In addition, a new method, Poly(I:C) immunization
with a live vaccine, has been shown to provide powerful
protection against VHSV challenge in olive flounder [15]. In vaccine
trials I and II in the present study, Poly(I:C) immunization offered
olive flounders protection against VHSV challenge. In vaccine trial I,
the survival rate was 96% in fish injected with VHSV at a dose of 106
TCID50 100 mL1 fish1 following Poly(I:C) injection. The surviving
fish from the Poly(I:C)-VHSV group showed 100% survival following
a subsequent VHSV challenge. In vaccine trial II, the survival rate of
all Poly(I:C)-VHSV groups against VHSV challenge was 100%, while
the survival rates of the DEPC-VHSV 6, 5, and 4 groups were 15%,
60%, and 75%, respectively. In an investigation of the efficacy of
Poly(I:C) immunization as a protective measure against VHS in
Japanese flounder via injection of Poly(I:C) followed by VHSV
challenge at a dose of 104.3 TCID50 100 mL1 fish1
, Takami et al. [15]
showed that a small dose of live vaccine (such as 104 TCID50/fish)
induced an immune response against the highly pathogenic VHSV