IMMEDIATE-EARLY TRANSACTIVATOR RTA OF EPSTEIN-BARR-VIRUS (EBV) SHOWS MULTIPLE EPITOPES RECOGNIZED BY EBV-SPECIFIC CYTOTOXIC T-LYMPHOCYTES

We analyzed the immediate-early transactivator Rta of Epstein-Barr vir us (EBV) for its role as a target for specific cytotoxic T lymphocytes (CTL), Panels of overlapping peptides covering the entire amino acid sequence of Rta were synthesized and used to induct and analyze specif ic CTL responses in EBV-positive donors. Using peptide-pulsed target c ells, we found nine different CTL epitopes that are distributed over t he entire protein sequence. One epitope restricted by HLA-A24 could he mapped to the decameric sequence DYCNVLNKEF between amino acid positi ons 28 and 37 of the Rta protein, A second epitope could he assigned t o the same region of Rta (residues 25 to 39) and was shown to be restr icted by HLA-B18. Another, minimal epitope could be mapped to the nona meric sequence ATIGTAMYK between amino acid positions 134 and 142; thi s peptide was restricted by HLA-A11. Another four epitopes were proven to be restricted by HLA-A2, -A3, -B61, and -Cw4 and were located betw een Rta residues 225 and 239, 145 and 159, 529 and 543, and 393 and 40 7. respectively. For two other epitopes, only the location within the Rta protein is known so far (residues 121 to 135 and 441 to 455); thei r exact HLA restriction patterns have not get been identified. Using t arget cells infected with recombinant vaccinia virus containing the ge ne for Rta, we showed that six of eight Rta-specific CTL lints recogni zed the corresponding peptides also after endogenous processing. These data suggest that Rta comprises an important target for EBV-specific cellular cytotoxicity. Together with recent findings of other immediat e-early and early proteins also acting as CTL targets, they reveal the role of proteins of the lytic cycle in the immune recognition of EBV- infected cells.