Inducing bursicon expression using 20-hydroxyecdysone (20E) increased immune response in Macrobrachium rosenbergii against Aeromonas hydrophila.

A bursicon (burs) is a neurohormone that regulates cuticle tanning after molting, as well as the immune response, in insects and crustaceans. This study investigated the relationship between ecdysteroids, burs expression and immune regulation following 20-hydroxyecdysone (20E) injection in Macrobrachium rosenbergii. Burs subunits (burs α and burs β) were highly expressed in the thoracic ganglia during the late pre-molt stage (D3). Significant upregulation of the burs α and burs β, anti-lipopolysaccharide factor (ALF) and crustacean hematopoietic factor (CHF) genes accompanied an increase in the hemocyte concentration. The efficacy of immune enhancement for disease protection from 20E injection showed that 20E treatment upregulated burs genes in thoracic and abdominal ganglia. ALF and CHF expression and phenol oxidase activity were significantly increased. The hemocyte proliferation percentage in hematopoietic tissue increased 12 h post-infection, while circulating hemocytes increased significantly within the first 24 h. Administering 20E decreased mortality in Aeromonas hydrophila-challenged prawns. This study demonstrated that the ecdysteroid 20E stimulated burs expression and improved the immune response to bacterial challenge, suggesting that this hormone plays a role in regulating the immune system during ecdysis.