TABLE 3.

Requirement of T-cell subsets for protection^a

Expt no.	Vaccine	Antibody	Treatment days	Challenge day	No. surviving vs total no.	MTD ± SDb	Log10 (viremia)c (significance [P])d
1	L(EV)	None	None	28	10/10	>21	1.7
	L(EV)	Anti-CD4	−3, −2, −1, 17 to 20	28	0/10	6.6 ± 0.52	7.8 (<0.00001)
	L(EV)	Anti-CD8	−3, −2, −1, 17 to 20	28	10/10	>21	2.7 (>0.05)
	L(EV)	Anti-CD4 + anti-CD8	−3, −2, −1, 17 to 20	28	0/10	6.4 ± 0.52	ND
	L(EV)	Anti-CD4	4, 11, 18, 25	28	1/10	7.1 ± 0.33	7.7 (<0.00001)
	L(EV)	Anti-CD8	4, 11, 18, 25	28	9/9	>21	1.8 (>0.05)
	L	None	None	28	0/10	5.0 ± 0.67	8.3 (<0.00001)
	None	Anti-CD4	−3, −2, −1, 17 to 20	28	0/10	5.2 ± 0.79	ND
	None	Anti-CD8	−3, −2, −1, 17 to 20	28	0/10	5.7 ± 1.2	ND
2	L(EV)	None	None	28	10/10	>21
	L(EV)	Anti-CD4	−3, −2, −1, 17 to 20	28	0/10	6.6 ± 0.55
	L(EV)	Anti-CD8	−3, −2, −1, 17 to 20	28	10/10	>21
	L(EV)	Anti-CD4	25, 26, 27	28	10/10	>21
	L(EV)	Anti-CD8	25, 26, 27	28	10/10	>21
	None	None	None	28	0/10	5.8 ± 1.0
	None	Anti-CD4	25, 26, 27	28	0/10	6.2 ± 0.79
	None	Anti-CD8	25, 26, 27	28	0/10	6.7 ± 0.48
	L(EV)	None	None	56	10/10	>21
	L(EV)	Anti-CD4	53, 54, 55	56	9/10	7.0
	L(EV)	Anti-CD8	53, 54, 55	56	10/10	>21
	None	None	None	56	0/10	5.3 ± 0.68

^aMice were immunized with L(EV) on days 0 and 21 and challenged on either day 28 or 56 with 10 PFU (300 LD₅₀) of mouse-adapted EBO-Z. Mice received either anti-CD4 or anti-CD8 MAbs or no treatment on the indicated days. Controls were either vaccinated with L(EV) and not treated or not vaccinated but treated with MAbs or immunized with L alone. In experiment 1, five mice from some of the groups were killed on day 32 (4 days after challenge) and serum viral titers were determined.

^bMTD, mean time to death in days of animals that died. SD, standard deviation.

^cLog₁₀ (mean serum viral titer) on day 4 postchallenge.

^dSignificance of difference in mean serum viral titer from that of the L(EV)-immunized, untreated group, by two-way t test. ND, not done.