The 'infective' process in scrapie and human spongiform encephalopathy disease

It is suggested that spongiform encephalopathy (SE) disease transmission does not occur by any classically defined 'infective' process. Rather, it is the case that conformationally altered prions in diseased animals are able, by targeting what may be an inherited, widely distributed, endogenous retroviral fragment, comprising the prion 'gene' system, to initiate the escalating synthesis of similar, but host-specified protein. Both initiation and the resulting progression are controlled and regulated by endogenous host genetic and other factors. While the prion system appears to be primarily involved, the intrinsic sequences of the invading prions also have a role in what appears to be a joint operation. A parallel may be drawn with EAE in that the disease is initiated by a small (myelin basic) protein, and in which, similarly, the ongoing process is host-specified, and regulated by genetic and other factors. The presence of polynucleotide in 'infective' inocula is probably unnecessary, if not irrelevant.