Immunostimulating effect of growth hormone: in-vivo administration of growth hormone in rainbow trout enhances resistance to Vibrio anguillarum infection

In-vivo administration of purified (nGH) and recombinant (rGH) chum salmon, Oncorhynchus keta, growth hormone enhanced the survival of rainbow trout, O. mykiss, against virulent Vibrio anguillarum. Macrophages obtained from rainbow trout that were treated in vivo with either GH preparation showed enhanced stimulation of the chemiluminescent responses induced by opsonized V. anguillarum cells and increased phagocytic activities. However, the serum bactericidal activity against V. anguillarum was not enhanced in fish injected with nGH or rGH. These findings show that in-vivo administration of either GH preparation can effectively prime macrophages and increase the resistance to V. anguillarum in rainbow trout.