Calreticulin enriched as an early-stage encapsulation protein in wax moth Galleria mellonella larvae

To investigate the molecular mechanism of the early-stage encapsulation reaction in insects, we purified a 47 kDa protein from injected beads into Galleria mellonella larvae. When a cDNA clone was isolated, the 47 kDa protein showed high homology with Drosophila and human calreticulin. Western blotting analysis showed that the 47 kDa protein was present in the hemocytes, but not in the plasma. When the early-stage encapsulated beads were coated with 47 kDa protein antibody and reinjected into G. mellonella larvae, any further encapsulation reaction was inhibited. These results suggest that calreticulin is involved in non-self recognition in invertebrate cellullar defense reactions.