title: Rapid assessment of bovine spongiform encephalopathy prion inactivation by heat treatment in yellow grease produced in the industrial manufacturing process of meat and bone meals.
abstract: BACKGROUND
  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 sterilizing processes, the cause of bovine spongiform encephalopathy (BSE) outbreaks are suspected to be feeding cattle meat and bone meals (MBMs) contaminated with the prion. To assess the validity of prion inactivation by heat treatment in yellow grease, which is produced in the industrial manufacturing process of MBMs, we pooled, homogenized, and heat treated the spinal cords of BSE-infected cows under various experimental conditions.
  
  
  RESULTS
  Prion inactivation was analyzed quantitatively in terms of the infectivity and PrPSc of the treated samples. Following treatment at 140°C for 1 h, infectivity was reduced to 1/35 of that of the untreated samples. Treatment at 180°C for 3 h was required to reduce infectivity. However, PrPSc was detected in all heat-treated samples by using the protein misfolding cyclic amplification (PMCA) technique, which amplifies PrPScin vitro. Quantitative analysis of the inactivation efficiency of BSE PrPSc was possible with the introduction of the PMCA50, which is the dilution ratio of 10% homogenate needed to yield 50% positivity for PrPSc in amplified samples.
  
  
  CONCLUSIONS
  Log PMCA50 exhibited a strong linear correlation with the transmission rate in the bioassay; infectivity was no longer detected when the log PMCA50 of the inoculated sample was reduced to 1.75. The quantitative PMCA assay may be useful for safety evaluation for recycling and effective utilization of MBMs as an organic resource.
authors.forename: Miyako
authors.initials: M
authors.lastname: Yoshioka
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okada
authors.forename: Noriko
authors.initials: N
authors.lastname: Shimozaki
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Yamamura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Murayama
authors.forename: Takashi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Shirou
authors.initials: S
authors.lastname: Mohri
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D001688:Biological Products / Q000378:metabolism; D015153:Blotting, Western / Q000662:veterinary; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D016643:Encephalopathy, Bovine Spongiform / Q000517:prevention & control*; D006651:Histocytochemistry / Q000662:veterinary; D006358:Hot Temperature; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008903:Minerals / Q000378:metabolism*; D018620:PrPSc Proteins / Q000032:analysis / Q000378:metabolism*
chemical_list: D001688:Biological Products; D008903:Minerals; D018620:PrPSc Proteins; C027762:bone meal