title: Processing and MHC class I presentation of human cytomegalovirus pp65-derived peptides persist despite gpUS2-11-mediated immune evasion.
abstract: Immune control of human cytomegalovirus (HCMV) infection can be mediated by CD8+ cytolytic T lymphocytes (CTL). Adoptive transfer of antiviral CTL confers protection against HCMV reactivation and disease. The tegument protein pp65 and the immediate-early 1 protein (IE1) are recognized to be major CTL targets, even though during productive infection the viral immunoevasion proteins gpUS2-11 act to suppress major histocompatibility complex (MHC) class I-restricted antigen presentation. Thus it was not clear how infected cells could be labelled with antigenic peptides in the face of immunoevasion. We show here that the immunodominant peptide pp65NLV was presented by MHC class I in cells infected with a gpUS2-11-competent virus. Presentation of pp65NLV was still detectable at 96 h post-infection, although at low levels. Partial suppression of pp65NLV presentation was dependent on the ability of the infecting strain to express gpUS2-11. MHC class I-restricted antigen presentation in HCMV-infected cells (encoding gpUS2-11) exhibited specificity for pp65-derived peptides, as infected fibroblasts did not present the IE1-derived nonapeptide IE1TMY. Remarkably, infected cells could restore pp65NLV peptide presentation after acid removal of MHC class I despite gpUS2-11 expression. This recovery was shown to be dependent on proteasome functionality. In contrast to IE1, pp65 peptides are loaded on MHC class I molecules to be transported to the cell surface at early and late times after infection in the face of gpUS2-11-mediated immunoevasion. pp65 is therefore the first example of an HCMV protein only incompletely subjected to gpUS2-11-mediated immunoevasion.
authors.affiliation: Institute of Virology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Besold
authors.affiliation: Institute of Virology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Frankenberg
authors.affiliation: Institute of Virology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Pepperl-Klindworth
authors.affiliation: Department of Hematology and Oncology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Kuball
authors.affiliation: Department of Hematology and Oncology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Theobald
authors.affiliation: Max von Pettenkofer Institut, Department of Virology, Ludwig-Maximilians-Universität München, Germany.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Hahn
authors.affiliation: Institute of Virology, Johannes Gutenberg-Universität, Mainz, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Plachter
mesh_terms: D000818:Animals; D002460:Cell Line; D003587:Cytomegalovirus / Q000276:immunology*; D003586:Cytomegalovirus Infections / Q000276:immunology; D052816:Foreskin; D005786:Gene Expression Regulation / Q000276:immunology; D015789:HLA-A2 Antigen / Q000235:genetics*; D015395:Histocompatibility Antigens Class I / Q000235:genetics*; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000502:physiology; D010750:Phosphoproteins / Q000737:chemistry / Q000502:physiology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014763:Viral Matrix Proteins / Q000737:chemistry / Q000502:physiology*
chemical_list: D015789:HLA-A2 Antigen; D015395:Histocompatibility Antigens Class I; D010446:Peptide Fragments; D010750:Phosphoproteins; D014763:Viral Matrix Proteins; C065418:cytomegalovirus matrix protein 65kDa