Genetic aspects of unconventional virus infections: the basis of the virino hypothesis.

The properties of genes involved directly or indirectly in the pathogenesis of scrapie and other unconventional (UCV) virus infections are reviewed. Reasons are presented for assigning paramount importance to the Sinc gene in mice and the Sip gene in sheep (the likely homologue of Sinc). The rationale is given for concluding that the agents of UCV infections have their own genomic molecules coding for strain differences. The virino hypothesis, which proposes that the infective form of the agent is an informational hybrid between the agent's genome and protective host proteins, is presented in detail, with an explanation of the postulated role of Sinc.