A histological procedure to study fungal infection in the wax moth Galleria mellonella

Abstract

The invertebrate model Galleria mellonella is a widely used factitious host to study the microbial pathogenesis in vivo. However, a specific procedure for the recovery and the processing of the infected tissues, important for a better understanding of the host-pathogen interactions, has not been reported to our knowledge. In the present study we describe a new procedure of fixation and processing of larval tissue that allows studying the larval topographic anatomy and assessing the morphological changes due to the fungal infection. Lepidopteran larvae were infected with Candida albicans strains displaying various biofilm-forming abilities. The whole larvae were then examined for tissue changes by histological techniques. We show that comparing cutting planes, serial transversal sections of paraffin-embedded larva result in better accuracy and information recovering. Using this technique, it was possible to preserve the integrity of G. mellonella internal structures allowing the detailed analysis of morphological differences in different experimental groups (i.e., healthy vs infected larvae). We were also able to study strain-related differences in the pathogenesis of C. albicans by observing the immune response elicited and the invasiveness of two isolates within the larval tissues.In general, by processing the whole larva and optimizing routinely histochemical stainings, it is possible to visualize and analyse infected tissues. Various degrees of pathogenicity (strain- or inoculum-related), and the infection time course can be described in details. Moreover, the host immune response events can be followed throughout the infectious process leading to a comprehensive picture of the studied phenomenon.

Histological changes in the larvae of the domestic mosquito Culex pipiens treated with the entomopathogenic fungus Beauveria bassiana

“…Lepidopteran larvae of Galleria mellonella were infected with fungus Candida albicans strains, in which the whole larvae were then examined for tissue changes by histological techniques. Various degrees of pathogenicity (strain-or inoculum-related), and the infection time course are described (Perdoni et al, 2014). Meanwhile the examination of histological sections of various parts of the digestive tract showed some changes in larvae of Locusta migratoria treated with Pseudomonas fluorescens especially at mesenteron level with alteration of the peritrophic membrane (Oulebsir-Mohandkaci and Doumandji-Mitiche, 2012).…”

Acetylcholine Protects against Candida albicans Infection by Inhibiting Biofilm Formation and Promoting Hemocyte Function in a Galleria mellonella Infection Model

“…After hemolymph extraction, the same larvae were processed for histology as previously described (25). Briefly, the larvae were inoculated with buffered formalin and processed by means of transverse-cut serial sections.…”

Galleria mellonella: An invertebrate model to study pathogenicity in correctly defined fungal species

“…Recently, Gomez-Lopez et al (GomezLopez et al 2014) quantified fungal burden in Aspergillus fumigatus infected larvae by RT-PRC. Additionally, fungal burden, or the development and morphology of fungal pathogens inside the host can be studied by histological procedures, which also allow to assess morphological changes of host tissue due to infections (Perdoni et al 2014). …”