"The fact the PrP isn't taken up by the Peyer's nodules questions whether PrP is really infectious, or whether PrP is really just a secondary marker of the presence of the scrapie agent," says Jeffrey.
His belief in this need to reappraise the fundamental understanding of prion diseases is enhanced by one more observation published in this same paper. The team pre-digested a mixture containing disease specific PrP with standard stomach contents, and then injected the resulting mixture into the gut. No PrP transferred into the villi. When they used a highly sensitive version of Western Blot analysis to examine the contents of this pre-digested mixture, they found only the faintest suggestion that some of the PrP had survived. This was despite the fact that the original mixture had a contained a high level of PrP.
"Think about it ?a sheep grazing in a field is not naturally exposed to highly infected brain and could only pick up a tiny amount of PrP from other tissues. This will then be exposed to 48 hours or more digestion before it arrives in the gut, and our experiments show that after this, the chance of there being more than an unmeasurably small amount of PrP left to absorb is very small," says Jeffrey.
"As sheep can become infected, the theoretical probability of this being due to an invisible sub-fraction of digestion resistant PrP molecules is unlikely. The possibility of there being infectious molecules other than PrP must therefore be seriously considered," says Jeffrey.
"A lot of people are completely wedded to the prion hypothesis of diseases like vCJD, but the more you deal with whole animals as opposed to relying purely on in vitro studies, the more cautious you are about saying that prion proteins alone cause the disease," says Martin Jeffrey.
In a commentary published in the same edition of the jo
Source:John Wiley & Sons, Inc.