GROWTH OF VENEZUELAN EQUINE ENCEPHALOMYELITIS VIRUS IN L CELLS I. GROWTH IN MONOLAYER CULTURES'

The spectrum of tissue culture susceptibility to Venezuelan equine encephalomyelitis virus in-cludes an extensive range of cell hosts obtained from primary tissue culture and from established cell lines (reviewed by Hardy, 1959). The present work describes the kinetics of growth and cytopathology resulting from the interaction of Venezuelan equine encephalomye-litis virus and L cells, as studied in monolayer culture. The cell line which originated from a single cell (Sanford, Earl, and Likely, 1948) proved to be uniformly susceptible to infection by this virus (Hardy and Brown, unpublished data). MATERIALS AND METHODS The virus strain, preparation of virus stock, titration procedure, and preparation of L cell tissue cultures have been described previously (Hardy, 1959). Infection of tissue culture. The usual procedure was designed to infect rapidly as many cells as possible by using high multiplicities of infection, so that a one-step or single cycle growth curve might be approached. After a confluent sheet of L cells had been grown in a T-60 Earle flask, the medium was removed and a high mouse intracerebral median lethal dose (MICLD5o) of virus contained in 1 ml was inoculated so that the input multiplicity of infection was approximately 100 to 400 (about 109-5 MICcLD5o per 107 cells). After a 1-hr contact period at room temperature or at 4 C, the culture was washed three times, 20 ml per wash, with medium no. 199 (Morgan, Morton, and Parker, 1950), containing 20 per cent horse serum (19980 HoS20). Twenty ml of fresh medium were then dispensed into the flask, sampled for residual I A preliminary report of this work was give