title: A dominant role for the immunoproteasome in CD8+ T cell responses to murine cytomegalovirus.
abstract: Murine cytomegalovirus (MCMV) is an important animal model of human cytomegalovirus (HCMV), a β-Herpesvirus that infects the majority of the world's population and causes disease in neonates and immunocompromised adults. CD8(+) T cells are a major part of the immune response to MCMV and HCMV. Processing of peptides for presentation to CD8(+) T cells may be critically dependent on the immunoproteasome, expression of which is affected by MCMV. However, the overall importance of the immunoproteasome in the generation of immunodominant peptides from MCMV is not known. We therefore examined the role of the immunoproteasome in stimulation of CD8(+) T cell responses to MCMV - both conventional memory responses and those undergoing long-term expansion or "inflation". We infected LMP7(-/-) and C57BL/6 mice with MCMV or with newly-generated recombinant vaccinia viruses (rVVs) encoding the immunodominant MCMV protein M45 in either full-length or epitope-only minigene form. We analysed CD8(+) T cell responses using intracellular cytokine stain (ICS) and MHC Class I tetramer staining for a panel of MCMV-derived epitopes. We showed a critical role for immunoproteasome in MCMV affecting all epitopes studied. Interestingly we found that memory "inflating" epitopes demonstrate reduced immunoproteasome dependence compared to non-inflating epitopes. M45-specific responses induced by rVVs remain immunoproteasome-dependent. These results help to define a critical restriction point for CD8(+) T cell epitopes in natural cytomegalovirus (CMV) infection and potentially in vaccine strategies against this and other viruses.
authors.affiliation: Nuffield Department of Clinical Medicine, Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hutchinson
authors.forename: Stuart
authors.initials: S
authors.lastname: Sims
authors.forename: Geraldine
authors.initials: G
authors.lastname: O'Hara
authors.forename: Jon
authors.initials: J
authors.lastname: Silk
authors.forename: Uzi
authors.initials: U
authors.lastname: Gileadi
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Cerundolo
authors.forename: Paul
authors.initials: P
authors.lastname: Klenerman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D006566:Herpesviridae Infections / Q000235:genetics / Q000276:immunology; D007111:Immunity, Cellular / Q000235:genetics* / Q000276:immunology; D016056:Immunodominant Epitopes / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D018146:Muromegalovirus / Q000276:immunology*; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
chemical_list: D016056:Immunodominant Epitopes; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex