Protective Studies in Mice and Monkeys with an Inactivated Japanese Encephalitis Virus Vaccine Grown in Hamster Diploid Cell Culture. ∗

Abstract

Summary

Formalin inactivated Japanese encephalitis virus vaccine prepared with a recently isolated strain (JEO) in tissue culture of a continuously propagated hamster embryo skin and muscle diploid cell has been tested for potency in mice and monkeys. Several lots of vaccine had a protective potency in the mouse test with intracerebral challenge similar to that required by the Japanese government. In 2 separate experiments in monkeys the vaccine produced substantital titers of HAI antibdy, reduced the amount of viremia after intranasal challenge and protected them from death. The potency of cell culture vaccine was compared to vaccine produced from mouse brain. In the mouse the cell culture vaccine gave better protection against challenge with a low passage strain, while the mouse brain vaccine protected better against the homologous high mouse passage Nakayama strain. In the monkey protection test, cell culture vaccine produced higher HAI antibody and much better protection against intranasal challenge with the low passage strain.