From a practical standpoint, larval rearing is relatively simple and economical, with widespread commercial availability globally. This aspect makes Tenebrio molitor larvae accessible to a broad scientific community and renders them a valuable resource for preclinical research.
A significant advantage of this model is its short lifespan, allowing for rapid results and contributing to reducing research times and costs. Additionally, the larvae's survival across a range of temperatures enables the study of host-pathogen interactions under conditions that more closely reflect the human physiological environment.
The increasingly widespread adoption of Tenebrio molitor larvae as a study model for human pathogenic microorganisms has been accompanied by the discovery of new antimicrobial peptides and inhibitors of virulence factors, suggesting potential therapeutic applications in the future.

References

Petronio Petronio G, Pietrangelo L, Cutuli MA, Magnifico I, Venditti N, Guarnieri A, Abate GA,
Yewhalaw D, Davinelli S, Di Marco R. Emerging Evidence on Tenebrio molitor Immunity: A Focus on Gene Expression Involved in Microbial Infection for Host-Pathogen Interaction Studies. Microorganisms. 2022 Oct 7;10(10):1983. doi: 10.3390/microorganisms10101983. PMID: 36296259; PMCID: PMC9611967.

Lozoya-Pérez NE, García-Carnero LC, Martínez-Álvarez JA, Martínez-Duncker I, Mora-Montes HM. Tenebrio molitor as an Alternative Model to Analyze the Sporothrix Species Virulence. Infect Drug Resist. 2021 Jun 3;14:2059-2072. doi: 10.2147/IDR.S312553. PMID: 34113132; PMCID: PMC8184153.

Galleria mellonella (“greater wax moth”) is part of the subfamily of Galleriinae belonging to the Pyralidae family of Lepidoptera. It lives in hives, feeding on wax and pollen. Its life cycle is about 7-8 weeks and consists of different phases: the egg, the larva that undergoes 6 larval stages before reaching the last instar, which takes about 5-6 weeks at a temperature between 25 ° -28 ° C, the pupa (chrysalis) and finally, after a further two weeks, the adult. The larvae develop from the egg in about five weeks and have a length of between 2 and 2.5 cm with a cream colour.

As an alternative model to mammals, larvae have numerous advantages for pre-clinical research, the study of host-pathogen interactions, toxin screening and toxicity studies. Among these, we find the presence of a humoral and cellular immune system; in addition, there are antimicrobial peptides similar to those found in the activation of the innate immune system of mammals. Finally, haemocytes are the primary cellular defence mediators with functions similar to human macrophages and neutrophils.

The large size of G. mellonella larvae allows a precise injection, without the need for anaesthesia, of substances to be tested (such as antibiotics, chemicals and pathogens), easy manipulation and collection of tissues and hemolymph that allow the study of the pathophysiology through, for example, proteomics approaches. All this is added to the low overall costs of livestock, even large ones, which provides a high-yield and economical experimental system. Their commercial availability expands worldwide. They are sold, for example, as bait for sport fishing, as food for pets. For these reasons, they are cheap, easy to find and do not require special equipment and premises such as animal enclosures used to breed mammals.

Furthermore, the use of G. mellonella does not require ethical approval. Thanks to the short duration of their life cycle, it is also possible to carry out studies and obtain relevant results in short periods, allowing to reduce the time and consequently the costs of research. Finally, unlike other invertebrate models such as Caenorhabditis elegans and Drosophila melanogaster, G. mellonella can survive at 37 ° C, thus mimicking conditions similar to human physiology. Human pathogens have evolved to adapt to the physiological temperature of their host for the synthesis and release of virulence factors. This makes G. mellonella a suitable model for screening for temperature-dependent host-pathogen interactions.

These advantages have convinced an increasing number of researchers to use G. mellonella larvae as a mini-host model for human-pathogenic microorganisms such as Bacillus cereus, Enterococcus faecalis, Listeria monocytogenes, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Escherichia coli, etc. In addition, over the past ten years, several antimicrobial peptides and virulence factor inhibitors have been discovered in G. mellonella. Their therapeutic potential in medicine and plant protection is currently being tested.