Fish immune response againts Neobenedenia sp. (capsalidae:monogenea) in yellowtail (Seriola lalandi)

Abstract

Neobenedenia sp. is a parasite that causes significant mortality and subsequent economic losses in yellowtail aquaculture. A dramatic change in the antigenic composition of this parasite occurs during its stage conversion. In this study, we evaluated first, the humoral parameters in serum and transcriptional immune response in spleen leukocytes of yellowtail infected with Neobendenia sp. In addition, in vitro assays were performed to study the stimulatory effects of larvae and adults antigens of Neobenedenia sp. on non-infected spleen leukocytes at 6 and 24 h post-stimulation. In this study, the results show an enhanced in total protein, myeloperoxidase and anti-protease activities in fish infected with Neobenedenia sp. compared with healthy fish. Induction of TLR`s and proinflammatory cytokines by spleen leukocytes during natural infection with Neobenedenia sp., suggest that this immune-related genes play an important role in the initiation of immune defense mechanism in controlling parasite infection. Interestingly, magnitudes of in vitro responses of spleen leukocytes were dependent on the stage of the parasite. An important stimulation of gene expression by adult antigens on spleen leukocytes was observed. Differential expression patterns of TLR s and target cytokines in yellowtail leukocytes at both in vivo and in vitro studies suggest that quality of yellowtail immune response is conditioned by Neobenedenia sp. development.