Figure 2. Production of syncytia by parental and chimeric viruses.

DF1 cells in six-well plates were infected with the indicated viruses at a multiplicity of infection (MOI) of 0.01 PFU/cell, incubated for 72 h, and visualized by photomicroscopy directly (A) or following immunoperoxidase staining using antiserum against the N protein of NDV, with viral antigen stained red (B).