Posted by ERV on June 11, 2008
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Last Saturday evening I went to a friends house to let Arnie play in their backyard, and today Im scratching a dozen mosquito bites.

Arg.

But what does a virologist think when they get mosquito bites?

West Nile! WHOOOO!!!

And what does a girl who studies HIV-1 env think of when she thinks of West Nile?

Convergent evolution! WHOOOWHOOO!!!


WN was all over the news a few years ago because it can kill people. But there is no reason to be a spaz about it. Im under the impression that lots of us have been infected with WN, got a minor fever, and recovered without even noticing anything was wrong. No big whoop.

That being said, if you think youve been infected with West Nile, and your pretty sure your brain is inflamed, please stop clicking around on ScienceBlogs and consult a local physician.

However, if youre feeling fine and just want to learn about West Nile as a virus, I can help you there!

WN is a flavivirus like a couple of other fun viruses, Yellow Fever and Hepatitis C. Theyre ‘cake’ viruses (one big transcript gets cut into lots of little proteins) as opposed to ‘cupcake’ viruses (individual transcripts for each protein). Their structure is a lot like the common cold, except coated in a lipid bilayer stolen from the host cell. That means they need ‘envelope’ proteins (E proteins) sticking out to interact with new host receptors, as you can see in this diagram of Hepatitis Cs replication cycle.

Flaviviral E proteins are made of folded up beta-sheets. After they bind to their host cell receptor, the virus is taken up in an endosome through receptor mediated endocytosis. As the pH of the endosome gets lower, the beta-sheets change conformation and mediate the fusion of the virus lipid bilayer with the host membrane– the point where the virus actually infects the host cell.

This is where things get cool– Influenzas hemagglutanin protein does the exact same thing— Binds to the host cell receptor, changes conformation as the pH of the endosome lowers, mediates fusion of the two membranes to cause the actual ‘infection’ event… but influenza and West Nile arent related at all. Flaviviruses are single stranded (+) sense RNA. Influenzas genome is made of several chunks of single stranded (-) sense RNA! So how do these two viruses have almost identical replication strategies?

Convergent evolution!

Flaviviral E proteins are beta sheets, influenzas hemagglutanin is made of alpha helices, but they ‘do’ the same thing! Just like insect and bat wings look totally different, but ‘do’ the same thing!

Cooooooool.

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Comments

  1. #1 J-Dog
    June 11, 2008

    Ah! I feel better already! Well, anyway, I hope I am not just in De-Nile…

  2. #2 Bob O'H
    June 11, 2008

    …taken up in an endosome through receptor mediated endocytosis

    Um, any chance of a cartoon for us whole-organism biologists?

    I love the way convergent evolution only shows similarities at one level: look more closely and you see that there are differences. It totally buggers up the common design arguments. As well as just being cool in itself.

  3. #3 HorsePunchKid
    June 11, 2008

    Do cake-style flaviviruses use mechanisms like readthrough suppression and ribosomal frameshifting for regulation like retroviruses do?

  4. #4 pondscm
    June 11, 2008

    A bit OT…are there any updates on CCR5delta32 and WN? Is CCR5delta32 still thought to confer elevated susceptibility to WN?

  5. #5 themadlolscientist
    June 11, 2008

    what does a girl who studies HIV-1 env think of when she thinks of West Nile?

    Convergent evolution! WHOOOWHOOO!!!

    You are one Sick Puppy. But in a good way. 🙂

  6. #6 The Backpacker
    June 11, 2008

    So can a virus tell if a cell is already infected by one of it’s brotheren and move on to more firtile ground or do they just work purly on the shot gun effect of gagilians (sp?) of them.

  7. #7 The Backpacker
    June 11, 2008

    oh and I forgot, THAT IS TOTALY WICKED

  8. #8 zer0
    June 11, 2008

    But what does a virologist think when they get mosquito bites?

    West Nile! WHOOOO!!!

    And what does a girl who studies HIV-1 env think of when she thinks of West Nile?

    Convergent evolution! WHOOOWHOOO!!!

    You’re so totally stalkable, errr…. adorable.

  9. #9 Sili
    June 11, 2008

    That was remarkably easy to follow.

    Thank you! I feel a little smarter.

  10. #10 PalMD
    June 11, 2008

    That being said, if you think youve been infected with West Nile, and your pretty sure your brain is inflamed, please stop clicking around on ScienceBlogs and consult a local physician.

    NOOOO!!!11!!!

    EMERGENCY ROOM!!!!

    In the summer of 02 I had quite a lot of experience with WNV. It truly sucks (when it actually makes you sick). If your brain is swelling in your head, CALL 911 (may not be valid in all countries).

  11. #11 ERV
    June 11, 2008

    Bob #2– click here, and then on the ‘animation’ tab! Its talking about LDL, but its the same idea. Oh, and you dont always need clathrin.

    #3– Yup!! They use allllll the tricks in the book!

    #4– I have never heard of that– Ill look into it!

    #6– Yup! So like, HIV-1 needs CD4 to infect cells– well after an HIV-1 virion infects a cell, it codes for proteins that down-regulate CD4 so no other viruses can get in! ‘Super infection’ can still happen, though (two viruses infecting the same cell). Thats where we get ‘recombinanat’ HIV (not subtype A, not subtype C, but subtype a-c), and where our ‘bird flu’ worries come from.

    Pal– Dont be silly. Unless you know there are naturopathic doctors staffing your local ER, you could be gambling with your life! Dont go to an ER! Schedule a colonic with your trusted ND physician to get the virus toxins flushed out of your body!

    For shame, Pal, for shame!

    @ others– stalkers bearing chocolate and/or cheesecake are always welcome. 😛

  12. #12 Brian Foley
    June 12, 2008

    The Online Macromolecular Museum has a nice 3D tutorial of how the flu virus envelope (HA protein) works:
    http://www.callutheran.edu/Academic_Programs/Departments/BioDev/omm/jmol/ha/ha.html

    They have another one of HIV-1 env too, but it was done with CHIME rather than JMOL, so it is tough to get it working (you need an older version of Netscape, the CHIME pluggin, etc to make CHIME tutorials work).

  13. #13 Papilio
    June 14, 2008

    But there is no reason to be a spaz about it.

    I take it you have no acquaintances with cerebral palsy?

  14. #14 Bacopa
    June 15, 2008

    Thnking you have West Nile is no joke. I had some kin of flu like illness a few weeks ago and I live in an SE Texas, which has a lot of WN virus. Chills, sweats, fever, headaches, weakness. Mostly over it in a few days and only thought it might be WN as I was getting better. Still, it was April, how could it be WN this early? Then the next week I read that we had the first confirmed case of WN.

    I know someone who is learnin how to walk all over again because of brain damage from WN. This is a serious disease even if most infected don’t suffer much from it.

    A few years ago when WN came to our area we were told to call the health department to pick up dead birds. But now they’re not so careful. WN kills a few of us every year and disables even fewer and we’re OK with that.

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