FIG. 3.
Single-step (A) and multiple-step (B) growth curves of wt CCV, rCCV-1, CCV-ΔTK, and CCV-ΔORF12. Virus was harvested from infected CCO cells at the indicated times postinfection (hpi), and titers were determined in triplicate by end-point dilution and titration on CCO cells. Averaged titers and 95% confidence intervals are illustrated. The morphology of syncytial plaques formed on CCO cells by rCCV-1, CCV-ΔTK, or CCV-ΔORF12 viruses was indistinguishable from that of wt CCV (inset). (C) Mean cumulative mortality of catfish fingerlings infected with wt CCV or rCCV-1 viruses at a dose of 1 × 104, 1 × 105, or 1 × 106 TCID50/liter. Although mortality significantly (P < 0.05) differed by CCV dose, mortality was not significantly different between the groups infected with the same dose of each different virus (P > 0.05).