Multiplication of the Virus of Foot-and-Mouth Disease in Culture

Summary: The infectivity curve of the virus of foot-and-mouth disease was studied in cultures of suspended trypsinized cattle-tongue epithelial cells. By this technique a known number of cells could be exposed to a known amount of virus. The pattern of multiplication was that adsorption of the virus by the cells occurred rapidly and, except with low concentrations of virus, was complete in 15–30 min. A latent period of about 2·5 hr. followed during which the virus was closely associated with the cells, was protected from the neutralizing action of antiserum, was not readily extractable but retained its infectivity. At the end of the latent period the infected cells became producers of virus at a rate estimated to be between 102 and 103 ID 50/15 min. At about 12 hr. the infectivity of the culture began to decline because of death of virus-producing cells and thermal inactivation of the virus.