Abstract

Vaccine development against sea louse (Caligus rogercresseyi) represents a preventive strategy to reduce parasitism in Chilean salmon farming, complementary to antiparasitic control methods. In this study, we demonstrated the protective effect in Atlantic salmon (Salmo salar) of an experimental W/O subunit vaccines targeting antigens sea louse, which has been evaluated and compared to effects elicited by control group (adjuvant + phosphate buffer saline). Five specific recombinant C. rogercresseyi proteins were combined in three different prototypes using a commercial adjuvant and injected by i.p. in fishes (167 g). Subsequently, after 492-degree days, protection, immune and antibody responses were analyzed. Vaccine prototype 2 induced a significant protection and reduction (P>0.05) against different stages of C. rogercresseyi when compared to non-vaccine group (control) fish by direct counting of parasites per fish, resulting in 50% and 48% of effectiveness against attached juvenile and adult stages, respectively, after 7 dpi. During the count of juveniles and adults (12 and 22 dpi), we observed a delay in the metamorphosis in the all vaccinated groups. In addition, prototype 1 and 3 increased of the relative mRNA expression of IgM and IgT in skin samples taken before the challenge, while, all prototypes increasing this relative mRNA expression in head kidney samples. Finally, ELISA test using serum from treated and control fish samples showed specific antibody responses against the three proteins of vaccinated salmon compared with control group during the 82 days of trial.