Stability of BSE infectivity towards heat treatment even after proteolytic removal of prion protein

Table 2 Infectivity measured by PrPSc positivity rates in Tgbov XV mice inoculated with brain homogenates after different treatments

Dose	No detergent	Detergent		Detergent; heat		Detergent; heat; keratinase
(¹⁰log g mL⁻¹)	no ppt	no ppt	ppt	no ppt	ppt	no ppt	ppt
−2	9/10 (2)	n.d	n.d	15/15 (0)	12/13 (2)	14/15 (0)	15/15 (0)
−3	12/13 (0)	n.d	n.d	5/15 (0)	14/15 (0)	14/16 (0)	n.d
−4	10/12 (0)	n.d	n.d	0/15 (0)	2/13 (2)	4/15 (1)	n.d
−5	3/12 (0)	3/15 (0)	10/15 (0)	1/15 (0)	n.d	3/16 (0)	n.d
−6	1/15 (0)	3/13 (2)	1/14 (1)	0/15 (0)	n.d	2/13 (2)	n.d
−7	0/15 (0)	2/15 (0)	1/14 (1)	0/15 (0)	n.d	1/15 (0)	n.d
−8	0/15 (0)	0/14 (1)	1/15 (0)
−9	0/14 (1)	0/15 (0)	0/15 (0)
¹⁰log ID₅₀ g⁻¹	6.2	6.4**	6.7**	4.6	5.3*	5.7

Disease rates were estimated as number of animals confirmed positive (based on testing for PrP^Sc) and the total number of animals that lived longer than 100 days post inoculation. Between parentheses the number of animals per dose group not included for disease validation because of early death i.e. < 100 days post inoculation. These animals were PrP^Sc negative by Western blotting. Dose was calculated using the percentages per group in the formula of Spearman and Kaerber. N.d.: not done; ppt = precipitated with methanol. Asterisks * and **: for enabling calculations, figures for the n.d. disease rates were borrowed per equal dose group respectively from the columns detergent/heat/no ppt and no detergent/no ppt.

ISSN: 1297-9716