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From: TSS (216-119-144-16.ipset24.wt.net)
Subject: Novel methods for disinfection of prion-contaminated medical devices [FULL TEXT]
Date: August 7, 2004 at 9:22 am PST

-------- Original Message --------
Subject: Novel methods for disinfection of prion-contaminated medical devices [FULL TEXT]
Date: Sat, 07 Aug 2004 11:20:51 -0500
From: "Terry S. Singeltary Sr."
To: Bovine Spongiform Encephalopathy
CC: cjdvoice@yahoogroups.com


Novel methods for disinfection of prion-contaminated
medical devices

Guillaume Fichet, Emmanuel Comoy, Christelle Duval, Kathleen Antloga,
Capucine Dehen, Aurore Charbonnier, Gerald McDonnell, Paul Brown,
Corinne Ida Lasmézas, Jean-Philippe Deslys

Summary
Background The unique resistance of prions to classic methods of
decontamination, and evidence that prion
diseases can be transmitted iatrogenically by medical devices pose a
serious infection control challenge to healthcare
facilities. In view of the widespread tissue distribution of the variant
Creutzfeldt-Jakob disease agent in human
beings, new practicable decontamination procedures are urgently needed.

Methods We adapted an in-vivo method using stainless steel wires
contaminated with prions to the hamster-adapted
scrapie strain 263K. A new in-vitro protocol of surface contamination
compatible with subsequent biochemical
detection of PrPres (protease-resistant form of the prion protein) from
the treated surface was developed to explore
the mechanisms of action of methods of decontamination under test. These
models were used to investigate the
effectiveness of innovative physical and chemical methods of prion
inactivation.

Findings Standard chemical decontamination methods (NaOH 1N, NaOCl 20
000 ppm) and autoclaving in water at
134°C reduced infectivity by >5·6 log10 lethal doses; autoclaving
without immersion was somewhat less effective
(44·5 log reduction). Three milder treatments, including a phenolic
disinfectant, an alkaline cleaner, and the
combination of an enzymatic cleaner and vaporised hydrogen peroxide
(VHP) were also effective. VHP alone, which
can be compatible with electronic components, achieved an approximately
4·5 log reduction in infectivity
(equivalent to autoclaving without water immersion).

Interpretation New decontamination procedures are proposed to ensure the
safety of medical and surgical
instruments as well as surfaces that cannot withstand the currently
recommended prion inactivation procedures.

For personal use. Only reproduce with permission from Elsevier Ltd.

Introduction

The occurrence in the UK in 1996 of variant Creutzfeldt-
Jakob disease (vCJD), linked to the consumption of
bovine spongiform encephalopathy (BSE)-tainted meat
products, raised concerns that human beings might
have been exposed to secondary infections by the
BSE/vCJD agent via medical procedures or the
administration of human derived biological products,
including blood. Many peripheral tissues from patients
with vCJD have been shown to be infectious, and by
contrast with sporadic Creutzfeldt-Jakob disease (sCJD),
the biochemical marker of prion diseases (PrPres, the
protease-resistant, pathological form of the prion
protein) is detectable in lymphoid organs like spleen,
tonsils, thymus, and appendix.1,2 We have also shown
that PrPres is present in the mucosa of the intestine and
in peripheral nerves in a non-human primate model of
vCJD.3 The iatrogenic risk of vCJD has recently been
substantiated by the report of a probable case of
transfusion-related disease.4

As a consequence, precautionary measures have been
implemented with regard to blood products, tissue
grafts, and the decontamination of surgical instruments.
Several iatrogenic transmissions of sCJD due to
neurosurgical instrument and electrode contamination
have been identified in the past.5,6 To avoid such events
in the future, regulatory measures have been taken
concerning the re-use and decontamination of
neurosurgical instruments.79 These measures consist
mainly of recommendations to use disposable
instruments or harsh decontamination proceduresie,
immersion in 1N NaOH for 1 h followed by porous load
autoclaving at 134°C for 18 min.9 Similar measures
should, if practicable, be taken for all surgical
instruments and for endoscopic devices, but are
hindered by the corrosive effect of either NaOH or
NaOCl and the incompatibility of autoclaving with all
devices containing plastic, gum, joints, or electronic
components.10

There is thus an urgent need to explore new
procedures and chemical formulations that are both
effective and practical for use on instruments and
surfaces. So far, most inactivation studies have used
residues from tested materials as inocula in standard
infectivity bioassays,7,8 although a strong correlation
between infectivity and PrPres has been documented in a
study of Cohn-fractionated plasma.11

A system based on the use of steel wires has been
previously described that mimics the contact of surgical
instruments in living organisms.12,13 We applied this
method to inactivation studies on prions bound to
surfaces. We tested several decontamination procedures
and chemical formulations, and devised three new
inactivation protocols applicable to fragile devices and
surfaces that were equal to or better than autoclaving at
134°C for 18 min.

Lancet 2004; 364: 52126
See Comment page 477
CEA/DSV/DRM/GIDTIP, Route
du Panorama, 92265
Fontenay-aux-Roses, France
(G Fichet DipBiol, E Comoy PhD,
C Duval, C Dehen, A Charbonnier,
C Lasmézas PhD, J-P Deslys PhD);
Anjou Recherche/Veolia water,
1 place de Turenne, 94417
Saint-Maurice Cedex, France
(G Fichet); Steris, Viables,
Basingstoke, UK
(G McDonnell PhD,
K Antloga MD); EFS-Nord de
France, 59800 Lille, France
(C Duval); and Bethesda,
Maryland, USA (P Brown PhD).
Correspondence to:
Dr Emmanuel Comoy, Groupe
dInnovation Diagnostique et
Thérapeutique sur les Infections
à Prions, CEA/DSV/DRM,
18 Route du Panorama, 92265
Fontenay-aux-Roses, France.
emmanuel.comoy@cea.fr
www.thelancet.com Vol 364 August 7, 2004 521

Articles
Methods
Animals
6-week-old female Syrian golden hamsters (Charles
River, France) were used in this study.14,15 All animals
were housed in level 3 care facilities officially registered
for prion experimental studies on rodents (agreement
number A 92-032-02 for animal care facilities,
agreement number 92-189 for animal experimentation).

Infectious material
The hamster-adapted scrapie strain 263K was stabilised
and propagated in the Syrian golden hamster.14,15 Brains
of hamsters at the terminal stage of the disease, typically
titrating 11010 to 11011 mean lethal doses (LD50) per
gram, were homogenised at 10% weight/volume in PBS
solution. Healthy hamster brain homogenate was used
for the negative controls.

Contamination of surfaces
Stainless steel wires were used for bioassays. Wires
(316 stainless steel, 5·0 mm length0·16 mm
diameter) were cleaned by ultrasonication in a 2%
Triton X-100 solution for 15 min, rinsed in distilled
water, and dried at 37oC for 1 h. The wires were
artificially contaminated by immersion in normal 10%
brain homogenate (negative controls) or scrapie brain
homogenate (positive controls) for 1 h at room
temperature. Wires were then dried for 16 h at room
temperature. Excess of unbound infectivity was removed
by rinsing for 5 min in PBS. To establish an end-point
titration and a dose-incubation period curve, wires were
immersed in serial 10-fold dilutions of positive
homogenate in negative homogenate. To assess the
effect of rinsing before implantation, additional control
wires (1103 and 1105 dilutions) were rinsed for
15 min in PBS after contamination and drying. For invitro
experiments, glass slides instead of stainless steel
wires were contaminated with 20 L of 10% brain
homogenate and dried at 37°C for 1 h.

Decontamination methods
All decontamination methods were done on three
independent batches of 5 contaminated wires. Wires
were then rinsed in 1 mL of distilled water, dried and
stored at 80oC before inoculation. For in-vitro studies,
contaminated glass slides were used and
decontaminated according to the same protocols.

Control treatments recommended by WHO included:9
immersion in NaOCl (freshly prepared solution at
20 000 ppm, 1 h, 20°C), in NaOH (1N, 1 h, 20°C), or
autoclaving in a porous load cycle (18 min, 134°C).
Decontamination methods under test included
autoclaving wires immersed in water (18 min, 134°C),
immersions in an enzymatic solution (Klenzyme,
STERIS, 0·8% v/v in water, 5 min, 43°C), an alkaline
cleaner (HAMO 100 Prion Inactivating Detergent,
STERIS, 1·6% v/v, 15 min, 43°C), formulated peracetic
acid (STERIS 20 at use dilution, 12 min, 55°C) or phenol
disinfectants (Environ LpH or LpHse, STERIS, 5% v/v,
30 min, 20°C). In parallel, batches of wires were treated
with the enzymatic cleaner (as above) followed by
immersion in water and autoclaving at 121°C for
20 min. Exposures to vaporised hydrogen peroxide
(VHP) were done in a sealed container directly coupled
to a VHP1000 Biodecontamination System.16 The latter
generated and maintained a dry (non-condensing)
hydrogen peroxide gas at a concentration of 1·0 to
1·5 mg/L, for 3 h at about 25°C. Wires were exposed to
VHP with or without previous treatment with an
enzymatic cleaner.

Bioassays
Wires were individually implanted into the prefrontal
subcortical region of anesthetised hamsters. Animals
were regularly monitored for clinical signs of
transmissible spongiform encephalopathy (TSE), and
killed at the terminal stage of the disease. LD50 values
were determined according to Reed and Muenchs
method.17 Diagnosis of TSE was confirmed by detection
of PrPres in brain by ELISA and western blot techniques,
according to a previously described protocol.18

In-vitro analysis of mechanisms of action
For in-vitro analysis, the dried inoculum was treated,
and, after removal from glass slides, resuspended in
120 L of water. Samples were treated or not with
increasing amounts of proteinase K for 10 min at 37°C,
2 Laemmli buffer was added, and 20 l of each extract
was used for PrPres detection.19

In the cases of LpH and LpHse, the product was added
4:1 to 20% brain homogenate in 5% glucose solution
and incubated for 30 min at 20°C. Since phenol inhibits
proteases, we had to extract PrPres from the phenolic
phase using an SAF protocol (previously described
omitting the proteinase K treatment, from a commercial
kit Bio-Rad).20 Samples were then treated with
increasing amounts of proteinase K. A sample
corresponding to 200 g of brain was loaded on a SDSpage
gel (12% polyacrylamide) and electroblotted onto a
PVDF membrane. Immunoblotting was done using a
mouse monoclonal antibody (SAF-60, raised against
hamster PrP, codon 142160) followed by a peroxidaseconjugated
goat anti-mouse antibody (Southern
Biotechnology Associates, Birmingham AL, USA).
Immunoreactivity was visualised by chemiluminescence
(ECL, Amersham, Orsay, France) and detected by
standard autoradiography.

Immunohistochemistry
Immunochemistry analyses were done as previously
described.3 Each brain containing the inserted wire was
fixed by immersion in Carnoys fluid, and then
transferred to butanol until paraffin embedding with
removal of the wire before microtome section.

522 www.thelancet.com Vol 364 August 7, 2004
For personal use. Only reproduce with permission from Elsevier Ltd.
Articles

5-m-thick sections were cut and mounted on polylysine-
coated slides. After treatment with proteinase K
(2 g/mL, 10 mins at 37°C), PrP was detected with a
monoclonal antibody coupled to biotine (SAF-32, raised
against hamster PrP, codon 7992, 1 g/mL, 2 h a t
room temperature).

Role of the funding source
This work has been partly supported (in-vivo studies) by
Steris Ltd. Steris had no role in the collection and
analysis of data, and the role of Steris in study design
was limited to protocols of wire decontamination.

Results
Wire contamination with serial dilutions of brain
homogenates from hamsters terminally ill with scrapie
(strain 263K), and implantation into recipient animals,
established a relation between the infectivity titre
(endpoint at 1105·6 LD50), the transmission rate, and
the incubation period (table 1). The progressive decrease
in the infection rate, along with an increase in the
incubation period as the dilution of the infective
material increases, is similar to previous findings with
direct inoculation of brain homogenate.15 Implantation
of two groups of wires rinsed for 15 min in PBS led to a
slightly lower attack rate in the bioassay when compared
with the unrinsed wires, with no prolongation of the
incubation period.

Our results are summarised in table 2. The reductions
of infectivity were obtained by comparing the attack rate
and incubation periods of the transmissions shown in
table 2 with those of the dilution series shown in table 1.
All treatments producing an infectivity reduction of
5·6 logs or more (corresponding to the threshold of
infectivity detection) are considered as having produced
complete decontamination within the limit of sensitivity
of our model.

Both WHO-recommended chemical treatments
(NaOH 1N and NaOCl 20 000 ppm)9 led to a complete
decontamination. However, inactivation by autoclaving
at 134°C for 18 min was incomplete unless the wires
were immersed in water during the autoclaving cycles.
The enzymatic cleaner resulted in partial
decontamination, but was greatly enhanced by
combination with autoclaving at 121°C. VHP by itself
reduced infectivity by about 4·5 logs, but resulted in
complete decontamination when combined with the
enzymatic cleaner. The alkaline cleaner achieved full
disinfection at the recommended temperature, as did
the phenolic disinfectant Environ LpH (previously
known as LpH, which had been shown to be effective in
suspension studies21).

The effects of treatments on the amount of PrPres and
its degree of protease resistance were investigated by
western blots using SAF-60 monoclonal antibody
(similar results were obtained with other antibodies of
different specificities; data not shown). To reproduce a
surface contamination and decontamination, the
treatments were applied on glass slides previously
contaminated with a controlled amount of brain
homogenate. The treated inoculum (still visible as a
transparent biofilm with all the treatments done) was
then scraped off and analysed for PrPres. Results were
reproducible from one experiment to another, even
when different brain homogenates were used. Moreover
similar results were obtained on steel surfaces (data not
shown).

In the absence of any decontamination procedure,
normal brain inoculum yielded a PrP signal up to a dose

www.thelancet.com Vol 364 August 7, 2004 523
Transmission Total death / Disease
rate (%) total number in days
Positive control duration(dilution)
1101 100% 12/12 90 (2)*
1102 100% 12/12 98 (5)*
1103 100% 12/12 117 (6)*
1104 100% 12/12 124 (11)*
1105 92% 11/12 201 (60)*
1106 22% 2/9 201 (39)*
1107 0% 0/12 >365
1108 0% 0/12 >365
1109 0% 0 /12 >365
1103 (PBS) 92% 11/12 114 (5)*
1105 (PBS) 46% 4/11 166 (43)*
Negative control (dilution)
110-1 0% 0/12 >365
Data are mean (SE). *Wires were rinsed in PBS for 15 min before inoculation.
Table 1: Infectivity of wires exposed to ten-fold serial dilutions of 263K
strain hamster scrapie brain homogenates
Treatments Transmission Total death / Disease duration Log
rate (%) total number in days (mean±sem) reduction
NaOCl 0% 0/8 >365 > 5·6
20000 ppm, 20°C, 1 h
NaOH 0% 0/12 >365 > 5·6
1N, 20°C, 1 h
Autoclaving* 60% 6/10 (7/10)a 197 (86)§ 4-4·5
134°C, 18 min
Autoclaving 0% 0/11 >365 > 5·6
134°C, 18 min
Enzymatic Cleaner+autoclaving! 10% 1/10 (4/10)a 242 ~ 5
0·8%, 43°C, 5 min/121°C, 20 min
Enzymatic Cleaner 100% 10/10 143 (12)§ ~ 3·5
0·8%, 43°C, 5 min
Alkaline Cleaner 0% 0/11 >365 > 5·6
1·6%, 43°C, 15 min
Peracetic acid 100% 12/12 155 (60)§ ~ 3·5
0·25%, 55°C, 12 min
Phenolic disinfectant 0% 0/11 >365 > 5·6
5%, 20°C, 30 min
VHP 33% 4/12 170 (33)§ ~ 4·5
1·5 mg/L, 25°C, 3 h
Enzymatic cleaner +VHP 0% 0/11 >365 l 5·6
0·8%, 43°C, 5 mins / 1·5 mg/L, 25°C, 3 h
*Wires were placed on support during autoclaving at 134°C. Wires were
immersed in water during autoclaving at 134°C. !After
the enzymatic cleaner treatment, wires were immersed in water and
autoclaved at 121°C. §Data are mean (SE). At the end of
the study, a few asymptomatic animals were positive for PrPres and
incorporated as a positive transmission.
Table 2: Effect of various treatments on contaminated wires
For personal use. Only reproduce with permission from Elsevier Ltd.
Articles

of 2 g/mL of proteinase K. In infected brain, the PrPres
persisted even at the proteinase K dose of 2 mg/mL
(figure 1A, control). Application of the VHP procedure
led to an increase of the PrPres signal in the absence of
proteinase K treatment; however, this PrPres species was
rendered fully proteinase K sensitive as shown by the
disappearance of the PrPres signal at the lowest dose of
2 g/mL PK (figure 1A).

The alkaline cleaner (composed of KOH with
detergents) combined a removal effect of PrPres with a
sensitisation to proteinase K (figure 1B, H2O and
alkaline cleaner panelslanes 5 to 8). The PrPres signal
disappeared completely at a proteinase K dose of
20 g/mL. Compared with unformulated alkali at the
same concentrations (0·006N of KOH or NaOH, equal
to the concentration of 0·16% of alkaline cleaner used in
the in-vitro experiment), PrPres signal was not removed
with 20 g/mL of proteinase K following alkali
treatment, whereas it was eliminated with 8 g/mL of
proteinase K for the alkaline cleaner (figure 1B). At the
recommended concentration used in the in-vivo study
(1·6%), no signal was observed (data not shown).
Moreover, this effect was observed at 43°C
(recommended temperature), whereas no effect on PrP
was seen at lower temperatures (below 25°C; data not
shown).

The phenolic compounds of Environ LpH degraded
the brain layer coated on glass slides into a sticky gum
incompatible with further experiments. Thus, we had to
undertake the decontamination procedure for the invitro
analysis of this formulation on brain homogenates.
Both Environ LpH (the formulation under test) and
LpHse (a distinct phenolic formulation) increased the
resistance of PrPc to proteinase K at the dose of
20 g/mL (lanes 4 and 1 in figure 2; plus data not
shown). At the same dose of 20 µg/mL proteinase K,
Environ LpH and LpHse treatments led to the
appearance of an aggregated form of PrPres (figure 2,
lanes 6 and 9 vs 2, note the band of higher molecular
weight). At the higher proteinase K dose of 2000 g/mL,
no difference was seen between each treatment and the
control (figure 2, lanes 7 and 10 vs 3).

Immunohistochemical analyses of the brains of wireimplanted
and diseased hamsters showed widespread
PrPres deposition at the terminal stage of disease in the
same regions as in hamsters inoculated with
homogenates (figure 3, B and C). Additionally, the area
directly adjacent to the wire was heavily stained with
PrPres (figure 3, B). In the brains of hamsters that
developed disease after implantation of wires treated
with procedures allowing only partial decontamination
(enzymatic cleaner alonefigure 3, D), the PrPres pattern
was broadly similar to that of the control hamsters
implanted with untreated wires (figure 3, B). Hamsters
implanted with treated wires showing no clinical signs
of neurological disease were killed at 400 days postinoculation
to verify the absence of incipient PrPres

524 www.thelancet.com Vol 364 August 7, 2004
A
VHP
Negative Positive
Control
Dry inoculum
PK (g/mL)
0
2
8
20
0
8
2
202000
Dry inoculum Negative Positive
8
PK (g/mL)
0
2
8
20
0
2
202000
20
30
40
20
30
40
MW
(kDa)
8 1 2 3 4 5 6 7 Lanes 9
1 2 3 4 5 6 7 8 Lanes
B
Alkaline
cleaner
0
2
8
20
0
2
8
20
Dry inoculum
PK (g/mL)
0
2
8
20
0
2
8
20
PK (g/mL)
H2O
NaOH
Dry inoculum
PK (g/mL)
KOH
Dry inoculum
Dry inoculum Negative Positive
Negative Positive
Negative Positive
Negative Positive
0
2
8
20
0
2
8
20
PK (g/mL)
0
2
8
20
0
2
8
20
20
30
40
20
30
40
20
30
40
20
30
40
Figure 1: Western-blot analysis of PrPres adsorbed on glass slide
surfaces and
treated with different chemical formulations and proteinase K
concentrations.
All lanes correspond to the analysis of 75 µg of brain equivalent. (A)
compares
VHP treatment versus control (untreated biofilm). (B) shows treatment at
43°C
with water, alkaline cleaner at 0·16%, and equivalent concentrations of
alkali
(0·006N KOH or NaOH).
For personal use. Only reproduce with permission from Elsevier Ltd.
Articles

deposition. No PrPres deposits were seen in hamsters
implanted with wires treated with either the reference
NAOH treatment or a combination of enzymatic cleaner
and VHP (figure 3, E and F) as observed in hamsters
implanted with negative control wires (figure 3, A).

Discussion
Using WHO reference treatments9 as decontamination
controls, we confirmed the effectiveness of 1N NaOH
and 20 000 ppm NaOCl to decontaminate wires coated
with hamster-adapted scrapie, as had been previously
shown for tissue suspensions.7,8 We also confirmed that
inactivation by autoclaving at 134°C for 18 min was only
complete when the wires were immersed in water:
incomplete inactivation of wires placed in the autoclave
on a dry support underlines the protective or fixing
effect which can occur when dried material is
autoclaved.23 Exposure to formulated peracetic acid at
55°C, currently recommended as a replacement for
glutaraldehyde for the decontamination of endoscopes,
yielded a 3·5 log reduction of infectivity, in accord with
data reported by other researchers,24,25 and in the same
range as decontamination using an enzymatic cleaner.
The use of this cleaner in the presence of VHP or with
conventional autoclaving at 121°C, produced nearly
complete decontamination. Further, the alkaline cleaner
and phenolic disinfectant Environ LpH were also shown
to be effective. The implication of these findings are as
follows. First, VHP is a non-corrosive gas disinfectant
and steriliser that can be used on fragile or inaccessible
surfaces of complex instrumentsfor decontamination
of fragile devices such as endoscopes, we propose the
use of the alkaline cleaner on wet instruments followed
(after drying) by a terminal VHP treatment. Second, the
combination of the enzymatic cleaner with conventional
121°C autoclaving is of special interest for use in
facilities that cannot support an extended 134°C cycle.
Finally, the alkaline cleaner, because of its formulation
with a moderate alkali concentration, is less corrosive
than currently recommended chemical decontamination
procedures and could also be amenable for use
on fragile instruments. Environ LpH may be useful for
environmental decontamination of large surfaces.
Biochemical PrPres analysis highlighted three different
mechanisms of action for the decontamination
procedures under test.

The alkaline cleaner reduced PrPres amounts and
increased PK sensitivity, similar to findings in studies
involving the use of brain homogenates.26 The higher
efficiency of the alkaline cleaner compared to an
equivalent concentration of pure alkaline solution
(NaOH or KOH) was probably due to a combination of
denaturation by the alkali and removal by the detergents
contained in the formulation. Moderate heating (43°C)
increased the efficiency of alkaline treatment (data not
shown).

VHP showed a different effect: a paradoxical increase
of PrPres in the absence of proteinase K treatment, but a
disappearance of PrPres at even the lowest concentration
of proteinase K (similar to uninfected controls). In
gaseous form, hydrogen peroxide seems to alter the
structure of the protein in such a way that normally
inaccessible epitopes of the molecules are exposed and
become immunoreactive, resulting in both enhanced
immunoreactivity and increased proteinase K sensitivity.
VHP has been shown in other studies to break
down proteins into smaller peptides (Antloga K,
McDonnell G, unpublished data).

A third type of effect was seen with Environ LpH. This
product increased both PrPc and PrPres aggregation,
leading to a slightly increased proteinase K resistance of
PrPc and the appearance of a high molecular weight
band for PrPres, which was neither eliminated nor

www.thelancet.com Vol 364 August 7, 2004 525
Brain homogenate
LpH LpHse
2000

20
2000
20
2000
20
2000
Control
2000
20
20
    
PK (g/mL)
Lanes 1 2 3 4 5 6 7 8 9 10
Figure 2: Effect of phenolic formulations Environ LpH and LpHse on PrPc and
PrPres
PrPres purified from the treated sample was treated with increasing
amounts of
proteinase K. All lanes correspond to the analysis of 200 g of brain
homogenate. Lanes 1, 4, 5, and 8 are non-infected brain homogenate; lanes 2,
3, 6, 7, 9, and 10 are scrapie brain homogenate.
Figure 3: PrP immunostaining of the brains of hamsters implanted with
contaminated wires
W=wire, PA=PrPres accumulation. Panels show magnifications of the areas
within the dotted frames in the insets.
No immunoreactivity in brain from an uninfected animal (A). PrPres
immunostaining present in the brains of an
animal implanted with a wire exposed to a 110-4 dilution of brain
homogenate (B), an animal inoculated intracerebrally
with 50 L of brain homogenate (C), and an animal implanted with a wire
treated by an enzymatic
cleaner solution (D). No immunoreactivity was detected in the brain of
an animal implanted with a wire treated
with enzymatic cleaner plus VHP (E) or with 1N NaOH (F). Detection of
PrPres was visualised with biotinylated-
SAF 32.
A
W
25
100
F
W
25
100
E
W
100
25
C
PA
25
100
D
W
PA
100
25
B
W
PA
100
25
For personal use. Only reproduce with permission from Elsevier Ltd.
Articles

rendered proteinase K sensitive. Furthermore, both
Environ LpH and LpHse had a similar effect on PrP
even though one removed infectivity, whereas the other
did not.27 These results suggest either a decontaminating
effect relying on a molecular entity other than PrP, or an
effect on PrPres that cannot be detected by the type of
immunological analysis performed in this study. In any
case, our data show that the assessment of
decontaminant efficacy should not rely solely on
western-blot analyses.

Our present study paves the way for testing innovative
decontamination procedures with use of an experimental
method designed to mimic medical or surgical
decontamination practices, and can be used in future
studies of other prion strains such as sCJD and vCJD.
Our data highlight different possible molecular
mechanisms leading to the decontamination effect and
warrant further investigations of these and other
formulations. A better understanding of these
mechanisms might facilitate the development of
biochemical methods for higher throughput screening
of useful decontamination and other inactivation procedures.
Of more immediate importance, we described
three procedures suitable for the decontamination of
fragile surgical instruments, one of which may also be
useful for medical devices containing electronic or video
components (eg, endoscopes, laparoscopes).

Contributors
J P Deslys, E Comoy, and G McDonnell were responsible for design
and management of this study. G Fichet undertook the biochemical
analyses and C Duval the in-vivo study. K Antloga prepared and assisted
with the wire preparation and decontamination. C Dehen did the
in-vitro study. A Charbonnier undertook the immunohistochemical
analyses. C I Lasmézas, G Fichet, E Comoy, G McDonnell, P Brown,
and J P Deslys drafted the manuscript.
Conflict of interest statement
K Antloga and G McDonnell are employees of the manufacturer who
provided the chemical components (Steris). All authors had full access
to all data and had responsibility for the decision to submit for
publication.
Acknowledgments
We thank Jacques Grassi and his colleagues (CEA-SPI) who provided
the anti-PrP antibodies. We also thank Peter Burke for critical reading
of the manuscript.
References
1 Wadsworth JD, Joiner S, Hill AF, et al. Tissue distribution of
protease resistant prion protein in variant Creutzfeldt-Jakob
disease using a highly sensitive immunoblotting assay. Lancet
2001; 358: 17180.
2 Head MW, Ritchie D, Smith N, et al. Peripheral tissue involvement
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