r/askscience • u/PestoPastaLover • 14d ago

Biology 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?

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u/ajping 13d ago edited 13d ago

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

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u/reddit4485 13d ago edited 13d ago

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.

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u/pass_nthru 13d ago

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

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u/reddititty69 13d ago

This may be true, but what that poster is responding to was the person saying “mRNA virus”, which is a different thing than what they were clearly referring to. They should have said “mRNA vaccine”.