The article discusses the study on infectious prions that cross species barriers to cause diseases by Castilla and colleagues. Prions cause transmissible spongiform encephalopathies and it contain misfolded form (PrPsc). The experiment use protein misfolding cyclic amplification (PCMA), an optimal version of polymerized chain reaction-like technique. It cites that the study offers evidence that transmission of prions across species barriers can cause diseases with different pathology.