title: Expression of the human cytomegalovirus UL11 glycoprotein in viral infection and evaluation of its effect on virus-specific CD8 T cells.
abstract: The human cytomegalovirus (CMV) UL11 open reading frame (ORF) encodes a putative type I transmembrane glycoprotein which displays remarkable amino acid sequence variability among different CMV isolates, suggesting that it represents an important virulence factor. In a previous study, we have shown that UL11 can interact with the cellular receptor tyrosine phosphatase CD45, which has a central role for signal transduction in T cells, and treatment of T cells with large amounts of a soluble UL11 protein inhibited their proliferation. In order to analyze UL11 expression in CMV-infected cells, we constructed CMV recombinants whose genomes either encode tagged UL11 versions or carry a stop mutation in the UL11 ORF. Moreover, we examined whether UL11 affects the function of virus-specific cytotoxic T lymphocytes (CTLs). We found that the UL11 ORF gives rise to several proteins due to both posttranslational modification and alternative translation initiation sites. Biotin labeling of surface proteins on infected cells indicated that only highly glycosylated UL11 forms are present at the plasma membrane, whereas less glycosylated UL11 forms were found in the endoplasmic reticulum. We did not find evidence of UL11 cleavage or secretion of a soluble UL11 version. Cocultivation of CTLs recognizing different CMV epitopes with fibroblasts infected with a UL11 deletion mutant or the parental strain revealed that under the conditions applied UL11 did not influence the activation of CMV-specific CD8 T cells. For further studies, we propose to investigate the interaction of UL11 with CD45 and the functional consequences in other immune cells expressing CD45.
  
  
  OBJECTIVE
  Human cytomegalovirus (CMV) belongs to those viruses that extensively interfere with the host immune response, yet the precise function of many putative immunomodulatory CMV proteins remains elusive. Previously, we have shown that the CMV UL11 protein interacts with the leukocyte common antigen CD45, a cellular receptor tyrosine phosphatase with a central role for signal transduction in T cells. Here, we examined the proteins expressed by the UL11 gene in CMV-infected cells and found that at least one form of UL11 is present at the cell surface, enabling it to interact with CD45 on immune cells. Surprisingly, CMV-expressed UL11 did not affect the activity of virus-specific CD8 T cells. This finding warrants investigation of the impact of UL11 on CD45 functions in other leukocyte subpopulations.
authors.affiliation: Department of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Ildar
authors.initials: I
authors.lastname: Gabaev
authors.affiliation: Department of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Endrit
authors.initials: E
authors.lastname: Elbasani
authors.affiliation: Clinical Cooperation Group Immunooncology, Helmholtz Centre Munich, Munich, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Ameres
authors.affiliation: Department of Virology, Hannover Medical School, Hannover, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Steinbrück
authors.affiliation: Institute of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Stanton
authors.affiliation: Centre for Experimental and Clinical Infection Research, Twincore, Hannover, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Döring
authors.affiliation: Department of Histology and Embryology and Center for Proteomics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia.
authors.forename: Tihana
authors.initials: T
authors.lastname: Lenac Rovis
authors.affiliation: Centre for Experimental and Clinical Infection Research, Twincore, Hannover, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kalinke
authors.affiliation: Department of Histology and Embryology and Center for Proteomics, Faculty of Medicine, University of Rijeka, Rijeka, Croatia.
authors.forename: Stipan
authors.initials: S
authors.lastname: Jonjic
authors.affiliation: Clinical Cooperation Group Immunooncology, Helmholtz Centre Munich, Munich, Germany German Center for Infection Research (DZIF), partner sites, Hannover and Munich, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Moosmann
authors.affiliation: Department of Virology, Hannover Medical School, Hannover, Germany German Center for Infection Research (DZIF), partner sites, Hannover and Munich, Germany messerle.martin@mh-hannover.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Messerle
mesh_terms: D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D003587:Cytomegalovirus / Q000276:immunology*; D005347:Fibroblasts / Q000821:virology; D006023:Glycoproteins / Q000096:biosynthesis / Q000276:immunology*; D006801:Humans; D008213:Lymphocyte Activation; D014764:Viral Proteins / Q000096:biosynthesis / Q000276:immunology*
chemical_list: D006023:Glycoproteins; D014764:Viral Proteins