3.1. Survival rate in vaccine trial I
Survival rates of fish intraperitoneally injected with live
[Poly(I:C)-VHSV] and formalin-treated (DEPC-FT VHSV) vaccines
were monitored (Fig. 2A). Only 2% (1 of 50 fish) mortality was
observed in the DEPC-FT VHSV group. The cumulative mortality
rate of the Poly(I:C)-VHSV group was 4% (2 of 50 fish) until 28 d
after inoculation. No fish in the naïve group died during the
experiment. However, the fish that were not pre-inoculated with
Poly(I:C) (DEPC-VHSV group) began to die 4 d after the VHSV
challenge and had a cumulative mortality rate of 80% at the end of
the experiment (Fig. 2A).
The surviving fish from the Poly(I:C)-VHSV and DEPC-FT VHSV
groups were challenged with VHSV at a dose of 106 TCID50
100 mL1 fish1 28 d after vaccination. Cumulative mortality was
monitored until day 28 after the VHSV challenge (Fig. 2B). Fish from
the naïve group began to die 4 d after the challenge and had a
cumulative mortality rate of 80% (Fig. 2B, Naïve-VHSV). Fish in the
Poly(I:C)-MEM10 and DEPC-FMEM10 groups began to die 4 d after
the challenge. The cumulative mortality rate was 90% in the
Poly(I:C)-MEM10 and DEPC-FMEM10 groups. No fish in the naïve
negative control group died during the experiment. The Poly(I:C)-
VHSV group had a 100% survival rate, while the DEPC-FT VHSV
group had an 80% survival rate (Fig. 2B).