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SUNDAY, FEBRUARY 11
5:00 - 6:00 pm Early Registration
MONDAY, FEBRUARY 12
7:30 am Registration, Morning Coffee |
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Emerging Concerns
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8:30 Welcome by Session Chairperson
Paul W. Brown, M.D.
8:45 Variant CJD: The End of the Beginning or the Beginning of the End?
Robert G. Will, M.D., National CJD Surveillance Unit, University of Edinburgh
Variant CJD incidence has been in decline in the UK since 1999 and the feared epidemic of this zoonotic disease has not yet materialized. A number of other countries have identified cases of vCJD, notably in France, but the overall non-UK incidence of vCJD is not increasing markedly. There is good evidence indicating that vCJD can be iatrogenically transmitted through blood transfusion but it is unlikely that this route of transmission will lead to a self-sustaining outbreak. Public health concerns are therefore in decline, but because of the potentially extended incubation periods, it will be many years before further outbreaks of vCJD can be excluded, for example through alternative mechanisms of transmission.
9:15 Sporadic CJD: Does Transmission through Blood Occur?
Maurizio Pocchiari, Ph.D., Director of Research-Virology, Istituto Superiore Di Sanita (Italy)
9:45 The 'Spontaneous' BSE Issue: Pros, Cons, and Strategies to Test the Hypothesis
Paul W. Brown, M.D.
Strategies to investigate the possible existence of sporadic BSE require systematic testing programs to identify cases in countries considered to have little or no risk of orally-acquired disease, or to detect a stable occurrence of atypical cases in countries in which orally-acquired disease is disappearing. To achieve 95% statistical confidence that the prevalence of sporadic BSE is no greater than one per million (i.e., the annual incidence of sporadic Creutzfeldt-Jakob disease in humans) would require negative tests in three million randomly selected older cattle. A link between atypical BSE and sporadic CJD, suggested by some laboratory studies but unsupported by epidemiological observation, might yet be established by the discovery of a specific molecular marker, or by trends in the incidence of atypical BSE and sporadic CJD.
10:15 Coffee Break, Poster and Exhibit Viewing in the
Exhibit Hall
10:45 Discrimination between CWD, BSE and Scrapie Strains:
An Evaluation of Tests
Michael Stack, Senior Researcher, TSE Molecular Biology, Veterinary Laboratories Agency
Bovine spongiform encephalopathy (BSE) has been implicated as the cause of the appearance in humans of new variant In Great Britain, during the 1980s, it is possible that BSE-contaminated meat and bone meal may have been fed to sheep, raising the possibility that BSE could have been transmitted to the national sheep flock, and could therefore be a potential secondary threat to public health. Molecular and immunohistochemical techniques which can discriminate between experimental BSE in sheep, and natural scrapie cases have been developed and evaluated in blinded ring trials. Increased surveillance for Transmissible Spongiform Encephalopathies (TSEs) in cervid populations across Europe is planned to start in 2007, and if a disease such as Chronic Wasting Disease (CWD) is discovered, one of the first questions would be whether the molecular profile is similar to that found for North American CWD cases, or could there have been contact with the agents of BSE or scrapie resulting in a change of disease profile? The tests evaluated in the blinded ring trials in Europe also offer potential discrimination between CWD and other animal TSEs, and could therefore be used to rule out BSE in cervids as another possible secondary threat to public health. This presentation will describe the principles of discrimination and the evaluation results obtained so far. |
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New Research Directions
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Session Chairperson:
Suzette A. Priola, Ph.D., Senior Investigator, Chief, TSE/Prion Molecular Biology Section, National Institutes of Health, NIAID, Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories
11:15 Developing Cell Cultures for Prion Studies
Sylvain Lehmann, Professor, Institut de Génétique Humaine du CNRS
Cell cultures susceptible to TSE agents represent relevant and useful experimental models for Prion studies. They have been used in particular to study TSE molecular events and to develop and validate innovative therapeutic approaches. More recently, prion infected cell culture models have been considered as an alternative to animal bioassays to detect the presence of infectivity. In fact, it was possible to obtain in specific cell culture paradigms a reliable and highly sensitive detection of prions that was much faster and at a lesser cost than in animals. Nevertheless, many problems persist with the use of these cell culture models including their standardization or the range of prion species and strains that they can detect.
11:45 Retroviral Infection Strongly Enhances the Release of Scrapie Infectivity in Cell Culture
Pascal LeBlanc, Ph.D., LaboRetro unité de virologie humaine, INSERM
Although there is much evidence to suggest that PrPSc, a misfolded form of the cellular prion protein PrPC, is the infectious agent of prion diseases, the mechanism of PrPSc transmission and the factors that affect its spread remain unknown. Here we show that the release of PrPSc from scrapie-infected cells is markedly enhanced by retroviral infection, implicating retroviruses in the spread of prion diseases and providing mechanistic insights into prion transmission.
12:15 Lunch on Your Own
(Luncheon Technology Workshops Available) |
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Infectivity
and Transmission
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1:20 Comments by Session Chairpersons
Kiki B. Hellman, Ph.D., President & Founder, The Hellman Group, LLC
Suzette A. Priola, Ph.D., Senior Investigator, Chief, TSE/Prion Molecular Biology Section, National Institutes of Health, NIAID, Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories
1:30 Infectivity in Urine of Hamsters Infected with Scrapie
Luisa Gregori, Ph.D., Assistant Director and Assistant Professor, VA Research Services and University of Maryland, BREF
Horizontal transmission from animal to animal of Transmissible Spongiform Encephalopathies (TSE) has been documented in the wild and in laboratory animals. The cause(s) of this transmission is not fully understood, although bodily excretions such as urine and feces are often proposed as potential sources of secondary exposure leading to horizontal transmissions. We report here on our investigation on infectivity in urine of TSE infected animals. Urine from hamsters infected with the 263K strain of scrapie was collected using metabolic cages and titered by intracerebral inoculation in the same animal species with the limiting dilution method. Five-ml equivalents of urine (diluted 1:3) were inoculated. After 357 days post inoculation, 11 animals developed scrapie with a titer of 2.3 +/- 0.4 ID/ml. No infectious have been observed in the cohort of animals inoculated with urine from control animals. Ten percent bladder and kidney tissue homogenates from infected hamsters were also titered using the end point titration method. At 343 days, the titers are 10(5.5) and 10(4.8) ID50/g for bladder and kidney, respectively. These results propose a new pathway of infection of the natural environment. The implications are far reaching from environmental contamination of pastures in the wild to risk management of domestic livestock and the safety of urine-derived therapeutic products.
2:00 Soil Minerals Enhance Prion Infectivity
Judd M. Aiken, DVM, Professor, Animal Health & Biomedical Sciences, University of Wisconsin-Madison, School of Veterinary Medicine
We have recently demonstrated that prions bind clay and silica. The binding of PrPSc to a common soil clay (montmorillonite) is avid and this interaction enhances infectivity. The implications of this enhancement of transmission are far-reaching and include how scrapie and CWD are environmentally transmitted. The ramifications of these findings with regard to food safely will also be discussed.
2:30 Transmission of BSE-301v Following Infection from the Small Intestine: A New Model for Investigating Iatrogenic Transmission Risks for vCJD
James Walker, Ph.D., Senior Project Manager, TSE Research Group, Health Protection Agency
The study explores the use of a novel challenge model designed to provide information on the levels of infectivity of tissues following infection from the small intestine. The model uses direct challenge via the small intestine to prevent the contamination of the oral cavity by the primary inoculum. Groups of VM mice (n=10) were inoculated with 100ul of 2% w/v BSE-301v infected brain homogenate directly into the small intestine and sacrificed at 3, 6, 9, 12, 15, 18, 21 weeks post-inoculation. Tissues including spleen, saliva, salivary gland, trigeminal ganglia, gingival margin, alveolar bone, dental pulp, posterior tongue, anterior tongue, and brain were removed at the appropriate time points and re-inoculated (intra-cranially) into groups of mice (n=6) which were sacrificed at a clinical end point. Results to date indicate that brain and spleen from mice inoculated via this route became infectious very early in the course of disease progression and achieved maximum infectious titers well before clinical symptoms became apparent. Western blot analysis for the presence of PrPSc in the brain samples does not correlate well with the levels of infectivity and this is currently being investigated further. These results will be discussed in connection with our understanding of the iatrogenic transmission.
3:00 Afternoon Refreshment Break, Poster and Exhibit Viewing in the Exhibit Hall
3:30 Transmission of the Italian Atypical BSE (BASE) in Humanized Mouse Models
Qingzhong Kong, Ph.D., Assistant Professor, Pathology, Case Western Reserve University
Bovine Amyloid Spongiform Encephalopathy (BASE) is an atypical BSE strain discovered recently in Italy, and similar or different atypical BSE cases were also reported in other countries. The infectivity and phenotypes of these atypical BSE strains in humans are unknown. In collaboration with Pierluigi Gambetti, as well as Maria Caramelli and her co-workers, we have inoculated transgenic mice expressing human prion protein with brain homogenates from BASE or BSE infected cattle. Our data shows that about half of the BASE-inoculated mice became infected with an average incubation time of about 19 months; in contrast, none of the BSE-inoculated mice appear to be infected after more than 2 years. These results indicate that BASE is transmissible to humans and suggest that BASE is more virulent than classical BSE in humans.
| 4:00
Production of Cattle Lacking Prion Protein |
Sponsored
by
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Jerry
Pommer, MS, Senior Director of Quality
Systems/Regulatory Affairs, Hematech, Inc.
Disruption of PrPC expression in mice, a species
that does not naturally contract prion diseases,
results in no apparent development abnormalities.
However, the impact of ablating PrPC function in
natural host species of prion diseases is unknown.
Here we report the generation and characterization
of PrPC-deficient cattle produced by a sequential
gene-targeting system. At 2 years of age, the cattle
are clinically, physiologically, histopathologically,
immunologically and reproductively, normal. Brain
tissue homogenates are resistant to prion
propagation in vitro, as assessed by a protein
misfolding cyclic amplification assay. PrPC-deficient
cattle may be a useful model for prion research and
could provide industrial bovine products free of
prion proteins. |
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4:15 Regulatory Panel Discussion:
Answers to the Regulatory Questions Regarding TSEs
David M. Asher, M.D., Laboratory Chief, Laboratory of Methods Development, FDA
Daniel Engeljohn, Ph.D., Deputy Assistant Administrator,
USDA FSIS OPPED, USDA
Morris Potter, DVM, HHS CFSAN OSCI, FDA
Richard Wiggins, Ph.D., Senior Science Advisor, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. EPA
5:30 Networking Reception in Exhibit Hall
6:30 Close of Day One |
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