Growth characteristics of virulent and attenuated strains of bluetongue virus serotypes 10, 11, 13 and 17.

The growth properties of wild type (WT) and live, attenuated vaccine (V) strains of bluetongue virus (BTV) serotypes 10, 11, 13 and 17 were compared. All BTV strains produced maximal yields when grown at 34 C and harvested 24-36 hr after infection. The 4 V strains were temperature-sensitive (ts) for growth at 39 C as compared to the corresponding WT strains. The 4 V strains were ts for plaque formation when 37 C was used as the nonpermissive temperature. One-step growth curves showed that only the V strain of type 13 had significantly altered growth kinetics as compared to the corresponding WT. All BTV strains were strongly cell associated throughout the growth cycle.