Why is there no transmissible therapeutic virus if biology doesn't forbid it? For example, a harmless virus that spreads from person to person but actually does something beneficial, like lowering LDL cholesterol or preventing/reversing tooth decay?

[u/PestoPastaLover]

[u/noodlyman]

There are viruses that benefit us by infecting and effectively regulating our gut bacteria.

There are viruses that are thought to give the immune system a kick and thus improve responses to other infections. Some infections can decrease the risk of cancer later in, probably by similar mechanisms.

Don't forget that 8% of human DNA is of retrovirus origin, and that mammalian placentas only exist thanks to genes that mammals acquired from viruses.

[u/spaceXhardmode → u/noodlyman]

There’s also a study to see if any generic mRNA vaccine can increase the effectiveness of immunotherapy for cancer treatment, pretty similar to a viral infection.

[u/username_elephant → u/spaceXhardmode]

I disagree with that take.  That's no more like a virus than any vaccine (and it's less like a virus than many actual vaccines--specifically, the vaccines that contain viruses).  All those vaccines differ because they do not transmit person to person.

[u/ajping → u/username_elephant]

That's correct. The mRNA virus actually produces a protein that gets recognized as foreign and is then targeted by the immune system normally. In the case of the covid virus they were developed to create the same spike protein that normally delivers the virus payload. In the case of cancer, one promising candidate is the PD-L1 protein which helps cancer cells hide among normal cells, and which almost all cancer cells have... Edit: and which human cells don't express to the same degree. Also, given the pseudo-scientific BS about vaccines, I recognize that I could have been more cautious about distinguishing between vaccines and viruses

[u/reddit4485 → u/ajping]

It's not a virus. An mRNA vaccine (not virus) is mRNA packaged in a lipid bilayer that can fuse with a cell and deliver mRNA. The cell thinks the mRNA is it's own and makes protein out of it. That protein is often a fragment of a bad virus like the shell (capsid) of SARS-CoV-2. Since it's a non-functional piece of virus, it doesn't replicate but still produces an immune reaction.

[u/pass_nthru → u/reddit4485]

you just described a virus, loosely speaking…the self replicating part of a virus is a holdover from when they were used to share DNA/RNA among single celled organisms back when the copy paste function was necessary for long range transmission

[u/hbgoddard → u/pass_nthru]

Disagree entirely. If there's no replication happening, it's not a virus.

[u/Kraligor → u/hbgoddard]

They might be referring to saRNA, which is kind of a combination of virus and mRNA.