Identification of MHC-II naturally processed and presented peptides derived from HHV-6B (strain Z29). MHC-II-peptide complexes were immuno-affinity purified from the total membrane fraction obtained from a T lymphoblastoid cell line infected with HHV-6B (Z29). Peptides were eluted off the purified complexes by acid treatment and separated from protein subunits using C4 columns. LC-MS/MS was used for analysis of the peptide mix and identification of eluted peptides sequences