[Histonet] RE: Prion Contamination

[Sharon Allen]

Hi,
I was reading your email of Jan. 15/09 on the subject of "Prion
Contamination". In it you had made the following statement, which I was
curious as to where this information had come from. 
"the procedure to inactivate using formic acid is followed before
fixation and processing. If the tissue is fixed (formalin or other
common fixatives) then you would be actually "fixing" the prion's
ability to NOT be inactivated". 
I had read again the WHO Guidelines on CJD that you had a link to &
could find no mention of the fact that the formic acid step for
de-activating the prions had to be done before any fixation. The WHO
instructions: P. 18 8.2.2 Histopathological examination: states "formic
acid treatment consists of placing small pieces of fixed tissue, no more
than 4 to 5 mm thick, in 50 to 100 ml of 95% formic acid for an hour". I
have been dealing with CJD brains for many years always following the
CDC, WHO & Health Canada guidelines but have never read any studies that
had indicated that the fixing in formalin made the treatment in formic
acid ineffective. If you have any further information I would really
appreciate seeing it. 
Thank you 
S. Allen
sallen <@t> hsc.mb.ca


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