Abstract
Summary
(1) Using a double agar overlay with neutral red in the second overlay only, JBE virus produced distinct plaques with sharp boundaries in monolayer cultures of HKC. They were clear and 4-6 mm in diameter after 6 days of cultivation. In contrast, the plaques produced in the same manner by JBE virus on chick embryo bottle cultures were hazy and 1-3 mm in diameter. (2) Plaque reduction neutralization tests were readily performed and proved to be more sensitive than these performed with the CPE method using monolayers in tubes with fluid medium. (3) A linear relationship was observed between plaque counts and virus concentration, permitting precise quantitative virus assay.
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