A comparative study of immunohistochemical methods for detecting abnormal prion protein with monoclonal and polyclonal antibodies

Transmissible spongiform encephalopathies are associated with the accumulation of abnormal prion protein (PrP(Sc)) in the central nervous system which can be detected immunohistochemically. Using a monoclonal antibody (L42) to an epitope on the first alpha-helix of ruminant PrP, we compared previously reported immunohistochemical antigen unmasking and "visualization" systems. In addition, a variety of polyclonal and monoclonal antibodies to other epitopes on ruminant PrP were assessed. Antigen unmasking by hydrated autoclaving and proteinase K treatments, and antigen detection with L42 and an avidin-biotin complex system, enabled intra- and extra-neuronal PrP(Sc)to be demonstrated in scrapie-affected sheep carrying three different PrP alleles, as well as in cases of bovine spongiform encephalopathy