Simple and specific detection of abnormal prion protein by a magnetic bead-based immunoassay coupled with laser-induced fluorescence spectrofluorometry.

Transmissible spongiform encephalopathies (TSEs), also termed prion diseases, are fatal neurodegenerative conditions that affect both humans and animals. The transmissibility and fatal nature of TSEs necessitate their rapid and accurate diagnosis. Laser-induced fluorescence (LIF) spectrofluorometry is useful for obtaining measurements on fluorescence-labeled targets with a high degree of sensitivity. In the present study, we applied this technology to the immunological detection of abnormal prion protein, PrPSc, which is a universal diagnostic marker for TSEs. The assay format consists of a magnetic bead-based sandwich immunoassay utilizing a biotin-conjugated capture antibody and a fluorophore-labeled detector antibody. By using one pair of anti-PrP monoclonal antibodies (MAbs), PrPSc in brain homogenates from various experimental and natural TSEs can be easily detected with high specificity. Furthermore, the assay proved to be applicable for the detection of PrPSc in the lymph nodes from deer with TSE. The sensitivity of the assay was shown to be comparable to standard immunoblotting, but has several advantages over conventional tests, in terms of flexibility, simplicity, specificity, and run time. These results provide an important basis for the development of an early diagnostic test with potential for multi-sample analysis.