Il sistema immunitario degli insetti: uno strumento per applicazioni biotecnologiche

Insects represent nearly 90 % of the animal beings on Earth and this taxon contains more species than any other groups of organisms. They can live in different ecological niches and are in continuous contact with several types of microorganisms. For this reason, they have evolved advanced immune response mechanisms, whose knowledge can become the source of biotechnological applications. Nowadays, "insect biotechnology", also known as "yellow biotechnology", is very popular and aims at developing and manufacturing different products in medicine, feed industry, and pest management based on insects. In this context, the silkworm, Bombyx mori, and the black soldier fly (BSF), Hermetia illucens, that belong to the orders of Lepidoptera and Diptera, respectively, play an important role. More in detail, B. mori has been used for centuries in sericulture, and represents a model organism among Lepidoptera for life science, pharmaceutical, and biotechnological studies. On the other hand, H. illucens is a natural decomposer, whose larvae have a high nutritional value, which makes them particularly suitable for the production of feedstuff. These two insects were used as model organisms for this PhD project. In particular, in this thesis two different biotechnological applications based on the immune system of insects are presented. The first chapter deals with the use of cellular and humoral immune markers to develop an alternative infection model for the screening of new antimicrobial compounds. Interestingly, B. mori can also be reared at 37 °C, thus mimicking human physiological conditions. We demonstrate that B. mori larvae represent an excellent candidate for the initial screening of glycopeptide antibiotics. Therefore, the use of this insect can be taken into consideration and included in preclinical tests to reduce the time required for the analyses and also the number of mammals used for this purpose. In the second chapter the characterization of the immune response of BSF larvae is reported. As mentioned above, this insect can be used to reduce organic waste and, at the same time, to obtain proteins and lipids for the production of feedstuff. Here, the cellular and the humoral immune responses were investigated in larvae infected with Gram-positive and Gram-negative bacteria. This study provides a starting point for the future manipulation of BSF immune response. In particular, by acting on environmental factors as the composition of the rearing substrate or the rearing temperature, the health status of the larvae and their pathogen resistance during mass rearing procedures could be improved and, consequently, the value of feedstuff products derived from this insect increased. The results here presented can be used as a platform for future biotechnological studies aimed at developing two different final products: the former exploitable in the field of drug research, while the second will contribute to improve circular economy.