We now have the complete pig (aka Sus scrofa) genome! You know what that means..........!!!
While I am a huge fan of all ERVs, including PERVs, PERVs hold a special place in my heart.
Physicians can use pig parts and organs for human transplants. Thanks to a pig, someone I love very much is alive today. It would be fantastic if pigs could be used to their full medical potential... but because of PERVs, some people who could benefit from a pig transplant, cannot.
Pigs have ERVs just like humans do. And some of their ERVs are relatively young, which means they have not entirely deteriorated yet, which means they might be able to code for a functional retrovirus.
Take someone who is sick, give them a pig organ, put them on immunosuppressive drugs... what if a PERV pops up? What if we get a new human retrovirus? What if we get a pig version of HIV? A trail of suffering and death, when all we wanted to do was save some lives.
Well, that has been studied, extensively, and we think it is safe. Clinical trials are going on around the world trying to help people with pig parts, and everyone is doing okay-- No PERVs.
But now that we have the entire pig genome sequenced, scientists have a lot more data to mine to see if there are any PERVs hiding behind piles of junk DNA. In fact, there are. These folks found 175 previously undescribed PERVs. Happily, they only found about 20 gamma-ERVs, and 4-beta-ERVs, that would have a shot in hell of doing anything-- They were almost complete. But none of them were complete. They all had deletions/mutations/mistakes in either gag, pol, or env, rendering them defective.
Unfortunately, we know from the XMRV fiasco that given the right conditions, fractured ERVs can create an infectious agent.
Happily, again, there is a lot of polymorphism between pigs and these ERV loci. If we study the almost-intact guys, figure out which ones are most likely to cause trouble, we could try to find pig lines that lacked one/the other/both/all of the trouble-makers.
We need options for our organ transplants, but aint nobody want a PERV inside of them.
Dumb question -- didn't the whole xmrv thing wind up uncovering an interesting lab phenomenon? Not a human disease agent, but a unexpected bit of weird getting into lab materials.(?) Could it have not caused more distorted lab results elsewhere if it had not been painfully sorted out via the Mikovits mistake? I'm not able to judge whether that was an amateur error or something that would confound a practicing scientist, or the value of whatever was learned in the episode.
I think the XMRV thing also shows that while ERVs from other a certain species, individually, may not be shown to infect human cells, there is always the chance that an in-vivo recombination could change that. Of course the benefits outweigh the risks at the moment but it should be a lesson not to let our guard down based on in-vitro data. There's always a chance.
A small step in a long journey - but a step none-the-less.
I wonder if we'll ever see pigs engineered to provide organs for transplant - one could conceive of a pig engineered to remove the PERVs, and with the porcine HLA loci removed and replaced with human MHC-Ib alleles. That would give you organs that could be transplanted with minimal/no need for immunosuppressives, while simultaneously removing the risk of PERV-to-human transmission.
and I wonder, if those pigs were ever made, if they'd let you make bacon out of them. Yummmmm, humanized bacon...
we could try to find pig lines that lacked one/the other/both/all of the trouble-makers.
... or just create one. Definitely within the realms of possibility these days.