Submitted to: Journal of Fish Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/14/2007
Publication Date: 2/14/2008
Citation: Wiedenmayer, A.A., Klesius, P.H., Evans, J.J., Shoemaker, C.A. 2008. The macrophage chemotactic activity of Edwardsiella tarda extracellular products. Journal of Fish Diseases. 31(5):331-342. Interpretive Summary: The fish pathogen, Edwardsiella tarda is economically important pathogen of many different species of fish. The mechanisms of pathogenesis are poorly defined, but infection causes an inflammatory response by white blood cells, primarily macrophages. The goal of this study was determined the role of extracellular products produced by E. tarda in the inflammatory response by macrophages. The results of the study demonstrated exposure of macrophage in vitro to E. tarda extracellular product promoted the chemokinectic movement of macrophages. Macrophage migration toward the extracellular product suggests that its excretion/secretion from invading E. tarda cells plays a role in the initation of the inflammatory response.
Technical Abstract: The chemoattractant capabilities of Edwardsiella tarda extracellular products (ECP) were investigated from two isolates, the virulent FL6-60 parent and less virulent RET-04 mutant. Chemotaxis and chemokinesis were assayed in vitro using blind well chambers with peritoneal macrophages obtained from Nile tilapia Oreochromis niloticus 5 d following squalene injection. Non-purified ECP derived from both isolates stimulated predominantly chemokinetic migration of macrophages. Additionally, the ECP were semi-purified by high pressure liquid chromatography. The FL6-60 parent ECP yielded higher molecular weight components than did the ECP from RET-04 mutant. The chemotactic activity of the macrophages for both the FL6-60 parent and RET-04 mutant semi-purified ECP was increased over the non-purified ECP and overall migration was primarily chemotactic. Exposure to ECP derived from virulent and less virulent of E. tarda isolates promoted chemokinetic movement of macrophages that may be involved in inflammatory responses of Nile tilapia to E. tarda infection.