FIG. 3.

Pathogenicity in sheep 277 of an attenuated BLV strain mutated in the transmembrane protein YXXL signaling motifs. Sheep 277 was infected with the attenuated BLV mutant 6073 Tyr carrying a T-to-G transversion located in the cytoplasmic domain of the viral gp30 transmembrane gene. Blood was collected at regular intervals postinfection. (A) Lymphocyte counts were determined by using a Coulter Counter, model ZN, and May-Grunwald and Giemsa staining, and proviral loads were quantified by real-time PCR. (B) Cryosections from a tumoral mesenteric lymph node stained with anti-CD21 (left panel) or with anti-CD4 (right panel) monoclonal antibodies and analyzed by confocal microscopy. B, B cell. (C) The profile of provirus integration sites was analyzed by inverse PCR of peripheral blood and tumor cells. The sizes of the fragments are indicated on the left. MW, molecular size markers (V; Roche). (D) Nucleotide sequence and corresponding sequence chromatogram (coordinates 6270 to 6299 according to reference 23) of a PCR product amplified from a tumor from sheep 277. The position of the T-to-G transversion is marked by an asterisk.