Table 1. Cell-associated viral load and detection of vaccine and challenge forms of SIV by PCR 4 days after challenge.

	SIVΔnef-vaccinated monkeys				Control nonvaccinated monkeys
Tissue examined	10121	11106	11111	10118	10659	10662	10655	10656
PBMC	0.33(V)	—	8(nd)	2(V)	2(C)	1(C)	0.33	2
Palatine tonsil	2(V)	—	8(V)	32(V)	8	32	32(C)	64(C)
Spleen	0.33(V)	—	32(V)	64(V)	4(C)	4	2	0.33
LN axillary	4(V)	0.33(V)	32(V)	32(V)	—	28	2	0.33
LN mesenteric	0.33(V)	—	2(V)	0.33(nd)	0.33	—	2	—
LN submandibular	0.33(V)	—	4(V)	64(V)	4	2(C)	1	—
LN retropharyngeal	0.33(V)	1(V/C)	4(V)	16(V)	16	16	2	1
Thymus	—	—	—	—	—	—	—	—

Cell-associated viral load expressed as infectious units per 10⁶ mononuclear cells. Characterization of reisolates by PCR are shown in parentheses.—, virus isolation negative; V, vaccine virus; C, challenge virus; nd, not done. In the control animals, we performed PCR on only one to two reisolates per monkey, as indicated, to verify the presence of wild-type challenge virus.