The Autoimmunity Problem.
Imagine a criminal with your face. The photo goes out to the police. What happens when they see you while on the lookout for him? Oh, I'm not the guy, Yeah buddy, sure, tell it to the judge.
There are a number of illnesses that get started by infection with some agent or the other, but end up damaging something remote. Classic examples are heart valve damage from rheumatic fever, secondary to a strep throat. Strep also can cause kidney damage via an immune mechanism.
Rheumatoid arthritis is now thought to be caused by urinary tract infection with Proteus mirabilis, normally found in the gut. Women get cross contamination much easier, get more bladder infections, and wind up with 3 to 5 times more RA.
In every case, it's mistaken identity. Immune system screwups.
Viral S protein is antigenic, causing antibodies to form that bind to it. But it also binds to 2 receptors we know of, chiefly the ACE2 one.
Let's represent the ACE2 receptor with an M. Normally it locks onto a substrate, v, that fits in the middle of the M. .
The S protein also fits into it in the middle like a V. It resembles the substrate. That's how the Virus gains entry, because like Vlad Dracula, it can't come in unless some fool invites it.
Our antibodies might lock up multiple S proteins at once, and look like a W, that can hold a couple V's each. A cop with 2 arms.
What would those antibodies do to the substrate?
Once a person has the circulating antibodies, there is a pretty fair chance that they will disrupt the normal communication we have with our ACE2 receptors.
What is that going to do to us long term? I don't know, Rut Row, Shaggy?
Moreover as long as we are making that normal substrate v, our immune system is going to assume that our infection is STILL running, because it cannot tell the difference between V and v, and pump out more and more W till all our good normal v is locked up tight.
Our bloodstream is going to become a v-W traffic jam. Imagine Volkswagons from here to Timbucktu. The kidneys are going to have to filter all that crap.