Table I.

Lethality of different ECTV isolates

Experiment	Virus	Dose (PFU)	Dead/total
1	Rev166	0.1	2/6
		1	3/6
		300	5/5
	WT	0.1	2/6
		1	4/4
		10	4/4
		300	5/5
	Δ166	300	0/5
		106	0/5
		107	0/4
		5 × 107	0/3
2	Rev166	0.1	1/6
		1	2/6
	WT	1	6/6
	Δ166	5 × 107	0/4
3	Rev166	0.2	2/6
		2	6/6
	WT	0.2	5/6
	Δ166	5 × 107	0/4
	189898-p7.5-EGFP	0.5	2/6
		5	6/6

Mice were infected with the indicated viruses serially diluted in PBS from stocks. For experiments 1 and 2, the dose was calculated according to the virus titer determined in the virus stock. For experiment 3, final dilutions were retitered. Based on the results, we estimate LD₅₀ values for the different viruses as follows: Rev166, <2; WT, <0.2; p7.5-EGFP, <5; Δ166, >5 × 10⁷. These experiments are independent of those in Fig. 2 C.