Content uploaded by Deborah R Taylor
Author content
All content in this area was uploaded by Deborah R Taylor on Aug 01, 2020
Content may be subject to copyright.
Journal of Virological Methods 121 (2004) 85–91
Inactivation of the coronavirus that induces severe acute respiratory
syndrome, SARS-CoV
Miriam E.R. Darnella, Kanta Subbaraob, Stephen M. Feinstonea, Deborah R. Taylora,∗
aCenter for Biologics Evaluation and Research, US Food and Drug Administration, 8800 Rockville Pike, HFM448, Bethesda, MD 20892, USA
bLaboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
Received 27 May 2004; accepted 15 June 2004
Available online 3 August 2004
Abstract
Severeacuterespiratory syndrome (SARS)is a life-threateningdisease caused bya novel coronavirustermedSARS-CoV.Due to theseverity
of this disease, the World Health Organization (WHO) recommends that manipulation of active viral cultures of SARS-CoV be performed in
containment laboratories at biosafety level 3 (BSL3). The virus was inactivated by ultraviolet light (UV) at 254 nm, heat treatment of 65◦Cor
greater, alkaline (pH > 12) or acidic (pH < 3) conditions, formalin and glutaraldehyde treatments. We describe the kinetics of these efficient
viral inactivation methods, which will allow research with SARS-CoV containing materials, that are rendered non-infectious, to be conducted
at reduced safety levels.
© 2004 Elsevier B.V. All rights reserved.
Keywords: SARS; Coronavirus; Virus inactivation; Tissue culture
1. Introduction
In late 2002, an outbreak of unusual life-threatening
respiratory disease of unknown etiology began in Guang-
dong Province, China. This disease was designated severe
acute respiratory syndrome (SARS) and was later deter-
mined by Drosten et al. (2003),Ksiazek et al. (2003),
and Rota et al. (2003), to be caused by a novel coro-
navirus, termed SARS-CoV. Since the identification of
coronavirus as the infectious agent for SARS, numerous
laboratories have begun research on this virus. Accord-
ing to the WHO, 8098 people were diagnosed with SARS
and 774 people died of this disease during the initial out-
break of 2003. Due to the severity of SARS disease and
the contagious nature of the causal agent, the WHO web-
site (http://www.who.int/csr/sars/biosafety2003 12 18/en/)
has provided guidelines for working safely with this coro-
navirus. The WHO recommends biosafety level 3 (BSL3)
as the appropriate containment level for working with live
∗Corresponding author. Tel.: +1 301 827 1878; fax: +1 301 496 1810.
E-mail address: taylord@cber.fda.gov (D.R. Taylor).
SARS-CoV, and there is a concern that another SARS out-
break could occur following an accidental exposure in a lab-
oratory. Since the end of the SARS epidemic in July 2003,
there have been three known cases of SARS in laboratory
researchers due to accidental exposure to the virus (Normile,
2004). Successful inactivation of the virus allows the trans-
fer of material from a BSL3 to a BSL2 environment and may
reduce the risk of accidental infections through unsafe labo-
ratory practices. Inactivated cell-culture derived viral stocks
may also be useful for the development of vaccines and the
study of their safety and immunogenicity. We examined the
efficiency of several methods of viral inactivation, including
methods that may inhibit viral replication or entry.
2. Materials and methods
2.1. Virus and cells
We infected African green monkey kidney (Vero E6)
cells with SARS-CoV (Urbani strain) that was kindly pro-
vided by Drs. L.J. Anderson and T.G. Ksiazek from the
0166-0934/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jviromet.2004.06.006
86 M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91
Centers for Disease Control and Prevention, Atlanta, GA.
Briefly, Vero E6 monolayer cells were infected by inoc-
ulating cultures with 50l of virus (106.33 TCID50 per
ml) in a final volume of 5ml Dulbecco’s modified Eagle’s
medium (DMEM) (Biosource International, Camarillo, CA)
in T150 flasks for 1h at 25 ◦C. Dulbecco’s modified Eagle’s
medium containing supplements (10% fetal bovine serum,
2 mM/ml l-glutamine, 100U/ml penicillin, 100 g/ml strep-
tomycin, and 0.5 g/ml fungizone) (Biosource International)
was added to the flask and the cells were incubated at
37◦C for 3 days. Supernatant was collected, clarified by
centrifugation, and stored at −70◦C as the viral stock.
The Vero cells were maintained in DMEM with supple-
ments. All personnel wore powered air-purifying respira-
tors (3M, Saint Paul, MN) and worked with infectious
virus inside a biosafety cabinet, within a BSL3 containment
facility.
2.2. Quantitation of viral titers
Viral titers were determined in Vero cell monolayers on
24 and 96-well plates using a 50% tissue culture infectious
dose assay (TCID50). Serial dilutions of virus samples were
incubated at 37◦C for 4 days and subsequently examined
for cytopathic effect (CPE) in infected cells, as described
by Ksiazek et al. (2003). Briefly, SARS-CoV-induced CPE
of infected cells was determined by observing rounded, de-
tached cells in close association to each other. Evidence of
inactivation was determined by absence of CPE in Vero cells,
indicating loss of infectivity.
2.3. UV light treatment
Ultraviolet light (UV) treatment was performed on 2ml
aliquots of virus (volume depth = 1cm) in 24-well plates
(Corning Inc., Corning, NY). The UV light source (Spec-
tronics Corporation, Westbury, NY) was placed above the
plate, at a distance of 3cm from the bottom of the wells
containing the virus samples. At 3cm our UVC light source
(254nm) emitted 4016 W/cm2(where W=10
−6J/s)
and the UVA light source (365nm) emitted 2133W/cm2,
as measured by radiometric analysis (Spectronics Corpo-
ration). After exposure to the UV light source, virus was
frozen for later analysis by TCID50 assay using CPE as the
endpoint.
2.4. Gamma irradiation treatment
We prepared 400 lsamples of SARS-CoVand keptthem
on dry ice during transport. Test samples were subjected to
gamma radiation (3000, 5000, 10,000, and 15,000rad) from
a60Co source, while control samples were protected from
exposure. Test and control samples were handled and trans-
ported identically, except test samples were exposed to the
gammaradiation source.Sampleswere keptfrozenuntil anal-
ysis of inactivation by TCID50 assay.
2.5. Heat treatment of virus
Weincubated 320l aliquotsof virusin 1.5ml polypropy-
lenecryotubes usinga heatingblock toachievethree different
temperatures (56, 65 and 75◦C). After heat treatment, sam-
ples were frozen for later analysis by TCID50 assay using
CPE as an endpoint.
2.6. Formaldehyde and glutaraldehyde treatment
Formaldehyde(37%, MallinckrodtBaker,Inc., Paris,KY)
and glutaraldehyde (8%, Sigma, Saint Louis, MO) were di-
luted 1:10 and 1:40 in sterile PBS. These diluted aldehy-
des were added to virus samples to achieve final dilutions
of 1:1000 and 1:4000 in 400l. The final concentrations of
formaldehyde were 0.037% (1:1000) and 0.009% (1:4000),
and the final concentrations of glutaraldehyde were 0.008%
(1:1000) and 0.002% (1:4000). The virus and aldehyde sam-
ples were incubated at 4, 25, and 37◦C, for up to 3 days.
The samples were mixed briefly with a vortex on each day.
The samples were stored at −70◦C until analysis by TCID50
assay.
2.7. pH treatment
Virus aliquots were adjusted to the desired pH using 5M
and 1M HCl or 5N and 1N NaOH. Subsequently, they were
divided into three aliquots, incubated at the desired temper-
ature (4, 25, and 37◦C), neutralized to a pH 7, and analyzed
for viral titer using the TCID50 assay.
2.8. Infectivity of viral RNA and detergent-disrupted
virions
Infected Vero cells were prepared by inoculation with
20l of virus at a 106.37 TCID50 per ml of SARS-CoV
in a final volume of 2ml in a T25 flask for 1 h at 25◦C.
DMEM with supplements was added to the flask and the
cells were incubated at 37◦C for 3 days. The monolayer
was washed with 1X phosphate buffered saline (PBS),
cells were lysed with the addition of 2.5ml of a phenol
and guanidine isothiocyanate solution (TRIzol Reagent,
Sigma), and cytoplasmic RNA was isolated according to the
manufacturer’s specifications. Vero cells were inoculated
with 10l of purified RNA in 0.5 ml DMEM. After an
hour, DMEM with supplements was added. Additionally,
Vero cells were transfected with cytoplasmic RNA using
DMRIE-C (Invitrogen Life Technologies, Carlsbad, CA)
according to the manufacturer’s instructions. Cells were
incubated at 37◦C, and observed for CPE on days 3 and 4.
To examine the infectivity of detergent-disrupted virions,
SARS-CoV infected Vero monolayer cells were washed and
dissociated with trypsin/versene, pelleted by centrifugation,
and washed with PBS. After centrifugation, the pellet was
lysed with sodium dodecyl sulfate/nonidet P-40 (SDS/NP-
40; 0.1% SDS, 0.1% NP-40, in 0.1x PBS; Sigma), frozen
M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91 87
at −70◦C, thawed, and clarified by centrifugation. The su-
pernatant was used to infect Vero cell monolayers in 6-well
plates, such that the final concentration of SDS was 0.002 or
0.018%. Three and four days following the inoculation, cells
were observed for evidence of CPE.
3. Results
3.1. Effect of radiation on the infectivity of SARS-CoV
UV light is divided into three classifications: UVA
(320–400nm), UVB(280–320 nm),andUVC (200–280nm).
UVC is absorbed by RNA and DNA bases, and can cause
the photochemical fusion of two adjacent pyrimidines into
covalently linked dimers, which then become non-pairing
bases (Perdiz et al., 2000). UVB can cause the induction of
pyrimidinedimers, but 20–100-foldless efficiently thanUVC
(Perdiz et al., 2000). UVA is weakly absorbed by DNA and
RNA, and is much less effective than UVC and UVB in in-
ducing pyrimidine dimers, but may cause additional genetic
damage through the production of reactive oxygen species,
which cause oxidization of bases and strand breaks (Tyrrell
et al., 2001).
To examine the inactivation potential of UVA and UVC,
virus stocks were placed in 24-well tissue culture plates and
exposed to UV irradiation on ice for varying amounts of
time, as indicated in Fig. 1A. Exposure of virus to UVC
light resulted in partial inactivation at 1min with increas-
ing efficiency up to 6min (Fig. 1A), resulting in a 400-fold
decrease in infectious virus. No additional inactivation was
observed from 6 to 10min. After 15 min the virus was com-
pletelyinactivatedto the limit of detectionof theassay,which
is ≤1.0 TCID50 (log10) per ml. In contrast, UVA exposure
demonstrated no significant effects on virus inactivation over
a 15min period. Our data show that UVC light inactivated
the SARS virus at a distance of 3cm for 15 min.
Astandard procedureto inactivateviruses duringthe man-
ufactureof biologicalproducts isgamma irradiation(Grieb et
al., 2002). To investigate the effect of gamma irradiation on
SARS-CoV, we subjected 400l of SARS-CoV to gamma
radiation (3000, 5000, 10,000, and 15,000rad) from a 60Co
source, while control samples were protected from exposure.
No effect on viral infectivity was observed within this range
of gamma irradiation exposure (Fig. 1B).
3.2. Effect of heat treatment on the infectivity of
SARS-CoV
Heat can inactivate viruses by denaturing the secondary
structures of proteins, and thereby may alter the conforma-
tion of virion proteins involved in attachment and replication
within a host cell (Lelie et al., 1987; Schlegel et al., 2001). To
test the ability of heat to inactivate the SARS-CoV, we incu-
bated virus in 1.5ml polypropylene cryotubes at three tem-
peratures (56, 65 and 75◦C) for increasing periods of time.
Fig. 1. Effect of radiation on the infectivity of SARS-CoV. (A) UV irradi-
ation. The UV lamp was placed 3cm above the bottom of 24-well plates
containing 2ml virus aliquots. Samples were removed at each time point,
frozen, and titrated in Vero E6 cells. The results shown are representative
of three independent experiments. (B) Gamma irradiation. Virus aliquots
(400l) were placed in cryovials on dry ice and exposed to the indicated
doseof gamma irradiation.Controlsamples were treatedidentically,without
radiation exposure. Samples were titrated in Vero E6 cells in triplicate. The
dotted line denotes the limit of detection of the assay.
We found that at 56 ◦C most of the virus was inactivated after
20min (Fig. 2A). However, the virus remained infectious at
a level close to the limit of detection for the assay, for at least
60min, suggesting that some virus particles were stable at
56◦C(Fig. 2A and C). At 65 ◦C, most of the virus was inac-
tivated if incubated for longer than 4min (Fig. 2B). Again,
some infectious virus could still be detected close to the limit
of detection for the assay, after 20min at 65◦C. While virus
was incompletely inactivated at 56 and 65◦C even at 60min,
it was completely inactivated at 75◦C in 45min (Fig. 2C).
Surprisingly, at both 56 and 65 ◦C the virus was inactivated
at early time points but at 60min a small amount of virus
was detected. One possible explanation for this result may
be the presence and subsequent dissociation of aggregates.
Taken together, these results suggest that viral inactivation
by pasteurization may be very effective.
3.3. Effects of formaldehyde and glutaraldehyde on the
infectivity of SARS-CoV
Formalin (dilute formaldehyde) has been used for a num-
ber of years to inactivate virus for use in vaccine products,
suchas the widely used andvery effectivepolio vaccine(Salk
andSalk, 1984).Other attemptsatusing formalininactivation
forgenerationof vaccinesforrespiratorysyncytial virus(Kim
88 M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91
Fig. 2. Effect of heat treatment on the infectivity of SARS-CoV. Virus
aliquots (400l) were incubated at (A, C) 56 ◦C, (B, C) 65 ◦C and (C)
75◦C. Samples were removed at the designated time, frozen, and titrated in
Vero E6 cells in triplicate. The dotted line denotes the limit of detection of
the assay.
etal., 1969)and measlesvirus (Fulginitiet al.,1967) werenot
useful, as they induced an aberrant immune response result-
ing from formalin-induced perturbations of the viruses. For-
malin inactivation occurs when nonprotonated amino groups
ofamino acids,such aslysine, combinewith formaldehydeto
form hydroxymethylamine. The hydroxymethylamine com-
bineswith theamino,amide, guanidyl,phenolic,or imidazole
groupof aminoacids tocreate inter-orintramolecular methy-
lene crosslinks (for review, see Jiang and Schwendeman,
2000).Fraenkel-Conrat (1954) observed the absorptionspec-
tra of several plant viruses and determined that formalin also
binds in a reversible manner to RNA, blocking reading of
the genome by RNA polymerase. Glutaraldehyde can also be
used to inactivate virus and is used as a disinfecting agent
of medical instruments, such as endoscopes (Tandon, 2000),
and as a fixative for electron microscopy (McDonnell and
Russell, 1999).
We examined formalin and glutaraldehyde inactivation of
the SARS-CoV by incubating virus samples with formalin or
glutaraldehydeattwo differentdilutions(1:1000and 1:4000).
Each of the diluted aldehydes was incubated with virus at 4,
25 or 37 ◦C. Both of the aldehydes exhibited temperature de-
Table 1
Effect of formaldehyde and glutaraldehyde inactivation of SARS-CoV
Virus Dilution Day 1 Day 2 Day 3
4◦C25
◦C37
◦C4
◦C25
◦C37
◦C4
◦C25
◦C37
◦C
Formaldehyde treatment
No 1:1000 xaxxxxxxxx
Yes 1:1000 x xxxxxxxx
Yes 1:4000 4.45 ±0.25b1.31 ±0.29 1.31 ±0.29 4.02 ±0.38 1.31 ±0.29 1.5 ±0 3.28 ±0.14 1.14 ±0.29 1.14 ±0.29
Glutaraldehyde treatment
No 1:1000 ≤1.0c≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0
Yes 1:1000 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0 ≤1.0
Yes 1:4000 2.70 ±0 1.31 ±0.29 ≤1.0 2.26 ±0.38 ≤1.0 ≤1.0 2.19 ±0.25 ≤1.0 ≤1.0
Yes No 5.28 ±0.29 5.09 ±0.58 4.03 ±0.14 5.03 ±0.14 4.86 ±0.29 3.36 ±0.29 5.12 ±0.14 4.1 ±0.52 2.78 ±0.14
aFormaldehyde treatment fixed the cells in the TCID50 assay so virus could not be detected.
bGeometric mean of triplicate samples ±S.D.
cThe limit of detection for the TCID50 assay is ≤1.0.
M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91 89
pendence in their ability to inactivate virus (Table 1). Neither
formalin nor glutaraldehyde, at a 1:4000 dilution, was able to
completely inactivate virus at 4◦C, even after exposure for 3
days (Table 1). At 25 and 37 ◦C, formalin inactivated most of
the virus, close to the limit of detection of the assay, after 1
day, yet some virus still remained infectious on day 3. How-
ever, glutaraldehyde completely inactivated the virus by day
2at25◦C and by day 1 at 37◦C. This suggests that both for-
malin and glutaraldehyde inactivation of SARS virus may be
efficientmethodsof inactivation,ifproper conditionsaremet.
3.4. Effect of pH changes on the infectivity of SARS
Weismiller et al. (1990) determined that a pH of 8.0 in-
duces a conformational change in the spike protein of the
coronavirus, mouse hepatitis virus (MHV), which enables
fusion of the virion with the host cell. However, Xiao et al.
(2003) determined that the spike protein of SARS-CoV me-
diated fusion with the host cell at a neutral pH. These data
suggest that different pH conditions affect the spike proteins
of coronaviruses, and the activity of the spike protein of the
SARS-CoV may be sensitive to changes in pH, possibly by
changing the infectious nature of the viral particles. There-
fore, we investigated the effect of different pH exposures on
the infectivity of SARS-CoV. After exposing SARS-CoV to
extreme alkaline conditions of pH 12 and 14 for 1 h, and sub-
sequently reversing the conditions to a neutralized, buffered
solution, the virus was completely inactivated (Fig. 3). Mod-
erate variations of pH conditions from 5 to 9 had little effect
on virus titer, regardless of the temperature. However, highly
acidic pH conditions of 1 and 3 completely inactivated the
virus at 25 and 37◦C. At 4 ◦C, a pH of 3 did not fully in-
activate the virus. These data indicate that the infectivity of
SARS-CoV is sensitive to pH extremes.
3.5. Infectivity of isolated viral RNA and isolated
proteins
Biochemical and molecular biology experiments may re-
quire the isolation of nucleic acids or proteins from virus-
Fig. 3. Effect of pH conditions on the infectivity of SARS-CoV. Virus
aliquots (2ml) were adjusted to the indicated pH condition, divided into
triplicate samples, incubated at the designated temperature for 1h, neutral-
ized, frozen, and titrated. The dotted line denotes the limit of detection of
the assay.
infectedcells. Weuseda phenoland guanidineisothiocyanate
solution (TRIzol, Sigma) to isolate cytoplasmic RNA from
SARS-CoV infected Vero cells. After inoculation of Vero
cells with the isolated RNA, we determined that SARS-CoV
RNA was not able to produce CPE in the cells (data not
shown). We also found that transfection of the cells with this
RNA, using a liposome-based transfection reagent (DMRIE-
C, Invitrogen, as per manufacturer’s instructions for RNA
transfection), was also not sufficient to cause infection of
Vero cells (data not shown).
Additionally, we tested the effectiveness of SDS/NP-40
treatment on inactivation of the SARS-CoV. Briefly, SARS-
CoV-infectedVerocells werelysed withan SDS/NP-40 solu-
tion,clarified by centrifugation,and thesupernatant wasused
to infect Vero cell monolayers. No CPE was observed in the
cells after 3 and 4 days, indicating that SDS/NP-40-induced
disruption of the virions was sufficient to prevent survival of
infectious particles.
4. Discussion
Inactivation of SARS-CoV can be achieved through a
number of techniques, given sufficient time and appropri-
ate temperature conditions. We caution that the inactivation
procedures discussed above were performed under specific
conditions. Due to the grave consequences of a potential
SARS-CoV human infection, great care should be taken to
ensurethat anyinactivationproceduresused tomakethe virus
safe for BSL2 conditions are effective for each viral stock.
We determined that greater than 15 min of UVC treatment
inactivated the virus while UVA light had no effect on via-
bility, regardless of duration of exposure. Duan et al. (2003)
examined the effect of UVC light on SARS-CoV at an inten-
sity of >90 W/cm2and a distance of 80cm, and determined
that inactivation of the virus occurred at 60min. Inactivation
may have occurred more efficiently in our study due to the
greater intensity of UVC light and the closer proximity of the
light source. We also examined the effect of gamma irradia-
tion on SARS-CoV, and found no decrease in infectivity at
the highest dose of 15,000rad. This result was not surpris-
ing, as the Centers for Disease Control and Prevention have
used a much higher dose of 2 ×106rad to inactivate poten-
tial SARS-CoV-infected serum specimens for study in BSL2
laboratories (Ksiazek et al., 2003). This dosage is in the same
range (3–4.5 ×106rad) that is necessary to inactivate viruses
in monoclonal antibody preparations (Grieb et al., 2002) and
bone diaphysis transplants (Pruss et al., 2002).
Our experiments showed that heat treatment of SARS-
CoV for 45 min at 75◦C resulted in inactivation of the virus,
while 90min at 56 and 65 ◦C was required for virus inac-
tivation. Laude (1981) determined that thermal inactivation
of another coronavirus, transmissible gastroenteritis virus of
swine, also occurred faster at higher temperatures, such as 47
and 55◦C, than at the lower temperature of 31 ◦C. Our data
are similar to the findings of Duan et al. (2003), wherein viral
90 M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91
inactivation occurred at 90, 60, and 30min after incubation
at 56, 65, and 75 ◦C, respectively. Heat is an effective means
of SARS-CoV inactivation, however, stocks containing viral
aggregates may require a longer duration of heat exposure.
We determined that formalin and glutaraldehyde inacti-
vatedSARS-CoVin atemperature- andtime-dependentman-
ner. While incubation at 4◦C inhibited the effect of these
chemicals, at 37◦C or room temperature, formalin signifi-
cantly decreased the infectivity of the virus on day 1, while
glutaraldehyde inactivated SARS-CoV after incubations of
1–2 days. As glutaraldehyde is commonly used to disinfect
medical instruments, especially endoscopes, care should be
taken to analyze time, temperature, and concentration re-
quirements necessary for complete SARS-CoV inactivation.
Weismiller et al. (1990) determined that a pH of 8.0 in-
duces a conformational change in the spike protein of the
coronavirus MHV that enables fusion of the virion with the
host cell. However, Xiao et al. (2003) determined that the
spike protein of SARS-CoV mediated fusion with the host
cell at a neutral pH. These data suggest that different pH
conditions affect the spike proteins of coronaviruses, and the
activity of the spike protein of SARS-CoV may be sensitive
to changes in pH, possibly by changing the infectious na-
ture of the viral particles. We determined that exposure of
SARS-CoV to extreme basic or acidic conditions caused in-
activation, while the virus remained stable within a range of
neutralpH. The pHof gastric secretionsof the stomachranges
from 1.0 to 3.5, while the small and large intestines range
from pH 7.5 to 8.0 (Guyton and Hall, 1997). Taken together,
these data suggest that ingestion of SARS-CoV would prob-
ably result in inactivation of most virions by stomach acid.
However, acidic conditions of the stomach may be partially
neutralized by a particularly large meal or antacid ingestion,
and under these conditions the virus might have a chance to
move through the stomach into the slightly basic conditions
of the intestines. Leung et al. (2003) have shown enteric in-
volvement of the SARS virus, as evidenced by the presence
of active viral replication in intestinal biopsy specimens from
five patients, and the isolation of SARS-CoV RNA in stool
specimens up to 10 weeks after onset of symptoms. These
data, coupled with the previously mentioned stability of the
virus to moderate pH conditions, suggest that the SARS virus
may survive ingestion and a fecal/oral route of infection may
be possible.
Our experiments showed that UVC light, heat, formalin,
glutaraldehyde, and extremes of pH, were able to inactivate
SARS-CoV. However, gamma irradiation at the doses tested,
was not sufficient to inactivate the virus. As expected, nei-
ther viral RNA alone nor virions disrupted by SDS/NP-40
wereinfectious. Theseconditionswere appropriateforour vi-
ral stocks as described, however, we caution that researchers
need to test viral stocks for complete inactivation before han-
dlingthe virusat lowersafety levels.These dataanalyze virus
samplesin tissue culture medium andwe arecurrently testing
the inactivation properties required of SARS-CoV in biolog-
ical (body) fluids. Understanding the ways in which SARS-
CoV can be inactivated, will allow the transfer of the virus
from BSL3 to BSL2 conditions, and will promote the study
of inactivated viral vaccines.
Acknowledgements
Wethank SpectronicsCorporationfor theuse ofUVlamps
and radiometer. We also thank Leatrice Vogel and Josephine
McAuliffe for technical assistance, Montserrat Puig for help-
ful suggestions and Kathryn Carbone, Jesse Goodman, Bill
Egan and Jerry Weir for their support.
References
Drosten, C., Gunther, S., Preiser, W., van der Werf, S., Brodt, H.-R.,
Becker, S., Rabenau, H., Panning, M., Kolesnikova, L., Fouchier,
R.A.M., Berger, A., Burguiere, A.-M., Cinatl, J., Eickmann, M.,
Escriou, N., Grywna, K., Kramme, S., Manuguerra, J.-C., Muller,
S., Rickerts, V., Sturmer, M., Vieth, S., Klenk, H.-D., Osterhaus,
A.D.M.E., Schmitz, H., Doerr, H.W., 2003. Identification of a novel
coronavirus in patients with severe acute respiratory syndrome. N.
Engl. J. Med. 348, 1967–1976.
Duan, S.-M., Zhao, X.-S., Wen, R.-F., Huang, J.-J., Pi, G.-H., Zhang,
S.-X., Han, J., Bi, S.-L., Ruan, L., Dong, X.-P., and SARS Research
Team, 2003. Stability of SARS coronavirus in human specimens and
environment and its sensitivity to heating and UV irradiation. Biomed.
Environ. Sci. 16, 246–255.
Fraenkel-Conrat, H., 1954. Reaction of nucleic acid with formaldehyde.
Biochim. Biophys. Acta 15, 307–309.
Fulginiti, V.A., Eller, J.J., Downie, A.W., Kempe, C.H., 1967. Altered
reactivity to measles virus: atypical measles in children previously
immunized with inactivated measles virus vaccines. JAMA 202,
1075–1080.
Grieb, T., Forng, R.-Y., Brown, R., Owolabi, T., Maddox, E., McBain,
A., Drohan, W.N., Mann, D.M., Burgess, W.H., 2002. Effective use of
gamma irradiation for pathogen inactivation of monoclonal antibody
preparations. Biologicals 30, 207–216.
Guyton, A.C., Hall, J.E., 1997. Secertory fuction of the alimentary tract.
Human Physiology and Mechanisms of Disease, sixth ed. W.B. Saun-
ders Company, Philadelphia (pp. 524–536).
Jiang, W., Schwendeman, S.P., 2000. Formaldehyde-mediated aggregation
of protein antigens: comparison of untreated and formalinized model
antigens. Biotechnol. Bioeng. 70, 507–517.
Kim, H.W., Canchola, J.G., Brandt, C.D., Pyles, G., Chanock, R.M.,
Jensen, K., Parrott, R.H., 1969. Respiratory syncytial virus disease in
infants despite prior administration of antigenic inactivated vaccine.
Am. J. Epidemiol. 89, 422–434.
Ksiazek, T.G., Erdman, D., Goldsmith, C.S., Zaki, S.R., Peret, T., Emery,
S., Tong, S., Urbani, C., Comer, J.A., Lim, W., Rollin, P.E., Dowell,
S.F., Ling, A.-E., Humphrey, C.D., Shieh, W.-J., Guarner, J., Pad-
dock, C.D., Rota, P., Fields, B., DeRisi, J., Yang, J.-Y., Cox, N.,
Hughes, J.M., LeDuc, J.W., Bellini, W.J., Anderson, L.J., and the
SARS Working Group, 2003. A novel coronavirus associated with
severe acute respiratory syndrome. N. Engl. J. Med. 348, 1953–
1966.
Laude, H., 1981. Thermal inactivation studies of a coronavirus, transmis-
sible gastroenteritis virus. J. Gen. Virol. 56, 235–240.
Lelie, P.N., Reesink, H.W., Lucas, C.J., 1987. Inactivation of 12 viruses
by heating steps applied during manufacture of a hepatitis B vaccine.
J. Med. Virol. 23, 297–301.
Leung, W.K., To, K.-F., Chan, P.K.S., Chan, H.L.Y., Wu, A.K.L., Lee, N.,
Yuen, K.Y., Sung, J.J.Y., 2003. Enteric involvement of severe acute
M.E.R. Darnell et al. / Journal of Virological Methods 121 (2004) 85–91 91
respiratory syndrome-associated coronavirus infection. Gastroenterol-
ogy 125, 1011–1017.
McDonnell, G., Russell, A.D., 1999. Antiseptics and disinfectants: activ-
ity, action, and resistance. Clin. Micro. Rev. 12, 147–179.
Normile, D., 2004. Mounting lab accidents raise SARS fears. Science
304, 659–661.
Perdiz, D., Grof, P., Mezzina, M., Nikaido, O., Moustacchi, E., Sage,
E., 2000. Distribution and repair of bipyrimidine photoproducts in
solar UV-irradiated mammalian cells. J. Biol. Chem. 275, 26732–
26742.
Pruss, A., Kao, M., Gohs, U., Koscielny, J., von Versen, R., Pauli, G.,
2002. Effect of gamma irradiation on human cortical bone transplants
contaminated with enveloped and non-enveloped viruses. Biologicals
30, 125–133.
Rota, P.A., Oberste, M.S., Monroe, S.S., Nix, W.A., Campagnoli, R.,
Icenogle, J.P., Penaranda, S., Bankamp, B., Maher, K., Chen, M.-
H., Tong, S., Tamin, A., Lowe, L., Frace, M., DeRisi, J.L., Chen,
Q., Wang, D., Erdman, D.D., Peret, T.C.T., Burns, C., Ksiazek, T.G.,
Rollin, P.E., Sanchez, A., Liffick, S., Holloway, B., Limor, J., Mc-
Caustland, K., Olsen-Rasmussen, M., Fouchier, R., Gunther, S., Oster-
haus, A.D.M.E., Drosten, C., Pallansch, M.A., Anderson, L.J., Bellini,
W.J., 2003. Characterization of a novel coronavirus associated with
severe acute respiratory syndrome. Science 300, 1394–1399.
Salk, D., Salk, J., 1984. Vaccinology of poliomyelitis. Vaccine 2, 59–74.
Schlegel, A., Immelmann, A., Kempf, C., 2001. Virus inactivation of
plasma-derived proteins by pasteurizaion in the presence of guanidine
hydrochloride. Transfusion 41, 382–389.
Tandon, R.K., 2000. Disinfection of gastrointestinal endoscopes and ac-
cessories. J. Gastroenterol. Hepatol. 15, 69–72.
Tyrrell, J.-L., Douki, T., Cadet, J., 2001. Direct and indirect effects of
UV radiation on DNA and its components. J. Photochem. Photobiol.
B 63, 88–102.
Weismiller, D.J., Sturman, L.S., Buchmeier, M.J., Fleming, J.O., Holmes,
K.V., 1990. Monoclonal antibodies to the peplomer glycoprotein of
coronavirus mouse hepatitis virus identify two subunits and detect
a conformational change in the subunit released under mild alkaline
conditions. J. Virol. 64, 3051–3055.
Xiao, X., Chakraborti, S., Dimitrov, A.S., Gramatikoff, K., Dimitrov, D.S.,
2003. The SARS-CoV S glycoprotein: expression and functional char-
acterization. Biochem. Biophys. Res. Commun. 312, 1159–1164.
