Development and Evaluation of Immunoprotective Efficacy of Membrane Protein Vaccine Against Scuticociliatosis.

OBJECTIVE

To develop a novel and efficient vaccine for controlling scuticociliatosis in turbot (Scophthalmus maximus), this study targeted the parasitic ciliate Pseudocohnilembus persalinus for membrane protein vaccine preparation.

METHODS

The immunoprotective efficacy and underlying molecular mechanisms of the vaccine were systematically evaluated through immunization-challenge experiments, immune parameter detection, and transcriptomic analysis.

RESULTS

Results showed that the serum IgM level in turbot immunized with the membrane protein vaccine reached its peak one week after the second immunization, which was significantly higher than that in the control group and the whole-cell protein vaccine group (p < 0.05). Additionally, the activities of serum peroxidase (POD), total superoxide dismutase (T-SOD), acetylcholinesterase (ACH), and lysozyme (LZM) were significantly enhanced (p < 0.05). At 24 h and 48 h post-challenge, the relative parasite reduction rates at the wound sites in the membrane protein vaccine group were 87.79% and 74.17%, respectively. Transcriptomic analysis revealed 1063 differentially expressed genes (DEGs) in the spleen tissue of turbot immunized with the membrane protein vaccine, including 734 upregulated and 329 downregulated genes. These DEGs were significantly enriched in pathways such as glycine, serine and threonine metabolism and one carbon pool by folate, which are involved in immune responses by regulating immune cell proliferation, antioxidant defense, and immune substance synthesis.

CONCLUSIONS

This study successfully developed a P. persalinus membrane protein vaccine with excellent immunoprotective efficacy and elucidated its molecular mechanisms of protection. It provides a novel vaccine candidate for the green control of turbot scuticociliatosis and offers a theoretical basis and technical support for the development of fish parasite subunit vaccines.