"The SARS-CoV-2 S protein on the membrane of infected cells can promote receptor-dependent syncytia formation, relating to extensive tissue damage and lymphocyte elimination." Liu Wenzhong, Li Hualan, 2021, pubmed
Is it understood that this expression of protein on the cell membrane of infected cells is to be distinguished and is different from presentation of that same protein within the MHC-cleft for immunization/priming purposes?
Simply said: the protein inducing syncytia formation is not presented within the Major histocompatibility complex but a (non-immunizing) "stand alone"?
(Only) one more reference I was able to find:
"In several coronaviruses, S protein that does not get assembled into virions transits to the cell surface where it mediates cell–cell fusion between infected cells and adjacent, uninfected cells."
Fehr/Perlman: Coronaviruses: An Overview of Their Replication and Pathogenesis (2015, "Protocol, Part of the Methods in Molecular Biology book series")
From this it might appear that presentation on cell surface is not within the MHC (thus not attracting T cytotoxic cells). Is that correct, is there any more reference?
Having received two answers it has become clear that this question should be split in two: 1. Is spike protein expressed as some regular cell membrane proteine by infected cells when inducing syncytia or is the protein expressed within the immunizing MHC? 2. If protein is expressed outside MHC does this exclude any presentation on MHC (as the cell considers itself in a regular state, of syncytia production that is). I consider 2 a new, different question, and mingling that in the question 1 asked seems confusing.