Virus Research 73 (2001) 57–65
The anticytomegaloviral activity of raltitrexed is abrogated
in quiescent mouse fibroblasts that overexpress thymidylate
synthase
Giorgio Gribaudo
a,
*, Ludovica Riera
a
, David Lembo
a
, Marco De Andrea
b
,
Lee F. Johnson
c
, Santo Landolfo
b
a
Department of Public Health and Microbiology, Uni6ersity of Torino, Via Santena,
9
-
10126
Turin, Italy
b
Immunogenetics and Experimental Oncology Center, C.N.R., Turin, Italy
c
Department of Molecular Genetics, The Ohio State Uni6ersity, Columbus, OH
43210
, USA
Received 16 June 2000; received in revised form 19 September 2000; accepted 22 September 2000
Abstract
Cytomegalovirus (CMV) replication in non-proliferating cells requires the coordinated expression of the host
enzymes responsible for deoxyribonucleotide synthesis. Thymidylate synthase (TS) is an essential cellular enzyme that
catalyzes de novo synthesis of thymidylic acid (dTMP). In this report we show that murine CMV (MCMV)
replication and DNA synthesis are inhibited in quiescent 3T6 fibroblasts by raltitrexed, a quinazoline-based folate
analog that specifically inhibits TS. This antiviral activity was abrogated in LU3-7 cells, a 3T6 derivative that
overproduces TS by about 50-fold. These observations indicate that the anticytomegaloviral activity of raltitrexed is
associated with TS inhibition and suggest that cellular TS activity is required for efficient CMV replication in
quiescent cells. © 2001 Elsevier Science B.V. All rights reserved.
Keywords
:
Cytomegalovirus; Thymidylate synthase; Antiviral activity; Raltitrexed; Overproducing LU3-7 cells
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1. Introduction
Cytomegaloviruses (CMV) are b-herpes viruses
that generally cause asymptomatic infections in
immunocompetent hosts and only behave as
severe pathogens in immunologically immature or
immunocompromised individuals (Mocarski,
1996; Fortunato and Spector, 1999; Griffith,
2000). Their success as opportunists depends on
their ability to establish latent infections, counter-
act host antiviral defense mechanisms and repli-
cate in tissues with relaxed immune surveillance
(Hengel et al., 1998; Lanani et al., 2000). Relevant
to all these activities is the ability of CMV to
productively replicate in differentiated post-mi-
totic cells. Here, however, CMV must overcome
very low levels of deoxyribonucleoside triphos-
phates (dNTPs) and the stringent repression of
* Corresponding author. Tel.: +39-11-6706623; fax: +39-
11-6636436.
E-mail address
:
gribaudo@molinette.unito (G. Gribaudo).
0168-1702/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
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