Assay for and Replication of Karshi (Mammalian Tick-Borne Flavivirus Group) Virus in Mice

摘要

Little is known about the replication of Karshi virus, a member of the mammalian tick-borne flavivirus group, in its rodent hosts. Therefore, we developed a novel quantitative real-time RT-PCR assay and measured the amount of viral RNA in selected tissues of infected Swiss Webster mice. Two-day-old mice were highly susceptible, with 100% fatality between days 9 and 12 after infection, while 9-day-old mice were less susceptible with death occurring only rarely. In nearly all cases, mice inoculated when 2-days old contained similar numbers of viral genome equivalents from blood and liver samples from any given mouse, with titers declining after day 7. In contrast, the amount of viral RNA in the brain began to rise rapidly 4 days after exposure, peaked at about 6 days after virus exposure with a (titer of > 10 (exp to the 13) genome equivalents/g), and remained at that level until euthanasia or death. Viral profiles were similar in needle-inoculated or tick-exposed mice.