Ulvan Polysaccharide Enhances the Efficacy of an Injectable Yersinia ruckeri Vaccine in Rainbow Trout (Oncorhynchus mykiss).

Authors

Mohammad Mazandarani, Majid Khanzadeh, Mohammad Sudagar, Hamed Paknejad, Ali Taheri Mirghaed, Ali Kavousi

Published in

Journal of fish diseases. Pages e70281. Aug 31, 2026. Epub Aug 31, 2026.

Abstract

This research was designed to explore the immunogenicity of the yersiniosis vaccine and the effect of Ulvan as a natural adjuvant on immune, antioxidant and survival parameters in Oncorhynchus mykiss. A total of 450 O. mykiss (mean body weight 52.90 ± 2.02 g) were allocated to three experimental treatments, each with three replicate tanks. Treatments were: (1) injectable inactivated Yersinia ruckeri vaccine (Vac), (2) the same vaccine formulated with Ulvan as an adjuvant (Vac + U) and (3) an unvaccinated control group (Ctrl) receiving phosphate-buffered saline (PBS). White blood cells were significantly elevated in all vaccine-treated groups compared with the Ctrl group on days 30 and 60 (p < 0.0001). In contrast, no significant treatment effects were observed for red blood cells (p = 0.1078), haemoglobin (p = 0.2646), or haematocrit (p = 0.2352) at either sampling time. There were no significant treatment impacts on total protein (p = 0.3330) or serum globulin (p = 0.6521) at the 30- or 60-day samplings. Conversely, serum albumin was notably elevated in the Vac + U group relative to the Ctrl at both 30 and 60 days (p = 0.0244). Vaccination induced pronounced increases in both serum immune (lysozyme, total immunoglobulin, NBT) and antioxidant (catalase, superoxide dismutase, glutathione peroxidase) parameters at 30 and 60 days post-immunization compared with Ctrls (p < 0.05). Antibody titers against yersiniosis were significantly higher in all vaccine-treated groups than in the Ctrl group at 30 and 60 days post-immunization (p < 0.0001). Survival rate after a two-week Y. ruckeri challenge was 73.33% (Vac), 86.66% (Vac + U) and 16.66% (Ctrl); survival in the vaccine-treated groups was notably higher than in the Ctrl group (p < 0.0001). The results indicated that both the vaccine and the Vac + U formulation enhanced biochemical markers, immune-antioxidant responses, serum antibody titers and survival following challenge with Y. ruckeri infection. Among the tested groups, the Vac + U demonstrated the greatest effectiveness, likely due to the presence of Ulvan as an adjuvant.

PMID:
42674674
Bibliographic data and abstract were imported from PubMed on 01 Sep 2026.

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