Y. Ando et al., ENHANCED CYTOPATHIC EFFECT OF HUMAN CYTOMEGALOVIRUS ON A RETINAL-PIGMENT EPITHELIUM CELL-LINE, K-1034, BY SERUM-FREE MEDIUM, Archives of virology, 142(8), 1997, pp. 1645-1658
Although human cytomegalovirus (HCMV) predominantly infects epithelial
cells in vivo, the majority of studies of HCMV gene expression and re
plication have been conducted using non-epithelial cell lines in part
because of the absence of a good experimental system using epithelial
cells. To address the nature of epithelial cell infection, we investig
ated the susceptibility of an epithelial cell line (K-1034) establishe
d from the retinal pigment epithelium to HCMV infection. This cell lin
e exhibited high susceptibility to HCMV, as evidenced by detection of
one of the immediate early antigens, IE2, in the nuclei of more than 8
0% of K-1034 cells at 24h following inoculation at a multiplicity of i
nfection of 3 plaque forming units per cell. However, the yield after
one-step growth of HCMV in K-1034 cells was about twenty-fold less tha
n that in human embryonic lung fibroblast cells. Cytopathic effect (CP
E) on K-1034 cells was not prominent in medium supplemented with 10% f
etal bovine serum and viral late antigens were detected in less than 5
% of K-1034 cells. Interestingly, infected cells expressing late antig
ens and exhibiting CPE were markedly increased in serum-free medium, e
ven though the yield of infectious HCMV and viral genome copy numbers
were almost the same in the different serum concentrations, due to vir
al instability in the absence of serum. Thus, the progression of late
antigens expression and the induction of CPE in infected epithelial ce
lls is influenced by physiological conditions, and are negatively regu
lated by some serum factor.