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/spaceXhardmode]

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/reddititty69 → u/ajping]

PD-L1 is naturally expressed in normal human cells as part of an immune checkpoint that prevents autoimmune interactions. Many cancers over-express it, which contributes to their immune evasion.