Novel antibacterial peptides induced by probiotics in Hermetia illucens (Diptera: Stratiomyidae) larvae

Abstract

There is a need to discover new therapeutic substances due to the emergence of deadly infectious diseases and various antibiotic resistance. We focused on the larvae that are utilized as a medical insect for the treatment of skin damage in Europe and America. This study was to investigate the pharmacological activities of novel antibacterial peptides isolated from Hermetia illucens larvae against the Klebsiella pneumoniae and Shigella dysenteriae. The larvae were immunized by probiotics (Lactobacillus casei) for 24 h. The hemolymph from the immunized larvae was fractionated through reverse‐phase chromatography. Peptides were purified using HPLC and the coomassie blue staining, and identified using Nano‐LC‐ESI‐MS/MS system. Antibacterial activities of the peptides were evaluated by turbidometric assay, liquid broth dilution assay, resazurin assay, and agar disk diffusion method. The minimum inhibitory concentrations (MICs) of the peptides were measured as 150 μg/mL through the turbidometric, liquid broth dilution, and resazurin assays. The peptides effectively inhibited their growth/proliferation as well as the survival rate of the tested bacteria. Furthermore, the immunized larvae exhibited overexpression of the peptides compared to non‐immunized larvae. These results demonstrate that the peptides induced by H. illucens exert strong antibacterial activity against Gram‐negative bacteria. The results suggest that the activation of the humoral immunity induced by immunization functioned to enhance the production of antibacterial peptides from the insect and their antibacterial properties. This study indicates the potential of the peptides produced from larvae as antibacterial peptide substance for the development of novel antibacterial drugs.

Larvae Mediated Valorization of Industrial, Agriculture and Food Wastes: Biorefinery Concept through Bioconversion, Processes, Procedures, and Products

“…Hemolymph from BSFL immunized with Lactobacillus casei (probiotic) were fractionated to identify specific peptides responsible for antibacterial activity and the fraction HP/F9 (screened by high-performance liquid chromatography (HPLC)) with inhibitory effects on the growth of bacteria was tested for in vitro cytotoxicity. The peptides did not exhibit a significant level of cytotoxicity; the results support the fact that BSFL can be used to produce AMP with unique properties, pharmacological action and complete cytocompatibility on bacteria and cells [124]. A novel cecropin-like peptide with a molecular weight of 4.84 kDa was isolated from BSFL and characterized.…”

Evaluation of the Antimicrobial Activity of an Extract of Lactobacillus casei-Infected Hermetia illucens Larvae Produced Using an Automatic Injection System

“…In a previous study, we reported that L. casei injection activated the immune system in HIL and induced AMP expression [ 23 ]. Therefore, we developed an AMIS using fine needles to inject HIL with L. casei in quantity ( Figure 1 A,D).…”

“…However, to trigger the mass production of AMPs, pathogens must be introduced into the body cavity because AMP expressions are up-regulated only after activation of the innate immune system [ 20 , 21 ]. In a previous study, we found that the antimicrobial activities of H. illucens larvae (HIL) extract and hemolymph were enhanced by infection with human or animal pathogens [ 22 ], and interestingly, Chol et al reported that probiotics induce AMPs in HIL [ 23 ]. Here, we developed an automatic mass injection system (AMIS) to establish a means of producing an extract of infected H. illucens larvae (iHIL-E), and then evaluated the antimicrobial activities of iHIL-E against antibiotic- and AMP-resistant bacteria and pathogens, such as Salmonella species, and against Lactobacillus species.…”

Antimicrobial Activity of an Extract of Hermetia illucens Larvae Immunized with Lactobacillus casei against Salmonella Species

“…However, H. illucens expresses/secretes AMPs in quantity only after innate immune system activation by a pathogen [ 20 , 21 ]. Choi et al previously demonstrated the antibiotic activity of purified peptide extract in hemolymph isolated from H. illucens larvae (HIL) immunized by Lactobacillus casei against Klebsiella pneumoniae (ATCC 13883) and Shigella dysenteriae (ATCC 9750) [ 22 ]. Here, to select an optimal AMPs inducer, we evaluated antimicrobial activity of HIL immunized with five Lactobacillus species and assessed the bactericidal activities of an extract of HIL immunized with a selected Lactobacillus species to determine the potential use of the extract as a natural antibiotic or preservative.…”