Effect of incubation temperature and serum content in agar overlay on plaque production by foot-and-mouth disease virus.

The numbers of plaques produced by foot-and-mouth disease virus in primary cultures of calf kidney cells conditioned to 24, 30, and 37 C were essentially the same if virus was absorbed at 37 C. Adsorption was as effective at 30 as at 37 C in cultures conditioned to the respective temperature, but 24 C was less effective under this condition. However, when the adsorption temperature for cultures conditioned to 37 C was decreased to 30 or 24 C, fewer plaques were produced than in cultures conditioned to and maintained at the lower temperatures during absorption. Comparison of the number of plaques produced in cultures overlaid with nutrient agar containing from 0.5 to 10% bovine serum revealed no difference in relation to serum concentration. However, plaque size was related directly to the concentration of serum in the overlay.