Validation of a luminescence immunoassay for the detection of PrPSc in brain homogenate

A luminescence immunoassay (LIA) was developed for the diagnosis of bovine spongiform encephalopathy (BSE) in brain tissue using two different monoclonal antibodies for capture and detection of the protease-resistant fragment of the pathological prion protein (PrP27-30). PrP27-30 currently represents the most reliable marker for the infectious particle (denominated prion) causing transmissible spongiform encephalopathies (TSEs). Internal and official validation studies of this assay are described using brain homogenates from ascertained BSE positive and negative cows. Using more than 300 positive and 1400 negative bovine or ovine samples, an excellent sensitivity and specificity of 100% were demonstrated. More than 1000-fold dilutions of a BSE positive homogenate still resulted in a clear positive signal. In combination with a simple homogenisation procedure for the preparation of the samples, this assay lends itself for large scale screening of cattle and sheep for TSEs using complete automation of the process.