Transmission of Scrapie by Steel-surface-bound Prions

Table 2 Transient insertion of infectious wires into brains of indicator mice

Inoculation	Sick/Total	Incubation Time ± s.d. (days)
Wires infected by exposure to scrapie brain
(a) Transient insertion into indicator mice
30 min	4/4^$	94 ± 10
120 min	2/2^#	100 ± 18^&
(b) Permanent insertion into indicator mice
Wires not previously inserted	3/3	71 ± 2
Wires after transient insertion for: 30 min	4/4	71 ± 3
120 min	5/5	68 ± 1
(c) Controls
Wires exposed to brain homogenate	6/6	76 ± 3
Brain homogenate (1%, 0.03 ml)	3/3	69 ± 3

Infectious wires were prepared by insertion for 5 min into the brain of C57Bl6 × 129Sv mice culled 121 days after i.c. inoculation with RML and washed with 50 ml PBS 5 times for 10 min. Infectious wires were inserted into brains of 6 deeply anaesthetised Tga20 indicator mice for the times indicated. The recovered wires were washed with 1 ml PBS and implanted into Tga20 indicator mice. As controls, wires incubated with centrifuged 10% homogenate (6.8 log LD50 units/ml) of the same brain and the homogenate itself were introduced into indicator mice.
^$Two of 6 mice died on the day of the intervention.
^#Four of 6 mice died within a day of the intervention.
^&Incubation times were 87 and 113 days.

ISSN: 1528-3658