Thanks for answering with a reference!

I am not asking about the peptide sequence, just the protein it is derived from. But, if you cannot share that right now, that's OK too. I'll look out for the publication.

However, assuming I am making an educated guess about the parent protein, I'd go with gp120/gp41 envelope (env). I may be totally wrong there and you guys may have another ace up your sleeve (do hope so, fingers crossed!). Good luck!