Prion protein immunohistochemical staining in the brains of monkeys with transmissible spongiform encephalopathy

Prion protein (PrP) immunohistochemical staining of the brains of common marmosets (Callithrix jacchus) with experimental transmissible spongiform encephalopathy is described. The monkeys (n = 17) had been injected, intracerebrally, 17-49 months previously with homogenates of brain tissue taken post mortem from a cow with BSE (n = 2 monkeys), a sheep with natural scrapie (n = 2 monkeys), human cases of growth hormone related Creutzfeldt-Jakob disease (CJD) (n = 2 monkeys), sporadic CJD (n = 5 monkeys), or Gerstmann-Sträussler-Scheinker disease (GSS) (n = 4 monkeys), or from monkeys with spongiform encephalopathy resulting from injection with brain tissue from these last two cases (n = 1 monkey from each case). Only diffuse PrP-staining was seen in monkeys injected with CJD-material whereas more aggregated deposits of PrP were seen in monkeys injected with BSE-, scrapie--and GSS-brain tissue. There were no patterns of staining specific to the brains injected with BSE-material that could be used to identify the origin of that inoculum. BSE--and scrapie-injected monkey brains could be distinguished from each other because in BSE-injected monkey brain the spongiform vacuolation was largely confined to subcortical structures whereas in scrapie-injected monkey brain the spongiform vacuolation was also prominent in the neocortex. The patterns of PrP deposition differed markedly between those seen in monkey brains injected with BSE-material or CJD-material, but the patterns of PrP staining seen in monkey brains injected with BSE-material were also seen in monkey brains injected with scrapie--or GSS-material. Overall there was a correlation between the length of the incubation period and the amount of aggregated PrP-staining, but no correlation between the neuropathological picture and the clinical presentation of neurological signs.