Project Summary

Improving Sensitivity, Precision, and Repeatability of the GFAP-ELISA for Detecting CNS Contamination in AMR-generated Tissues Compared to the Immunohistochemical Protocol Used by USDA-FSIS

Principle Investigator(s):
Kim L. Hossner, Keith E. Belk, Robert S. Yemm, Gary L. Mason, Bruce A. Cummings, Stacey Sonnenshein, M. C. S. Reddy, John N. Sofos, John A. Scanga, J. Daryl Tatum, Gary C. Smith
Colorado State University
Completion Date:
May 2003



The presence of brain or spinal cord as an inadvertent contaminant of meat may result from the stunning of livestock, the splitting of the carcass or the preparation of advanced meat recovery (AMR) products from the vertebral column. In light of current consumer concern about bovine spongiform encephalopathy (BSE), a disease transmitted by consumption of central nervous system (CNS) tissue, a reliable analytical test for CNS tissue in meat products is essential to ensure consumer confidence and allay consumer fears of BSE agents in meat products. 

A method to detect the presence of CNS tissue in meat products has been developed. The method uses a fluorimetric enzyme-linked immunosorbent assay (F-ELISA) for the detection of glial fibrillary acidic protein (GFAP), an antigen which is highly, but not completely, restricted to astrocytes and satellite cells in the CNS. The F-ELISA was sensitive to 0.2ng GFAP, had an intra-assay coefficient of variation (CV) of 2.0% and an inter-assay CV of 14.1%. Bovine spinal cord and brain demonstrated dose-response curves which were parallel to GFAP standards, while peripheral sciatic nerve and cervical ganglia also cross-react at very high concentrations. Using this assay, levels of GFAP in bovine tissues were measured of approximately 2,000ng/mg in spinal cord, 600ng/mg in brain, 12ng/mg in sciatic nerve and 2-4ng/mg in cervical dorsal root ganglia. A comparison of this method with the Ridascreen ELISA and an earlier colorimetric GFAP ELISA has been published.

The CSU F-ELISA provides a method to detect small amounts of CNS tissue in meat products which is simple, cost-effective and efficient. This assay forms the basis for a commercially available kit for the detection of CNS tissue in meat products, the 10/5 Ridascreen assay developed by R-Biopharm AG.

This study was designed to compare three methods for detecting CNS tissue in AMR-generated comminuted beef –that differ in either sampling protocol or laboratory testing methodology – for their sensitivity, repeatability and precision. These methods are: 1. The Colorado State University F-ELISA for GFAP; 2. The R-biopharm GFAP-ELISA; and 3. The USDA Eastern Laboratory immunohistochemical procedure. In addition, modifications of the commercial R-Biopharm protocol were examined to improve its sensitivity, repeatability and precision.

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