TABLE 1.

Rechallenge after initial TBEV exposure under passive protection^a

Initial treatment	Survival (%)	MST (days)	No. of animals (no. of exper- iments)
Mouse TBEV antiserum plus
1,000 PFU of TBEV	82 ± 7	15.1 ± 3.1	38 (4)
PBS	0 ± 0	10.7 ± 0.5	40 (4)
1,000 PFU of UV-inactivated TBEV	0 ± 0	10.0 ± 0.2	40 (4)
Human TBEV Ig plus
1,000 PFU of TBEV	81 ± 5	14.0 ± 1.2	164 (13)
PBS	18 ± 3	12.4 ± 0.4	168 (13)
1,000 PFU of UV-inactivated TBEV	22 ± 6	12.0 ± 0.7	150 (11)

^aMice were injected s.c. with 0.2 ml of either a 1:3-diluted mouse TBEV hyperimmune serum or a 1:10-diluted human TBEV Ig preparation 2 h before they were injected i.p. with 1,000 PFU of TBEV, PBS, or the equivalent of 1,000 PFU of UV-psoralen-inactivated TBEV (initial treatment). After 70 days (recipients of murine TBEV hyperimmune serum) or 28 days (recipients of human TBEV Ig), mice were rechallenged by i.p. injection of 1,000 PFU of TBEV, and their survival was recorded. The results presented are the mean (± SEM) survival percentages and the MST (in days) of mice that died. The data presented were collected from the indicated number of independent experiments, with groups of 8 or more mice each.