Impact of the Diet on the Mortality and on Gene Expression of the Antimicrobial Peptide Tenecin 3 in Tenebrio molitor Larvae Infected by Beauveria bassiana

Abstract

Large-scale insect rearing can be subjected to microbial infections, leading to serious economic losses. When possible, the use of antibiotics is to be avoided for insects intended as feed or food and new strategies to preserve the health of the farmed insects are required. The effectiveness of insect immune system depends on several factors, including the nutritional composition of the diet. The possibility to modulate immune responses through the diet is currently a topic of great interest from an application point of view. We evaluated the effect of two different diets on the survival rate and gene expression of the antimicrobial peptide Tenecin 3 in uninfected and Beauveria bassiana-infected Tenebrio molitor L. larvae. A wheat bran diet, mixed 50% with brewers’ spent grains, could positively influence the expression of Tenecin 3 gene when uninfected T. molitor is allowed to develop on such a substrate from early larval stages. Even if, in our trial, the diet with added brewers’ spent grains could not reduce the mortality of the larvae infected with B. bassiana, higher transcriptional levels of the antifungal peptide were observed in insects fed this diet, depending on the timing of diet administration.

Immune Reactions of Vector Insects to Parasites and Pathogens

“…The extent of networking occurring with other species in complex ecological communities will also affect host finding, biting and disease transmission [ 36 ]. Other determinants include the sex and developmental stage of the vector [ 60 , 61 ], as well as physiological factors such as the host nutrition [ 62 ] and the fitness costs of immunity [ 63 ]. In addition, the route of entry and survival in the host will also dictate the nature of the immune response [ 64 ].…”

Insect Antimicrobial Peptides: Advancements, Enhancements and New Challenges

“…The energy reallocation from anabolism to insect immune responses leads to a lower insect growth that may be deleterious in some insect productions (e.g., when the AMP extraction is not the only production of interest). Recent studies report changes in the expression of AMP encoding genes after rearing diet modulation alone and not necessarily following an immune challenge [ 30 , 31 , 32 , 33 ]. Interestingly, these variations showed to be more beneficial than the addition of bacteria to standard diet [ 30 ].…”

“…monofloral pollen showed higher apidaecin 1 and abaecin coding gene expression level [ 136 ]. Brewers spent grain-added diet leads to increased AMP expression in H. illucens and T. molitor rearing [ 30 , 33 ].…”

“…In recent years, the research on insect AMPs is moving towards new perspectives. With the increasing interest for alternative protein sources, in addition to the possibility of exploiting the antimicrobial activity of insects as food or feed, there would be the possibility of modulating the production of AMPs through diet for the purpose of safeguarding the health of insects in mass rearing [ 30 , 31 , 32 , 33 ]. Furthermore, applications to protect post-harvested fruits and foodstuffs have been proposed [ 27 , 34 , 35 ].…”

The Effects of Diet on the Immune Responses of the Oriental Armyworm Mythimna separata

“…For instance, “under” and “over” nutrition can lead to immunodeficiency diseases and increase susceptibility to infection in humans and mice [ 8 , 9 ]. Like vertebrates, insects acquire nutrients from their diet, and the nutritional values of the ingested diets affect the strength of insects’ immune responses [ 3 , 6 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”