2005 Annual Report 4d.Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and the Italian Reference Centre for Animal TSE (CEA) at the Istituto Zooprofilattico Sperimentale, Turin, Italy. Additional details of research can be found in then report for the parent project 3625-32000-073-00D, Transmission, Differentiation, and Pathobiology of Transmissible Spongiform Encephalopathies. The aim of the cooperative research project conducted by the CEA and ARS is to compare the U.S. bovine spongiform encephalopathy (BSE) isolate and the bovine amyloidotic spongiform encephalopathy isolates (BASE) identified in Italy. The first objective was to determine whether diagnostic methods routinely used by USDA are able to identify the Italian BASE cases. For this purpose, CEA received the immunohistochemistry (IHC) protocol developed by APHIS-USDA. The IHC protocol was reproduced and standardized in the CEA laboratory and will be applied to the Italian BSE and BASE cases. Furthermore, fixed brainstem sections and frozen brainstem material from Italian BSE and BASE cases will be sent to ARS for analysis using USDA IHC and Western blot (WB) methods. These studies will enable us to determine whether the present diagnostic tools (IHC and WB) employed at the USDA will be able to detect the Italian BASE cases and also enable us to compare Italian BSE and BASE with the U.S. BSE cases.