Endogenous retroviruses

Is it possible that in vitro fertilization could/has already created new endogenous retroviruses in the human genome? For example, if a retrovirus from contaminant in the medium or from co-cultured animal cells penetrated the egg cell?

Apparently from 1988 to 2001 human embryos were often co-cultured with cow and green monkey cells in order to make them grow better. Could this cause a pandemic? I know pig endogenous retroviruses have been shown to be able to infect human cells in vitro, so surely it’s a possibility right?

Endongenous retroviruses aren’t going to cause a pandemic because they stay in the genome, they don’t wander around like regular retroviruses. They might cause disease in people who caught them during the IVF that generated said people but while the popularity of IVF has been rising that’s still a small percentage of people world-wide, not nearly enough to qualify as a pandemic of any sort.

Couldn’t they spread within say a few generations though once the IVF-infected people start having their own children?

Again, IVF-generated people are not common, only a tiny percentage of the population. It would take a really, really long time for the number of them and their descendants to amount to any significant number compared to the world population. Of course, it would be bad for the small number of people affected, no question, but it wouldn’t represent a pandemic.

There is also the possibility that those produced by IVF may be at greater than average risk for fertility problems as well, which if true may further reduce the spread of any hypothetical ERV they may carry.

So while it might be possible for IVF to result in a new ERV in an individual you have to remember that

  1. few if any ERV’s cause disease (so far as I know, there has been no definite link between a human ERV and a disease)
  2. ERV’s by their nature are not as contagious as regular retroviruses
  3. Even if a non-human ERV infected a human embryo during IVF it appears, based on statistics regarding existing ERV’s, unlikely to cause disease
  4. People produced by IVF are more likely to have been conceived by parents with fertility problems which, if genetic, may be passed on to their IVF offspring who would likewise be less likely to reproduce than average and even if they did are unlikely to have a lot of kids
  5. IVF produced people are a tiny minority, so
  6. Even IF an IVF person acquired a new ERV and IF they reproduced there are so few of them in the overall population that it would be a LOT of generations before such a disease amounted to any significant numbers, if ever.

Frankly, you’d be better off worrying about getting hit by lightning or bit by a shark or winning a big lottery jackpot as all of those are very much more likely.

Co-culturing could provide opportunities for viruses to jump species, but it would be a drop in the ocean. There are already ample opportunities within nature and our animal husbandry practices.

Yeah, the human genome is estimated to be 3-8% ERV’s as it is, as is true for pretty much everything else. No disaster has ensured, and some of them may have even been appropriated for useful purposes.

Once an ERV is in a genome doing things to harm the host is only going to impeded its own reproductive success. Evolution favors ERV’s that are either neutral in effect or provide a benefit, the harmful ones are eliminated or at least sharply reduced in incidence just as any other bad gene.

Can endogenous retroviruses also spread via agriculture?

Viruses, including retroviruses can cross from one species to another - and agriculture practices can provide opportunities for this to happen - for example, keeping ducks and pigs in close proximity may provide a path for viruses to cross from birds to mammals.