An isolated protein comprises respective amino acid sequences of each of a plurality of CTL epitopes from two or more different herpesvirus antigens and further comprises an intervening amino acid or amino acid sequence between at least two of said CTL epitopes comprising proteasome liberation amino acids or amino acid sequences and, optionally, Transporter Associated with Antigen Processing recognition motifs. The isolated protein is capable of rapidly expanding human cytotoxic T lymphocytes (CTL) in vitro and eliciting a CTL immune response in vivo upon administration to an animal as an exogenous protein. Typically, the isolated protein comprises no more than twenty (20) CTL epitopes derived from cytomegalovirus and/or Epstein-Barr virus antigens.
