Could HIV be frozen out?

January 1, 2007 8:56 PM

Could HIV be treated cryogenically?

Could body temperature be lowered enough to kill the AIDS virus? I remember reading some years ago about patients who were chilled to a 'storage' temperature for heart operations, then thawed out afterward. Could something similar work for HIV or other viral diseases?

posted by atchafalaya to science & nature (13 comments total)

I think most viruses can survive being completely frozen, most simple forms of life can.
posted by delmoi at 9:03 PM on January 1, 2007

Also, in those heart operations, the body temprature never got below freezing, it was just lowered to something really low in order to slow down the beating of the heart. The heart never stopped, it was only slowed down, IIRC.
posted by delmoi at 9:04 PM on January 1, 2007

Hearts are stopped and body temperature reduced for delicate brain and heart operations. The lowest temperature I've seen is 28 degrees C, which would not affect the HIV viral life cycle one bit.

If freezing killed HIV, we'd have a much safer blood supply, among other benefits. Unfortunately, it does not.
posted by ikkyu2 at 9:09 PM on January 1, 2007

HIV is a retrovirus that hides in the host's DNA. Even if the virus were intolerant to being chilled, this would have no chance of working.
posted by zennie at 9:36 PM on January 1, 2007

HIV is a member of the subclass of retroviruses. Animal retroviruses propagate themselves as particles containing RNA. When they infect a host cell, the RNA is converted into DNA (thus the name "retrovirus") and the viral DNA is spliced into the host genome. Once there it can remain latent for an extended period of time, or immediately start producing viral particles. The particles are the primary means by which a retrovirus virus spreads from cell to cell. (Although not the only one.)

There are a number of types of viruses that can remain latent in human cells including Retroviruses, Herpes Viruses (including Chicken Pox), and Papillomaviruses (warts). These are difficult to completely "cure." Usually viral "cures" attempt one or more of the following strategies:
1: Priming the immune system's own ability to destroy both particles and latent cells.
2: Inhibiting the production of viral particles.
3: Blocking the ability of viral particles to enter cells.
4: Reducing the symptoms caused by viral infection.

To cut to the point, it is doubtful that chilling the body would destroy either HIV particles, or latent HIV copies in immune system cells.
posted by KirkJobSluder at 9:45 PM on January 1, 2007

Remember that viruses are right on the edge of what we even call living, and it's a longstanding debate as to whether they can even be considered alive or not. They don't have cells or anything, they are just small bundles of genetic material and some protein. There are probably viruses that can "survive" (fingerquotes) in a near total vacuum of space and/or at hundreds of degrees below zero. You would certainly kill the host body long before you killed the virus if you tried to attack it by environmental means.
posted by Rhomboid at 10:21 PM on January 1, 2007

nonscientific answer, but i imagine donated blood is stored in pretty cold conditions, and it can still suport viable viruses.
posted by twistofrhyme at 10:25 PM on January 1, 2007

For things that are not as hard to kill as retroviruses, changing the body temperature can help, though. That's supposedly the benefit of a fever.
posted by hattifattener at 11:11 PM on January 1, 2007

Viruses are crystals. Freezing doesn't kill viruses, in the same way that putting table salt in the freezer doesn't change the salt. Indeed, freeze-drying is used as a storage mechanism, to recover infectious viruses for later study.

However, virus proteins can be inactivated by chemical changes, such as a change in acidity (pH). Unfortunately, host proteins are also as vulnerable, so with such a medical therapy it would still be necessary to find a way to distinguish between virus and host.
posted by Blazecock Pileon at 11:44 PM on January 1, 2007

For things that are not as hard to kill as retroviruses, changing the body temperature can help, though. That's supposedly the benefit of a fever.

A fever has no effect on viral proteins, but it does increase cytokine production and — by raising body temperature — make chemical reactions related to cytokine and general immune enzyme activity more energetically favorable, amplifying the immune response.

Another beneficial side effect is that a fever does help fight off bacterial invaders while your body is working hard to clear out the viral infection.

If a fever developed to the point that viral proteins were to denature, host proteins would also denature (your brain would "melt").
posted by Blazecock Pileon at 11:54 PM on January 1, 2007

I've frozen HIV particles many times. I do research on retroviruses. Whenever we want to store virus for later use, we put it at -80C. The amount of virus lost upon each freeze-thaw cycle is only about 5-fold. So if we freeze a sample with 100,000 infectious particles, we get back about 20,000 after freezing and thawing. But freeze a person and you pretty much lose all viability!

Blazecock pileon, viruses aren't crystals! Some viruses can be crystallized experimentally, but I don't think HIV or other enveloped viruses are even among those.

And zennie has a good point. Since part of the retroviral life cycle involves existence in proviral form in a host chromosome, even killing all the particles will leave you with the intact proviruses, which will give rise to new particles to reestablish the infection.
posted by shoos at 1:47 AM on January 2, 2007

What great answers! Thank you, everybody!
posted by atchafalaya at 5:37 AM on January 2, 2007

I'm too lazy to research this, but I have a vague memory that cryotreatment is one of the quack therapies that's been offered to AIDS patients. Desperate, go to Mexico, hope the freezing saves you.
posted by Nelson at 10:45 AM on January 2, 2007