Survival of equine encephalomyelitis virus (Eastern type) for eleven years at 4 degrees C. in the presence of cysteine hydrochloride

A strain of Eastern equine encephalomyelitis virus was maintained for 11 years by (1) periodic repassage in guinea pig and developing chick embryo between the periods of storage in the dry-ice cabinet and (2) by storage at 4 °C. in the presence of cysteine hydrochloride without repassage. No change in pathogenicity or antigenicity of either clone was noted.

The maturation of Western equine encephalomyelitis virus and its release from chick embryo cells in suspension

Experiments are presented in which the plaque assay technique was used to study the intracellular appearance and release of Western equine encephalomyelitis virus in suspensions of infected chick embryo fibroblasts. No intracellular virus could be found during the 1st hour after adsorption in spite of the fact that more than 10(14) cells per ml. proved to be infected. This is taken to indicate that the infecting particle loses its infectivity upon entering a susceptible cell. The first progeny virus was detectable in the cells between 1 and 2 hours after infection, and it increased in amount exponentially during the following 3 hours. The released virus as measured in the supernatant fluid increased at the same rate as the intracellular virus but exceeded it in amount by a factor of about twenty at all times during the period of exponential increase. More than 100 particles were spontaneously released from each cell, by the end of the period of exponential increase, yet the maximum number of intracellular infective particles at any instant during this period was never more than an average of from 4 to 10 per cell. Calculations based on these findings indicate that, on the average, a virus particle is released from the cell within 1 minute after it gains the property of infectiousness.

The viral range in vitro of a malignant human epithelial cell (strain HeLa, Gey). II. Studies with encephalitis viruses on the Eastern, Western, West Nile, St. Louis, and Japanese B types

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One-step growth curve of Western equine encephalomyelitis virus on chicken embryo cells grown in vitro and analysis of virus yields from single cells

The rate of adsorption of WEE virus onto chicken embryo cells in vitro was determined both on a cell layer and on a cell suspension. One-step growth curves were determined in cell suspensions and on cell layers. The latent period varied between 2 and 3(1/2) hours; it was shorter on cell layers and decreased with higher multiplicity of infection. The shortest period is probably the real latent period. The growth curves of the virus showed an initial exponential rise and reached a maximal constant value after 6 to 8 hours. The maximum virus yield per cell varied between 200 and 1000 on the cell layer, and between 100 and 200 in suspended cells. The yield of single infected cells was determined. An analysis of the distributions of the individual yields obtained after various periods of virus growth led to two main conclusions: (1) that virus is released from the same cell over a long period of time; (2) that one phase of the intracellular virus growth is exponential.