Abnormal PrP (PrPSc) and infectivity in central nervous system and lympho-reticular system of natural Atypical/Nor98 scrapie incubating or affected animals bearing various genotypes at codons 136, 141, 154 and 171 of the Prnp gene.

Two different methods were applied to detect PrPSc presence in tissue homogenate that were used for mice inoculation: WB (TeSeE WB kit – BioRad, using SHa31 as anti-PrP antibody) and ELISA (TeSeE Sheep and Goat– BioRad). Additionally when formalin fixed tissue was available, PrPSc immunohistochemistry was also carried out (using 8G8 antibody). (++) indicate a case were minimal PrPSc labelling was observed after the exam of a serial series of slides. In some cases (+), the tissue homogenates were heated (60°C −10 min) in order to destroy contaminating bacteria before bioassay. Such heat treatment might have reduced infectivity level in these samples in an unknown proportion. Mice were considered positive when abnormal PrP deposition was detected in brain. Incubation periods are presented as mean +/−SD (in days) except for that dilution with which less than 50% of mice were found positive. In that case (*) incubation periods of the positive mice are individually presented. In the different tissues, infectious titres were estimated on the basis of incubation period in mice (Figure 4). This estimation was only performed when the attack rate was 100% and data from more than 5 animals were available.ND: not done.