The presence of disease-associated prion protein in skeletal muscle of cattle infected with classical bovine spongiform encephalopathy

Abstract

The aim of this study was to investigate the presence of disease-associated prion protein (PrP(Sc)) in the skeletal muscle of cattle infected with classical bovine spongiform encephalopathy (C-BSE). The study was carried out systematically in 12 different muscle samples from 43 (3 field and 40 experimental) cases of C-BSE; however, muscle spindles were not available in many of these cases. Therefore, analysis became restricted to a total of 31 muscles in 23 cattle. Even after this restriction, low levels of PrP(Sc) were detected in the muscle spindles of the masseter, intercostal, triceps brachii, psoas major, quadriceps femoris and semitendinosus muscles from 3 field and 6 experimental clinical-stage cases. The present data indicate that small amounts of PrP(Sc) are detectable by immunohistochemistry in the skeletal muscles of animals terminally affected with C-BSE.

Fig. 1.

Sections of skeletal muscles from cattle infected with classical BSE. Detection and localization of PrP^Sc in muscle spindles of the triceps from a field case (BSE/JP22), quadriceps from an orally-infected case (ID#5413), psoas major from an intracerebrally infected cattle (ID#3728) and pectoralis (control). Granular PrP^Sc immunolabeling (brown) was observed in intrafusal myofibers. Depicted are H&E staining (left column) and PrP^Sc staining by IHC using the conventional 2-step polymer (center column) or the TSA biotin system (right column). Bar=50 µm.

Fig. 2.

Western blot analysis of proteinase K-digested PrP^Sc in skeletal muscle samples of cattle infected with natural and experimental C-BSE. Detection of PrP^Sc in the skeletal muscle samples from cattle (lane 1–3, BSE/JP17; lane 4, BSE/JP22) with natural BSE (A), cattle (ID#5413) with experimental C-BSE through an intracerebral route (B) and cattle (ID#5466) with experimental C-BSE through an oral route (C). The muscle tissues tested are indicated above the lanes: 1, masseter muscle; 2, semitendinosus muscle; 3, triceps brachii muscle; 4, semitendinosus muscle; 5, masseter muscle; 6, triceps brachii muscle; 7, intercostal muscle; 8, quadriceps femoris muscle; 9, triceps brachii muscle; and 10, intercostal muscle. Lanes a, b and c represent the results of triplicate samples. The equivalent of 100 mg of tissue was loaded in each lane. Western blots were probed with a monoclonal antibody T2 to detect PrP^Sc. +, positive; −, negative. Lane m, mouse scrapie-infected brain was used as the positive control (1.6 µg brain eq.). Molecular markers are shown on the left (in kDa).