An IDP16 protein from Xenorhabdus bovienii depresses the immune response in Galleria mellonella

Abstract:

Abstract:［Objective］ A protein with insect immunodepressive activity was purified from Xenorhabdus bovienii，a bacterial symbiosis of entomopathogenic nematode． To determine the function of this protein in the pathogenesis of bacterium-nematode symbiosis，we detected the effect of this protein on immune response in Galleria mellonella．［Methods］Proteins from extracellular extact of X． bovienii were purified using ammonium sulfate precipitation，HiTrap Q HP chromatography，HiTrap Butyl FF chromatography，and HiTrap SP HP chromatography． Intra-hemocoel injection assay followed by observation of hemolymph melanization was used for activity determination． Fluorescent microspheres and sepharose beads were used to assess the effect of purified protein on phagocytosis and encapsulation of hemocytes，respectively． The purified protein was identified by 2-D and MS anlysis． The full-length encoding gene was cloned by PCR，and expressed with pET 30a in Escherichia coli． The recombinant protein was purified by Ni-NTA affinity chromatography． ［Results］ An immunodepressive protein was purified and designed as IDP16，which can inhibit the phenoloxidase activity，and weaken the phagocytosis and encapsulation of Galleria mellonella hemocytes． The encoding gene was then cloned and expressed in E． coli． The recombinant protein was also determined to be immunodepressive．［Conclusion］The IDP16 protein from Xenorhabdus bovienii can depress the immune response in insect，which may play an important role in bacteria-host interaction．