So as I understand it most covid rapid tests test for the nucleocapsid protein. But the nucleocapsid protein is generally enveloped by the viral envelope in covid, as I understand it. How then are antibodies able to bind to, and covid rapid tests able to detect, this nucleocapsid protein if it's enveloped by the viral envelope? Would it not be better to test for the spike protein or something else on the viral envelope itself?
I don't understand that much about virology etc. but I was reading about this and now I'm going down a rabbit hole and hoping someone can clear this up for me.
I'm not 100% sure about this so someone feel free to correct me, but afaik, in any sample you take, you will get the virus in many stages of construction. viral production inside a host cell normally kills the cell by bursting it, and the contents of the cell, which will include the viral components as well as fully assembled viral particles, then exit and continue on. They don't all wait to be finished before deciding to burst the cell. So in the saliva, mucus, etc. it would be pretty standard to find whole viral particles but also any other part of the virus as well. From a quick look at the wikipedia page, it seems like the nucleocapsid protein is also expressed at a high level, so it would make sense for it to be common in a sample from an infected person.