Straining the prion hypothesis

Aguzzi and Weissmann in their News and Views feature1 correctly state that research on the molecular genetics of PrP protein has contributed greatly to our knowledge of the transmissible spongiform encephalopathies (TSEs). But their firm belief that these diseases are caused by rogue proteins (‘prions’) leads them to misrepresent alternative hypotheses of the nature of the agent, dismissing all non-believers as “the die-hard pro-virus faction”1. In fact, the prion hypothesis is far from proven: the precise nature of a prion still eludes identification and the prion hypothesis has yet to explain satisfactorily the many strains of TSE2. The alternative ‘virino’ hypothesis is not a conventional virus hypothesis, but it addresses the diversity of biological properties of the TSEs2. It proposes an agent-specific replicable informational molecule, yet to be identified, bound to a protective host protein, PrP.