Severe acute respiratory syndrome (SARS) is a newly emerging, highly transmissible and fatal disease caused by a previously unknown coronavirus (SARS-CoV). Existing in non-identified animal reservoirs, SARS-CoV continues to represent a threat to humans because there is no effective specific antiviral therapy for coronavirus infections.
Objectives
Starting from the observation that cyclopentenone cyclooxygenase (COX) metabolites are active against several RNA viruses, we investigated the effect of the COX inhibitor indomethacin on coronavirus replication.
Methods
Work involving infectious SARS-CoV was performed in biosafety level 3 facilities. SARS-CoV was grown in monkey VERO cells and human lung epithelial A549 cells, while canine coronavirus (CCoV) was grown in A72 canine cells. Antiviral activity was analysed by determining infective virus titres by TCID50, viral RNA synthesis by Northern blot analysis and real-time RT-PCR, and viral protein synthesis by SDS-PAGE analysis after 35S-methio-nine-labelling. Antiviral efficacyin vivowas determined by evaluating virus titres in CCoV-infected dogs treated orally with 1 mg/kg body weight indomethacin (INDO).
Results
Unexpectedly, we found that INDO has a potent direct antiviral activity against the coronaviruses SARS-CoV and CCoV. INDO does not affect coronavirus binding or entry into host cells, but acts by blocking viral RNA synthesis at cytoprotective doses. This effect is independent of cyclooxygenase inhibition. INDO's potent antiviral activity (>1,000-fold reduction in virus yield) was confirmedin vivoin CCoV-infected dogs.
Conclusions
The results identify INDO as a potent inhibitor of coronavirus replication and suggest that, having both anti-inflammatory and antiviral activity, INDO could be beneficial in SARS therapy.
References
1.
DrostenC., GuntherS., PreiserW.Identification of a novel coronavirus in patients with severe acute respiratory syndrome.N Engl J Med2003; 348: 1967–1976.
2.
RotaP., ObersteM., MonroeS.Characterization of a novel coronavirus associated with severe acute respiratory syndrome.Science2003; 300: 1394–1399.
3.
LaiM.M.C., HolmesK.V.Coronaviridae: the viruses and their replication. In Field's Virology, 4th edn2001; pp. 1163–1185. Edited by KnipeD.M., & HowleyP.. Philadelphia, USA: Lippincott, Williams & Wilkin.
SkowronskiD.M., AstellC., BrunhamR.C.Severe acute respiratory syndrome (SARS): a year in review.Annu Rev Med2005; 56: 357–381.
6.
SantoroM.G.Antiviral activity of cyclopentenone prostanoids.Trends Microbiol1997; 276: 276–281.
7.
MorimotoR.I., SantoroM.G.Stress-inducible responses and heat shock proteins: new pharmacologic targets for cytopro-tection.Nature Biotechnol1998; 16: 833–838.
8.
RossiA., KapahiP., NatoliG.Anti-inflammatory cyclopentenone prostaglandins are direct inhibitors of IκB kinase.Nature2000; 403: 103–108.
9.
SantoroM.G., RossiA., AmiciC.NF-κB and virus infection: who controls whom.EMBO J2003; 22: 2552–2560.
10.
BernasconiD., AmiciC., La FraziaS., IanaroA., SantoroM.G.The IκB kinase is a key factor in triggering influenza A virus-induced inflammatory cytokine production in airway epithelial cells.J Biol Chem2005; 280: 24127–24134.
11.
AmiciC., BelardoG., RossiA., SantoroM.G.Activation of IκB kinase by herpes simplex virus type 1. A novel target for anti-herpetic therapy.J Biol Chem2001; 276: 28759–28766.
12.
StroherU., DiCaroA., LiY.Severe acute respiratory syndrome-related coronavirus is inhibited by interferon-alpha.J Infect Dis2004; 189: 1164–1167.
13.
RozeraC., CarattoliA., De MarcoA., AmiciC., GiorgiC., SantoroM.G.Inhibition of HIV-1 replication by cyclopentenone prostaglandins in acutely infected human cells: evidence for a transcriptional block.J Clin Invest1996; 97: 1795–1803.
14.
DecaroN., PratelliA., CampoloM.Quantitation of canine coronavirus RNA in the faeces of dogs by TaqMan RT-PCR.J Virol Methods2004; 119: 145–150.
15.
CastillettiC., BordiL., LalleE.Coordinate induction of IFN-α and -γ by SARS-CoV in the absence of virus replication.Virology2005; 10: 163–169.
16.
PratelliA., EliaG., MartellaA.Prevalence of canine coronavirus antibodies by an enzyme-linked immunosorbent assay in dogs in the south of Italy.J Virol Methods2002; 102: 67–71.
17.
PratelliA., TinelliA., DecaroN.Safety and efficacy of a modified-live canine coronavirus vaccine in dogs.Vet Microbiol2004; 99: 43–49.
RaneA., OelzO., FrolichJ.C.Relation between plasma concentration of indomethacin and its effect on prostaglandin synthesis and platelet aggregation in man.Clin Pharmacol Ther1978; 23: 658–668.
20.
AraiI., MaoG.P., OtaniK., KonnoS., KikuchiS., OlmarkerK.Indomethacin blocks the nucleus pulposus-induced effects on nerve root function. An experimental study in dogs with assessment of nerve conduction and blood flow following experimental disc herniation.Eur Spine J2004; 13: 691–694.
21.
VaneJ.R., BottingR.M.Mechanism of action of anti-inflammatory drugs.Adv Exp Med Biol1997; 433: 131–138.
22.
TegerderI., PfeilschifterJ., GeisslingerG.Cyclooxygenase-independent actions of cyclooxygenase inhibitors.FASEB J2001; 15: 2057–2072.
23.
YangZ.Y., WernerH.C., KongW.P.Evasion of antibody neutralization in emerging severe acute respiratory syndrome coronaviruses.Proc Natl Acad Sci USA2005; 102: 797–801.
