In vitro Cultivation and Cytopathogenicity of Vesicular Exanthema Virus.

Discussion and Conclusions An agent capable of producing typical vesicular exanthema in swine has been propagated through 16 passages in a swine embryo tissue culture system. In the course of these passages the original material has been diluted to 10-19, so that it is highly unlikely that any infective material from the original inoculum was carried through all 16 passages. Multiplication of this agent in tissue culture was accompanied by extensive degeneration of epithelial cellular outgrowths which thus provided a simple means for in vitro assay of this virus. Considerable investigation is still required to determine the sensitivity and reliability of the system of tissue culture assay, whether in swine embryonic tissues or adult tissues such as kidney epithelium. Preliminary experiments have indicated that plaque formation on swine kidney epithelium using the method of Dulbecco7 is feasible. Evidence that the cytopathogenic agent was in fact the B type of the virus of vesicular exanthema was provided by the following observations: 1) The agent produced clinical vesicular esanthema in swine with wbiequent immunity to challenge with known 1I type virus, without loss of susceptibility to infection with the A type virus. 2) Specific complement fixation was obtained when tissue culture agent was mixed with serum from guinea pigs hyperimmunized with N type virus, but not when mixed with serum from guinea pigs hyperimmunized with the A type. 3) Neutralization of the cytopathogenic effect was observed in tissue culture when the agent was mixed with 13 type immune swine serum but not when mixed with A type antiserum.