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Journal of Virology, May 1999, p. 4171-4180, Vol. 73, No. 5
Department of Biochemistry and Molecular
Pharmacology,
Received 28 October 1998/Accepted 25 January 1999
A two-cell system for the stimulation of herpes simplex virus type
1 (HSV-1) from an in vitro model of long-term (quiescent) infection is
described. Rat pheochromocytoma (PC12) cells differentiated with nerve
growth factor were infected with HSV-1 strain 17. Little, if any,
cytotoxicity was observed, and a quiescent infection was established.
The long-term infection was characterized by the absence of all
detectable virus in the culture medium and little, if any, detectable
early or late viral-gene expression as determined by reverse
transcriptase PCR analysis. The presence of HSV-1 DNA was determined by
PCR analysis. This showed that approximately 180 viral genomes were
present in limiting dilutions where as few as 16 cells were examined.
The viral DNA was infectious, since cocultivation with human corneal
fibroblasts (HCF) or human corneal epithelial cells (HCE) resulted in
recovery of virus from most, if not all, clusters of PC12 cells.
Following cocultivation, viral antigens appeared first on PC12 cells
and then on neighboring inducing cells, as determined by
immunofluorescent staining, demonstrating that de novo viral protein
synthesis first occurred in the long-term-infected PC12 cells.
Interestingly, the ability to induce HSV varied among the cell lines
tested. For example, monkey kidney CV-1 cells and human hepatoblastoma
HepG2 cells, but not mouse neuroblastoma cells or undifferentiated PC12
cells, mediated stimulation. This work thus shows that (i) quiescent
HSV infections can be maintained in PC12 cells in vitro, (ii) HSV can
be induced from cells which do not accumulate significant levels of
latency-associated transcripts, and (iii) the activation of HSV gene
expression can be induced via neighboring cells. The ability of
adjacent cells to stimulate HSV gene expression in neuron-like cells
represents a novel area of study. The mechanism(s) whereby HCF, HCE,
and HepG2 and CV-1 cells communicate with PC12 cells and stimulate
viral replication, as well as how this system compares with other in
vitro models of long-term infection, is discussed.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Human Corneal Cells and Other Fibroblasts Can
Stimulate the Appearance of Herpes Simplex Virus from Quiescently
Infected PC12 Cells
*
Corresponding author. Mailing address: Rm. 238, Jefferson Center for Biomedical Research of Thomas Jefferson
University, 700 E. Butler Ave., Doylestown, PA 18901-2697. Phone: (215)
489-4948. Fax: (215) 489-4920. E-mail:
block{at}lac.jci.tju.edu.
Journal of Virology, May 1999, p. 4171-4180, Vol. 73, No. 5
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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