FIG. 2.

Lack of reversion of the R3-G4 deletion mutant and maintenance of the attenuated phenotype after injection of blood from sheep 245 into naïve recipient hosts. (A) Nucleotide sequence and corresponding sequence chromatogram of a PCR product from DNA from sheep 245 amplified using primers encompassing the R3-G4 deletion (coordinates 7011 to 6605 according to reference 23). (B) Blood from sheep 245 was injected into two BLV-free animals, 1086 and 1091 (▪). Their proviral loads (in numbers of genome copies per 100 cells) were quantified by real-time PCR at 7 months postinfection and compared to the levels reached in sheep infected with wild-type (▾) and attenuated (×) viruses (IG4, CRE, R3-G4, and 6073 Tyr mutants). Statistical relevance (NS, not statistically significant, and *, statistically significant) was calculated according to the two-tailed unpaired Student t test.