I'm a graduate student studying the molecular and biochemical evolution of HIV within patients and within populations. I also study epigenetic control of ERVs.
EMAIL!
Dear ERV--
I have a question about virus transportation inside, say, blood. I did a rough estimate of the average virus Reynolds Number and it turned out to be around .0051. So aside from some good old Brownian Motion, those viruses aren't really going anywhere without some sort of flagella or what-have-you. Do any viruses have a propulsion mechanism or do they all just loaf around wait for stuff to bump into them?
Cool question!
Short answer- No, viruses dont have their own propulsion systems :) That would require ATP and a means to generate ATP, ie metabolism. Viruses dont have that (they steal everything from their hosts).
But that doesnt mean viruses are at the mercy of Brownian Motion!
Viruses are the masters of mind control-- they might not be able to move on their own, but they can take control of our cells!
To use HIV-1 as an example, HIV-1 doesnt just hang out in your vagina waiting for a CD4+ T-cell. to wander by (which is good, cause thats not going to happen). Vaginas have sentinal dendritic cells that pick up HIV-1 viruses (like a friggen chauffeur) and carry them to lymph nodes. Lymph nodes full of nommy, nommy CD4+ T-cells.
Mission accomplished, no viral locomotion needed.
Other viruses, like vaccinia, hijack cellular processes to help them infect more cells. It creates an actin 'rocket pack' to propel itself into nearby cells. Yeah. Actin shoots out the infected cells membrane like Wolverines claws, and into cells 'next door', infecting them. Im not lying (green dots are the virus, red tails the actin):
Those were two examples of viral 'movement' that I could think of off the top of my head-- Ill try to think of some more (just cause its cool). Now randomness certainly plays a part in viral infection (you can be exposed to HIV-1 without being permanently infected), but viruses are not at the mercy of randomness just because they dont have their very own perfectly designed propulsion systems :P
Life Science
Comments
Dr. Horrible -soon to be a blog entry illustration for mad and less-than-mad scientists everywhere.
Posted by: chancelikely | July 25, 2008 1:47 AM
Posted by: Aaron Golas | July 25, 2008 1:57 AM
I thought dendritic cells usually destroy HIV in most cases, was I wrong in that?
Posted by: Jared | July 25, 2008 2:03 AM
I think it would be really informative if you did a post about this.
Posted by: steve s | July 25, 2008 2:54 AM
Steve, viral dose plays a role in whether or not HIV exposure results in infection, as well as the host immune system and various mutations which impact binding of the virus to cell surfaces. http://vir.sgmjournals.org/cgi/reprint/81/7/1719.pdf
That provides some good information about infectious load and progression...
Posted by: Jared | July 25, 2008 4:44 AM
Oh, I know about things like viral load and infectious dose. I just think it's a great subject for ERV to blog about, because a lot of people don't know much about those topics.
Posted by: steve s | July 25, 2008 5:28 AM
Hey, cool, I went to a Seminar by the guy who made the Vaccinia video when I was an undergrad.
Posted by: Confused | July 25, 2008 6:54 AM
I read somewhere that 14 viral cells can be enough for HIV infection. The usual "file info, forget source" mechanism is operating, though. I just tagged it as relatively reliable.
Go to my personal blog (link) for a mystery aerial photo.
Posted by: Monado | July 25, 2008 8:43 AM
Damn, those viruses are just whizzing right along on that actin. Seems like they can't go too far out of the cell, if that area to the right is indeed the cell boundary.
I also found this video of the same process as the one Abbie posted:
http://www.youtube.com/watch?v=lOblMwjwG-s&feature=related
So what determines the direction of Actin-rocketpack motion?
Posted by: Alex M | July 25, 2008 8:54 AM
<Family Feud Applause>
Good answer!
</Family Feud Applause>
Posted by: Optimus Primate | July 25, 2008 9:41 AM
Another great educational post! Thanks.
Posted by: EyeNoU | July 25, 2008 10:22 AM
It never even occurred to me to wonder how viruses spread throughout a body. I just had a vague notion that they spread simply by diffusion as they multiplied, which sounds implausible now that I think about it. Thanks for the great post!
Posted by: Yoo | July 25, 2008 11:50 AM
@Steve #6 - "Oh, I know about things like viral load and infectious dose. I just think it's a great subject for ERV to blog about, because a lot of people don't know much about those topics. "
Raising my hand right now! :-)
Posted by: Stacy S. | July 25, 2008 5:41 PM
Aaron Golas, Listeria monocytogenes can hijack the host cell's actin polymerase and use it to move around the cytosol. I watched a vid of this in college. They look like little motorboats on a lack.
Alex M I am not sure what determines directionality. I would guess there's probably a binding site for the actin polymerase on one part of the cell body or virus coat.
Posted by: Rogue Epidemiologist | July 25, 2008 7:43 PM
Oh mía Signora!!
Sorry if this seems too invasive. But i only wanted to encourage you to keep on with this nice job you are into...
A physicist (trying to learn some biology) from the other side of the Atlantic, who is really enjoying your style... And no, i´m not italian ;-)
Waiting for your next post... I remain.
Cheers Ms. Smith.
Posted by: petroski | July 26, 2008 1:47 PM
What about herpesviruses zooming up and down axons? Those are pretty cool.
Posted by: Brian | July 26, 2008 5:11 PM
Bad Horse called. He got your application.
Posted by: Joshua Zelinsky | July 27, 2008 2:56 AM
Is that Neal Patrick Harris? from like-- Harold and Kumar movies
Posted by: Amplexus | July 28, 2008 2:13 AM
What the world needs now is a virus that decimates Japanese beetles.
Posted by: Tegumai Bopsulai, FCD | July 28, 2008 11:27 AM
And here I thought the virus just whistled for its horse, climbed aboard, and road off into the sunset.
Thank you for the informative post.
Posted by: Gary Bohn | July 29, 2008 3:08 PM