title: A role for intercellular antigen transfer in the recognition of EBV-transformed B cell lines by EBV nuclear antigen-specific CD4+ T cells.
abstract: The CD4+ T cell response to EBV may have an important role in controlling virus-driven B lymphoproliferation because CD4+ T cell clones to a subset of EBV nuclear Ag (EBNA) epitopes can directly recognize virus-transformed lymphoblastoid cell lines (LCLs) in vitro and inhibit their growth. In this study, we used a panel of EBNA1, 2, 3A, and 3C-specific CD4+ T cell clones to study the route whereby endogenously expressed EBNAs access the HLA class II-presentation pathway. Two sets of results spoke against a direct route of intracellular access. First, none of the clones recognized cognate Ag overexpressed in cells from vaccinia vectors but did recognize Ag fused to an endo/lysosomal targeting sequence. Second, focusing on clones with the strongest LCL recognition that were specific for EBNA2- and EBNA3C-derived epitopes LCL recognition was unaffected by inhibiting autophagy, a postulated route for intracellular Ag delivery into the HLA class II pathway in LCL cells. Subsequently, using these same epitope-specific clones, we found that Ag-negative cells with the appropriate HLA-restricting allele could be efficiently sensitized to CD4+ T cell recognition by cocultivation with Ag-positive donor lines or by exposure to donor line-conditioned culture medium. Sensitization was mediated by a high m.w. antigenic species and required active Ag processing by recipient cells. We infer that intercellular Ag transfer plays a major role in the presentation of EBNA-derived CD4 epitopes by latently infected target cells.
authors.affiliation: Cancer Research U.K. Institute for Cancer Studies, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Graham S
authors.initials: GS
authors.lastname: Taylor
authors.forename: Heather M
authors.initials: HM
authors.lastname: Long
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Haigh
authors.forename: Martin
authors.initials: M
authors.lastname: Larsen
authors.forename: Jill
authors.initials: J
authors.lastname: Brooks
authors.forename: Alan B
authors.initials: AB
authors.lastname: Rickinson
mesh_terms: D017951:Antigen Presentation / Q000235:genetics / Q000276:immunology*; D000956:Antigens, Viral / Q000096:biosynthesis / Q000235:genetics; D016175:B-Lymphocyte Subsets / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism / Q000821:virology; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D002999:Clone Cells; D018920:Coculture Techniques; D018984:Epitopes, T-Lymphocyte / Q000276:immunology* / Q000378:metabolism; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D005110:Extracellular Space / Q000235:genetics / Q000276:immunology*; D005822:Genetic Vectors; D006801:Humans; D008213:Lymphocyte Activation / Q000235:genetics; D014616:Vaccinia virus / Q000235:genetics
chemical_list: D000956:Antigens, Viral; D018984:Epitopes, T-Lymphocyte; D019309:Epstein-Barr Virus Nuclear Antigens