ical dysfunction and myc terminal disease significantly earlier than Prnp+/o mice: the mean incubation time was 27669 days for Prnp+/o and Oritavancin (diphosphate) biological activity 226613 days for Tg940 PrPz=o mice after high dose ic myc inoculation. Therefore, PrPmyc contributes to, rather than interfering with, prion pathogenesis in Prnp+/o mice. In all terminally sick PrPz=o mice tested we detected proteinase myc K resistant material in brain and spleen after ic or ip inoculation with RML prions. To distinguish between wild-type PrPSc and PrPSc we stained Western blots of brain homogenates myc with an anti-myc antibody. PK-resistant PrPSc was myc clearly detectable under these conditions, indicating that PrPmyc itself is convertible, and suggesting that this phenomenon z=o contributed to the shortened incubation periods in PrPmyc mice. Comparison of immunohistochemically stained brain sections of z=o terminal Prnp+/o 22761436 and Tg940 PrPmyc mice did not reveal any striking differences in 23300835 the extent and topography of reactive astrocytic gliosis, vacuolar degeneration and PrP aggregates. generation of Tg940 PrPo=o mice. Western blot analysis of brain myc homogenate from these second-passage ic-inoculated Tg940 o=o PrPmyc mice revealed PK-resistant PrP; these mice had clinical signs of scrapie and developed vacuolation in the neuropil, intense astrogliosis, and abundant PrP aggregates. For control, Tg940 PrPo=o mice were inoculated with non-infectious myc brain homogenate. These mice showed no evidence of vacuolar degeneration or nerve cell loss, and only mild astrogliosis when aged. As an additional method to distinguish between PrPSc derived from wild-type PrP and PrPmyc we performed histoblot analysis of z=o cryosections of terminal Tg940 PrPo=o mice and Tg940 PrPmyc myc mice. Using anti-PrP and anti-myc antibodies, we could specifically detect PK-resistant PrP in terminal C57BL/6 mice, Tg940 PrPo=o and Tg940 PrPz=o mice. myc myc This technique allowed us to map the distribution of PrPSc in different transgenic mice. We then investigated whether PrPmyc infectivity would increase upon serial transmission, as frequently observed in strain adaptation. Brain homogenate derived from RML-inoculated Tg940 PrPz=o mice was passaged into Tg940 PrPo=o mice which myc myc all got sick after 590656 days . One of these second-passage mice was used as a source for a third passage into 5 Tg940 PrPo=o mice. All of them show similar neurological signs as myc in the second passage, but with a shorter incubation period of 367638, which is suggestive of strain adaptation. We then tested whether deposition of PrPSc accompanies prion replication, defined as increase in prion infectivity. Samples from Tg940 PrPo=o mice after the second passage were used to infect myc the PK1 subclone of N2a neuroblastoma cells in the Scrapie cell assay in endpoint format. As shown in the Fig. 3 J the titer for the PrPSc is the same as the standard RML. myc o=o Crude brain 
homogenates from Tg940 PrPmyc mice were subjected to immunoprecipitation experiments with paramagnetic microbeads coupled to mouse monoclonal anti-myc antibody. Release of myc-containing protein complexes from beads was carried out by exposing the beads to an excess of the synthetic epitope-mimicking myc peptide described above. Control experiments were carried out to verify the specificity of the eluted proteins, and included incubation of beads with 129S2/SvPas wild-type brains followed by elution with the myc peptide, as well as incubation of beads wit
