Pathogenesis of iridovirus: in vitro influence on macrophage activity and cytokine-like protein production in fish

Abstract

In recent years, iridovirus-like agents have been recognized as the cause of several diseases in fish. An iridovirus-like pathogen isolated from catfish (Ictalurus melas) was tested in vitro on the macrophage activity and cytokine-like protein (IL-1, IL-6) production in carp (Cyprinus carpio L.), rainbow trout (Oncorhynchus mykiss) and sheatfish (Silurus glanis L.). The influence of the iridovirus on pronephric macrophage activity was examined by studying the respiratory burst activity (RBA) and potential killing activity (PKA) as well as the production of cytokines by pronephric leukocytes stimulated by ConA. The results showed that iridovirus decreased the RBA and PKA in carp, rainbow trout and sheatfish. The highest inhibitory effect was observed in sheatfish (70 % of activity), compared to carp (35 % activity) and rainbow trout (20 % activity). The production of cytokines by pronephric leukocytes had a similar pattern. The results showed that iridovirus decreased significantly (P < 0.05) the IL-1-like protein and IL-6-like protein production and the highest inhibitory influence in sheatfish was observed. This preliminary in vitro comparative study demonstrated a suppressive influence of the iridovirus-like pathogen on macrophage activity and cytokine-like protein production in carp, rainbow trout and sheatfish, but the highest immunosuppressive effect was observed in sheatfish.