Abstract
Summary
A strain of A2/Hong Kong/68 virus was adapted to growth at 25° in calf kidney tissue culture and a virus suspension was prepared for administration to volunteers after a total of 10 passages at 25°, including 2 terminal dilution purifications. The low temperature grown virus acquired a temperature sensitive defect which restricted its growth at 40 °, a temperature at which the wild-type virus grew without restriction. The low temperature-adapted virus appeared to exhibit reduced infectivity for man, but was not attenuated since illness occurred when sufficient virus was administered to infect all volunteers.
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