Another, far different, scenario comes to mind. Where there is significant similarity to engogenous retroviral peptide motifs, the human host may see them as “ALTERED SELF”. That MAY be a prescription for an allergenic response, such as those that happen when haptens (e.g. penicillin) bind to host proteins. The development of reaginic antibody (IgE) responses may be elicited, or delayed type hypersensitivity from the T cell arm of the human response.
Regions that may be recognized as altered self may be deleterious is included in any vaccine formulation. There was in fact a SARS vaccine used in mice that elicited an allergic response upon challenge.
So, we already know that the fusion peptide(s) and aromatic-rich regions of coronaviruses have properties that make them potentially cytotoxic. Now we know of regions that may be reaginic.
In formulating a vaccine without allergic or cytotoxic side effects, we may have a problem here.
Bill