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Laboratory Studies
Dispatch
Interferon-ß 1a and
SARS Coronavirus Replication
Lisa E. Hensley,* Elizabeth A. Fritz,* Peter B. Jahrling,* Christopher
L. Karp,† John W. Huggins,* and Thomas W. Geisbert*
*U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick,
Maryland, USA; and †Cincinnati Children’s Hospital Medical Center, Cincinnati,
Ohio, USA
Suggested citation
for this article:
Hensley LE, Fritz EA, Jahrling PB, Karp CL, Huggins JW, Geisbert TW.
Interferon-ß 1a and SARS coronavirus replication. Emerg Infect
Dis [serial online] 2004 Feb [date cited]. Available from: URL:
http://www.cdc.gov/ncidod/EID/vol10no2/03-0482.htm
A global outbreak
of severe acute respiratory syndrome (SARS) caused by a novel coronavirus
began in March 2003. The rapid emergence of SARS and the substantial
illness and death it caused, have made it a critical public health issue.
Because no effective treatments are available, an intensive effort is
under way to identify and test promising antiviral drugs. Here, we report
that recombinant human interferon-ß 1a potently inhibits SARS
coronavirus replication in vitro.
The recent global outbreak of severe acute respiratory syndrome (SARS)
has quickly gained notoriety as a newly emerging infectious disease. The
etiologic agent was identified as a coronavirus (SARS-CoV) that is not
closely related to any of the previously characterized coronaviruses (1,2).
As of September 26, 2003, a total of 8,098 probable cases of SARS have
occurred with 774 deaths.
No antiviral treatments are currently available against SARS-CoV. SARS
cases have been treated symptomatically according to the severity of the
illness. A treatment protocol consisting of antibacterial agents and a
combination of ribavirin and methylprednisolone was recently proposed.
However, the therapeutic value of ribavirin remains uncertain because
it has no activity against SARS-CoV in vitro. Molecular modeling studies
suggest that rhinovirus 3Cpro inhibitors may be useful for
SARS therapy, but results of recent testing of the lead molecule, AG7088,
in vitro were negative (3).
Previous studies showed that some coronaviruses, including avian infectious
bronchitis virus, murine hepatitis virus, and human coronavirus 229E,
are susceptible to type I interferons in vitro or in vivo (4–7).
Therefore, we evaluated the in vitro efficacy of a recombinant human type
I interferon (IFN), IFN-ß 1a (Serono International, Geneva, Switzerland),
against three different isolates of SARS-CoV (Tor2 and Tor7 [kindly provided
by Heinz Feldman] and Urbani) using yield reduction assays. The IFN-ß
1a preparation employed in this study was selected because it is currently
used as part of the most effective treatment regimen for relapsing forms
of multiple sclerosis (8), and more importantly, because
it was shown to have antiviral activity (as measured in a vesicular stomatitis
virus cytopathic assay system) 14 times greater than the currently available
treatment using IFN-ß 1b (9).
In the current study, Vero E6 cells were treated with concentrations
(5,000 to 500,000 IU/mL) of IFN-ß 1a either 24 h before or 1 h after
inoculation with the SARS-CoV (multiplicity of infection 0.1 PFU/cell),
and monitored for cytopathic effect and production of infectious SARS-CoV
at 24, 48, and 72 hours postinfection. Inhibition of the SARS-CoVs by
IFN-ß 1a was dependent on both time of drug administration and time
of culture sampling after SARS-CoV infection. Production of infectious
SARS-CoV was potently inhibited (>99.5% or 2.00 log10
PFU/mL) at 24 h postinfection by pretreatment of Vero E6 cells with IFN-ß
1a at all concentrations tested (Figure 1). By
72 h postinfection, inhibition of SARS-CoV production by IFN-ß 1a
had declined for all three SARS-CoVs with inhibition (>70%)
being detected in the Tor7 (Figure 1) and Urbani
isolates (data not shown). IFN-ß 1a was somewhat less effective
at inhibiting SARS-CoV replication when employed after infection of cultures
(Figure 1). Nonetheless, production of infectious
SARS-CoVs was considerably reduced (>90% or 1.00 log10
PFU/mL) at 24 and 48 h postinfection. Protection of Vero E-6 monolayers
against SARS-CoV–induced cytopathic effects by preinfection or postinfection
treatment with IFN-ß 1a was dramatic, even at 72 h p.i. (Figure
2). Additional concentrations of IFN-ß 1a (0.5–5,000 IU/mL)
were tested to determine the 50% inhibitory concentration (IC50).
Pretreatment of Vero E6 cells with concentrations as low as 50 IU/mL,
or posttreatment of cells with concentrations at 500 IU/mL, provided a
50% reduction with the Tor2 isolate at 24 h postinfection.
Faced with a burgeoning epidemic of SARS cases and a lack of effective
treatment options, identifying compounds with antiviral activity that
could be potential therapeutics has become a high priority. Our report
suggests that IFN-ß 1a may be effective as a treatment for SARS-CoV
infections. As noted above, IFN-ß 1a is currently being used for
a variety of clinical indications, including multiple sclerosis and has
shown dose-dependent efficacy in several clinical trials. Importantly,
IFN-ß 1a exhibited potent antiviral activity at doses that have
already been shown to have acceptable safety profiles in animals (10).
Thus, we report the identification of a compound that may be suitable
for rapid development as a treatment for SARS-CoV infection.
Acknowledgments
We thank Dr. Heinz
Feldman for his kind provision of Tor2 and Tor7 isolates.
This study was supported,
in part, by NIH grant R21 AI053539.
Dr. Hensley is a
staff microbiologist in the Virology Division, United States Army Medical
Research Institute of Infections Diseases. She specializes in the pathogenesis
and immunobiology of high-hazard virus infections in animal models for
vaccine and antiviral drug development.
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