Application of Real-Time Quaking-Induced Conversion assay to investigate the presence of pathological prion protein in extra-neural tissues of cattle with natural Low BSE.

Introduction. Three BSE strains are now known: Classical BSE (C-BSE) and two atypical forms named High BSE (H-BSE) and Low BSE (L-BSE). C-BSE is the best known unlike the atypical forms. Currently there is very little information on the peripheral distribution of the pathological prion protein (PrP^Sc) in cattle with naturally occurring atypical BSE. Epidemiological data suggest a spontaneous origin of atypical BSE cases and therefore their eradication is impossible. Furthermore, the relationship between C-BSE and vCJD triggers worries about food safety. Thus monitoring BSE in cattle using highly sensitive methods is important to reduce the risk of contaminated meat entering the food chain.

Objectives. To develop and standardize suitable protocols to investigate the distribution of PrP^Sc in the peripheral tissues of cattle with natural L-BSE by using Real-Time Quaking-Induced Conversion (RT-QuIC) assay.

Methods. RT-QuIC analyses were carried out on the brain, several peripheral tissues and edible organs collected from Italian cattle with natural L-BSE.

Results and Discussion. Seeding activity was observed in the skeletal muscles of cattle with L-BSE; while none was detected in any of the other tissues and organs, suggesting a neuromuscular tropism of the L-BSE agent. According to our previous studies, although it has not been possible to quantify the pathological marker, it is likely that skeletal muscles may harbour L-BSE infectivity.

Conclusion. Our results confirm the need to have a systematic surveillance of the bovine population destined for slaughter in order to promptly identify atypical BSE cases and eliminate them from the food chain.