Expression of EHV5 antigens in EHV5-inoculated (MOI 1 or 10) B lymphocytes. At indicated time points, supernatant was collected for virus titration and cells were fixed and immunofluorescently stained for EHV5 antigens. Representative confocal images of EHV5 antigen expression (Sultan; green) in B lymphocytes. Cell nuclei were counterstained with Hoechst 33342 (blue). The scale bar represents 5 µm (upper panel). The percentage of EHV5-positive cells was calculated based on 300 cells counted in 5 distinct fields (lower left panel). The virus titer was determined in supernatant on RK13 cells (lower right panel). Data are represented as mean ± SD and asterisks indicate significant differences (*P < 0.05) between MOI 1 and 10. Experiments were performed on cells from 3 individual horses.