Immune priming of Galleria mellonella larvae with Bacillus thuringiensis affects coagulation and phenoloxidase activity upon subsequent infection

Immune priming is a phenomenon that allows invertebrates, which are devoid of acquired immunity, relying on memory T-cells and antibodies, to achieve better protection after subsequent infection. In this short report, we present new investigations of the immune response of primed Galleria mellonella larvae after infection with Bacillus thuringiensis. We compared two related aspects of immune response – hemolymph coagulation and the activity of phenoloxidase in the primed and non-primed larvae after the injection of the lethal dose of B. thuringiensis. The in vivo assay showed that coagulation of hemolymph in response to the bacterial injection occurred more efficiently in the primed animals in comparison to the non-primed ones. Further, we showed that the activity of phenoloxidase was also higher in the primed, infected larvae. Both parameters of insect immune response may contribute to the increased resistance of primed G. mellonella to further infection with B. thuringiensis.