Prions, infectious agents associated with transmissible spongiform encephalopathy, are primarily composed of the misfolded and pathogenic form (PrPSc) of the host- encoded prion protein. Because PrPSc retains infectivity after undergoing routine sterilization processes, bovine spongiform encephalopathy (BSE) outbreaks are suspected to be caused by feeding cattle prion-contaminated meat and bone meals (MBMs). To assess the validity of prion inactivation by heat treatment in yellow grease, which is produced the industrial manufacturing process of MBMs, we pooled, homogenized, and heat-treated the spinal cords of BSE-infected cows under various experimental conditions. Prion inactivation was analysed quantitatively in terms of the infectivity and the PrPSc content of the treated samples. Following treatment at 140°C for 1 h, infectivity decreased to 1/35 of that of the untreated samples. Treatment at 180°C for 3 h was required to reduce infectivity to 0%. However, PrPSc was detected in all heat-treated samples by using the protein misfolding cyclic amplification (PMCA) technique, which amplifies PrPSc in vitro. The results of quantitative analysis of the inactivation efficiency of BSE PrPSc by using PMCA exhibited a strong linear correlation with the transmission rate in the bioassay. The quantitative PMCA assay may be useful in safety evaluation for recycling and effective utilization of MBMs as an organic resource.
(Pathology and Pathophysiology Research Division)
Yoshioka M. et al (2013) BMC Vet. Res. 9(1):134