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supapoopascoopa t1_jcjvu3o wrote

Endogenous retroviruses are defective, only vertically transmitted like other genes, and none yet found are competent to produce virions. But they are all in some sense heritable infections and also “infect” new cells every time a cell divides.

Some can produce proteins and even entire viral like particles using host machinery. These proteins are associated with autoimmune diseases and certain cancers. One could argue these are “active” infections in terms of causing symptoms.

The takehome message as usual is that nature in general and viruses in particular don’t give a hoot about arbitrary definitions.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1187282

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Uncynical_Diogenes t1_jcm5rm0 wrote

Replying to -Metacelsus- (#2,256,253)

They might carry it, sure, but I’d argue it was likely their great-grandparent^nth that was actually infected.

I think this line of inquiry is more about re-emergence of previously-dormant ERVs. As a human, some ~1-8% of my DNA is ERVs, depending on who you ask, but I’m pretty confident that I was never infected by any of them myself. I was just born carrying them.

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Uncynical_Diogenes t1_jcm6cq8 wrote

Replying to Reisevi3ber (#2,256,028)

“Which ones” is probably not a super stellar question because they probably have quite boring technical names, and the list of ones we actually have found and named is likely much smaller than the list of potential causative agents.

References 4-7 of the linked text:

> 4. Boller K, Konig H, Sauter M, et al. Evidence that HERV-K is the endogenous retrovirus sequence that codes for the human teratocarcinoma-derived retrovirus HTDV. Virology 1993;196:349–53. [PubMed] [Google Scholar]

>5. Lower R, Boller K, Hasenmaier B, et al. Identification of human endogenous retroviruses with complex mRNA expression and particle formation. Proc Natl Acad Sci U S A 1993;90:4480–4. [PMC free article] [PubMed] [Google Scholar]

>6. Nelson PN. Retroviruses in rheumatic diseases. Ann Rheum Dis 1995;55:441–2. [PMC free article] [PubMed] [Google Scholar]

>7. Nelson PN, Lever AML, Smith S, et al. Molecular investigations implicate human endogenous retroviruses as mediators of anti-retroviral antibodies in autoimmune rheumatic disease. Immunol Invest 1999;28:277–89. [PubMed] [Google Scholar]

Some rheumatic conditions and at least one cancer have been at least linked to expression of human ERV’s, if not necessarily the causative agents of such.

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yakiddenme1 t1_jcm7wcz wrote

Yes, almost all endogenous viruses will cause an active infection with symptoms of one kind or another if an organism is stressed enough. But sometimes the symptoms these viruses cause can actually be for the betterment or detrement of the host.

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Neurokeen t1_jcmt6y7 wrote

Replying to -Metacelsus- (#2,256,253)

It actually gets to a really interesting question as to "what counts as infected?"

If there's latent proviral inserts that never activate and propagate, to the point that they're ubiquitous in the DNA of the host, then it strains the definition a bit in most contexts. If you're doing genomics then for those purposes it makes sense to call it an infection. If you're doing something at the level of epidemiology, then probably not.

Having a bunch of boundary cases in definitions is pretty much a staple for biology though, so it's not worth losing any sleep over.

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docmeow t1_jcmxth0 wrote

While not really an endogenous retrovirus capable of causing disease by itself, this occurs to an extent in cats. In cats, Feline Leukemia Virus (FeLV) is present as both an exogenous retrovirus, and integrated into the genome several times as an endogenous retroviruses. Several strains of FeLV Subtype B occurs when the "env" region of endogenous FeLV recombines with exogenous FeLV. This "new" virus is not generally considered transmissible, but causes cancers to develop in the cat.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8387034/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7152252/

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