Immunohistochemistry of PrPsc Within Bovine Spongiform Encephalopathy Brain Samples with Graded Autolysis

Abstract

Bovine spongiform encephalopathy (BSE) is a transmissible neurodegenerative disease of cattle. Clinical diagnosis can be confirmed by investigation of both spongiform changes and abnormal prion protein (PrPsc), a marker considered specific for the disease. Tissue autolysis, often unavoidable in routine field cases, is not compatible with histological examination of the brain even though PrPsc is still detectable by immunoblotting. To determine how autolysis might affect accurate diagnosis using PrPsc immunohistochemistry, we studied 50 field samples of BSE brainstem (obex) with various degrees of autolysis. We demonstrated that the antigen-unmasking pretreatments necessary for PrPsc immunohistochemistry were compatible with the preservation of autolyzed brain sections and that PrPsc detection was unaffected by autolysis, even though anatomic markers were sometimes lost. In tissue samples in which anatomic sites were still recognizable, PrPsc accumulation was detected in specific gray matter nuclei. In samples with advanced autolysis, PrPsc deposits were still observed, at least at the cellular level, as an intraneuronal pattern. We found that the sensitivity of PrPsc immunohistochemistry as a diagnostic method for BSE was undiminished even by severe tissue autolysis.

How the surveillance system may bias the results of analytical epidemiological studies on BSE: prevalence among dairy versus beef suckler cattle breeds in France

“…It appeared that 68% of the BSE cases found with the screening test had already displayed clinical signs before death, either characteristic of BSE or sufficiently suggestive, which is consistent with the Swiss data [6]. Another discussion point is the specificity of BSE detection, that is comparable for the MRS and TS programs since the confirmation tests are the same, Western blot [10] and/or immunohistochemistry [4] carried out at the reference laboratory. Concerning sensitivity, combining the MRS and TS of cattle at risk allowed to check every bovine aged two years and more at the time of death or euthanasia, which appears to be an efficient method to detect a 100% lethal disease.…”

“…Detected BSE cases included two types of animals; first were clinically suspect animals [13] confirmed at the national reference laboratory (AFSSA Lyon, France) using western blot [10] or immunohistochemistry [4] -i.e. cases found with the MRS -.…”

Diagnosis of Transmissible Spongiform Encephalopathies in Animals: A Review

“…The PrP Sc is very resistant to degradation, and its detection is not significantly compromised by autolysis. 18,22,99 Trials to evaluate the performance of rapid tests before approval by the EU now include a category of poor-quality samples, mostly autolytic. 24 However, the early accumulation of PrP Sc in the brain is very neuroanatomically restricted, and the biggest threat to sensitivity in the autolyzed tissues is the uncertainty as to whether the target areas were actually tested.…”

Estimating the trend of the French BSE epidemic over six birth cohorts through the analysis of abattoir screening in 2001 and 2002

“…BSE cases were test positive animals detected through the screening programme at the abattoir, with either of the two tests: Prionics-check (Roche Diagnostic, Mannheim, Germany) or Platelia BSE (Biorad, Trend of the BSE epidemic in France 301 Marnes la Coquette, France), and confirmed positive at the National Reference Laboratory (AFSSA Lyon, France) with western blot [19] or immunohistochemistry [9]. A total of 158 BSE cases were included in the study, respectively 87 in 2001 and 71 in 2002.…”