Antiviral activity of nucleoside analogues against norovirus.
BACKGROUND
Norovirus (NoV) is the leading cause of epidemic gastroenteritis worldwide. The lack of a cell culture has significantly hampered the development of effective therapies against human NoV. Clinically approved nucleoside and non-nucleoside analogues have been used successfully against RNA viruses.


METHODS
In this study, we evaluated the efficacy of four nucleoside analogues (2'-C-MeC, 2'-F-2'-C-MeC, β-D-N(4)-hydroxycytidine [NHC] and lamivudine) on Norwalk virus (NV) RNA levels and protein expression in NV replicon-harbouring cells (HG23 cells), and their efficacy in blocking murine norovirus (MNV) replication in RAW 264.7 cells.


RESULTS
2'-C-MeC and 2'-F-2'-C-MeC reduced MNV RNA levels and infectivity in RAW 264.7 cells in a concentration- and time-dependent manner. The median effective concentrations (EC(50)) of 2'-C-MeC and 2'-F-2'-C-MeC were 6.9 μM and 12.7 μM, respectively. 2'-C-MeC, 2'-F-2'-C-MeC and NHC reduced NV RNA levels and protein expression in HG23 cells. For the NV replicon, the EC(50) of 2'-C-MeC (1.3 μM) was comparable to the antiviral activity of NHC (1.5 μM) and twofold more potent than 2'-F-2'-C-MeC (3.2 μM). The combination of 2'-C-MeC/ribavirin resulted in modest synergistic activity, whereas NHC/ribavirin was antagonistic for NV replication in HG23 cells.


CONCLUSIONS
The antiviral activity of 2'-C-MeC against strains of two different NoV genogroups and the low EC(50) suggest that this nucleoside analogue may be effective against the more prevalent GII NoVs. In the absence of a vaccine, antiviral agents could be an effective intervention to control the spread of human NoV in populations at a high risk for NoV disease.
Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. vcostantini@cdc.gov
Verónica P
VP
Costantini
Tony
T
Whitaker
Leslie
L
Barclay
David
D
Lee
Tamara R
TR
McBrayer
Raymond F
RF
Schinazi
Jan
J
Vinjé
D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003562:Cytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D005759:Gastroenteritis / Q000188:drug therapy / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology*; D051379:Mice; D029322:Norovirus / Q000187:drug effects* / Q000472:pathogenicity / Q000502:physiology; D012367:RNA, Viral / Q000032:analysis; D012254:Ribavirin / Q000494:pharmacology; D013997:Time Factors; D014779:Virus Replication / Q000187:drug effects
C577202:4-amino-1-(3,4-dihydroxy-5-(hydroxymethyl)-3-methyltetrahydrofuran-2-yl)pyrimidin-2(1H)-one; D000998:Antiviral Agents; D012367:RNA, Viral; C504520:2'-deoxy-2'-fluoro-2'-C-methylcytidine; D003841:Deoxycytidine; D019259:Lamivudine; D012254:Ribavirin; D003562:Cytidine; C010737:N(4)-hydroxycytidine