Vaccines developed for fish have been focused on protecting Salmonidae species against virus and intracellular bacteria; where a Th1 and cellular response is generally required to improve the protection, which is characteristic of saponin adjuvants. Complementary studies confirmed the adjuvanticity effect and protection of saponin adjuvant alone or in combination formulated with different antigen types in varied fish species against distinct viruses and bacteria.
Saponin adjuvant saponin adjuvants can effectively stimulate both humoral and cellular immune responses. Saponin adjuvants significantly boosted the protective efficacy of the DNA vaccine against the infectious spleen and kidney necrosis virus (ISKNV) in intramuscularly injected Chinese perch (Figure 1) [1]. The vaccination of rock bream against RIBV improved RPS by 93.34% in a prime-boost immunization regimen [2]. Protection against VHSH was improved by orally administering olive flounders with prime and boost immunization using adjuvanted vaccines of saponin combined with chitosan. Seventy days after infection, olive flounder were re-challenged with VHSV; 80–100% of the previously immunized fish survived, but 100% of the previously unexposed fish perished [3].
MUCOSAL ROUTES OF ADMINISTRATION
Two studies have evidenced the higher protection induced by the mucosal administration of saponin adjuvanted vaccine to olive flounders (oral) and turbot (immersion) fishes against viruses, though not always reaching the same survival rate as immunization via parenteral route [2,3]. Oral vaccinations adjuvanted with saponins could be used to prevent VHSV. Based upon toxicity studies, a concentration below 1.45 mg/fish is recommended as safe for administration to olive flounder [3].
References
1. Fu, X. et al., 2014. Protective immunity against infectious spleen and kidney necrosis virus induced by immunization with DNA plasmid containing mcp gene in Chinese perch Siniperca chuatsi. Fish & Shellfish Immunology, Volume 40, pp. 259-266.
2. Jung, M.-H., Kole, S. & Jung, S.-J., 2022. Efficacy of saponin-based inactivated rock bream iridovirus (RBIV) vaccine in rock bream (Oplegnathus fasciatus). Fish & Shellfish Immunology, Volume 121, pp. 12-22.
3, M.-H., Jung, S.-J. & Kim, T., 2022. Saponin and chitosan-based oral vaccine against viral haemorrhagic septicaemia virus (VHSV) provides protective immunity in olive flounder (Paralichthys olivaceus). Fish & SHellfish Immunology, Volume 126, pp. 336-346.
