Caligus rogercresseyi is an ectoparasitic that produces the greatest economic losses in the salmon industry. Therein, v accine-based control strategies for this sea louse have long been desired . T he genome and the transcriptome data reported for C. rogercresseyi, allow the identification of putative antigens using the reverse vaccinology approach. This study aimed to evaluate the efficacy of vaccine prototypes during t he sea lice infestation and their effects in host-parasite transcriptome modulation.
Atlantic salmon were immunized with recombinant proteins peritrophin, and cathepsin identified from sea louse genome. Four experimental group were vaccinated with different prototypes peritrophin , cathepsin, peritrophin/cathepsin (P/C) combination and PBS as control. Follow 400 UTAs, vaccinated salmons were infested with 35 copepodid per fish . Sea lice attachment were evaluated at 7 and 25 days post infestation (dpi). Samples of head kidney and skin tissues , and C. rogercresseyi female were taken f or mRNA Illumina sequencing. RNA-seq analysis were performed . Moreover, for contigs differently express GO and KEEG pathway analysis were performed . In addition, the morphometry of adult lice exposed to immunized fish was evaluated.
Fish vaccinated with cathepsin, and P/C showed 57% efficacy, reducing adult lice bunder. Transcriptome analysis indicated a vaccine -dependent gene modulation , both at 7 and 25 dpi . Furthermore, at 7 dpi fish vaccinated with P/C and cathepsin showed an upregulation of genes associated whit metal ion binding, molecular processes energy production comparing with the control group . While at 25 dpi for Atlantic salmon and sea lice, genes associated with ATP binding, calcium ion binding, iron ion binding and zinc ion binding were strongly upregulated . Notably, the morphometric analysis shows difference in shapes between C. rogercresseyi exposed to vaccinated fish, with 8.3% of the shape explained by canonical variables 1 and 2. The results suggested that the vaccine prototypes stimulate energetic metabolism in salmon at 7 dpi. In addition, competition for metal ions between the host and the parasite in the infestation was evidenced. Finally, this study uncovered the molecular responses produced during host-parasite interaction in vaccinated fish and provide a new strategy for sea lice control in the salmon industry.
Acknowledgments: This study was funded by FONDAP grant #15110027 and ANID-PCHA/Doctorado Nacional (Grant 2018-21180084).