Plaque formation by Teschen disease virus and the effect of certain associated factors.

A plaque assay method was developed for Teschen disease virus using primary pig kidney cultures in which neutral red stain was incorporated in the agar overlay medium. Certain factors associated with the plaque-forming ability of the virus were standardized. Cultures allowed to adsorb the virus for 45-60 minutes at 28 and 37 C, gave maximal plaque count. The virus infected the cellular layer through the agar medium. Plating efficiency of the virus was enhanced by using a small volume of inoculum. Addition of serum to the medium was not required. Neutral red concentration in the agar overlay medium affected the number of plaques. Statistical analysis demonstrated the uniformity of the plaque counts and their linear relationship to virus concentration. Isolation of the virus by the plaque technique from infected spinal cord supernatant fluid was achieved.