Characterization of a pattern recognition molecule vitellogenin from carp (Cyprinus carpio)

Pattern recognition proteins function in innate immune responses by binding to molecules on the surface of invading pathogens and initiating host defense reactions. To explore the role of vitellogenin (Vg) in fish innate immunity, we purified Vg from Carp by gel filtration combined with diethylaminoethyl (DEAE) chromatography. The purified Vg was confirmed by MALDI-TOF mass spectrometry. Antibacterial activity analysis showed that Vg inhibited bacterial activity to Escherichia coli and Staphylococcus aureus in a dose-dependent manner. Vg bound to the surface of Gram-negative and Gram-positive bacteria. It also agglutinated E. coli and S. aureus and weakly to Saccharomyces cerevisiae. Vg showed a strong binding activity to lipopolysaccharides from Gram-negative bacteria. Vg-treated macrophage enhanced phagocytosis to E. coli and S. aureus. Vg also bind with macrophage function as opsonins to promote phagocytosis. The results suggest that Vg serves as a pattern recognition molecule and opsonins in antibacterial defense and as an effector in fish innate immunity.