From Alzheimer’s to Zebrafish: Eclectic Science and Regulatory Stories 122
brains and spinal cords from cattle 30 months of age and older. The 2008 rule, Title 21 Part
589.2001, called the Enhanced Feed Ban, became effective on 27 April 2009.
Sterilization
The transmissible agent of vCJD (PRPSc) is not readily destroyed by conventional steril-
ization, and transmissions by neurosurgical equipment, including instruments and EEG
depth electrodes, and in recipients of pituitary growth hormone, dura mater or corneal
grafts have been reported.16 Iatrogenic (resulting from the action of a physician) trans-
mission of the CJD agent has been reported in more than 250 patients worldwide.17,18
Unfortunately, the incubation period of vCJD is unknown but could be several decades,
thus it is unlikely that any iatrogenic cases have yet emerged.19
Previous work indicated that prion protein bound to steel wire was resistant to most
conventional reprocessing procedures, including enzymatic cleaning, fixatives, acidic
treatments and autoclaving (steam at 134ºC for 18 minutes combined with enzymatic
cleaning). Because of the unusual resistance of PRPSc, special decontamination procedures
are needed to prevent accidental transmission. Studies have been done in an in vitro car-
rier assay using steel wires contaminated with the disease associated prion protein and
scrapie brain homogenates from hamsters.20,21 The wires were implanted into the brains
of hamsters after treatment for decontamination and subsequently monitored for their
potential to trigger clinical disease or subclinical cerebral PRPSc deposition within an
observable period of 500 days. The most effective treatment consisted of incubating the
wires in 1.0 M NaOH for one hour at 23ºC, 2.5% NaOCl for one hour at 23ºC, an alkaline
cleanser (used at a concentration of 1%) for 10 minutes at 55ºC or 0.2% sodium dodecyl
sulfate (SDS)/0.3% NaOH for 10 minutes at 23ºC led to complete decontamination in
terms of detectable infectivity, as well as to efficient removal of residual brain material
from carriers.22 The authors mention that similar methods should be validated for human
transmissible spongiform encephalopathy agents on different types of instrument sur-
faces. The most stringent chemical and autoclave sterilization methods for transmissible
spongiform encephalopathies are currently outlined in Annex III of the WHO infection
control guidelines.23
Final Thoughts
There is still much to be learned about the mysterious and deadly prion. It was recently
reported that US researchers have discovered a new form of prion disease that does not
act like related illnesses, such as mad cow disease, but instead causes brain damage simi-
lar to that produced by Alzheimer’s disease. In this study, the researchers examined mice
that were genetically engineered to process prion proteins in a unique way.24 Then, they
exposed them to scrapie. The treated mice did not develop holes in the brain like those
typically caused by prion diseases. Instead, they developed plaques that resembled a form
of human Alzheimer’s. If a treatment is found for this new form of prion disease, it may
also be useful in Alzheimer’s disease.
References
1. Thomas L. A Long Line of Cells. Book of the Month Club, New York, New York 1975.
2. Griffin BE. “Unconventional viruses or prions.” BMJ 1985 290(issue?):1765-6.
3. Suppattapone S. “What makes a prion infectious.” Science. 2010 327:1091-2.
4. Taubes G. “The game of the name is fame, but is it science?” Discover. 1986 7(12):28-52.
5. Lemmer K, et al. “Decontamination of surgical instruments from prions. II. In vivo findings with a model
system for testing the removal of scapie infectivity from steel surfaces.” J Gen Virology. 2008 89(issue?):348-358.
6. Harrison PJ,Roberts GW. “How now mad cow?” BMJ. 1992 304(issue?):929-30.
7. Ibid.
8. Kuru Information Page. NINDS website. http://www.ninds.nih.gov/disorders/kuru/kuru.htm. Accessed 17
January 2011.
brains and spinal cords from cattle 30 months of age and older. The 2008 rule, Title 21 Part
589.2001, called the Enhanced Feed Ban, became effective on 27 April 2009.
Sterilization
The transmissible agent of vCJD (PRPSc) is not readily destroyed by conventional steril-
ization, and transmissions by neurosurgical equipment, including instruments and EEG
depth electrodes, and in recipients of pituitary growth hormone, dura mater or corneal
grafts have been reported.16 Iatrogenic (resulting from the action of a physician) trans-
mission of the CJD agent has been reported in more than 250 patients worldwide.17,18
Unfortunately, the incubation period of vCJD is unknown but could be several decades,
thus it is unlikely that any iatrogenic cases have yet emerged.19
Previous work indicated that prion protein bound to steel wire was resistant to most
conventional reprocessing procedures, including enzymatic cleaning, fixatives, acidic
treatments and autoclaving (steam at 134ºC for 18 minutes combined with enzymatic
cleaning). Because of the unusual resistance of PRPSc, special decontamination procedures
are needed to prevent accidental transmission. Studies have been done in an in vitro car-
rier assay using steel wires contaminated with the disease associated prion protein and
scrapie brain homogenates from hamsters.20,21 The wires were implanted into the brains
of hamsters after treatment for decontamination and subsequently monitored for their
potential to trigger clinical disease or subclinical cerebral PRPSc deposition within an
observable period of 500 days. The most effective treatment consisted of incubating the
wires in 1.0 M NaOH for one hour at 23ºC, 2.5% NaOCl for one hour at 23ºC, an alkaline
cleanser (used at a concentration of 1%) for 10 minutes at 55ºC or 0.2% sodium dodecyl
sulfate (SDS)/0.3% NaOH for 10 minutes at 23ºC led to complete decontamination in
terms of detectable infectivity, as well as to efficient removal of residual brain material
from carriers.22 The authors mention that similar methods should be validated for human
transmissible spongiform encephalopathy agents on different types of instrument sur-
faces. The most stringent chemical and autoclave sterilization methods for transmissible
spongiform encephalopathies are currently outlined in Annex III of the WHO infection
control guidelines.23
Final Thoughts
There is still much to be learned about the mysterious and deadly prion. It was recently
reported that US researchers have discovered a new form of prion disease that does not
act like related illnesses, such as mad cow disease, but instead causes brain damage simi-
lar to that produced by Alzheimer’s disease. In this study, the researchers examined mice
that were genetically engineered to process prion proteins in a unique way.24 Then, they
exposed them to scrapie. The treated mice did not develop holes in the brain like those
typically caused by prion diseases. Instead, they developed plaques that resembled a form
of human Alzheimer’s. If a treatment is found for this new form of prion disease, it may
also be useful in Alzheimer’s disease.
References
1. Thomas L. A Long Line of Cells. Book of the Month Club, New York, New York 1975.
2. Griffin BE. “Unconventional viruses or prions.” BMJ 1985 290(issue?):1765-6.
3. Suppattapone S. “What makes a prion infectious.” Science. 2010 327:1091-2.
4. Taubes G. “The game of the name is fame, but is it science?” Discover. 1986 7(12):28-52.
5. Lemmer K, et al. “Decontamination of surgical instruments from prions. II. In vivo findings with a model
system for testing the removal of scapie infectivity from steel surfaces.” J Gen Virology. 2008 89(issue?):348-358.
6. Harrison PJ,Roberts GW. “How now mad cow?” BMJ. 1992 304(issue?):929-30.
7. Ibid.
8. Kuru Information Page. NINDS website. http://www.ninds.nih.gov/disorders/kuru/kuru.htm. Accessed 17
January 2011.