Thermal and physical stresses induce a short-term immune priming effect in Galleria mellonella larvae

Abstract

a b s t r a c tExposure of larvae of Galleria mellonella larvae to mild physical (i.e. shaking) or thermal stress for 24 h increased their ability to survive infection with Aspergillus fumigatus conidia however larvae stressed in a similar manner but incubated for 72 h prior to infection showed no elevation in their resistance to infection with A. fumigatus. Stressed larvae demonstrated an elevated haemocyte density 24 h after initiation of the stress event but this declined at 48 and 72 h. Larval proteins such as apolipophorin, arylophorin and prophenoloxidase demonstrated elevated expression at 24 h but not at 72 h. Larvae maintained at 37°C showed increased expression of a range of antimicrobial and immune-related proteins at 24 h but these decreased in expression thereafter. The results presented here indicate that G. mellonella larvae are capable of altering their immune response following exposure to mild thermal or physical stress to mount a response capable of counteracting microbial infection which reaches a peak 24 h after the initiation of the priming event and then declines by 72 h. A short-term immune priming effect may serve to prevent infection but maintaining an immune priming effect for longer periods may be metabolically costly and unnecessary while living within the colony of another insect.

Galleria mellonella experimental model for bat fungal pathogen Pseudogymnoascus destructans and human fungal pathogen Pseudogymnoascus pannorum

“…The present study provided proof that the G. mellonella experimental system is amenable to an extended temperature range from 5°C to 37°C. It is well-known that temperature affects G. mellonella immune response to pathogens; however, the relevant previous studies focused on the effects of pre-incubation periods as they related to the immune responses [28,29]. Importantly, the current study differs from earlier publication in that the larvae were maintained at room temperature until infection and were not placed at 5°C and 15°C until after infection.…”

Two-spotted cricket as an animal infection model of human pathogenic fungi

“…Silkworms and the greater wax moth larva can be used as animal infection models at 37°C (25)(26)(27), but their infection sensitivities to fungi are drastically increased at 37°C compared to that at a lower temperature (19,(28)(29)(30)(31). The increased infection sensitivity of these insects at 37°C is considered to be due to damage to the immune system at a high temperature (32)(33)(34).…”

A temperature shock can lead to trans‐generational immune priming in the Red Flour Beetle, Tribolium castaneum

“…mellonella larvae show an increase in haemocyte density and elevated expression of prophenoloxidase and two antimicrobial peptides (Browne et al. ). However, little is known about the influence of stress on the immune system in the context of trans‐generational effects.…”

“…In Galleria mellonella, it is shown that mild physical and/or thermal stress leads to short-term immune priming, protecting the larvae against infection with Aspergillus fumigatus. Furthermore, treated G. mellonella larvae show an increase in haemocyte density and elevated expression of prophenoloxidase and two antimicrobial peptides (Browne et al 2014). However, little is known about the influence of stress on the immune system in the context of trans-generational effects.…”