Transmissible spongiform encephalopathies: Assessment of exposure risk in the histological working environment using GC-MS detection of fatty acids as marker for central nervous tissues

Abstract

To elucidate the risk of occupational exposure to the agent of transmissible spongiform encephalopathies (TSE) in the histological working environment, we assessed the principal suitability of three analytical methods for the detection of tissues of the central nervous system (CNT). We tested a neuron-specific enolase (NSE) Western blot, a glial fibrillary acidic protein (GFAP) ELISA and the GC-MS detection of some CNT typical fatty acids (FAs): ω9-tetracosenic acid, ω7-tetracosenic acid, lignoceric acid, and cerebronic acid. Histological sample processing (formalin fixation, dehydration, paraffin embedding) affected both of the immunochemical approaches considerably. The NSE Western blot produced negative results without exception. The results for the GFAP ELISA were better but still far too insensitive. Thus, both methods were judged to be unsuitable in their present form without major analytical adjustment. GC-MS sensitivity remained unaffected by the formalin fixation process. Sensitivity was reduced in the course of the final dehydration step using xylene in the histological sample processing. However, this reduction was found to be rather moderate (range 42–59%) when compared to the immunochemical methods. Overall, we judged GC-MS to be a promising analytical approach for the assessment of a potential TSE exposure risk via airborne CNT particles in the histological working environment. All the FAs we tested showed very low but detectable baseline contents. Thus, cut-off values must be used in the present GC-MS approach. The most suitable FA turned out to be ω9-tetracosenic acid due to the greatest difference between its content in histological CNT samples and the respective cut-off value (689:1). Preliminary results by GC-MS monitoring of CNT via ω9-tetracosenic acid (and other FAs) on filters of routinely used vacuum cleaners and on filters after air sampling indicate that the airborne CNT/TSE exposure risk in the histological laboratory is minor if existing at all. However, further in depth studies will have to validate our preliminary findings and assess these results in the light of possible future data on human oral and/or pulmonary TSE susceptibility.