Figure 2

IBV replication kinetics in blood monocytes (KUL01 ⁺ cells). The monocytes were inoculated with IBV B1648 or M41 at a m.o.i. = 5. Percentage of viral antigen positive KUL01⁺ cells was determined in B1648 and M41 infected blood mononuclear cells at 0, 6, 12, 24, 48 and 72 hpi by double immunofluorescence. For viral antigen positive cells, the solid line represents the mean values of the B1648 group, the dashed line represents the mean values of the M41 group and the dotted line represents the mean values of the mock group. Intracellular and extracellular virus titers of cell lysate and supernatant were determined at designated time points. For viral titers, the solid line represents the mean values of the intracellular virus titers, the dashed line represents the mean values of the extracellular virus titers and the dotted line represents the mean values of the inactivation curve. An asterisk (*) indicates a significant difference of viral antigen positive KUL01⁺ cells between B1648 and M41 (P < 0.05). The inactivation curve shows the drop of virus titers at 37 °C in culture medium due to inactivation events.