An enzyme-linked immunosorbent assay for glial fibrillary acidic protein as an indicator of the presence of brain or spinal cord in meat

The current methods to detect central nervous system (CNS) tissue in blood, lungs, or meat are cumbersome, time consuming, and costly. The objective o f this study was to use glial fibrillary acidic protein (GFAP), which is re stricted to the CNS, in an enzyme-linked immunosorbent assay (ELISA) for th e detection of CNS tissue in blood and muscle from beef cattle. Bovine brai n, cerebral cortex, spinal cord, sciatic nerve, diaphragm, blood clots, and other skeletal muscle were obtained from three animals at slaughter. The l imit for detection of GFAP was approximately 1.0 ng and the standard curve was linear up to 40 ng. Tissue samples gave responses parallel to the GFAP standard, suggesting that standard and unknown samples were immunoreactivel y identical. No GFAP was detected in skeletal muscle (ground beef, shoulder clod, and diaphragm) and blood clots. Trace amounts (13.5 to 51 ng/mg) wer e present in sciatic nerve. In contrast, high levels of GFAP (55 to 220 mu g/mg) were present in spinal cord, cerebral cortex (17 mu g/mg); and whole brain (9 to 55 mu g/mg). In a storage study using two animals in two separa te studies, immunoreactive GFAP was detectable for up to 8 days at 4 degree s C in all tissues containing neural elements. Thus, mixtures of muscle wit h spinal cord or brain retained almost 80% of their immunoreactivity after 8 days at 4 degrees C, while brain and spinal cord alone retained approxima tely 50% and 25%, respectively, of their initial activities. In a repeat ex periment, 80 to 100% of the initial activity was retained in these tissues after 8 days at 4 degrees C. The results of the current study demonstrate t hat the GFAP ELISA provides a valid and repeatable method to detect CNS tis sue contamination in meat.