system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't mRNA vaccines require an adjuvant?

Most other vaccine types, especially the inactivated virus/bacteria or subunit vaccines require the co-administration of an adjuvant to elicit a good immune response leading to immunity. Vector vaccines, to my knowledge, also contain an "adjuvant" in the form of the actual virus used to deliver the DNA to cells. mRNA vaccines do not seem to require an adjuvant, and in fact the most successful mRNA vaccines have modifications on the RNA portion to *reduce* immunogenicity. Why is this? Do the RNA and lipids used in the vaccine have properties that somehow allow the immune system to decisively react to them, or their translation products, as "foreign" antigens?


ETA: I understand how general immunology and innate immunity works (I have been an MSc. structural biologist for ~10 years) with regards to MHC and TLR pathways, but I don't understand the molecular mechanism of *why* our immune systems seem to respond so effectively to 'intercellular' pathogens (eg. extracellularly expressed antigen subunits) as opposed to 'intracellular' antigens like protein/ protein subunits from vaccines without an adjuvant (although we do not seem to have this 'problem' during natural bacterial or fungal infections, presumably due to the abundance of immunogenic molecules present in bacterial cell membrane lipids etc)
gpt
RNA itself has an adjuvant effect. Biontech mentions it in their presentation.

It makes sense for the body to defend itself against foreign RNA, before they express any foreign proteins.

There are so-called RNA sensors which are tightly regulated to prevent sensing of self-RNA.

Toll-like receptors can sense RNA, there are also pattern recognition receptors in the cytosol.