Figure 2.

Intracerebral lentiviral vector administration. a: Western blot analysis of frontal brain of transgenic PrP-Fc₂ mice,8 and PBS-treated and ψPrPFc-treated animals. Using anti-PrP antibody,3 sustained PrP-Fc₂ expression was detected 6 months after virus injection in the brain of ψPrPFc-treated animals, but not in the spleen. b: Severe spongiosis and astrogliosis in terminally sick PBS-treated animals, but no sign of prion-associated pathology in a ψPrPFc-treated animal sacrificed 170 dpi, similarly to age-match uninoculated mice. Sections were stained with H&E and immunostained with GFAP for detection of astrocytosis. c. Whereas PrP^Sc signals were visible in wt brains and spinal cords at terminal stage, no or weak signals were present in the brain and spinal cord of a ψPrPFc-treated animal sacrificed at the same time point. However, spleens of treated and controls animals exhibited similar quantities of PrP^Sc. d: NaPTA-enhanced quantitative Western analysis showed that PrP^Sc accumulation in the tested ψPrPFc-treated brain was 0.03% of the tested PBS-treated brain. To reach a comparable intensity level for Western blot quantification, control samples were diluted linearly up to 32 times, whereas for ψPrPFc-treated brains, PrP^Sc was concentrated by NaPTA precipitation from 125- or 250-fold more starting material than was used directly for Western blot in the case of PBS-treated mouse, lane 1. e: Prion infectivity, determined in the brain of one ψPrPFc-treated animal by the scrapie cell assay in endpoint format (SCEPA), was reduced by 4.2 log TCl/g tissue compared to PBS-treated animals. f: Survival of scrapie-infected mice treated with PBS or ψPrPFc. Whereas PBS-treated mice (n = 4) succumbed to disease at 175 ± 5 dpi, ψPrPFc-treated animals (n = 3) had an extended survival of 72 days (247 ± 8 dpi).