I think this is not just because of viruses, but also healthy autoimmunity. Finding even your own cell internals in the bloodstream would mean there is work to

I think this is not just because of viruses, but also healthy autoimmunity. Finding even your own cell internals in the bloodstream would mean there is work to do for the immune system. E.g. auto-antibodies may increase with tumor burden, as cell rupture caused by apoptosis, or necrosis attract immune cells and cascade recruitment of more, which is usually a good thing. Anyway, AFAIK the mRNA breakthrough wasn't with the mRNA itself, but rather the delivery vehicle to avoid said immune response. I don't think your example of cystic fibrosis, and generally chronic illnesses, are prime targets for mRNA based therapy, as the genetic defect isn't causally targeted by mRNA tech. You would force all cells (with non-discriminatory vehicles) to produce the missing protein repeatedly. Much better target for gene therapy. I don't think people see the future of mRNA in substituting into the delicate machinery of the cell continuously. I think the possible therapy target are of the type raw, simple one-hit wonders. Very much alike traditional medication approaches, with the twist of excellent drug delivery avoiding extracellular pharmacokinetics, e.g. vitamin C has very different, even antagonistic roles in the intra- vs extracellular space, and of course liver-fistpass and immunological clearance. mRNA tech is not gene therapy (although, there is of course effective overlap).