A Structural Atlas of TAP Inhibition by Herpesviruses and Poxviruses

Abstract In the host–pathogen arms race, herpesviruses and poxviruses encode proteins that sabotage the transporter associated with antigen processing (TAP), thereby suppressing MHC-I antigen presentation and enabling lifelong infection. Of the five known viral TAP inhibitors, only the herpes simplex virus protein ICP47 has been structurally resolved. We now report cryo-electron microscopy structures of TAP in complex with the remaining four: BNLF2a (Epstein–Barr virus), hUS6 (human cytomegalovirus), bUL49.5 (bovine herpesvirus 1), and CPXV012 (cowpox virus), assembling a structural atlas of viral TAP evasion. Employing divergent sequences, folds and conformational targets, these viral inhibitors converge on a common strategy: they stall TAP from the alternating access cycle, precluding peptide entry into the ER and shielding infected cells from cytotoxic T-cell surveillance. These findings reveal striking functional convergence and provide a structural framework for rational antiviral design.