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The effect of formic acid on BSE and scrapie infectivity in fixed and unfixed brain-tissue
D M Taylor1, J M Brown, K Fernie
1BBSRC and MRC Neuropathogenesis Unit, Institute for Animal Health, Edinburgh, UK.
Abstract:
Brain-tissue infected with scrapie-like agents remains infectious after histological fixation, and represents a source of occupational exposure. Infectivity titres in formol or paraformaldehyde-lysine-periodate (PLP)-fixed mouse-brains infected with the 301V strain of BSE agent were reduced by around six logs following treatment with formic acid. After PLP fixation and formic acid treatment, no infectivity was detectable in mouse-brain infected with the 87V strain of scrapie agent. Similarly-treated mouse-brain infected with the ME7 strain of scrapie agent showed a titre loss of approximately 5 logs. No infectivity was detectable in PLP-fixed, BSE-infected bovine brain after formic acid treatment, but this was an unreliable result. With unfixed brain homogenates, formic acid reduced the titre of ME7 by > or = 5.0 logs; technical problems limited the measured loss of BSE infectivity to > or = 1.0 logs. These studies confirm that formic acid treatment during fixation of brain-tissue significantly reduces the infectivity titres of scrapie-like agents, thus reducing the level of any occupational exposure.
Insights
Formic acid treatment significantly reduces prion infectivity in fixed brain tissue, decreasing occupational exposure risks. This method effectively lowers the infectious agent
Area of Science:
- Neuroscience
- Infectious Diseases
- Biochemistry
Background:
- Brain tissue infected with scrapie-like agents, including Bovine Spongiform Encephalopathy (BSE) and Creutzfeldt-Jakob disease (CJD) agents, remains infectious after standard histological fixation.
- This persistence poses a significant occupational exposure risk for laboratory personnel handling infected tissues.
Purpose of the Study:
- To evaluate the efficacy of formic acid treatment in reducing the infectivity of scrapie-like agents in fixed brain tissues.
- To assess the impact of formic acid on prion infectivity titres in various experimental models, aiming to mitigate occupational hazards.
Main Methods:
- Infectivity titres of scrapie-like agents (BSE 301V, scrapie 87V, scrapie ME7) were measured in mouse brains fixed with formol or paraformaldehyde-lysine-periodate (PLP).
- Fixed and unfixed brain homogenates were treated with formic acid.
- Infectivity was quantified by log titre reduction following formic acid treatment.
Main Results:
- Formic acid treatment reduced infectivity titres by approximately six logs in PLP-fixed mouse brains infected with BSE 301V.
- No detectable infectivity remained in PLP-fixed, formic acid-treated mouse brains infected with scrapie 87V or BSE.
- Significant titre reductions (around 5 logs) were observed for scrapie ME7 in both fixed and unfixed brain homogenates.
Conclusions:
- Formic acid treatment is a highly effective method for significantly reducing the infectivity of scrapie-like agents in fixed brain tissue.
- This decontamination strategy substantially lowers the risk of occupational exposure to infectious prions during histological procedures.