Table 3. Frequency of SIV RNA positive cells in protected, superinfected vaccinates and challenge controls by in situ hybridisation.

Group	Identity	Vaccine duration	Weeks to ISH	Frequency of SIV ISH +ve cells
				Spl	PLN	MLN	S.Int	Thy
Protected	B202	20 (A)	40	+	+	+	+	+
vaccinates	B203	20 (A)	40	+	+	+	+	+
	B205	20 (A)	40	+	+	+	+	+
	B206	3 (B)	23	+	+	+	+	+
	B207	3 (B)	23	+	+	+	+	+
	B208	3 (B)	23	+	+	+	+	+
Superinfected	B204	20 (A)	40	+++	+	+	+	+
vaccinates	B209	3 (B)	23	+	+	+	+	+
Challenge	B210	(C)	20	+	+	++	+	+
controls	B211	(C)	20	+	+	+	+	+
	B212	(C)	20	+++	+	++	+	+
	B213	(C)	20	++	+	+	++	+

All vaccinates were challenged with the same dose of SIVsmE660 for the same duration (20 weeks); the total time to sampling is indicated by the vaccination duration of 20 or 3 weeks and group (A–C). The frequency of SIV positive (+ve) cells determined by in situ hybridisation (ISH) is shown for each tissue. Lymphoid tissues sampled were spleen (Spl), peripheral and mesenteric lymph nodes (PLN, MLN), small intestine (S.Int) and thymus (Thy) collected post-mortem. A grading system of + (0.5–6.8), ++ (6.9–13.8) and +++ (>13.8) cells/mm³ was employed.