You have to remember, as TexasTom wrote, that it is misfolded a-syn that is the culprit, not properly folded a-syn which is an essential protein that enables neurotransmitters in the body. Another issue is, which TexasTom didn't get exactly right, is that misfolded a-syn is not an actual prion (e.g. Creutzfeldt-Jakob disease), but rather prion-like. There is a difference as a prion is self-derived, self-sustaining, and infectious. Alpha synuclein, being prion-like, is believed like other neurological misfolded proteins (e.g. amyloid, tau, etc.) to be what is now referred to as a transcellular prionoid. Prionoids are proteins that demonstrate prion-like propagation between cells within a disease context (e;g. Alzheimer's or PD) but have limited evidence for organism infection or transmission.

PubMed Central Image Viewer.

With regard to blood filtering, it would the misfolded prionoid a-syn that you would want to remove, not necessarily all a-syn. This is what the vaccines we have been following target. I'm not aware of any research showing that people on dialysis have a lower instance of Parkinson's. Alternatively, I have seen research that shows that people with end-stage-renal-disease (ESRD) have a significantly higher chance of developing PD. These people would all be on dialysis.

Great analysis Tupelo. The Parkinson's blood filter would require the dialysis filtration to be changed to filter out AS not blood/kidney toxins. Reducing misfolded AS seems to be the goal, although I'm not sure present technology can filter out only misfolded AS using an assay. I think the idea with Prothena is to reduce overall AS in the hopes that will result in lower misfolded AS and thus improve symptoms. Everyone has AS so I'm not sure what levels of AS are considered to be normal. Perhaps these studies on AS will determine that.