FIG. 2.

Effect of the presence of StxA1 and the enzymatic mutant E167D on BLV expression by cultured PBMC from BLV-positive cattle. PBMC from BLV-positive cattle were cultured with StxA1 (1.0 μg/ml) or enzymatic mutant E167D (1.0 μg/ml) or without toxin and were harvested at 24, 48, and 72 h postculture. Cells (A) and culture supernatants (B) were assayed for expression of BLV proteins p24 and gp51 by blotting the lysed cells or cell-free culture supernatants onto nitrocellulose and probing with mouse monoclonal antibodies to p24 and gp51 followed by anti-mouse Ig antibody conjugated to alkaline phosphatase. Blots were developed using 5-bromo-4-chloro-3-indolylphosphate and nitroblue tetrazolium as the substrate, and the reaction intensities were quantified using a densitometer. PBMC from BLV-negative cattle were used as controls. The experiment was performed four times with PBMC from three BLV-positive cattle, and the results of a representative experiment are shown.