> I didn't look into the details too much, but as far as I can understand it's not clear yet how those antibodies (the ones created against this protein) work,

> I didn't look into the details too much, but as far as I can understand it's not clear yet how those antibodies (the ones created against this protein) work, because antibodies are supposed to be used outside of the cells, but the nucleocapsids are only present inside the cells and then inside the virus. You are correct, the antibodies are made and they end up not recognizing the nucleocapsid protein while it is in the virus but when the infected cell displays internal proteins with MHC I, which helps T-Cells target the infected cell. MHC I displays self and MHC II displays proteins that have been "eaten" by the surveillance cells of the immune system.