A monoclonal antibody against chorion proteins of the sea bass Dicentrarchus labrax (Linnaeus, 1758): Studies of chorion precursors and applicabilityin immunoassays

The monoclonal antibody DLE7 was obtained against 44- to 50-kDa polypeptide s solubilized from the vitelline envelope of the Mediterranean sea bass Dic entrarchus labrax. In Western blot analysis of chorion lysates it recognize d cross-reactive bands at 44 kDa, 48 kDa, and 110 kDa. Previous affinity bl otting with concanavalin-A showed that most of solubilized bands were glyco sylated. Enzymatic deglycosylation of chorion proteins followed by Western blot analysis with DLE7 showed that the 48-kDa and 110-kDa antigens were di fferentially affected by endoglycosidase-F treatment. When DLE7 was employe d in immunofluorescence analysis, isolated chorions and ovarian cryosection s stained intensely. Positivity was also observed in liver cryosections of spawning females but not in liver of males and nonspawning females. To stud y the origin and delivery of chorion proteins, DLE7 was used in Western blo t analysis of liver homogenates and blood serum of spawning females. Cross- reacting bands were detected in liver (90 kDa) and serum (180 kDa, 50 kDa). DLE7 was also used for the first time to set up an indirect ELISA assay to detect egg antigens in the blood of egg-producing females, raising the pos sibility of using DLE7 as a female-specific marker of spawning for sea bass .