FIG. 3.

Proviral loads in the infected sheep. The proviral loads were estimated from blood lysates prepared at 40 months or just before the death of the animal (Table 1). Starting from an equivalent volume of 2 μl of blood, the viral sequences were amplified by 22 cycles of PCR with two oligonucleotides (5′- TGGAAAGAACTAACGCTGACGG-3′ at position 6450 [16] and 5′-CCCCAACCAACAACACTTGCTT-3′ at position 7060). The DNAs were then analyzed by Southern blot hybridization with a viral probe corresponding to the X3C sequences (positions 6528 to 6997 [16]). As controls for semiquantification, serial dilutions of a blood lysate from sheep 210, which was infected with the 344 virus, were amplified in parallel under similar conditions: 5× concentrated (conc.) (10 μl of lysate), 1× lysate (corresponding to 2 μl of blood), and 5× and 25× dilutions (dil.). A lysate from an uninfected sheep (no. 120) was used as a negative control. The sizes of the amplified fragments are indicated in base pairs.