Entry of human cytomegalovirus into retinal pigment epithelial and endothelial cells by endocytosis.
OBJECTIVE
Human retinal pigment epithelial (RPE) cells and endothelial cells (HUVECs) are targets of human cytomegalovirus (HCMV) infection in vivo with significantly protracted replication in vitro compared with that in fibroblasts. This study analyzes the kinetics and mechanisms of HCMV entry into both cell types.


METHODS
RPE cells were obtained from donor eyes. HUVECs were isolated from human umbilical cords. HCMV entrance was followed by electron microscopy and immunofluorescence in the presence of lysosomotropic agents and cytochalasin B.


RESULTS
Human cytomegalovirus entered into RPE cells and HUVECs as early as 5 minutes after virus- cell contact. Entry was mediated by endocytosis, whereas HCMV enters fibroblasts through fusion. Most internalized viral particles and dense bodies appeared to be degraded within vacuoles. Viral entry, transport of viral proteins to the nucleus, and onset of viral transcription (immediate early [IE] protein expression) were significantly blocked by cytochalasin B. Lysosomotropic agents did not significantly reduce IE expression in RPE cells or HUVECs.


CONCLUSIONS
This study shows that HCMV penetrates these highly specialized relevant cells via endocytosis. The low level of infection and the delay in the onset of HCMV expression seen in these cells compared with fibroblasts may be related to the sequestration and degradation of incoming viral particles in endocytic vacuoles.
Bodaghi
B
B
Unité d'Immunologie Virale, Institut Pasteur, Paris, France. bodaghi@pasteur.fr
Slobbe-van Drunen
M E
ME
Topilko
A
A
Perret
E
E
Vossen
R C
RC
van Dam-Mieras
M C
MC
Zipeto
D
D
Virelizier
J L
JL
LeHoang
P
P
Bruggeman
C A
CA
Michelson
S
S
D000643:Ammonium Chloride / Q000494:pharmacology; D002462:Cell Membrane / Q000648:ultrastructure / Q000821:virology; D002478:Cells, Cultured; D002738:Chloroquine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D003587:Cytomegalovirus / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D004730:Endothelium, Vascular / Q000737:chemistry / Q000648:ultrastructure / Q000821:virology*; D005347:Fibroblasts / Q000821:virology; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008561:Membrane Fusion; D010857:Pigment Epithelium of Eye / Q000737:chemistry / Q000648:ultrastructure / Q000821:virology*; D014764:Viral Proteins / Q000032:analysis; D014779:Virus Replication / Q000502:physiology
D014764:Viral Proteins; D000643:Ammonium Chloride; D003571:Cytochalasin B; D002738:Chloroquine