Immunohistochemical detection and localisation of prion protein in brain tissue of cattle, sheep and goats

The misfolding of the cellular prion protein into its pathogenic isoform prion—a proteinaceous infectious particle-causes fatal neurodegenerative diseases. These prion diseases are classified as transmissible spongiform encephalopathies, which may arise from genetic mutations, infectious transmission or sporadic occurrence. They are characterised by protein aggregation and progressive neurodegeneration. In humans, prion diseases include Kuru, Creutzfeldt-Jakob disease, variant Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker-Syndrome, and fatal familial insomnia. In animals, they include atypical and classical scrapie in sheep and goats, atypical and classical bovine spongiform encephalopathy, also known as “mad cow disease”, and chronic wasting disease in cervids. Although the mechanisms underlying neurodegeneration and the role of neuroinflammation in these disorders remain insufficiently understood, characteristic features include spongiform changes, neuronal loss, gliosis, and accumulation of the pathogenic isoform of the prion. To date, there is no reliable ante mortem diagnostic test for these encephalopathies. The diagnosis is confirmed postmortem, and immunohistochemistry is one of the key diagnostic techniques. This review article summarises the available research data about prion diseases, focusing on the detection and localisation of the pathogenic isoform of the prion protein in brain tissue of cattle, sheep, and goats using immunohistochemical analysis.