FIG. 2.

Experimental scheme and analysis of proviral DNA in splenocytes. (A) Experimental scheme. Two infected/treated and two control noninfected/nontreated mice were mated at the same time to ensure synchronized deliveries. Immediately after birth and before breastfeeding could occur, the pups were distributed as follows: eight neonates from each litter were kept with their natural mothers for nursing, whereas another eight were transferred to a foster mother in order to have animals born to infected/treated mice nursed by control mice and vice versa. All neonates were infected with FrCas^E 3 days after birth and followed for signs of illness, anti-FrCas^E antibodies, and viral propagation using several criteria (see the text). Analysis at early time points required the sacrifice of two animals per time point. (B) RT-PCR detection of FrCas^E Env mRNA in the spleen. Two animals per group were sacrificed at the indicated times. The spleens were recovered and pooled for RNA preparation. Subgenomic FrCas^E Env mRNA accumulation was assayed by RT-PCR as described in Materials and Methods. β-Actin was used as an internal invariant amplification standard. WM, molecular weight marker.