Short-term heat shock affects the course of immune response in Galleria mellonella naturally infected with the entomopathogenic fungus Beauveria bassiana

•Infection of G. mellonella with B. bassiana affects the apolipophorin III level.•Hemolymph of G. mellonella retrieved from heat shock contains more apoLp-III.•Strong heat shock inhibits expression of immune-relevant genes in infected larvae.•ApoLp-III expression in the fat body is higher in animals retrieved from heat shock.•Infected animals exposed to heat shock show higher lysozyme and antifungal activity.

We aimed to investigate how exposition of infected insects to short-term heat shock affects the biochemical and molecular aspects of their immune response. Galleria mellonella larvae were exposed to 43 °C for 15 min, at the seventy second hour after natural infection with entomopathogenic fungus Beauveria bassiana. As a result, both qualitative and quantitative changes in hemolymph protein profiles, and among them infection-induced changes in the amount of apolipophorin III (apoLp-III), were observed. Heat shock differently affects the expression of the tested immune-related genes. It transiently inhibits expression of antifungal peptides gallerimycin and galiomicin in both the fat body and hemocytes of infected larvae. The same, although to a lesser extent, concerned apoLp-III gene expression and was observed directly after heat shock. Nevertheless, in larvae that had recovered from heat shock, apoLp-III expression was higher in comparison to unshocked larvae in the fat body but not in hemocytes, which was consistent with the higher amount of this protein detected in the hemolymph of the infected, shocked larvae. Furthermore, lysozyme-type activity was higher directly after heat shock, while antifungal activity was significantly higher also in larvae that had recovered from heat shock, in comparison to the respective values in their non-shocked, infected counterparts. These results show how changes in the external temperature modulate the immune response of G. mellonella suffering from infection with its natural pathogen B. bassiana.

Graphical abstractDownload full-size image