The effect of cold shock on the immune response of the greater wax moth Galleria mellonella after infection with entomopathogenic bacteria Bacillus thuringiensis

Insect immune system consists of only innate mechanisms relied on cellular and humoral branches. Many defence proteins and peptides exist or appear in response to infection in insect’s hemolymph. The interaction between the infected host and the entomopathogen occurs in the conditions of external environment. In this work the greater wax moth larvae of Galleria mellonella were subjected to a temperature of 120C for a short period of time, directly before infection with entomopathogenic bacteria Bacillus thuringiensis. It appeared that the induction of the immune response was higher in cold-shocked animals than in larvae permanently reared at the optimal temperature of 28 0C. This enhanced immune response was manifested as higher antibacterial and lysozyme-type activity detected in full hemolymph, and as a higher level of peptides of molecular weight below 10 kDa having antibacterial activity. Moreover, other changes in the contents of proteins in the hemolymph were observed. These changes concerned inter alia apolipophorin III, the multifunctional protein of immune significance. Its level was higher in the hemolymph of animals pre-exposed to cold shock than in nonshocked, infected ones. Altogether our results indicate that the interdependence mechanisms occur between cold shock and the immune response.