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

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.

Identification of H-type BSE in Portugal

“…1(a) and (b)) indicative of an atypical form as reported in natural and experimental H-type BSE cases. 10,12,13 Interestingly not all H-type BSE cases show this feature as with other natural cases a fine punctate deposition in the neuropil was the predominant feature reported. 11 This suggests the existence of some variability in PrPres distribution; however more data of natural cases is needed.…”

“…In a few H-type BSE natural cases, minimal spongiform lesions (solitary tract nucleus and spinal tract nucleus of trigeminal nerve) and mild PrPres deposits (neuropil punctate and coarse particulate, intraneuronal and intraglial types) were reported in brainstem (both at the obex-dorsal motor nucleus of the vagus nerve, caudal olivarius nucleus, cunneate nucleus, hypoglossal nucleus, spinal tract nucleus of trigeminal nerve, solitary tract nucleus, reticular formation-and at the midbrain). [10][11][12] In H-type BSE experimentally challenged cattle, animals developed either dull or a nervous clinical phenotype. PrPres immunolabelling showed PrPres accumulation predominantly at the obex, as intraglial type in the white matter tracts including the cerebellum.…”

Classical and Atypical Bovine Spongiform Encephalopathy: Epidemiology, Pathogenesis and Diagnosis

“…types, which are mildly present in the hypoglossal and olivary nucleus and moderately present at the level of DMVN nucleus, NST, NSTV, and reticular formation [54]. Glial, intraneuronal, perineuronal, and linear tracts are also frequent in BASE cases in different brain areas.…”

“…As regards natural H-type BSE, in the brainstem, granular, intraneuronal, linear, intraglial, and punctate PrPSc deposits are the most characteristic types, mainly detected at the level of the DMVN, NST, NSTV, and in the reticular formation; however, there is some variability in PrPSc distribution among different H-BSE cases [54] (Figure 7). Regarding experimental H-type BSE, large amounts of PrPSc are diffusely deposited in the cerebral cortex, basal ganglia, thalamus, hypothalamus, brainstem, and spinal cord.…”

Downregulation of β-Soluble N-Ethylmaleimide-Sensitive Factor Attachment Protein: Proteomics-Based Identification in Early-Stage Prion Disease

“…Definitive diagnosis can be made postmortem by a histological examination [4,5] of the brain showing the characteristic spongiform changes, astrogliosis and amyloid plaques. Immunohistochemical and Western blot bovine spongiform encephalopathy confirmatory methods also can be used for bovine spongiform encephalopathy surveillance currently in place [6]. It is possible that some infected animals may never develop clinical symptoms but remain asymptomatic carriers who can potentially transmit the disease to other individuals [7].…”