2008 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project with Dr. Maria Caramelli from the Italian BSE Reference Laboratory in Turin, Italy, is to conduct comparative studies with the U.S. bovine spongiform encephalopathy (BSE) isolate and the atypical BSE isolates identified in Italy. The studies will cover the following areas: 1. Evaluation of present diagnostics tools used in the U.S. for the detection of atypical BSE cases. 2. Molecular comparison of the U.S. BSE isolate and other typical BSE isolates with atypical BSE cases. 3. Studies on transmissibility and tissue distribution of atypical BSE isolates in cattle and other species. 1b.Approach (from AD-416) This project will be done as a Specific Cooperative Agreement with the Italian BSE Reference Laboratory, Istituto Zooprofilattico Sperimentale del Piemonte, in Turin, Italy. It is essential for the U.S. BSE surveillance program to analyze the effectiveness of the U.S diagnostic tools for detection of atypical cases of BSE. Molecular comparisons of the U.S. BSE isolate with atypical BSE isolates will provide further characterization of the U.S. BSE isolate. Transmission studies are already underway using brain homogenates from atypical BSE cases into mice, cattle and sheep. It will be critical to see whether the atypical BSE isolates behave similarly to typical BSE isolates in terms of transmissibility and disease pathogenesis. If transmission occurs, tissue distribution comparisons will be made between cattle infected with the atypical BSE isolate and the U.S. BSE isolate. Differences in tissue distribution could require new regulations regarding specific risk material (SRM) removal. 3.Progress Report The aim of the cooperative research project "Study of atypical BSE" led by CEA (Italian Reference Centre for Animal TSE) and USDA is to compare Italian and U.S. Bovine sponigiform encephalopathy (BSE) confirmatory protocols in the detection of classical (C-) and atypical (H- and L-type) BSE cases. In the course of this project samples of Italian C-BSE and Italian L-type BSE (BASE), both frozen and formalin fixed, have been sent to USDA laboratories in Ames, to undergo Western blot and Immunohstochemical (IHC) comparison studies for PrP**Sc detection according to U.S. and Italian methods. In 2007, the comparative study between U.S. and Italian BSE confirmatory protocols was performed. The collaborator sent a scientist to Ames to assist in performing the Italian IHC protocol on the BSE samples chosen for the study. Results obtained showed that the Italian and U.S. IHC procedures were alike in PrP**Sc detection regarding its distribution, deposition pattern and intensity of staining on all the C-, L- and H-type BSE cases considered. In addition, the U.S. protocol evidenced the characteristic presence of plaques in the frontal cortex of the Italian BASE case similar to the Italian protocol. Methods used for monitoring include email, site visits, and periodic written reports. This project addresses NP 103, component 8.