Water Extract Promotes the Expression of Proinflammatory and Th1-Type Cytokines and Delay the Onset of Mortality in Cobia () During subsp. Infection.

Cobia () is a marine fish of high economic value that grows at a fast rate. However, intensive fish farming has led to disease outbreaks in cobia cultures, which is highly costly to the industry. The impact of infectious diseases on cobia production has led to the inappropriate and increased use of chemicals and antibiotics, which negatively affects the environment and human health and promotes the spread of drug-resistant pathogens. Hence, prophylactic measurements, such as the use of immunomodulators, are required to improve the health of cultured animals against pathogens. In this study, we examined the effects of water extract (SSWE) in cobia and . We found that treatment with SSWE could significantly increase the expression of cytokines (e.g., , , , , and ) and chemokines (e.g., ) in primary cultured head kidney leukocytes. Intraperitoneal injection of SSWE (20 μg/g body weight) promoted higher expression of , , , , chemokines (e.g., ), and antibodies (e.g., ) in head kidney and spleen tissues of the fish compared with other dose levels. Additionally, we describe for the second time (only after India) of the isolation of subsp. () from a deadly epizootic in cage-farmed cobia. An intraperitoneal inoculation of SSWE before challenge showed that SSWE treatment could delay the onset of mortality of cobia. Finally, fish that received SSWE intraperitoneally before infection with exhibited elevated expression of Th1-type cytokines, namely, , , , and . At the same time, the expression of Th2-related factors (such as in the head kidney, and and in the spleen) were lower for the fish that received SSWE instead of PBS before the challenge. The results indicate that SSWE treatment facilitates the induction of Th1-type cytokines in cobia to fight against infection and has the potential to be used as an immunostimulant and vaccine adjuvant for fish.