Evaluation of two sets of immunohistochemical and Western blot confirmatory methods in the detection of typical and atypical BSE cases

Chiara Porcario,Cristiano Corona,Alice Z Perazzini,Christina M Loiacono,Justin J Greenlee,Amir N Hamir,S Mark Hall,Barbara Iulini,Cristina Casalone,Pierluigi Acutis,Jürgen A Richt,Maria Caramelli,Francesca Martucci

doi:10.1186/1756-0500-4-376

Abstract

BackgroundThree distinct forms of bovine spongiform encephalopathy (BSE), defined as classical (C-), low (L-) or high (H-) type, have been detected through ongoing active and passive surveillance systems for the disease.The aim of the present study was to compare the ability of two sets of immunohistochemical (IHC) and Western blot (WB) BSE confirmatory protocols to detect C- and atypical (L- and H-type) BSE forms.Obex samples from cases of United States and Italian C-type BSE, a U.S. H-type and an Italian L-type BSE case were tested in parallel using the two IHC sets and WB methods.ResultsThe two IHC techniques proved equivalent in identifying and differentiating between C-type, L-type and H-type BSE. The IHC protocols appeared consistent in the identification of PrPSc distribution and deposition patterns in relation to the BSE type examined. Both IHC methods evidenced three distinct PrPSc phenotypes for each type of BSE: prevailing granular and linear tracts pattern in the C-type; intraglial and intraneuronal deposits in the H-type; plaques in the L-type.Also, the two techniques gave comparable results for PrPSc staining intensity on the C- and L-type BSE samples, whereas a higher amount of intraglial and intraneuronal PrPSc deposition on the H-type BSE case was revealed by the method based on a stronger demasking step.Both WB methods were consistent in identifying classical and atypical BSE forms and in differentiating the specific PrPSc molecular weight and glycoform ratios of each form.ConclusionsThe study showed that the IHC and WB BSE confirmatory methods were equally able to recognize C-, L- and H-type BSE forms and to discriminate between their different immunohistochemical and molecular phenotypes. Of note is that for the first time one of the two sets of BSE confirmatory protocols proved effective in identifying the L-type BSE form. This finding helps to validate the suitability of the BSE confirmatory tests for BSE surveillance currently in place.

Highlights

Three distinct forms of bovine spongiform encephalopathy (BSE), defined as classical (C-), low (L-) or high (H-) type, have been detected through ongoing active and passive surveillance systems for the disease
BSE was first detected in the United Kingdom (UK) in 1986 [2], where the disease grew to epidemic proportions in the cattle population, with approximately 184,600 cases diagnosed [3]
- punctate type consisting of powdery and diffuse PrPSc staining throughout the neuropil;

Summary

Introduction

Three distinct forms of bovine spongiform encephalopathy (BSE), defined as classical (C-), low (L-) or high (H-) type, have been detected through ongoing active and passive surveillance systems for the disease. Obex samples from cases of United States and Italian C-type BSE, a U.S H-type and an Italian L-type BSE case were tested in parallel using the two IHC sets and WB methods. TSEs include bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep and BSE was first detected in the United Kingdom (UK) in 1986 [2], where the disease grew to epidemic proportions in the cattle population, with approximately 184,600 cases diagnosed [3]. Passive and active surveillance programs were developed to monitor cattle populations for the presence of BSE. Active surveillance programs require BSE testing by rapid screening tests at the abattoir of apparently healthy cattle of a certain age and of fallen/dead stock

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