The Strain-Encoded Relationship between PrPSc Replication, Stability and Processing in Neurons is Predictive of the Incubation Period of Disease

Prion strains are characterized by differences in the outcome of disease, most notably incubation period and neuropathological features. While it is established that the disease specific isoform of the prion protein, PrP Sc , is an essential component of the infectious agent, the strain-specific relationship between PrP Sc properties and the biological features of the resulting disease is not clear. To investigate this relationship, we examined the amplification efficiency and conformational stability of PrP Sc from eight hamster-adapted prion strains and compared it to the resulting incubation period of disease and processing of PrP Sc in neurons and glia. We found that short incubation period strains were characterized by more efficient PrP Sc amplification and higher PrP Sc conformational stabilities compared to long incubation period strains. In the CNS, the short incubation period strains were characterized by the accumulation of N-terminally truncated PrP Sc in the soma of neurons, astrocytes and microglia in contrast to long incubation period strains where PrP Sc did not accumulate to detectable levels in the soma of neurons but was detected in glia similar to short incubation period strains. These results are inconsistent with the hypothesis that a decrease in conformational stability results in a corresponding increase in replication efficiency and suggest that glia mediated neurodegeneration results in longer survival times compared to direct replication of PrP Sc in neurons.