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Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.
To the Editor: A novel coronavirus has been
identified as the etiologic agent of severe acute respiratory syndrome (SARS),1-3 for which there
is no specific treatment. Small interfering RNAs (siRNAs) are double-stranded
RNAs that direct sequence-specific degradation of messenger RNA in mammalian
cells.4 It is also possible, however, that
siRNAs could specifically interfere with viral RNA.
We designed six 21-mer SARSis (siRNAs [GENSET SA Ltd, Paris, France]
targeting different sites of the replicase 1A region of the SARS coronavirus
[SARS-CoV] genome; siRNA sequences in the senses strands: GUGAACUCACUCGUGAGCUCdTdT
[SARSi-1]; GUACCCUCUUGAUUGCAUCdTdT [SARSi-2]; GAGUCGAAGAGAGGUGUCUdTdT [SARSi-3];
GCACUUGUCUACCUUGAUGdTdT [SARSi-4]; CCUCCAGAUGAGGAAGAAGdTdT [SARSi-5]; and
GGUGUUUCCAUUCCAUGUGdTdT [SARSi-6]). We then performed 3 in vitro experiments
to test their antiviral effects. In the first, we transfected monkey kidney
cells (FRhk-4) with 1 of the 6 siRNAs. In addition to these 6 groups of cells,
we also created 2 groups of control cells—1 transfected with an unrelated
siRNA targeting luciferase (GL2i),5 and
the other with the medium. OligoFectamine (Invitrogen Corp, Carlsbad, Calif)
was the transfection reagent. All groups of cells were incubated for 8 hours
before infection with SARS virus GZ50 strain. Thirty-six hours after viral
infection, cytopathic effects were judged with phase-contrast microscopy.
The cells were then fixed with –20°C ethanol for 10 minutes and
immunostained with a SARS-CoV–specific antibody isolated from acute
covalent sera of confirmed SARS patients. The coronavirus antigens were detected
by indirect immunofluorescence assay using a fluoroscein isothiocyanate–coagulated
antibody1,2 (Inova Diagnostic
Inc, San Diego, Calif). To quantify the viral genomic RNA, real-time polymerase
chain reaction was performed as described previously.2
He M, Zheng B, Peng Y, et al. Inhibition of SARS-Associated Coronavirus Infection and Replication by RNA Interference. JAMA. 2003;290(20):2665–2666. doi:10.1001/jama.290.20.2665
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