This study is looking at the appendix, not any brain tissue. Without considering symptoms, it's possible that altered PrP expression and/or folding in the appendix does not cause vCJD or result from exposure to PrP(Sc).
Also, these antibodies are not very selective for a given confirmation. Idk how this made it into the BMJ because standard in the PrP field is a protease resistance assay given the issues with Ab specificity.
This article is from the UK National Centre for Infectious Disease Surveillance and Control and is cited by by the NHS and widely in the literature.
I am not an expert in the field, but it seems relevant to consider latent or asymptomatic PrP expression when assessing how often it crosses the species barrier.
Also, these antibodies are not very selective for a given confirmation. Idk how this made it into the BMJ because standard in the PrP field is a protease resistance assay given the issues with Ab specificity.