Transmission of kuru Creutzfeldt–Jakob disease (kCJD) to mice. Graph shows days of incubation in the 9 intracerebrally inoculated Tga20 mice at passage 1 (p1) [607 ± 26 (SEM)]. Brain homogenates from passage 1 mice a and b with an ≈200-day difference in incubation time then were inoculated into both Tga20 and CD-1 mice. Brains a and b yield the same incubation time. Reductions in passage 2 (p2) incubations indicate agent adaptation in both mouse genotypes, with Tga20 mice showing a greater reduction. By passage 3 (p3), Tga20 mice provide a rapid kCJD model.

Sporadic Creutzfeldt–Jakob disease (sCJD) and kuru (kCJD) tissue differences. The first row (A–C) shows low-magnification images of brain from passage 2 CD-1 mice with sCJD versus those with kCJD. All mice became sick at similar times (377, 384, and 403 days) yet still show that specific neuronal nuclei are affected. Both sCJD isolates (LU and MA) induce pathological prion protein (PrP) in the medial thalamus (dark red at arrow) like SY-CJD (12). Kuru infection (C) provokes extensive PrP deposits in a much larger thalamic region (Th) and in hippocampus (Hp), a band of cortical gray (Cx), and temporal lobe/Ammon's horn (Am). Profound differences in spleen PrP are seen with sCJD (D) versus kCJD (E) in passage 2 CD-1 mice. The third row (F–I) shows kCJD brains in Tga20 mice with spongiform lesions in temporal cortex at passage 1 (F), intense gliosis with red-stained astrocytes (G), and abnormal PrP deposits in hippocampus at passage 3 (H). Cerebellum (I) shows pathological PrP deposits consistent with degenerating synaptic boutons (arrows) that become more prominent with further digestion (SI Methods) (i.e., they contain PrP amyloid).

The prion protein (PrP) and PrP-res bands [proteinase K (PK)+ lanes] in CD-1 mouse brain homogenates and in GT1 cultures assayed on Western blots (SI Methods). Only the variant Creutzfeldt–Jakob disease (vCJD) agent shows a unique ≈19-kDa band (at dot). Kuru samples show one mouse with a long (55-day) clinical course (494-day lane) with more PrP-res than mice with typical 15–20 day signs; all kuru (kCJD) mice (268- and 401-day lanes), including Tga20 mice, show the same PrP-res profile. The 22L-sc CD-1 mouse (asterisk) was inoculated with 22L-sc-infected N2a cells displaying an N2a-specific but not agent-specific PrP band pattern (9–11), yet these cells reproduced their original 22L-sc incubation time and neuropathology (9–11) and the type I brain PrP pattern in mice (22L-sc lane). Protein loads and mouse passages are noted. The GT1 lanes show GT1-cell-specific PrP and PrP-res patterns (e.g., the heavily glycosylated top band in undigested brain homogenates is at 34 kDa, whereas it is at 39 kDa in GT1 homogenates). Kuru brain homogenates rapidly, reproducibly, and stably infected GT1 cells, as shown by the high levels of PrP-res (kCJD lane, >4 experiments), whereas sCJD gave only subliminal infection with the same homogenate exposure (SI Methods). The 13-kDa PrP-res marker in GT1 cells (arrow) is diagnostic for Japanese isolates in GT1 cells but not brain (FU-CJD lanes), but the 19-kDa doublet, found only in vCJD brain infections (at dot), is again seen in GT1 cultures. The band profile in kCJD is comparable with those of 22L-sc and 263K-sc in GT1 cells but required much higher amounts of protein to be loaded to each lane, as noted. Uninfected lanes (Nl) show no PrP-res.