Surveillance of chronic wasting disease (CWD) in Japan

Abstract

Chronic wasting disease (CWD) in cervids including elk, mule deer, and white-tailed deer, is a member of the transmissible spongiform encephalopathies (TSEs). CWD is a serious problem in North America. The detection of abnormal isoforms of prion protein (PrPSc) is a key factor for the diagnosis of CWD, similar to other TSEs. The surveillance program for TSEs in animals is conducted by the Ministry of Agriculture, Forestry, and Fishery (MAFF) and is targeted to sheep, goats, and deer. In Japan, several different anti-prion protein (PrP) monoclonal antibodies (mAbs) are utilized for bovine spongiform encephalopathy (BSE) confirmation. Since CWD does not occur naturally in Japan, the immunoreactivity of the antibodies against PrPSc found in deer was not known. In this study, we examined the immunoreactivities of these antibodies against PrPSc found in CWD. The protocols that are used in Japan for confirmation of BSE cases are Western blot (WB) and immunohistochemistry (IHC). We used these same protocols to examine CWD positive brain samples which were provided by Dr. A. Davis of the National Veterinary Service Laboratory, USA. Mabs. T1, T2, 44B1, and 72-5, were used successfully to detect PrPSc in CWD affected mule deer brains by WB. In IHC, PrPSc was detected with mAbs T2, 44B1, and polyclonal antibody B103. These results determined that the antibodies used for BSE confirmation are also applicable to CWD, as for scrapie. These same antibodies could detect PrPC from Japanese deer by WB without proteinase digestion. The amino acid sequence of PrP of Japanese deer was found to be the same as sequence as the one reported for mule deer. These antibodies were then used for CWD surveillance in Japan. When 127 of hunter-killed deer from Hokkaido were examined, PrPSc was not detected in any of the animals.