Speculation on SARS Origins

JediJeremy writes "Nature has this article on the possibility that the SARS virus is a cross between mammal and bird viruses. The article does go on to say that this is totally speculation and that a mammal virus could have mutated. But it raises some interesting points, such as a possible new bio-terror weapon."

Comments

Unlikely

[spin2cool]

This "crossing" seems somewhat unlikely, since virus genomes do not do any sort of recombination that allows them to exchange genetic material. (unlike mammals, birds, and other things that reproduce sexually). The accumulation of random mutations is much more likely, especially considering that viruses have very few defenses agains mutation, and little, if any, DNA (or RNA) repair mechanisms.

Re:Unlikely

[mlush]

since virus genomes do not do any sort of recombination that allows them to exchange genetic material.

All you need to get recombination between virual 'species' is a double infection or a single cell ie a bird and mammal virus infect the same cell at the same time (an unlikely event but given the numbers of virus sloshing around happens from time to time). When they replecate there is a lot of 'naked' viral genomic DNA which spends a lot of time recombining with the host genome and each other (assuming they have sequences in common).

The accumulation of random mutations is much more likely, especially considering that viruses have very few defenses agains mutation, and little, if any, DNA (or RNA) repair mechanisms.

Absolutly true the virus has no repair mechanisms OTOH the host cell which they hijack to replecate in has all the DNA repair mechanisms it needs (I don't think there are RNA repair mechaninisms for obvious reasons).

In any case the conclusions are based on sequence comparison it is very unlikely that a mamalian gene randomly mutated to look like a bird virus gene

Re:Unlikely

[angel'o'sphere]

Sorry, but thats utterly wrong.
Virus 'live' in animal or human cells. There are a lot of virus which are 'similar' to easch other. Especially influenza virus are of that kind.
Its well known that pigs, humans, chickens and ducks and likely other birds are breeding ground for influenza virus.
(In europe e.g. it is forbidden to raise pigs and chicken together in the same stable ...
The reason is, chicken influenza virus can live and breed in pig and vice versa.
Often they are harmless for the animals, but not for humans. If a chicken is infected by two different virus, the virus crossbreed, creating a new virus. Heck, what do you think from where every year the "new" influenza is comming from? And what do you think why you have to inoculate every winter again?
Influence is likely the most dangerous virus on planet, with the most different strands and the highest "mutation" rate. What you call mutating is primaryly crossbreeding.
I really wonder why a magazine like nature with that reputation calls that "speculative". Its a well known fact that SARS is a crossbreed of bird and pig virus, just like most influenza spreading every winter over north europe and north america.
Crossbreeding happens in this way: a animal s infected with more than one influenza virus. So its cells create "virus particle". The virus particle combine to virus, just like Drexlers nanotech dream. They self assemble. During assembly all particles which are "compatible" combine, regardless of the source they sprang from. A lot dont 'work' as virus after wards, but some become completely new virus, often VERY dangerous.

angel'o'sphere

Diploid viruses can recombine

[Anonymous Coward]

This may not fit the example of SARS, but diploid viruses like HIV can recombine with other strains in vivo.

I bet there will turn out to be other totally epigenetic mechanisms for a virus to be changed by the vector it travels though as well.

Re:artificial origin

[Aglassis]

You said: " it's seems pretty probable to me that this might be of artificial origin, accidentally or intentionally

with the massive amounts of research we have going on right now with the virii (using them to fight cancer; finding cure for AIDS; studying influenza; sequencing virii's DNA) it's possible that we might have artificially produced SARS or have abused a population of some virus to the point that the population experienced a high mutation rate (e.g. if we tagged them with radiation-produced molecules, which is common practice for studying their spread in an animal)"

This is unlikely, since the SARS-CoV is not more closely related to any known type of coronavirus than any other. If it were a modified virus it should be very similar to a known class of coronavirus.