[thedoc (OP)]

Viruses - are they any good?  Are any of them actually good for us or symbiotic?  For example, cowpox provides immunity to smallpox.
Asked by Simon


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[thedoc (OP)]

We answered this question on the show...

This may be true, despite that fact that most people think of a virus as being something that makes them feel awful! 
A recent piece of research in Nature magazine, by US [img float=right]/forum/copies/RTEmagicC_Herpes_simpex_virus_06.jpg.jpg[/img]scientist Skip Virgin, suggests that being infected by one of the family of viruses known as Herpes viruses, such as herpes simplex, which causes cold sores, or Epstein-Barr virus, which causes glandular fever can help to boost the function of the immune system. 
When they infected mice with the rodent equivalents of either of these infections, the mice developed a much better immune response to other pathogens than mice which had never been infected. 
To prove this, they exposed the mice to the bacteria which causes plague and also listeria; they found these mice to be 100% protected against these bacteria compared with animals which had never been infected with a Herpes virus, which all died. 
When they studied these mice, they found signalling molecules called interferon gamma were being produced at a much higher level than normal, and this molecule is known to stimulate the immune system.
They think that, because we've been living with members of the herpes viruses for millions of years, the body has come to rely on infection to provide additional gene functions, or immune stimulating factors, which our body no longer has. 
This programmes a more powerful the immune system, and we get benefit. 
It's almost a symbiosis, we give the virus a home and it gives us a better immune system...

[CliffordK]

There is a group of viruses known as satellite viruses which require a second virus to be able to actively infect cells.  An example is Hepatitis D, unfortunately, co-infection between Hepatitis D & Hepatitis causes a more severe disease.

However, there may be some virus super-infections that in fact make the disease less severe.  This class of satellite viruses is often termed as a Virophage.  I believe all viruses termed as virophages are non infectious to humans, but perhaps there will be some discovered, or perhaps engineered in the future.

There are, however, many bacteriophages, or viruses that are specifically adapted to infect bacteria.  Apparently in Russia, they have administered bacteriophage therapy as a treatment for human disease, and it may be an alternative for treatment of new highly resistant strains of "super-bugs".

Other than the cowpox mentioned above, there are a few vaccines that are delivered as live-attenuated viruses, for example OPV (Oral Polio Vaccine) is a live-attenuated virus, but it also occasionally leads to a vaccine associated disease.

Viruses are currently being tested as a method for delivering gene therapy to cells as they naturally are designed to deliver small packets of genes to cells, and they may also be naturally predisposed to infect very specific types of cells allowing the therapy to be targeted to specific tissue types.

In many cases, exposure to a virus may give lifelong immunity to that virus.  In the past, parents might even intentionally infect their children with chicken pox because it was believed to be safer for children to contract the disease than for adults to contract the disease.

[cheryl j]

A few years ago there was a frenzy in main stream newspapers about influenza virus causing remission of certain kinds of cancer. I haven't seen anything about it since. According to this link, they've been playing around with this idea for a while, but without much long term success.

http://jnci.oxfordjournals.org/content/91/20/1709.long

[cheryl j]

I was in Chapters today looking at books before my daughter's orthodontist appointment and I stumbled on one called  Virolution by Frank Ryan. He's a physician and evolutionary biologist and his book is about the effects of viral DNA in the genome of humans and other animals. According to one review (I haven't read it yet) his theory is "that instead of being merely agents of pathology, viruses can also work together with their host to help it survive."

Anyway, here is the Amazon link if it is a topic you are interested in. http://www.amazon.ca/Virolution-Frank-Ryan/dp/0007315120

[RD]

...  Virolution by Frank Ryan. He's a physician and evolutionary biologist and his book is about the effects of viral DNA in the genome of humans and other animals ...

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