Department of Marine Bio and Medical Sciences, Hanseo University, Republic of Korea.
Department of Aqualife Medicine, Chonnam National University, Republic of Korea.
Fish Shellfish Immunol. 2022 Jul;126:336-346. doi: 10.1016/j.fsi.2022.05.044. Epub 2022 May 26.
Production losses of olive flounder (Paralichthys olivaceus) have increased owing to viral haemorrhagic septicaemia virus (VHSV) infection. In this study, we determined safe concentrations of orally administered saponin and chitosan by analysing serum enzyme (AST/ALT) levels as biochemical markers of hepatic injury. Furthermore, we demonstrated the efficacy, duration of protection, and safety of saponin and chitosan-based vaccines with inactivated VHSV (IV). Oral administration of saponin, chitosan, and their combination did not induce fish mortality at all tested concentrations (0.29, 1.45, and 2.9 mg/g of fish body weight/day) 10 days after administration. However, AST level was high at a dose >0.29 mg/g of fish body weight/day. Both saponin and chitosan were found to be safe and acceptable for vaccination studies at a dose of 0.29 mg/g of fish body weight/day. Administration of IV alone did not induce protection at 2 and 4 weeks post vaccination (wpv). Olive flounders administered saponin + IV and chitosan + IV vaccines had higher immunity against VHSV with relative percentage survival (RPS) of 12.5-7.5% and 0-20.1%, respectively; however, additional immunisation with combination of saponin + chitosan + IV clearly enhanced the protection with RPS values of 10-15%, 26.7%, 42.9%, and 37.5% at 4, 8, 12, and 20 wpv, respectively. Although the RPS value of oral immunisation was not comparable to that of injectable vaccines, the manufacturing process is simple and oral administration causes less stress to juvenile fish. To investigate the development of a protective immune response, olive flounder were re-challenged with VHSV (10 TCID/fish) at 70 days postinfection; 100% of the previously unexposed fish died, whereas 80-100% of the previously immunised fish survived. Our results showed the possibility of developing preventive measures against VHSV using saponin and chitosan-based oral vaccines with inactivated virus.
由于病毒性出血性败血症病毒 (VHSV) 感染，橄榄石斑鱼的产量损失增加。在这项研究中，我们通过分析血清酶（AST/ALT）水平作为肝损伤的生化标志物来确定口服皂苷和壳聚糖的安全浓度。此外，我们用灭活的 VHSV（IV）证明了皂苷和壳聚糖基疫苗的功效、保护持续时间和安全性。口服皂苷、壳聚糖及其组合在给药后 10 天在所有测试浓度（0.29、1.45 和 2.9mg/g 鱼体重/天）下均未引起鱼类死亡。然而，AST 水平在剂量>0.29mg/g 鱼体重/天时较高。在 0.29mg/g 鱼体重/天的剂量下，发现皂苷和壳聚糖均安全且可接受用于疫苗接种研究。单独给予 IV 不会在接种后 2 周和 4 周（wpv）引起保护。给予皂苷+IV 和壳聚糖+IV 疫苗的橄榄石斑鱼对 VHSV 的免疫力更高，相对存活率（RPS）分别为 12.5-7.5%和 0-20.1%；然而，用皂苷+壳聚糖+IV 的组合进行额外免疫接种可明显增强保护作用，在 4、8、12 和 20 wpv 时的 RPS 值分别为 10-15%、26.7%、42.9%和 37.5%。虽然口服免疫的 RPS 值与注射疫苗不可比，但制造过程简单，口服给药对幼鱼的压力较小。为了研究保护性免疫应答的发展，橄榄石斑鱼在感染后 70 天用 VHSV（10 TCID/鱼）重新攻毒；以前未暴露的鱼 100%死亡，而以前免疫的鱼 80-100%存活。我们的结果表明，使用基于皂苷和壳聚糖的口服疫苗和灭活病毒可能开发针对 VHSV 的预防措施。
