1.   There is no direct evidence of the prion hypothesis.

2.   According to the prion hypothesis, however, they are caused by misfolded proteins.

3.   Others say the prion hypothesis remains to be proved.

4.   Prusiner countered his critics by saying that no experiment has disproved the prion hypothesis.

5.   The greatest champion of the prions hypothesis is Dr. Stanley Prusiner of the University of California in San Francisco.

6.   The prion hypothesis has never gone down easily among scientists.

7.   Yet, Brown said, the new paper does not disprove the prion hypothesis.