Figure 4

ADE in FV3 is Fc-dependent and independent of complement. (A) Protein A (300 μg/mL) was either incubated with BF-2 cells or anti-FV3 serum and pre-immune serum for 30 minutes at room temperature. FV3 (~50 PFU) was incubated with anti-FV3 serum or pre-immune serum and was then added to BF-2 cells (+/- protein A) and were overlaid 2 hours later. FV3 (~50 PFU) was incubated with anti-FV3 serum or pre-immune serum (+/- protein A) and then was added to BF-2 cells and were overlaid 2 hours later. Forty-eight hours post-overlay plaques were counted and expressed as a relative percentage of a control FV3 infection. (B) Rabbit anti-FV3 serum or rabbit pre-immune serum were heat-inactivated or incubated with zymosan A or EGTA for one hour before the addition of FV3 (~50 PFU). FV3+anti-FV3 serum or FV3+pre-immune serum complexes were added to BF-2 cells, which were subsequently overlaid. Forty-eight hours post-overlay, plaques were counted and were compared as a relative percentage to BF-2 cells infected with FV3 in the absence of serum. Experiments were completed in at least 3 independent trials with mean plaque values shown.