Received: 14-08-2014 / Accepted: 29-11-2014
Most vaccines usedin aquaculture are killed or inactivated pathogens. The goal of vaccination is the generation ofimmune response to administerantigen able to provide long -term protection against infection. To achive this objective, it requires the addition of an adjuvant. Among adjuvants, oil adjuvants are the most common used for vaccine in aquaculture. However, there were few studies describing mechanism reaction tooil adjuvant in fish. This study injected killed a polyvalent vaccines imulsified with Montanide TMISA 760 adjuvant against V.alginolyticus, V. parahaemolyticus, and V. harveyi causing Vibriosis in cobiaRachycentron canadum. The musculartissuesat the injection site was sampled at day 7, 14 và 21 post vaccination and fixed by buffer formaline 10% for histological observations. Histological sections were cut and stained by H&E to observe structure changes caused by oil adjuvant. The result showedthe the oil dropletsdeposited in the muscle and the muscular fibers were broken atthe injectionsite7 dayspost vaccination. At 14dyas post vaccination the sign of immune responsewith inflammatory cells surrounding the oil droplets forming granuloma.The inflamatorylesions and granuloma were observed more obvious at y 21days post vaccination. This study indicated that oil-based vaccine not only induced cellular immune response but also causedserious side-effectsat the injection site in cobia.