• Vaccine Name: VHSV Inactivated Vaccine Chitosan Adjuvant
• Target Pathogen: Viral haemorrhagic septicaemia virus
• Type: Inactivated or "killed" vaccine
• Status: Research
• Host Species for Licensed Use: None
• Host Species as Laboratory Animal Model: olive flounder
• Antigen: Inactivated VHSV (Jung et al., 2022)
• Preparation: VHSV (10 TCID50/mL) was inactivated by adding 0.3% formalin with continuous stirring using a magnetic stirrer at 4 ◦C for 24 h. Complete inactivation of the inactivated VHSV (IV) was confirmed by re- inoculation into FHM cells and infection in olive flounder. The combination of saponin and chitosan was used for the evaluation of survival rate at two different concentrations (0.29 and 2.9 mg/g of fish body weight/day). Adjuvant mixtures were mixed using a magnetic stirrer. IV (10^8.8 TCID50/mL) (50% of the total volume) was added to each combination and homogenised on ice for 15 min using PolytronPT 1200E homogeniser (Kinematica, Switzerland) followed by gentle vortexing. (Jung et al., 2022)
• Immunization Route: oral
• Description: Inactivated VHSV vaccine using Chitosan adjuvant protects olive flounder against VHSV challenge. (Jung et al., 2022)

Fish Response

• Vaccination Protocol: Trial III was conducted to study the duration of protection of saponin (0.29 or 2.9 mg) + IV (inactivated virus), chitosan (0.29 or 2.9 mg) + IV, and saponin (0.29 or 2.9 mg) + chitosan (0.29 or 2.9 mg) + IV vaccines. In this study, for primary immunisation, 120 fish (12.1 ± 0.2 g, 10.4 ± 0.6 cm) in each group were orally administered saponin + IV, chitosan + IV, and saponin + chitosan + IV. Each formulation was mixed with feed constituting 1% of total body weight and orally administered for 10 days. Additionally, 120 fish in the non-administered (virus-injected control) and naive groups were maintained at 21–23 ◦C in tanks (200 L) with continuous supply of seawater and aeration. (Jung et al., 2022)
• Side Effects: The group administered 2.9 mg of chitosan displayed severe red liver after 14 days of initial administration. Therefore, our results indicated that oral administration of chitosan at a dose of 2.9 mg (2916 mg/kg of fish) was toxic to olive flounder. (Jung et al., 2022)
• Challenge Protocol: At 4, 9, 14, and 20 wpv (weeks post vaccination), each group of 15 fish was infected with VHSV (106.8 TCID50/100 μL/fish) via i. p. route and maintained for 21, 21, 35, and 91 days, respectively, in an aquarium containing 30 L of UV-treated seawater at 15 ◦C. All survivors from 20 wpv groups (Trial III) at 70 dpi were re-challenged with VHSV. The survivors were administered vaccines containing saponin + IV (10 and 9 fish), chitosan + IV (9 and 8 fish) and saponin + chitosan + IV (10 and 10 fish), respectively, for the administration doses of 0.29 and 2.9 mg. (Jung et al., 2022)
• Efficacy: For the first challenge, the RPS values obtained after were 15%, 0%, 42.9%, and 25% (0.29 mg chitosan + IV), and 10%, 0%, 0%, and 12.5% (2.9 mg chitosan + IV) for the respective challenge time points. For re-challenge, the survival rate was 100% for chitosan (2.9 mg) + IV and 80% in the chitosan (0.29 mg) + IV group. Specific mortality was observed after six days in the virus-infected control group (not previously exposed to virus) with characteristic clinical signs of VHSV and 100% mortality rate at 12 dpi. (Jung et al., 2022)