Health
Scientific Committees
Scientific Steering Committee (former MDSC)
Outcome of discussions
Considerations
on the safety of amino acids from human hair hydrolysate
used in cosmetic products for topical application, with
regard to Transmissible Spongiform Encephalopathy risks:
adopted by the Scientific Steering Committee at its meeting
of 25-26 May 2000
Opinion
Amino acids obtained from the hydrolysis
of human hair sourced from hairdressers and barbers are
used by the cosmetics industry for incorporation into hair-
and skin-care products. These cosmetic products that may
contain human hair hydrolysates are used and applied
topically on humans and animals. The Scientific Steering
Committee (SSC) was requested to prepare an opinion on the
safety of these amino acids with regard to the risk of
contamination with TSE infectivity. It addressed the
following specific questions:
- Can amino acids obtained by hydrolysis
of human hair be considered safe with regard to possible
TSE infectivity if they were produced by hydrolysis with
hydrochloric acid (maintained at a concentration of >20%
throughout the whole process which is carried out at 100
oC over a period of six hours)?
- Are there other conditions or
restrictions that might need to be considered such as a)
the geographical source of the raw material, b) the
molecular size of the end-product, and c) the impurity
content of the end-product?
- Is it possible to define other
processing conditions that are more effective with regard
to the inactivation of TSE infectivity?
Given the fact that the cosmetic
products that may contain human hair hydrolysates are used
and applied topically, awaiting the results of the
inactivation experiments with spiked material which are in
progress, awaiting information from the industry on the
composition of the end product and therefore on the
condition that the end product is only composed of
amino-acids, the Scientific Steering Committee shares the
conclusions of the Working Group which was established to
address these questions in detail. The report of the
Working Group is attached. The conclusions can be
summarised as follows:
- There is no evidence that hair or skin
become intrinsically infected with TSE agents but the
evidence is based on a limited number of bioassays;
- There is no likely means by which they
could become contaminated with TSE agents if collected from
healthy, living individuals whose scalp skin was
healthy;
- The amino acid manufacturing process
has a capacity for inactivating TSE infectivity;
- Topical application excludes,
according the current knowledge, any possible transmission
of prions.
- There would be no justification in
sourcing hair from selected geographic areas;
- There is no justification for
requiring the molecular weights of the end product to be
monitored.
- There is no need to identify
manufacturing procedures that more efficiently inactivate
TSE agents during the production of the amino acids by acid
hydrolysis.
- Crystallisation gives additional
purification.
More generally it may be concluded that
human hair obtained from living individuals in
hairdresser's and barber's shops that are incubating TSEs
is unlikely to be inherently infected. The same conclusion
has to be drawn for the skin-tissue that is likely to be a
contaminant of the hair. Thus, the risk resulting from the
use of human hair to provide amino acids for incorporation
into human hair- and skin-care products would appear to be
negligible, particularly since the manufacturing methods
discussed above have the capacity to inactivate
significantly more infectivity than might ever be present
in such tissues.
However, the above opinion may need to
be reconsidered should the end product be a mixture
containing also impurities and longer polypeptides.
Considerations on the safety of amino acids from human
hair hydrolysate used in cosmetic products for topical
application, with regard to Transmissible Spongiform
Encephalopathy risks:
WORKING GROUP REPORT
I. Background
Amino acids obtained from the hydrolysis
of human hair sourced from barbers are used by the
cosmetics industry for incorporation into hair- and
skin-care products. The cosmetic products that may contain
human hair hydrolysates are used and applied topically.
They may also be used in animals. In any event consumers
may have them applied to them e.g. in the hairdressers but
they also apply them themselves. Furthermore amino acids
from this source could be used also in medicines and
biologicals. It is quite possible that the eyes can be
exposed to cosmetic products and this could be a more
effective route of transmission of TSE infectivity as could
broken skin that might exist in users. The classical
process for the complete hydrolysis of proteins is a
treatment with 6M hydrochloric acid during 22 hours and at
105°C. This however results also in the destruction of part
of the sulfur containing amino-acids (e.g., cystine and
methionin) which are used in cosmetic products.
The Scientific Steering Committee (SSC)
was requested to prepare an opinion on the safety of these
amino acids with regard to the risk of contamination with
TSE infectivity. It addressed the following specific
questions:
- Can amino acids (e.g., L-cystine and
L-cysteine in the crystal form) obtained by hydrolysis of
human hair be considered safe with regard to possible TSE
infectivity if they were produced by hydrolysis with
hydrochloric acid (maintained at a concentration of >20%
throughout the whole process which is carried out at 100
oC over a period of six hours)?
- Are there other conditions or
restrictions that might need to be considered such as a)
the geographical source of the raw material, b) the
molecular size of the end-product, and c) the impurity
content of the end-product?
- Is it possible to define other
processing conditions that are more effective with regard
to the inactivation of TSE infectivity?
Hereafter follows the report of the
working group which was established to address these
questions in detail.
II. On the first question
:
Can amino acids obtained by hydrolysis of human hair
be considered safe with regard to possible TSE
infectivity if they were produced by hydrolysis with
hydrochloric acid (maintained at a concentration of
>20% throughout the whole process which is carried out
at 100
oC over a period of six hours)?
The human hair that is used as a source
of these amino acids is collected from barbers following
normal haircutting. The first point that needs to be
addressed is whether or not there is any evidence that the
normal form of the PrP
C is expressed in hair. This is important
because there is clear evidence that TSE infectivity cannot
replicate in tissues that are devoid of PrP
C (Büeler
et al, 1993). However, it is noted that all cells in
the body contain the PrP gene and therefore have the
potential to express PrP
C even if they do not normally do so. Weak
expression of the PrP
C was immunohistochemically demonstrated in
normal human epidermis. But it was strongly upregulated in
inflammatory skin diseases, warts and tumours (Pammer
et al, 1998). Although Pammer
et al (1998) do not specifically mention or
illustrate scalp skin or hair follicles, it could be
assumed that both behave in the same way as the epidermis
in other parts of the body. Thus, at least theoretically,
hair follicles would have the prerequisite for PrP
Sc production and deposition in hairs. Also, in
a trangenic mouse model, PrP
c does appear to be expressed in some of the
cellular populations of skin (Lemaire-Vielle, 2000)
1
.
On the other hand, PrP
C expression in a tissue does not
per se dictate that it will support the replication
of infectivity. There are tissues that express PrP
C but do not replicate infectivity. The capacity
of any given tissue to replicate infectivity probably
depends partly upon the level of expression of PrP
C but also on a number of other factors. Thus
the presence of PrP
C is not a predictor of the presence of PrP
Sc in that tissue even if the patient was
clinically affected with CJD. However, it is presently not
known what level is needed to support replication of
infectivity.
The cutting of hair does not essentially
involve trauma to tissue other than hair, but haircutting
implements such as scissors can be expected to frequently
cause minor trauma to the scalp, resulting in the
contamination of hair with skin-tissue. Also, scales of
skin tissue in the form of dandruff would be expected to
commonly contaminate hair. Thus, in assessing the TSE risk
from hair, one is forced to consider also the TSE risk from
skin, especially (Lemaire-Vielle, 2000) from epidermis
cells or keratinocytes. If infectivity was actually
contained in hair and skin, which are shed naturally, and
the infectivity titre was sufficiently high the incidence
of the human TSEs amongst hairdressers and others
occupationally involved with hair would be expected to be
detectable given the widespread nature of the resulting
contamination. It is important to note that the products
that contain the amino acids derived from hair are used for
topical application to skin and hair. There is evidence
that even high levels of TSE infectivity do not establish
infection when brought into contact with intact skin, but
infection does takes place when the skin surface has been
broken by scarification (Taylor
et al, 1996). In that case, impure products may
constitute a risk if there had been PrP
Sc replication, but the WG recognises that the
risk is extremely small. It is also noted that cosmetic
products could come in contact with the eye (particularly
of children) or with broken skin and thus provide a
potentially more efficient route of infection if any was
present.
The absence of any evidence for the
presence of TSE infectivity in hair or skin has been
acknowledged by Masters
et al (1980)
2
, the SSC (EC, 1998, 1999a), the
SC-MPMD
3
(EC, 1999b) and EMEA (1992). Similarly, no
infectivity was detected in bioassays carried out on the skin
of sheep with scrapie (Stamp
et al, 1959) and cattle with BSE (SEAC, 1994). These
skin samples would, of course, also carry hair even if they
had been shaved. Bovine skin/hair is also reported on in the
BSE Progress report of the UK Ministry of Agriculture, Food
and Fisheries (MAFF, 1999) and is based on the work of the
Neuropathogenesis Unit (NPU) reported in the EC Consultation
on TSE in 1993, (Fraser and Foster, 1994).
An important point is that there is no
means by which hair collected during haircutting from
humans that are incubating TSEs could become contaminated
by contact with high-risk tissues such as those of the
central nervous system, provided the person was living at
the time of collection or, if it is a deceased person, no
autopsy with opening the skull was previously
performed.
Mould
et al (1965) observed a loss of less than one log of
scrapie infectivity after exposure to a pH of 2.1 at 2
oC for 24 hours. Similarly, Brown
et al (1986) observed a loss of only 1.8 logs after
exposure to 1M hydrochloric acid for an hour at room
temperature. However, hair is hydrolysed for six hours at
100
oC. Although Appel, Groschup & Riesner
(1999) have reported that exposure to 1M hydrochloric acid
for an hour at temperatures of 65
oC or higher leads to almost complete
inactivation, the level of surviving infectivity in these
experiments could well have been higher than that
calculated. This is because these calculations were based
upon incubation period assays, and these can considerably
underestimate infectivity levels (compared with the true
values obtained by bioassays) when infectivity has been
exposed to partially-inactivating procedures (Taylor
et al, 1999; 2000). Nevertheless, given that the
infectivity level in hair and skin is undetectable and
either nil or extremely low, the high titre losses of TSE
agent after treatment with hot 1M hydrochloric acid at 65
oC reported by Appel, Groschup & Riesner
(1999) suggest that the process used for the hydrolytic
extraction of amino acids from human hair is likely to
result in a safe product. This is because the actual
extraction process involves exposure of the hair to
approximately 6M hydrochloric acid for six hours at a
temperature of 100
oC. Bioassays are in progress from validation
studies that involved exposing hair to a commercial
hydrolytic process in which the process was spiked with
hamster scrapie agent (Riesner & Appel, 1999). However,
the conditions used in these studies were not identical to
the ones that the SSC have defined. For example, the
temperature at which the process was carried out was
>105
oC, compared with the temperature of 100
oC defined by the SSC. Also, the final
concentration of hydrochloric acid in the process was
approximately 10%, which contrasts with the > 20%
concentration that the SSC considered for hydrolysed
proteins derived from bovine hides (see: Update of the SSC
opinion of 22-23 October 1998 on the Safety of hydrolysed
proteins, adopted on 25-26 May 2000). Also, it is evident
that Riesner & Appel (1999) believe that the bioassays
in hamsters need only take 150-200 days. Unfortunately,
this is not the case; late positives are a common
consequence of chemical and physical treatment of the
agent. Incubation periods of more than 400 days have been
observed frequently (Taylor, 1993), the maximum being 618
days (Taylor, 1999b). It has been recommended that such
bioassays should be maintained for eighteen months
(Pocchiari
et al, 1991) or two years (Brown
et al, 1986) to detect late positives.
III. On the second question
:
Are there other conditions or restrictions that might
need to be considered such as a) the geographical source
of the raw material, b) the molecular size of the
end-product, and c) the impurity content of the
end-product?
As discussed above, there is no evidence
that hair or skin are inherently infected or are likely to
become adventitiously contaminated with TSE infectivity
under the conditions of collection specified. Furthermore,
as discussed above, the hydrolytic process used to
manufacture the amino acids appears to have the capacity to
inactivate any low level of TSE infectivity that might
theoretically be present in the raw material. Also, since
CJD occurs world-wide (though vCJD is currently
geographically restricted),
any restrictions on the geographical sourcing of raw
materials would appear to be unwarranted. It is noted
that neither PrP studies nor bioassays of skin and hair
have been reported from patients with vCJD. If it was
necessary to reduce any theoretical risk from such
patients, then geographical sourcing advice could be
given.
The question has been raised as to
whether the end-products should be subjected to monitoring
to determine whether the hydrolytic process has been
efficient. The suggested criterion is to determine the
average/maximum molecular weight of the end-product of the
hydrolysis. The question is what molecular weight would
represent the cut-off point between acceptable and
non-acceptable products, should the end-product not consist
of pure amino acids but of a mixture of amino acids and
longer polypeptides. To some extent, this exercise has
already been carried out with regard to the safety of
polypeptides that are derived by alkaline hydrolysis from
the "fleshings" obtained from bovine hides and are
permitted to be incorporated into ruminant feed.
In its update of 25-26 May 2000 of the
opinion of 22-23 October 1998 on the Safety of hydrolysed
proteins, the SSC states:
"(...) it may be concluded that a
molecular weight of <10.000D cannot be seen as an
absolute guarantee for safety, per se. The criterion is
indicative, and not exclusive for the quality of the
hydrolysing process and of the safety regarding possible
residual TSE infectivity of the final product. It seems
theoretically possible that the infectious fraction
(segment, part) of the BSE-agent could be smaller. However,
a product with most of the molecules having a MW of <
10.000D has most likely been produced by means of
production processes which, together with appropriate
sourcing and respecting the other safety conditions given
in the above cited SSC-opinion, guarantee a safe product. A
limited range of molecular weights above the target value
of less than 10.000D is therefore unlikely to affect the
safety of the final product, provided, of course, all the
other criteria of the opinion are complied with. Thus, a
molecular weight below 10.000D may be used as an indicator
but not as a safety guarantee per se."
As to the possible the impurity content
of the end product, the working group sees no reason to
consider possible impurities in the end product as a
possible reason for concern, provided of course that it can
be excluded that these impurities are due to, for example,
contamination with possible TSE-infected materials.
IV. On the third question
:
Is it possible to define other processing conditions
that are more effective with regard to the inactivation
of TSE infectivity?
It does not appear necessary to define
conditions that are more effective with regard to the
inactivation of TSE agents during the processing of human
hair to provide amino acids for incorporation into hair-
and skin-care products. If the above assessments had
indicated that there was any significant degree of risk,
the aim would have been to identify more rigorous
manufacturing methods. However, the perceived level of risk
is such that this is considered to be unnecessary.
V. Summary conclusions
The Working Group summarises its
conclusions as follows,
provided only free amino acids are present in the
product:
- There is no evidence that hair or skin
become infected with TSE agents;
- There are no likely means by which
they could become contaminated with TSE agents if collected
from healthy, living patients with a healthy scalp;
- The amino acid manufacturing process
has a capacity for inactivating TSE infectivity;
- The cosmetic products that may contain
human hair hydrolysates are used and applied only
topically. It is noted that the eye could be exposed to
cosmetics or that broken skin may exist and that these
routes of exposure could be more efficient. Nevertheless
this type of application excludes, according the current
knowledge, transmission of prions.
- There would be no justification in
sourcing hair from selected geographic areas unless a
particular risk was perceived from patients incubating
vCJD. There is currently however, no evidence of such a
risk;
- There is no justification for
requiring the molecular weights of the end products to be
monitored; (however such monitoring may be indicated if the
end product is a mixture containing also impurities and
longer polypeptides.)
- There is no reason for concern over
microbiological impurities
4
in the amino acid end-products;
- There is no need to identify
manufacturing procedures that more efficiently inactivate
TSE agents during the production of the amino acids by acid
hydrolysis.
VI. Overall conclusions
The available evidence suggests that
human hair obtained from living individuals in barber's
shops that are incubating TSEs is unlikely to be inherently
infected. The same conclusion has to be drawn for the
skin-tissue that is likely to be a contaminant of the hair.
Thus, the use of human hair to provide amino acids for
incorporation into human hair- and skin-care products would
appear to be safe, particularly since the manufacturing
methods discussed above have the capacity to inactivate
significantly more infectivity than might ever be present
in such tissues.
VII. Acknowledgements:
The above report was prepared by a
Working Group of the Scientific Steering Committee,
composed as follows: Dr. D.Taylor (rapporteur),
Dr.R.Bradley, Prof.Budka, Prof. J.-Y. Cesbron,
Prof.D.Dormont, Prof.F.Kemper, Prof.M.Vanbelle,
Prof.M.Vandevelde, Prof.J.Vives-Rego.
VIII. References
Appel T.R., Groschup, M.H. & Riesner, D. (1999)
Acid inactivation of hamster scrapie prion rods (poster
123).
Abstracts of a Symposium on the Characterisation and
Diagnosis of Prion Diseases in Animals and Man.p 169;
Tubingen, 23-25 September 1999.
Brown, P., Rohwer, R.G. & Gajdusek, D.C. (1986)
Newer data on the inactivation of scrapie virus or
Creutzfeldt-Jakob disease virus in brain tissue.
Journal of Infectious Diseases
153, 1145-1148.
Büeler, H., Aguzzi, A., Sailer, A.
et al (1993) Mice devoid of PrP are resistant to
scrapie.
Cell
73, 1339-1347.
E.C. (European Commission) (1998) Report and
scientific opinion on the safety of hydrolysed proteins
produced from bovine hides. Adopted by the Scientific
Steering Committee at its meeting of 22-23 October
1998.
E.C. (European Commission) (1999a) Minutes of the
meeting of 18-19 February 1999 of the Scientific Steering
Committee.
E.C. (European Commission) (1999b) Report and
scientific opinion on the safety of skin. Adopted by the
Scientific Committee on Medicinal Products and Medical
Devices at its meeting of 24 March 1999.
E.C. (European Commission) (1999c) Minutes of the
meeting of 22-23 April 1999 of the Scientific Steering
Committee.
E.C. (European Commission) (2000) Revised Report and
scientific opinion on the safety of hydrolysed proteins
produced from bovine hides. Adopted by the Scientific
Steering Committee at its meeting of 25-26 May 2000.
EMEA, 1992. Note for guidance Guidelines for
minimizing Risk of transmitting Agents causing Spongiform
Encephalopathy via Medicinal Products. Prepared by the
Committee for proprietary Medicinal Products: Ad hoc
working Party on Biotechnology / Pharmacy and Working Party
on Safety of Medicines. In: Biologicals,
20: 155-158.
Fraser, H., Foster, J., 1994. Transmission to mice,
sheep and goats and bioassay of bovine tissues. In: R
Bradley and B Marchant eds. Transmissible sponfiform
encepahalopathies. A consultation on BSE with the
Scientific Veterinary Committee. EC Brussels 14-15 Sep
1993. Pp 145-159.
Lemaire-Vieille, C., Schulze, T., Podevin-Mimster, V.,
Follet, J., Bailly, Y., Blanquet-Grossard, F., Decavel,
J-P., Heinen, E., Cesbron, J-Y., (2000). Epithelial and
endothelial expression of the green fluorescent protein
gene under the control of bovine prion protein (PrP
) gene regulatory sequences in transgenic mice.
PNAS,
97 (10): 5422-5427.
MAFF, 1999. Bovine spongiform enephalopathy: A
progress report. MAFF UK London
.
Masters, C.J., Gajdusek, D.C. and Gibbs, C.J.,
(1980). The spongiform encephalopathies: the natural
history of CJD and its relationship to kuru and scrapie.
In: Search for the cause of multiple sclerosis and other
chronic diseases of the central nervous system. First
International Symposium of Hertie Foundation in
Frankfurt/Main, September 1979. A Boese, ed. Verlag Chemie,
Weinheim. Pp 295-313.
Mould, D.L., Dawson, A. McI. & Smith, W. (1965)
Scrapie in mice. The stability of the agent to various
suspending media, pH and solvent extraction.
Research in Veterinary Science
6, 151-154.
Pammer, J., Weninger, W. and Tschachler, E. (1998)
Human keratinocytes express cellular prion-related proteins
in vitro and during inflammatory skin disease. American
Journal of Pathology
153, 1353-1358.
Pocchiari, M., Peano, S., Conz, A.
et al (1991) Combination ultrafiltration and 6M
urea treatment of human growth hormone effectively
minimizes risk from potential Creutzfeldt_Jakob disease
virus contamination.
Hormone Research
35, 161-166.
Riesner, D. & Appel, T. (1999) Risk assessment
for L-cystine, L-cysteine and derived products from keratin
(human hair).
SEAC (1994) Transmissible spongiform
encephalopthies: a summary of present knowledge and
research. London; HMSO.
SSC (1998) Listing of specified risk materials: a
scheme for assessing relative risks to man.
A Re-edited Version of of the Opinion Originally Adopted
on 9 December 1997.
Stamp, J.T., Brotherston, J.G., Zlotnik, I., Mackay,
J.M.K. & Smith, W. (1959) Further studies on
scrapie.
Journal of Comparative Pathology
69, 268-260.
Taylor, D.M. (1993) Inactivation of SE agents.
British Medical Bulletin
49, 810-821.
Taylor, D.M. (1999a) A report to the SSC on the
safety of hydrolysed proteins obtained from bovine
hides.
Taylor, D.M. (1999b) The effectiveness of prion
inactitivation methods.
Proceedings of the IBC International Event on
BioTherapeutics: Animal-based BioTherapeutics.
Washington; 12-16 October 1999.
Taylor, D.M., McConnell, I. and Fraser, H. (1996).
Scrapie infection can be established readily through skin
scarification in immunocompetent but not immunodeficient
mice.
Journal of General Virology,
77, 1595-1599.
Taylor, D.M., Fernie, K. & Steele, P.J. (1999)
Letter to the editor.
Molecular Medicine
5, 701.
Taylor, D.M., McConnell, I. & Ferguson, C.E.
(2000) Closely similar values obtained when the ME7
strain of scrapie agent was titrated in parallel by two
individuals in separate laboratories using two sublines of
C57BL mice.
Journal of Virological Methods
86, 35-40.
Attachment: Short report to the SSC, adopted by
the TSE/BSE
ad hoc Group at its meeting of 15 April 1999 on
the basis of a Working Group report drafted by
Dr.D.M.Taylor, and attached as annex 3to the SSC minutes
of 22-23 April 1999.
Subject: Hydrolysed proteins: are they more safe
if their molecular weight is less than 10kD?
It has been argued that these products
might be considered to be safe if the hydrolysed proteins
have a MW of <10 kD. The basis for such a suggestion
would be the knowledge that PrP
sc has a MW of 27-30kD.
The TSE/BSE ad hoc Group is of the
opinion that the use of such a criterion could lead to a
false sense of security because it is not known whether
protein sub-components or peptides of low MW derived from
PrP
Sc can trigger the conversion of PrP
C to PrP
Sc. However, one needs to bear in mind that the
27-30 kD PrP
Sc is itself a sub-component. It is the
resistant 'core' that remains after proteolytic digestion
of the full-length PrP
Sc protein that has a MW of 33-35kDa. Therefore,
there is existing formal proof that a somewhat truncated
form of PrP
Sc can convert PrP
C into PrP
Sc. It is known that more severely truncated
forms of PrP
C can be converted to PrP
Sc. For example, a PrP
C peptide consisting of only 21 residues had
properties akin to PrP
Sc.
6 It was neurotoxic, and had a tendency to form
amyloid fibrils analogous to the scrapie-associated fibrils
(SAF) found in brain extracts from TSE-infected
individuals. It must be assumed that this truncated form of
PrP
Sc might convert non-truncated PrP
C to PrP
Sc. Also, a form of PrP
C containing only 106 residues (MW approximately
10 kDa) was converted to PrP
Sc
in vitro.
7 In addition, when this truncated PrP was
expressed in transgenic mice that were deficient for
wild-type PrP, these mice developed scrapie when challenged
with the RML strain of mouse-passaged scrapie agent,
demonstrating the convertibility of this 106 residue PrP
C to PrP
Sc.
8 More importantly, when brain-tissue from the
scrapie-infected PrP106 mice was passaged into mice of the
same genotype, they developed scrapie.
8 These data confirm that PrP
C peptides with a MW of approximately 10 kDa can
not only be converted to PrP
Sc, but that they can also convert PrP
C to PrP
Sc. The above data tend to confirm the opinion
that declaring hydrolysed proteins safe if the resulting
peptides are <10 kDa could lead to a false sense of
security.
The TSE/BSE
ad hoc Group considers that only low levels of BSE
infectivity could be present in the raw materials. The two
typical manufacturing processes described in the SSC
opinion of 22-23 October 1998 are likely to completely
inactivate even considerably higher levels of BSE
infectivity than could ever be present under worst-case
conditions. This is because of the combinations of heat
(especially steam under pressure) and alkali that are used.
A variety of data are available that show the effectiveness
of heat combined with alkali on BSE and scrapie agents.
1-5
References
1.
Ernst, D.R. and Race, R.E. 1993. Comparative
analysis of scrapie agent inactivation. J. Virol.
Methods,41; 193-202.
2.
Prusiner, S.B., McKinley, M.P., Bolton, D.C., Bowman,
K.A., Groth, D.F., Cochran, S.P., Hennessey, E.M.,
Braunfeld, M.B., Baringer, J.R. and Chatigny, M.A.
1984. Prions: methods for assay, purification, and
characterisation. In: K. Maramorosch and H. Koprowski
(Editors), Methods in Virology, 8. Academic Press, New
York, pp 293-345.
3.
Taguchi, F., Tamai, Y., Uchida, K., Kitajima, R.,
Kojima, H., Kawaguchi, T., Ohtani, Y. and Miura, S.
1991. Proposal for a procedure for complete
inactivation of the Creutzfeldt-Jakob disease agent. Arch
Virol, 119; 297-301.
4.
Taylor, D.M, Fernie, K. and McConnell, I., 1997.
Inactivation of the 22A strain of scrapie agent by
autoclaving in sodium hydroxide. Vet Microbiol 58.
87-91.
5.
Taylor, D.M., Fernie, K. & Steele, P.J., 1999.
Boiling in sodium hydroxide inactivates mouse-passaged BSE
agent. Abstracts of a Meeting of the Association of
Veterinary Teachers and Research Workers. p 22.
Scarborough; 29 March-1 April 1999.
6.
Forlini, G., Angeretti, N., Chiesa, R., Monzani, E.,
Salmona, M., Bugiani, O. & Tagliavini, F., 1993.
Neurotoxicity of a prion protein fragment.
Nature
362, 543-546.
7.
Muramoto, T., Scott, M., Cohen, F.E. & Prusiner,
S.B., 1996 Recombinant scrapie-like protein of 106
amino acids is soluble. Proc Nat Acad Sci 93,
15457-16462.
8. Supattapone,S., Bosque, P., Muramoto,
T., Wille, H., Aagaard, C., Peretz, D., Nguyen,H.O.,
Heinrich, C., Torchia, C., Safar, J., Cohen, F.E.,
DeArmond, S.J. Prusiner, S.B. & Scott, M., 1999. Prion
protein of 106 residues creates an artificial transmision
barrier for prion replication in transgenic mice.
Cell 96, 869-878.
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1
Lemaire-Vieille et al (2000) built transgenic mice
expressing a green fluorescent protein reporter gene
under the control of 6.9 kb of the bovine PrP gene
regulatory sequences. The tg mice exposed under the UV
light exhibited very clearly a fluorescent signal in the
skin, the nails and the hair. Histological analysis of
the skin showed a fluorescence signal in basal and
spinocellular keratinocytes and in the external root
sheet of the hair follicles and its associated sebaceous
gland.
2
Masters et al (1980) reported no infectivity in the
hair of human patients with CJD but there is no
indication of how many patients were tested.
3
At its meeting of 24 March 1999, the
Scientific Committee on Medicinal Products and Medical
Devices (SC-MPMD) stated: "Pammer et al (1998)
unequivocally demonstrate the presence of PrPc in the
skin. By this finding, they extend the range of tissues
known to express PrPc. The theoretical possibility that
skin contains also PrPSc, the pathologic form of the
prion, or TSE infectivity in significant amounts is not
supported by the majority of observations. However,
crucial experiments as a search for PrPSc in the skin
have not yet been performed. The methods are easily
available. Until those studies are completed there is no
sound justification for a change in policy regarding the
use of hides and skins for the preparation of
gelatine."
4
Toxics, heavy metals, radioelements, etc. not
included.
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