FIG. 3.

Characterization of mutant viruses encoding mutant GP5. (A) Single-step growth kinetics of wt (FL-12) and various mutant PRRSVs in MARC-145 cells. Cells in six-well plates were infected with PRRSV at an MOI of 3, culture supernatants were collected at the indicated times after infection, and virus titers were determined. Average titers with standard deviations (error bars) from three independent experiments are shown. (B) Plaque morphology of mutant viruses. Arrows and arrowheads show plaques that are less clear. Boxes show representative plaques that have been magnified in succeeding panels. (C) Magnified images of representative plaques from wt PRRSV (FL-WT) and one mutant virus (FL-N34/51A). (D) trans-Complementation to recover mutant PRRSVs; quantitative analysis of mutant virus recovery from cells expressing wt GP5 protein. The average yields of viruses from three independent experiments with standard deviations (represented by error bars) are shown.