title: Impaired killing of HCMV-infected retinal pigment epithelial cells by anti-pp65 CD8(+) cytotoxic T cells.
abstract: OBJECTIVE
  Host defense against infection by human cytomegalovirus (HCMV) is ensured in great part by cytotoxic CD8(+) T lymphocytes (CTLs) directed against the tegument protein pp65. The hyperimmediate release of incoming pp65 into the major histocompatibility complex (MHC) class I pathway after fusion of the virus with the cell membrane provides a very early mechanism of defense. In retinal pigment epithelial (RPE) cells HCMV is known to enter through endocytosis. This study was conducted to determine whether this means of penetration into the cells would allow the virus to elude immune surveillance.
  
  
  METHODS
  Infection of RPE cells with HCMV AD169 was performed for 6 hours, 48 hours, and 8 days. Expression of intracellular pp65 in RPE cells and in the astrocytoma reference cell line U373MG was evaluated by flow cytometry, fluorescence microscopy, and Western blot analysis. Killing of both HCMV-infected cell lines by HLA-A2-restricted CD8(+) CTLs directed against pp65 was monitored by (51)Cr-release assays.
  
  
  RESULTS
  RPE cells were not lysed by CTLs directed against incoming pp65, contrary to U373MG. Moreover, both cell lines were not killed by anti-pp65 CTLs later after infection, because of the MHC class-I-downregulating effect of HCMV unique short (US2-11) proteins.
  
  
  CONCLUSIONS
  In RPE cells, both HCMV entry through endocytosis and the immunosuppressive effect of US proteins could allow the virus to evade immune surveillance at any stage of infection, which could promote viral spreading within the retina.
authors.affiliation: National Institute of Health and Medical Research (INSERM), Toulouse, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Allart
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Lulé
authors.forename: Brigitte
authors.initials: B
authors.lastname: Serres
authors.forename: Thomas
authors.initials: T
authors.lastname: Jones
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Davignon
authors.forename: François
authors.initials: F
authors.lastname: Malecaze
authors.forename: Christian
authors.initials: C
authors.lastname: Davrinche
mesh_terms: D015153:Blotting, Western; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D003587:Cytomegalovirus / Q000502:physiology*; D003602:Cytotoxicity, Immunologic / Q000502:physiology*; D005434:Flow Cytometry; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008856:Microscopy, Fluorescence; D010750:Phosphoproteins / Q000276:immunology*; D010857:Pigment Epithelium of Eye / Q000378:metabolism / Q000821:virology*; D011233:Precipitin Tests; D013602:T-Lymphocytes, Cytotoxic / Q000502:physiology*; D014763:Viral Matrix Proteins / Q000276:immunology*
chemical_list: D010750:Phosphoproteins; D014763:Viral Matrix Proteins; C065418:cytomegalovirus matrix protein 65kDa