Abstract
Summary
From the results of these experiments to develop a more potent virus in the egg, it is concluded that the greatest amount of virus of the Japanese Nakayama strain of encephalitis would probably be obtained in chick embryos by using 7- or 8-day-old embryonated eggs inoculated into the yolk with 0.5 cc amounts of mouse brain virus of a potency of 10-8.5 or better, and incubating 36 hours at 95° to 96° F. The use of normal rabbil serum in the diluent might raise the potency slightly, but would be contra-indicated if there was a possibility of carrying over another foreign protein into any prospective vaccine. Because of the constant lethal effect, inoculation of the egg yolk is of value for titration of this virus and for use in other quantitative experiments. At no time, however, did the titrations of egg tissue reach as high endpoints as those obtained with the mouse brain virus.
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