Table 1. Abnormal PrP (PrP^Sc) 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.

						PrPSc			tg338 transmission
Case	Genotype	Origin	Age	Category	Tissues	WB	ELISA	IHC	Positive mice	Incubation period in days (mean +/−SD)*	Estimated infectious titre(IC ID50 in tg338/g)
1	AFRQ/AFRQ	FR	6 years	clinical	Cerebral cortex	pos	pos	pos	6/6	209+/−12	108.7
					Brainstem	neg	neg	pos++	6/6	256+/−14	105.5
					Prescapular LN	neg	neg	neg	3/5	334+/−10	ND
2	ALRQ/ARR	PT	6 years	fallen stock (additional case)	Cortex	pos	pos	pos	6/6	231+/−17	106.7
					Retropharyngeal LN+	neg	neg	ND	5/6	349+/−76	ND
3	ARR/ARR	PT	8 years	fallen stock (additional case)	Cerebral cortex	pos	pos	pos	6/6	221+/−19	106.7
					Retropharyngeal LN+	neg	neg	ND	4/6	348+−37	ND
4	AFRQ/VRQ	PT	9 years	fallen stock (additional case)	Cerebral cortex+	pos	pos	pos	6/6	239+/−28	106
					Retropharyngeal LN+	neg	neg	ND	0/6	>650
5	AHQ/AHQ	NO	3,5 years	clinical	Cerebellum	pos	pos	pos	5/5	224+/−21	106.7
					Parotideal LN	neg	neg	neg	2/2	285–298*	104.4
6	AHQ/AHQ	NO	7,5 years	slaughter	Cerebellum	pos	pos	pos	5/5	248+/−15	105.8
					Popliteal LN	neg	neg	neg	1/10	401*	ND
7	ARR/ARR	NO	7 years	slaughter	Cerebellum	pos	pos	pos	5/5	279+/−46	105.8
					Thoracic spinal cord	neg	neg	neg	5/5	346+/−85	102.9
					Prescapular LN	neg	neg	neg	0/6	>650

Two different methods were applied to detect PrP^Sc 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, PrP^Sc immunohistochemistry was also carried out (using 8G8 antibody). (⁺⁺) indicate a case were minimal PrP^Sc 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.