Abstract
Summary
Variola virus was lethal for mice by intracerebral route when relatively high doses were inoculated. Lower doses produced erratic death patterns. Virus proliferated in mouse brain reaching peak titer between 48 and 72 hours. Amount of virus at peak titer was dependent on quantity of virus inoculated. Ten consecutive passages of the virus in mouse brain were successfully carried out. The most important factor which appeared to influence successful serial passage of the virus was level of titer attained in preceding passage. This titer was, in turn, dependent on size of inoculating dose, time of harvest and age of mouse. The passaged virus was identical with parent strain with respect to a number of properties examined.
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