Location: Virus and Prion Research2010 Annual Report
1a. Objectives (from AD-416)
Obj. 1. Assess the cross species transmissibility of transmissible spongiform encephalopathies (TSEs) in livestock and wildlife. Obj. 2. Investigate the pathobiology of TSEs in natural and secondary hosts. Obj. 3. Investigate pathogenesis and ante mortem detection of bovine spongiform encephalopathy (BSE). Obj. 4. Develop a method to detect central nervous system (CNS) tissue contamination on carcasses. Obj. 5. Discover effective methods to inactivate TSE agents in agricultural settings.
1b. Approach (from AD-416)
Studies are focused on the four animal Transmissible Spongiform Encephalopathy (TSE) agents found in the United States: bovine spongiform encephalopathy (BSE); scrapie of sheep and goats; chronic wasting disease (CWD) of deer, elk, and moose; and transmissible mink encephalopathy (TME). These agents will be tested for cross-species transmissibility into various livestock and cervid species using both oral and intracerebral inoculation. Sites of accumulation, routes of infection, methods of isolate differentiation, and in the case of BSE, genetics of susceptibility and ante-mortem diagnostics, will be investigated. Existing technology developed at the National Animal Disease Center and those used in the meat packing industry for the detection of fecal contamination on carcasses will be adapted to detect CNS tissue contamination on carcasses. Methods of TSE inactivation will be evaluated for efficacy in agricultural settings.
3. Progress Report
The project plan involves 5 objectives: 1) Assess cross-species transmissibility of transmisible spongiform encephalopathy (TSEs) in livestock and wildlife; 2) Investigate the pathobiology of TSEs in natural and secondary hosts; 3) Investigate pathogenesis and antemortem detection of bovine spongiform encephalopathy (BSE); 4) Develop a method to detect central nervous system (CNS) tissue contamination on carcasses; and 5) Determine effective methods to inactivate TSE agents in agricultural settings. In meeting objective 1 of our project plan, Assess cross-species transmissibility of TSEs in livestock and wildlife, numerous experiments assessing the susceptibility of various TSEs in different host species have been initiated and are ongoing. Ability to initiate additional experiments is dependent upon the completion of the previous year(s) experiments, and at the initiation of such experiments they have a planned timeframe of 60 months unless disease develops prior to that time. Pertaining to objective 2, deer were previously inoculated with blood from chronic wasting disease (CWD) -affected deer. At this time, several animals have developed clinical signs consistent with CWD. Approaches to strain typing of various TSE agents by biochemical means have been successful but with challenges associated with different genetic backgrounds. In order to meet research goals described in objective 3, Investigate pathogenesis and antemortem detection of BSE, classical and atypical BSE isolates have been inoculated into cattle. While work is ongoing to increase the number of animals containing the E211K polymorphism, a potential cause of genetic BSE, this will provide the only means by which to prove that the polymorphism may cause BSE. Objective 4, Develop a method to detect CNS tissue contamination on carcasses, has been completed. Objective 5, Determine effective methods to inactivate TSE agents in agricultural settings: laboratory investigations of TSE inactivation have been initiated and the results utilized to design animal bioassays to confirm the preliminary results. In addition, a natural host model for use in TSE inactivation is being investigated. Such a model would provide a much-needed tool in the development of inactivants for TSEs.
1. Inoculation of domestic and European bovine spongiform encephalopathy (BSE) isolates into cattle. To date, no side-by-side comparison of domestic BSE has been made with European BSE isolates. Between February 16-18, 2010, ARS researchers at Ames, Iowa, inoculated cattle with domestic and European BSE isolates. This study is expected to last at least 2 years before all animals will show signs of clinical disease and will provide the first direct comparison of these isolates and provide sufficient material for future studies of BSE. The start of research efforts on 24 milestones characterizing atypical versus classical BSE are dependent on tissues obtained at the completion of this animal study.
2. Production of cattle containing the rare 211K PRNP allele associated with genetic bovine spongiform encephalopathy (BSE). The 211K PRNP allele identified as being associated with genetic BSE had been identified in only 1 living animal, limiting the ability to actively study the impact of this allele on BSE. ARS researchers at Ames, Iowa, with cooperators at Iowa State University, produced 13 calves to date (about half containing this allele) using superovulation and embryo transfer. Production of these calves initiates a long-term animal study testing the hypothesis that this rare, naturally-occurring allele is a cause of genetic BSE in older cattle. This also enables ARS scientists to expand and preserve a unique scientific resource for the study of BSE as some of these calves are now being used to expand the pool of infectious BSE material from the Alabama 2006 BSE case, which is another resource in limited supply, and will ultimately allow proof of the existence of genetic BSE.
Adhikary, R., Mukherjee, P., Krishnamoorthy, G., Kunkle, R.A., Casey, T.A., Rasmussen, M.A., Petrich, J.W. 2010. Fluorescence Spectroscopy of the Retina for Diagnosis of Transmissible Spongiform Encephalopathies. Analytical Chemistry. 82(10):4097-4101.