Fig. 2.

In vitro growth characteristics of E1ΔCys mutant viruses relative to parental BICv. (A and B) Primary swine macrophage cell cultures were infected (MOI = 0.01) with each of the single (A) and double (B) E1ΔCys mutant viruses or BICv. Virus yields were calculated by titration at times after infection of SK6 cells. Data represent means and standard deviations from two independent experiments. Sensitivity of virus detection, ≥log₁₀ 1.8 TCID₅₀/ml. (C) Foci of infection of single and double E1ΔCys mutant viruses and parental BICv were detected on SK6 cell monolayers by immunoperoxidase staining using anti-E2 MAb WH303.