Interaction of human papillomavirus type 11 E7 protein with TAP-1 results in the reduction of ATP-dependent peptide transport

Human papillomaviruses (HPVs) cause benign and malignant epithelial tumors of the respiratory and genital mucosa. We previously reported that recurren t respiratory papillomas caused by HPV 6/11 express low levels of antibody- detectable TAP-1, the protein that transports peptides into the endoplasmic reticulum for assembly and presentation by MHC Class I, and that the exten t of TAP-1 immunostaining is inversely related to the frequency of disease recurrence. We have now determined a mechanism for the reduction in TAP-I d etection. Anti-TAP-1 antibody immunoprecipitated very low amounts of protei n from papilloma cells. However, immunoprecipitation of calreticulin, anoth er member of the MHC I assembly complex, coprecipitated TAP-I at levels com parable to those of uninfected cells. Immunoprecipitation of an HPV-positiv e cell line with either anti-TAP-1 or anti-calreticulin coprecipitated HPV E7 protein. Finally, purified HPV 11 E7 protein inhibited ATP-dependent pep tide transport in vitro. We propose that the interaction of E7 with TAP-I p revents TAP-I antibody detection and efficient peptide transport, resulting in poor presentation of viral antigen on HPV-infected cells and thus failu re to mount an effective immune-mediated prevention of disease recurrence. (C) 2001 Academic Press.