Biochemical characterisation of European goat TSE isolates and discrimination from goat BSE.

Introduction
Diagnosis of goat TSEs including BSE is largely based on experience in sheep. Small ruminants surveillance in the EU shows that there is considerable infection circulating amongst goats, which calls sometimes for close investigation of samples with BSE like profile. This study focused on collecting TSE positive samples from different regions in Europe and comparing these with each other and with BSE using several parameters for PrPres immuno-chemical analysis in triplex Western blots
Methods
Brain stem material from field TSE cases mostly from different herds in seven different EU countries (Table I), and from experimentally challenged BSE and scrapie goats (Table II) were collected and centrally aliquotted for distribution to project partners. Four independent PrPres parameters were
investigated using triplex Western blotting: glycoprofile (mAb L42), dual population composition (L42/SAF84 mAb ratio at 24 kDa band), N-terminal cleavage by MW of unglycosylated band (mAb Sha31) and antibody ratio (mAbs 12B2/Sha31), and proteolytic susceptibility of the core region comparing two different pH/PK digestion conditions (mAb L42). Atypical/Nor98 scrapie is in Wblot far different from other TSE types and not included in these parameter calculations.
Results
Using the four parameters, the results showed that all field isolates could be distinguished as either classical, atypical/Nor98 (n=1) or CH1641-like (n=1) scrapie (Figure 1 glycosylation markers; Figure 2 protease resistance markers); all Italian cases exhibited a reduced 12B2 specific PrPres‑N‑terminus content, between that of scrapie and BSE. Sheep and goat experimental CH1641 scrapie behaved similar, including the one field case UKB2. Some cases were incompletely analyzed due to low signal intensity. Challenge generated samples were behaving as classical scrapie and BSE, as expected.
Conclusion
This four-parameters approach appeared powerful in discrimination between BSE, classical scrapie, atypical/Nor98 scrapie and CH1641 scrapie, AND was indicative for Italian scrapie as a separate cl. scrapie type. The biochemical procedures for discriminating BSE, scrapie, CH1641 and atypical scrapie can be applied to both goat and sheep, provided that a PrP polymorphism check has been performed to exclude a negative effect for the antibodies used. In anyway, the antibodies used are not dependent of the most critical PrP polymorphisms: wild type, 142M, 146S, 146D, 154H, 211Q or 222K.