FIG. 4.

(A) Growth curves of the recombinant CSFV mutants and the wt virus. SK6 cells were infected with CSFV Alfort/Tübingen (wt), V-H297K (RNase negative), or V-C171d (dimerization negative) at an MOI of 0.1 and harvested by freezing and thawing at the indicated time points. Titers were determined by immunofluorescence staining with monoclonal antibody a18 at 72 h p.i. The curves represent the mean values from four individual experiments. Standard deviations are indicated. (B) Inactivation kinetics of wt CSFV and mutant V-C171d. Virus stocks (titers adjusted with tissue culture medium) were incubated at 37°C. Samples were taken for titration at the indicated time points. The graph shows the mean values from two independent experiments.