Induction of Mx protein in Atlantic cod with poly I:C: Immuno-cross reactive studies of antibodies to Atlantic salmon Mx with Atlantic cod

A polyclonal rabbit antiserum directed against the conserved region of the Atlantic salmon antiviral Mx1 protein was used to detect the putative Atlantic cod Mx protein using Western and dot blotting. A doublet band at about 75 kDa and 65 kDa was detected by Western blotting in kidney and spleen extracts of cod 3 and 4 days after i.p. injection with poly I:C but not in control fish injected with PBS. In blood leucocyte lysates, similar immunostaining could also be detected in Atlantic cod weakly after injection with PBS and more intensely after injection with poly I:C, suggesting some constitutive expression of Mx protein by leucocytes.Dot blot analysis showed that the Mx protein level was significantly higher in spleen, kidney, liver and gill of cod at least up to 4 days after injection with poly I:C when compared with the PBS-injected controls.