Immunochemical detection of tissue from the central nervous system via myelin proteolipid protein: adaptation for food inspection and development of recombinant bivalent Fab mini-antibodies.

Bovine spongiform encephalopathy (BSE) is transmitted by the ingestion of central nervous system (CNS) tissue of infected animals. Food inspection must, therefore, test for the presence of CNS tissue in meat and meat products. A Western blot assay for the specific CNS tissue marker myelin proteolipid protein (PLP) was optimized with considerably reduced analysis time, solvent consumption, and detection limit (0.001% CNS tissue in minced beef). Further, a PLP-specific recombinant bivalent fragment antigen binding mini-antibody (anti-PLP Fab) was obtained from a commercial phage display library. Western blot analysis with the anti-PLP Fab selectively detected CNS tissue in minced beef with a detection limit of 0.025%. Model experiments for meat processing revealed that assay sensitivity decreased with increasing temperature and prolonged heating time. A market survey with 687 sausage samples was performed using PLP-Western blot and enzyme-linked immunosorbent assay (ELISA) for glial fibrillary acidic protein (GFAP). Five samples were tested clearly positive by both assay systems, whereas in an additional six samples, CNS tissue was detected only by GFAP ELISA and in two samples only by PLP-Western blot.