Insect immunity. Purification and properties of three inducible bactericidal proteins from hemolymph of immunized pupae of Hyalophora cecropia

Effects of dietary glycerol monolaurate on growth and digestive performance, lipid metabolism, immune defense and gut microbiota of shrimp (Penaeus vannamei)

The advancement of the Penaeus vannamei industry in a sustainable manner necessitates the creation of eco-friendly and exceptionally effective feed additives. To achieve this, 720 similarly-sized juvenile shrimp (0.88 ± 0.02 g) were randomly divided into four groups in this study, with each group consisting of three replicates, each tank (400 L) containing 60 shrimp. Four experimental diets were formulated by adding 0, 500, 1000, and 1500 mg kg-1 glycerol monolaurate (GML) to the basal diet, and the feeding trial lasted for 42 days. Subsequently, a 72-h White Spot Syndrome Virus (WSSV) challenge test was conducted. Polynomial orthogonal contrasts analysis revealed that with the increase in the concentration of GML, those indicators related to growth, metabolism and immunity, exhibit linear or quadratic correlations (P < 0.05). The results indicate that the GML groups exhibited a significant improvement in the shrimp weight gain rate, specific growth rate, and a reduction in the feed conversion ratio (P < 0.05). Furthermore, the GML groups promoted the lipase activity and reduced lipid content of the shrimp, augmented the expression of triglyceride and fatty acid decomposition-related genes and lowered the levels of plasma triglycerides (P < 0.05). GML can also enhanced the humoral immunity of the shrimp by activating the Toll-like receptor and Immune deficiency immune pathways, improved the phagocytic capacity and antibacterial ability of shrimp hemocytes. The challenge test revealed that GML significantly reduced the mortality of the shrimp compared to control group. The 16S rRNA sequencing indicates that the GML group can increases the abundance of beneficial bacteria. However, 1500 mg kg-1 GML adversely affected the stability of the intestinal microbiota, significantly upregulating intestinal antimicrobial peptide-related genes and tumor necrosis factor-alpha levels (P < 0.05). In summary, 1000 mg kg-1 GML was proven to enhance the growth performance, lipid absorption and metabolism, humoral immune response, and gut microbiota condition of P. vannamei, with no negative physiological effects.

Dietary vitamin C reduces mortality of pacific white shrimp (Penaeus vannamei) post-larvae by Vibrio parahaemolyticus challenge

This study was conducted to investigate whether optimal vitamin C (VC) levels can enhance non-specific immune response and antioxidant capacity and reduce mortality of Pacific white shrimp (Penaeus vannamei) post-larvae when infected with Vibrio parahaemolyticus. Six experimental diets were formulated to contain six different VC levels of 0, 40, 80, 120, 160 and 320 mg/kg diet (designated as C0, C40, C80, C120, C160 and C320, respectively). Shrimp post-larvae (39.1 ± 0.47 mg) were randomly distributed to 24 tanks with 40 shrimp per tank. Four replicate groups of shrimp were fed one of the diets for 43 days. VC supplemented groups showed significantly higher growth performance than C0 group. Shrimp fed C120 diet had significantly improved feed utilization efficiency than shrimp fed C0 diet. VC concentrations in hepatopancreas and gills were significantly higher with the increase in dietary VC levels. Optimal dietary VC levels significantly upregulated the expressions of growth and digestive enzyme-related genes such as IGF-1, IGF-BP, amylase, trypsin and chymotrypsin, and also upregulated the expressions of innate immunity and antioxidant-related genes such as prophenoloxidase, crustin, penaiedin-3a, superoxide dismutase, glutathione peroxidase and catalase in hepatopancreas. Shrimp fed C80, C120 and C160 diets showed significantly increased resistance to V. parahaemolyticus than shrimp fed C0 diet. The optimum dietary VC level for the shrimp post-larvae was established to be 80.2 mg/kg diet by a broken-line regression analysis based on the growth. The findings from the challenge test indicated that VC levels over 83.0 mg/kg diet could enhance disease resistance of the shrimp against V. parahaemolyticus.

Antibiotics suppress the expression of antimicrobial peptides and increase sensitivity of Cydia pomonella to granulosis virus

Cydia pomonella granulovirus (CpGV) is a highly specific and environmentally friendly pathogenic virus successfully used as a biological insecticide against codling moth larvae. Continuous application of CpGV has led to high levels of resistance in codling moth, Cydia pomonella (C. pomonella). Nevertheless, the specific molecular mechanisms underlying the development of resistance in codling moths to CpGV have been rarely investigated. This study explored the potential antiviral immune roles of codling moth antimicrobial peptides (AMPs) against CpGV. A total of 11 AMP genes classified in cecropin, defensin, gloverin, and attacin subfamilies, were identified in the codling moth genome. The cecropin and gloverin subfamilies were found to be the ancestral genes of the AMP gene family. The expression of two AMP genes (CmGlo1 and CmAtt1) significantly increased following CpGV challenge, and CmGlo1 and CmAtt1 gene silencing resulted in a significant increase in CpGV replication in codling moth larvae. The hemolymph and fat body serve as major viral immune functional tissues in codling moth larvae. Moreover, zhongshengmycin significantly reduced the diversity and abundance of codling moth larvae gut microbiota, thereby suppressing the expression of CmAtt1 AMP gene. We also found that the combination of the virus with zhongshengmycin would enhance the insecticidal effects of CpGV. This study provides the first explanation of the molecular mechanisms driving CpGV immune function development in codling moths, approached from the perspective of the codling moth itself. Additionally, we introduced an alternative approach to combat codling moth in the field by combining antibiotics with biopesticides to amplify the insecticidal effects of the latter.

Safety evaluation and effects of dietary phlorotannins on the growth, health, and intestinal microbiota of Litopenaeus vannamei

Phlorotannins are phenolic compounds with diverse biological activities, yet their efficacy in aquatic animals currently remains unclear. This investigation scrutinized the influence of phlorotannins on the growth, immunity, antioxidant capacity, and intestinal microbiota in Litopenaeus vannamei, concurrently evaluating the potential adverse effects of phlorotannins on L. vannamei. A base diet without phlorotannins supplementation was used as a control, and 4 groups of diets with different concentrations (0, 0.5, 1.0, 2.0 g kg-1) of phlorotannins were formulated and fed to juvenile shrimp (0.25 ± 0.01 g) for 60 days followed by a 24-h challenge with Vibrio parahaemolyticus with triplicate in each group. Compared with the control, dietary 2.0 g kg-1 phlorotannins significantly improved the growth of the shrimp. The activities of enzymes related to cellular immunity, humoral immunity, and antioxidants, along with a notable upregulation in the expression of related genes, significantly increased. After V. parahaemolyticus challenge, the cumulative survival rates of the shrimp demonstrated a positive correlation with elevated concentrations of phlorotannins. In addition, the abundance of Bacteroidetes and functional genes associated with metabolism increased in phlorotannins supplementation groups. Phlorotannins did not elicit any detrimental effects on the biological macromolecules or histological integrity of the hepatopancreas or intestines. Simultaneously, it led to a significant reduction in malondialdehyde content. All results indicated that phlorotannins at concentrations of 2.0 g kg-1 can be used as safe feed additives to promote the growth, stimulate the immune response, improve the antioxidant capacity and intestinal health of L. vannamei, and an protect shrimp from damage caused by oxidative stress.

In vitro immune analysis of serum from the hemolymph of the anomuran crab Albunea symmysta (Linnaeus, 1758) displayed diversified reactions

The present investigation aims to substantiate that serum from the hemolymph of anomuran crab Albunea symmysta encompasses multiple immunological reactions in in vitro condition. The serum highly agglutinated human O erythrocytes in the presence of Ba2+. Distinct and unique sugar binding capacity of serum towards laminarin, N-acetyl sugars and higher binding specificity towards a glycoprotein, fetuin was inferred. In vitro enhancement of melanin synthesis due to enhanced oxidation of 3, 4-dihydroxy-dl-phenylalanine (dl-DOPA) by preincubation of nonself molecules with serum phenoloxidase (PO) was documented. Similarly, dl-DOPA oxidation by serum PO was reduced when preincubated with chemical inhibitors and copper chelators. Further, the crab serum lysed the vertebrate erythrocytes with maximum hemolysis against chicken and it unveiled dependency on divalent cation, serum concentration, ionic strength, pH, temperature and time interval. Occurrence of maximum hemolysis at a concentration of 30 µl, pH 8.0, temperature 37 °C and time interval of 60 min in the presence of Ba2+ were documented. Interestingly, serum hemolysis was reduced by different osmoprotectants suggesting a colloid-osmotic mechanism involving in hemolysis. It was observed that A. symmysta serum had antimicrobial activity against Gram-positive Staphylococcus aureus and fungal pathogen Candida albicans. The serum showed higher glycan content, potent lysozyme and free radical scavenging activity suggesting the existence of potential immune molecules of therapeutic use. These results clearly demonstrated the diversified immunogenicity of A. symmysta serum confirming a highly conserved non-specific immunity of crustaceans.

Dietary Poly-β-Hydroxybutyrate Improved the Growth, Non-specific Immunity, Digestive Enzyme Activity, Intestinal Morphology, Phagocytic Activity, and Disease Resistance Against Vibrio parahaemolyticus of Pacific White Shrimp, Penaeus vannamei

This study assessed the effects of dietary supplementation of poly-β-hydroxybutyrate (PHB) on growth performance, feed efficiency, non-specific immunity, digestive enzyme capacity, phagocytic activity, hemocyte count, intestinal morphology, and disease resistance against Vibrio parahaemolyticus of Pacific white shrimp (Penaeus vannamei). Six diets were prepared by supplementing graded levels of PHB at 0.00, 0.25, 0.50, 1.00, 2.00, and 4.00% (Con, P0.25, P0.5, P1.0, P2.0, and P4.0, respectively). Triplicate groups of 90 shrimps (initial body weight 0.25 ± 0.01 g) per treatment were randomly assigned and fed an experimental diet for 56 days. The growth performance of shrimp was significantly improved by 1% dietary PHB supplementation. PHB-included diets fed shrimp showed significantly improved hepatopancreatic trypsin, chymotrypsin, and pepsin activities. Villus height was significantly increased with dietary PHB supplementation, and villus width was increased at a 1% inclusion level. P0.25, P0.5, and P4.0 groups significantly increased phenoloxidase activity, and the P2.0 group significantly increased anti-protease activity compared to the Con group. The survival of shrimp challenged against V. parahaemolyticus was higher in P0.5, P1.0, and P2.0 groups than in the Con diet. Dietary PHB supplementation improved weight gain, digestive enzyme activity, intestinal morphology, non-specific immunity, and disease resistance against V. parahaemolyticus of shrimp. According to the above observations, the optimal dietary PHB supplementation level for maximum weight gain would be 1% for Pacific white shrimp.

Development strategies and application of antimicrobial peptides as future alternatives to in-feed antibiotics

The use of in-feed antibiotics has been widely restricted due to the significant environmental pollution and food safety concerns they have caused. Antimicrobial peptides (AMPs) have attracted widespread attention as potential future alternatives to in-feed antibiotics owing to their demonstrated antimicrobial activity and environment friendly characteristics. However, the challenges of weak bioactivity, immature stability, and low production yields of natural AMPs impede practical application in the feed industry. To address these problems, efforts have been made to develop strategies for approaching the AMPs with enhanced properties. Herein, we summarize approaches to improving the properties of AMPs as potential alternatives to in-feed antibiotics, mainly including optimization of structural parameters, sequence modification, selection of microbial hosts, fusion expression, and industrially fermentation control. Additionally, the potential for application of AMPs in animal husbandry is discussed. This comprehensive review lays a strong theoretical foundation for the development of in-feed AMPs to achieve the public health globally.

Peptides with Antimicrobial Activity in the Saliva of the Malaria Vector Anopheles coluzzii

Mosquito saliva plays a crucial physiological role in both sugar and blood feeding by helping sugar digestion and exerting antihemostatic functions. During meal acquisition, mosquitoes are exposed to the internalization of external microbes. Since mosquitoes reingest significant amounts of saliva during feeding, we hypothesized that salivary antimicrobial components may participate in the protection of mouthparts, the crop, and the gut by inhibiting bacterial growth. To identify novel potential antimicrobials from mosquito saliva, we selected 11 candidates from Anopheles coluzzii salivary transcriptomic datasets and obtained them either using a cell-free transcription/translation expression system or, when feasible, via chemical synthesis. Hyp6.2 and hyp13, which were predicted to be produced as propeptides and cleaved in shorter mature forms, showed the most interesting results in bacterial growth inhibition assays. Hyp6.2 (putative mature form, 35 amino acid residues) significantly inhibited the growth of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Serratia marcescens) bacteria. Hyp13 (short form, 19 amino acid residues) dose-dependently inhibited E. coli and S. marcescens growth, inducing membrane disruption in both Gram-positive and Gram-negative bacteria as indicated with scanning electron microscopy. In conclusion, we identified two A. coluzzii salivary peptides inhibiting Gram-positive and Gram-negative bacteria growth and possibly contributing to the protection of mosquito mouthparts and digestive tracts from microbial infection during and/or after feeding.

Insect Antimicrobial Peptides as Guardians of Immunity and Beyond: A Review

Antimicrobial peptides (AMPs), as immune effectors synthesized by a variety of organisms, not only constitute a robust defense mechanism against a broad spectrum of pathogens in the host but also show promising applications as effective antimicrobial agents. Notably, insects are significant reservoirs of natural AMPs. However, the complex array of variations in types, quantities, antimicrobial activities, and production pathways of AMPs, as well as evolution of AMPs across insect species, presents a significant challenge for immunity system understanding and AMP applications. This review covers insect AMP discoveries, classification, common properties, and mechanisms of action. Additionally, the types, quantities, and activities of immune-related AMPs in each model insect are also summarized. We conducted the first comprehensive investigation into the diversity, distribution, and evolution of 20 types of AMPs in model insects, employing phylogenetic analysis to describe their evolutionary relationships and shed light on conserved and distinctive AMP families. Furthermore, we summarize the regulatory pathways of AMP production through classical signaling pathways and additional pathways associated with Nitric Oxide, insulin-like signaling, and hormones. This review advances our understanding of AMPs as guardians in insect immunity systems and unlocks a gateway to insect AMP resources, facilitating the use of AMPs to address food safety concerns.

Immunomodulatory potential of Sarcophaga argyostoma larval hemolymph as a natural alternative to berenil in treating Trypanosoma evansi in vivo

This study compared effects of diminazene aceturate (berenil), commonly used to treat domestic animals infected with Trypanosoma evansi, with the hemolymph of Sarcophaga argyostoma larva. The hemolymph may be acting as a possible natural alternative to berenil, based on immunomodulation mediated inflammatory response. Inflammatory mediators and histopathological changes in liver, kidney, and spleen of albino mice experimentally infected with T. evansi were studied. Mice were divided into five groups: G1, uninfected, untreated (negative control); G2, T. evansi infected (positive control); G3, infected and treated with berenil; G4, infected and treated with hemolymph; G5, infected and treated with hemolymph 3 days before infection (prophylactic group). Animals in (G4) and (G5) exhibited a significant overall reduction in serum levels of IFN-γ. However, the reduction in TNF-α and IL-6 levels was more limited compared to (G2) and (G3). Notably, an elevation in IL-10 levels was observed compared to animals in other groups. Furthermore, the groups treated with hemolymph demonstrated an alleviation of T. evansi infection in contrast to the other groups. This study highlights that the administration of Sarcophaga argyostoma larval hemolymph at a dosage of 0.5 ml/kg significantly inhibited T. evansi organisms in vivo, showcasing a pronounced trypanocidal effect.

Effects of Dietary Zinc on Growth, Haematological Indices, Digestive Enzyme Activity, Tissue Mineralization, Antioxidant and Immune Status of Fingerling Heteropneustes fossilis

A 12 week feeding trial was conducted to evaluate the effects of dietary zinc levels on Heteropneustes fossilis. Triplicate groups of fish were fed isoproteic (CP; 400 g/kg) and isocaloric (GE; 17.89 kJ/g) diets increasing levels of zinc (0, 5, 10, 15, 20, 25, 30 mg/kg) achieved by supplementing zinc sulphate heptahydrate to basal diet. Analysed concentrations of zinc in diets were 10.68, 15.83, 21.34, 26.74, 30.61, 34.91 and 41.34 mg/kg. Growth indices increased linearly (P<0.05) up to 26.74 mg/kg Zn. The protein and ash content of whole body also improved significantly up to 26.74 mg/kg Zn. Whole body fat content showed inverse pattern. Haematological parameters also showed an improving trend with the increase in dietary zinc up to 26.74 mg/kg and then levelled off. Activities of antioxidant enzymes were improved with the increase in dietary zinc level up to 26.74 mg/kg followed by no significant change (P>0.05). Serum lysozyme activity also exhibited the similar pattern. Immune response in terms of the activities of lysozyme, alkaline phosphatase and myeloperoxidase was also improved with the increase in dietary zinc levels up to 26.74 mg/kg. Dietary zinc levels affected significantly the whole body as well as vertebrae mineralization. Broken-line regression analysis of weight gain, vertebrae zinc activity, serum superoxide dismutase and protease activity against increasing amounts of dietary zinc revealed that the inclusion of zinc in diet in the range of 26.82-29.84 mg/kg is optimum for growth, haematological indices, antioxidant status, immune response and tissue mineralization in fingerling H. fossilis. The information obtained from present study would be helpful in formulating the zinc-balanced commercial feeds to improve the growth and health status of this important fish, thus contributing to aquaculture production and strengthening the food security.

The P4' Peptide-Carrying Bacillus subtilis in Cottonseed Meal Improves the Chinese Mitten Crab Eriocheir sinensis Innate Immunity, Redox Defense, and Growth Performance

This study developed a recombinant Bacillus subtilis to carry the LGSPDVIVIR peptide (cmP4) isolated from the hydrolyzed products of cottonseed meal with excellent antioxidant and immune-enhancing properties in vitro. It was carried as a tandem of five cmP4 peptides (cmP4') to be stably expressed on a large scale. Then, its effectiveness was evaluated in Chinese mitten crab (Eriocheir sinensis) based on growth performance, redox defense, and innate immunity. A total of 280 crabs (mean body weight: 41.40 ± 0.14) were randomly assigned to seven diets including a control one (without B. subtilis) and six experimental ones with different doses (107,108, and 109 CFU/kg) of unmodified and recombinant B. subtilis, respectively, for 12 weeks. Each diet was tested in four tanks of crabs (10/tank). In terms of bacterial dosages, the final weight (FW), weight gain (WG), hemolymph and hepatopancreatic activities of superoxide dismutase (SOD), catalase (CAT), lysosome (LZM), acid phosphatase (ACP) and alkaline phosphatase (AKP), and hepatopancreatic transcriptions of cat, mitochondrial manganese superoxide dismutase (mtmnsod), thioredoxin-1 (trx1), and prophenoloxidase (propo) all increased significantly with increasing B. subtilis dosages, while hemolymph and hepatopancreatic malondialdehyde (MDA) content and the transcriptions of toll like receptors (tlrs), NF-κB-like transcription factor (relish), and lipopolysaccharide-induced TNF-α factor (litaf) all decreased remarkably. In terms of bacterial species, the recombinant B. subtilis group obtained significantly high values of FW, WG, hemolymph, and hepatopancreatic activities of SOD, CAT, LZM, ACP, and AKP, and the transcriptions of mtmnsod, peroxiredoxin 6 (prx6), and propo compared with the unmodified B. subtilis, while opposite results were noted in hemolymph and hepatopancreatic MDA content and the transcriptions of tlrs, relish, and litaf. These results indicated that dietary supplementation with 109 CFU/kg of recombinant B. subtilis can improve the growth performance, redox defense, and nonspecific immunity of E. sinensis.

Fluorescence-Polarization-Based Assaying of Lysozyme with Chitooligosaccharide Tracers

Lysozyme is a well-known enzyme found in many biological fluids which plays an important role in the antibacterial protection of humans and animals. Lysozyme assays are used for the diagnosis of a number of diseases and utilized in immunohistochemistry, genetic and cellular engineering studies. The assaying methods are divided into two categories measuring either the concentration of lysozyme as a protein or its activity as an enzyme. While the first category of methods traditionally uses an enzyme-linked immunosorbent assay (ELISA), the methods for the determination of the enzymatic activity of lysozyme use either live bacteria, which is rather inconvenient, or natural peptidoglycans of high heterogeneity and variability, which leads to the low reproducibility of the assay results. In this work, we propose the use of a chemically synthesized substrate of a strictly defined structure to measure in a single experiment both the concentration of lysozyme as a protein and its enzymatic activity by means of the fluorescence polarization (FP) method. Chito-oligosaccharides of different chain lengths were fluorescently labeled and tested leading to the selection of the pentasaccharide as the optimal size tracer and the further optimization of the assay conditions for the accurate (detection limit 0.3 μM) and rapid (<30 min) determination of human lysozyme. The proposed protocol was applied to assay human lysozyme in tear samples and resulted in good correlation with the reference assay. The use of synthetic fluorescently labeled tracer, in contrast to natural peptidoglycan, in FP analysis allows for the development of a reproducible method for the determination of lysozyme activity.

Dietary β-Glucan Alleviates Antibiotic-Associated Side Effects by Increasing the Levels of Antioxidant Enzyme Activities and Modifying Intestinal Microbiota in Pacific White Shrimp (Litopenaeus vannamei)

Antibiotics and their secondary metabolites are commonly found in aquatic ecosystems, leading to the passive exposure of many aquatic animals to low doses of antibiotics, which can affect their health. However, there is limited information available on how to mitigate the side effects of antibiotics on normal aquatic animals. This study aimed to investigate the potential of dietary β-glucan to alleviate the side effects induced by antibiotics in Pacific white shrimp (Litopenaeus vannamei) (0.37 ± 0.02 g). A six-week feeding trial was conducted with four dietary treatments including a control, 1 g/kg β-glucan (β-glucan), 50 mg/kg oxytetracycline (OTC), and a combination of 50 mg/kg OTC and 1 g/kg β-glucan (Mix) groups. At the end of the trial, the growth performance, intestinal microbial composition, antioxidant capacity, and immune response of the shrimp were assessed. There were no significant differences in growth performance among the groups, but the condition factor of the shrimp in the Mix group was significantly decreased when compared to the control and β-glucan groups. The activities of hepatopancreas catalase (CAT) and serum phenol oxidase in the OTC group were significantly lower than those in the control group. On the other hand, the activities of hepatopancreas superoxide dismutase and CAT enzymes in the β-glucan group were significantly higher than those in the OTC group. The supplementation of β-glucan in combination with antibiotics significantly increased the CAT activity and bacteriolytic activity compared to the OTC and control groups, respectively. Moreover, an analysis of the intestinal microbiota revealed that the Observed_species estimator in the Mix group was significantly higher than that in the control group. Dietary antibiotics significantly increased the abundance of Actinobacteria at the phylum level, but the Mix group showed no significant difference. The supplementation of β-glucan in combination with antibiotics also significantly increased the relative abundance of Meridianimaribacter compared to the control group. Additionally, the synergistic influence of β-glucan with antibiotics increased the beta diversity of intestinal microbiotas. These findings suggest that the supplementation of β-glucan in combination with antibiotics on Pacific white shrimp can alleviate the low antioxidant capacity and immune response caused by antibiotics while enhancing the intestinal microbial composition. This provides a potential solution to mitigate the negative impacts of antibiotics in aquaculture.

The immunotoxicity mechanism of NH4Cl exposure to Litopenaeus vannamei based on the cerebral ganglion-eyestalk-haemocytes axis

Ammonia nitrogen, as a water environmental toxin, poses a potential threat to aquatic animals. Although NH4Cl stress is known to cause immunotoxicity, mechanistic pathways linking stress networks in the neuroendocrine system to immunotoxicity remain poorly understood. In this study, firstly, using transcriptome analysis of cerebral ganglion and eyestalk in shrimp, we identified significant changes in genes related to biogenic amines, acetylcholine, crustacean hyperglycemic hormones, and neuropeptide F. Additionally, expression patterns of neuroendocrine factors in different tissues of shrimp were evaluated to explore the sources of these factors. Here, we showed that NH4Cl exposure activates acetylcholine (ACh) neurons in cerebral ganglion of shrimp and dramatically upregulates high affinity choline transporter 1 (ChT1) gene expression. The knockdown of ChT1 gene enhanced the immunity of haemocytes in shrimp compared with saline and GFP dsRNA groups. And after eyestalk ablation, the levels of neuroendocrine factors in the cerebral ganglion and thoracic ganglion were disturbed, and haemocytes parameters induced by NH4Cl were significantly decreased. Combined with different doses of NH4Cl exposure experiments, we demonstrated that: (1) In a short period of NH4Cl exposure, the neuroendocrine factors CRH-ACTH-cortisol and 5-HT-DA in the cerebral ganglion-eyestalk axis of shrimp play a major role in regulating haemocytes immunity; (2) With the prolongation of exposure, the immunotoxicity induced by NH4Cl was mainly due to the release of more ACh in the cerebral ganglion, which promoted the release of NPF in the thoracic ganglion, and CHH and NPF in the eyestalk, as well as weakened the effect of biogenic amines. Subsequently, these neuroendocrine factors regulate immunity through intracellular signaling pathways. Collectively, these results established a new mechanism that NH4Cl might directly regulate haemocytes immunotoxicity through the cerebral ganglion and thoracic ganglion; or through the cerebral ganglion-eyestalk axis or cerebral ganglion-thoracic ganglion axis cause haemocytes immunotoxicity.

Continuous flow stimulation had no significant effect on the growth rate but was conducive to the swimming performance, spontaneous behavior, and nonspecific immune parameter of juvenile Percocypris pingi

Flow stimulation before release into the wild may contribute to improved survivability of farmed fish. However, the effects of flow stimulation on the survival rate of fish depend on the fish species and exercise regime, such as exercise type, duration, and intensity. In this study, juvenile Percocypris pingi swam for 18 h per day for 8 weeks under different water speeds, 3 cm s-1 (control) and 1, 2, and 4 body lengths (bl) s-1 , at 20°C. Then, parameters related to the growth rate, swimming capacity, spontaneous activity, and immune function were measured. We found that (1) continuous flow stimulation had no significant influence on the growth but was conducive to the increase in the relative carcass mass; (2) continuous flow stimulation at 2 or 4 bl s-1 enhanced the aerobic swimming capacity (Ucrit ), which may be due to an increase in anaerobic exercise capacity (endurance time) rather than to changes in maximum metabolic rate and aerobic scope; (3) continuous flow stimulation at 4 bl s-1 led to a significant increase in spontaneous activity, which was mainly due to the higher percent time spent moving as compared with the controls; and (4) continuous flow stimulation at 2 bl s-1 may contribute to improving the nonspecific immune parameter (lysozyme activity) in juvenile P. pingi. Our findings suggest that continuous flow stimulation at 2 or 4 bl s-1 for 18 h per day for 56 days at 20°C before release in wild may be a suitable training regime for improving the survival rate of cultured juvenile P. pingi.

Edible insects in food

Edible insects, with their high protein and lipid content, offer a safe and cost-effective alternative to traditional protein sources. They are environmentally friendly, emitting fewer greenhouse gases and requiring less water than livestock farming. Their rapid reproduction, efficiency, and labor-saving qualities make them attractive for industry. However, the unappealing appearance of edible insects hinders consumer acceptance. To overcome this, materialization technologies should be developed, and negative perceptions addressed with objective data. Promoting the nutritional value, safe rearing, disease prevention, and cost-efficiency of edible insects can boost consumer interest. Commercializing various insect products is crucial to revitalize their integration into the food industry.

Edible Insects: A New Sustainable Nutritional Resource Worth Promoting

Edible insects are a highly nutritious source of protein and are enjoyed by people all over the world. Insects contain various other nutrients and beneficial compounds, such as lipids, vitamins and minerals, chitin, phenolic compounds, and antimicrobial peptides, which contribute to good health. The practice of insect farming is far more resource-efficient compared to traditional agriculture and animal husbandry, requiring less land, energy, and water, and resulting in a significantly lower carbon footprint. In fact, insects are 12 to 25 times more efficient than animals in converting low-protein feed into protein. When it comes to protein production per unit area, insect farming only requires about one-eighth of the land needed for beef production. Moreover, insect farming generates minimal waste, as insects can consume food and biomass that would otherwise go to waste, contributing to a circular economy that promotes resource recycling and reuse. Insects can be fed with agricultural waste, such as unused plant stems and food scraps. Additionally, the excrement produced by insects can be used as fertilizer for crops, completing the circular chain. Despite the undeniable sustainability and nutritional benefits of consuming insects, widespread acceptance of incorporating insects into our daily diets still has a long way to go. This paper provides a comprehensive overview of the nutritional value of edible insects, the development of farming and processing technologies, and the problems faced in the marketing of edible insect products and insect foods to improve the reference for how people choose edible insects.

Effects of dietary dihydromyricetin on growth performance, antioxidant capacity, immune response and intestinal microbiota of shrimp (Litopenaeus vannamei)

A 56-day culture trial was conducted to evaluate the effects of dietary dihydromyricetin (DMY) on growth performance, antioxidant capacity, immune response and intestinal microbiota of shrimp (Litopenaeus vannamei). 840 healthy shrimp (1.60 ± 0.21 g) in total were fed with four different levels of DMY diets at 0 (Control), 100 (D1), 200 (D2), and 300 (D3) mg/kg, respectively. Samples were collected after the culture trial, and then, a 7-day challenge experiment against Vibrio parahaemolyticus was conducted. The results demonstrated that DMY significantly enhanced the activity of protease, amylase and lipase as well as the expression of lipid and protein transport-related genes (P < 0.05). The results of plasma lipid parameters indicated that DMY reduced lipid deposition, manifested by significantly (P < 0.05) decreased plasma total cholesterol (T-CHO), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C). The expression of genes involved in fatty acid β-oxidation and triglyceride catabolism was significantly up-regulated (P < 0.05), and genes involved in triglyceride synthesis were significantly down-regulated in DMY groups when compared to control group (P < 0.05). Moreover, dietary DMY also significantly (P < 0.05) increased the total antioxidant capacity (T-AOC), antioxidant enzymes activity and glutathione (GSH) content of shrimp, and a significant increase of total hemocytes count (THC), phagocytic rate (PR), antibacterial activity (AA) and bacteriolytic activity (BA) was observed in DMY groups (P < 0.05). The addition of DMY to the diet significantly augmented immune response by up-regulating the expression of genes related to toll-like receptors (Toll) signaling pathway, immune deficiency (IMD) signaling pathway and intestinal mucin. Furthermore, dietary DMY could modulate the composition and abundance of intestinal microbiota. In conclusion, DMY showed promising potential as a functional feed additive for shrimp to improve the growth performance and physiological health.

PAMPred: A hierarchical evolutionary ensemble framework for identifying plant antimicrobial peptides

Antimicrobial peptides (AMPs) play a crucial role in plant immune regulation, growth and development stages, which have attracted significant attentions in recent years. As the wet-lab experiments are laborious and cost-prohibitive, it is indispensable to develop computational methods to discover novel plant AMPs accurately. In this study, we presented a hierarchical evolutionary ensemble framework, named PAMPred, which consisted of a multi-level heterogeneous architecture to identify plant AMPs. Specifically, to address the existing class imbalance problem, a cluster-based resampling method was adopted to build multiple balanced subsets. Then, several peptide features including sequence information-based and physicochemical properties-based features were fed into the different types of basic learners to increase the ensemble diversity. For boosting the predictive capability of PAMPred, the improved particle swarm optimization (PSO) algorithm and dynamic ensemble pruning strategy were used to optimize the weights at different levels adaptively. Furthermore, extensive ten-fold cross-validation and independent testing experimental results demonstrated that PAMPred achieved excellent prediction performance and generalization ability, and outperformed the state-of-the-art methods. It also indicated that the proposed method could serve as an effective auxiliary tool to identify plant AMPs, which would be conducive to explore the immune regulatory mechanism of plants.

Bioactive Peptides Derived from Edible Insects: Effects on Human Health and Possible Applications in Dentistry

Novel foods, including edible insects, are emerging because of their nutritional characteristics and low environmental impacts and could represent a valid alternative source of food in a more sustainable way. Edible insects have been shown to have beneficial effects on human health. Insect-derived bioactive peptides exert antihypertensive, antioxidant, anti-inflammatory, and antimicrobial properties and have protective effects against common metabolic conditions. In this review, the roles of edible insects in human health are reported, and the possible applications of these peptides in clinical practice are discussed. A special mention is given to the role of antimicrobial peptides and their potential applications in controlling infections in orthodontic procedures. In this context, insects' antimicrobial peptides might represent a potential tool to face the onset of infective endocarditis, with a low chance to develop resistances, and could be manipulated and optimized to replace common antibiotics used in clinical practice so far. Although some safety concerns must be taken into consideration, and the isolation and production of insect-derived proteins are far from easy, edible insects represent an interesting source of peptides, with beneficial effects that may be, in the future, integrated into clinical and orthodontic practice.

Topoisomeric Membrane-Active Peptides: A Review of the Last Two Decades

In recent decades, bioactive peptides have been gaining recognition in various biomedical areas, such as intracellular drug delivery (cell-penetrating peptides, CPPs) or anti-infective action (antimicrobial peptides, AMPs), closely associated to their distinct mode of interaction with biological membranes. Exploiting the interaction of membrane-active peptides with diverse targets (healthy, tumoral, bacterial or parasitic cell membranes) is opening encouraging prospects for peptides in therapeutics. However, ordinary peptides formed by L-amino acids are easily decomposed by proteases in biological fluids. One way to sidestep this limitation is to use topoisomers, namely versions of the peptide made up of D-amino acids in either canonic (enantio) or inverted (retroenantio) sequence. Rearranging peptide sequences in this fashion provides a certain degree of native structure mimicry that, in appropriate contexts, may deliver desirable biological activity while avoiding protease degradation. In this review, we will focus on recent accounts of membrane-active topoisomeric peptides with therapeutic applications as CPP drug delivery vectors, or as antimicrobial and anticancer candidates. We will also discuss the most common modes of interaction of these peptides with their membrane targets.

Immunotoxicity and the mechanisms of aflatoxin B1-induced growth retardation in shrimp and alleviating effects of bile acids

Aflatoxin B1 (AFB1) is one of the most toxic mycotoxins prevalent in the environment and food chain, posing severe health risks to humans and animals. Bile acids are natural detergents synthesized from cholesterol and play a key role in the excretion of toxins in vertebrates. Here, pacific white shrimp (Litopenaeus vannamei) served as an animal model to examine the toxicity mechanisms of AFB1 and assess the potential alleviating effects of bile acids against AFB1. Our results revealed that AFB1 exposure significantly inhibited the growth performance and immune response of shrimp, accompanied by AFB1 accumulation and histological damage. Mechanistically, AFB1-induced DNA damage activated DNA repair mechanisms and induced the arrest of cell cycle via the ATR-cyclin B/cdc2 pathway. Additionally, AFB1 directly suppressed the immune response and growth performance of shrimp by inhibiting Toll and IMD pathways and the secretion of digestive enzymes. Notably, dietary bile acids significantly reduced AFB1 accumulation and alleviated AFB1-induced growth retardation and immunotoxicity in shrimp, and CCKAR, ATR, and Relish may be key mediators of the alleviating effects of bile acids. Our study provided new insights into the toxicity mechanisms of AFB1 in invertebrates and highlighted the potential of bile acids to alleviate AFB1 toxicity.

Mosquito pericardial cells upregulate Cecropin expression after an immune challenge

Most mosquito-transmitted pathogens grow or replicate in the midgut before invading the salivary glands. Pathogens are exposed to several immunological factors along the way. Recently, it was shown that hemocytes gather near the periostial region of the heart to efficiently phagocytose pathogens circulating in the hemolymph. Nerveless, not all pathogens can be phagocyted by hemocytes and eliminated by lysis. Interestingly, some studies have shown that pericardial cells (PCs) surrounding periostial regions, may produce humoral factors, such as lysozymes. Our current work provides evidence that Anopheles albimanus PCs are a major producer of Cecropin 1 (Cec1). Furthermore, our findings reveal that after an immunological challenge, PCs upregulate Cec1 expression. We conclude that PCs are positioned in a strategic location that could allow releasing humoral components, such as cecropin, to lyse pathogens on the heart or circulating in the hemolymph, implying that PCs could play a significant role in the systemic immune response.

Genome-Wide Identification of Trachinotus ovatus Antimicrobial Peptides and Their Immune Response against Two Pathogen Challenges

Golden pompano, Trachinotus ovatus, as a highly nutritious commercially valuable marine fish, has become one of the preferred species for many fish farmers due to its rapid growth, wide adaptability, and ease of feeding and management. However, with the expansion of aquaculture scale, bacterial and parasitic diseases have also become major threats to the golden pompano industry. This study, based on comparative genomics, shows the possibility of preferential evolution of freshwater fish over marine fish by analyzing the phylogenetic relationships and divergence times of 14 marine fish and freshwater fish. Furthermore, we identified antimicrobial peptide genes from 14 species at the genomic level and found that the number of putative antimicrobial peptides may be related to species evolution. Subsequently, we classified the 341 identified AMPs from golden pompano into 38 categories based on the classification provided by the APD3. Among them, TCP represented the highest proportion, accounting for 23.2% of the total, followed by scolopendin, lectin, chemokine, BPTI, and histone-derived peptides. At the same time, the distribution of AMPs in chromosomes varied with type, and covariance analysis showed the frequency of its repeat events. Enrichment analysis and PPI indicated that AMP was mainly concentrated in pathways associated with disease immunity. In addition, our transcriptomic data measured the expression of putative AMPs of golden pompano in 12 normal tissues, as well as in the liver, spleen, and kidney infected with Streptococcus agalactiae and skin infected with Cryptocaryon irritans. As the infection with S. agalactiae and C. irritans progressed, we observed tissue specificity in the number and types of responsive AMPs. Positive selection of AMP genes may participate in the immune response through the MAPK signaling pathway. The genome-wide identification of antimicrobial peptides in the golden pompano provided a complete database of potential AMPs that can contribute to further understanding the immune mechanisms in pathogens. AMPs were expected to replace traditional antibiotics and be developed into targeted drugs against specific bacterial and parasitic pathogens for more precise and effective treatment to improve aquaculture production.

Application of antimicrobial peptides in plant protection: making use of the overlooked merits

Pathogen infection is one of the major causes of yield loss in the crop field. The rapid increase of antimicrobial resistance in plant pathogens has urged researchers to develop both new pesticides and management strategies for plant protection. The antimicrobial peptides (AMPs) showed potential on eliminating plant pathogenic fungi and bacteria. Here, we first summarize several overlooked advantages and merits of AMPs, which includes the steep dose-response relations, fast killing ability, broad synergism, slow resistance selection. We then discuss the possible application of AMPs for plant protection with above merits, and highlight how AMPs can be incorporated into a more efficient integrated management system that both increases the crop yield and reduce resistance evolution of pathogens.

Can BioSAXS detect ultrastructural changes of antifungal compounds in Candida albicans?-an exploratory study

The opportunistic yeast Candida albicans is the most common cause of candidiasis. With only four classes of antifungal drugs on the market, resistance is becoming a problem in the treatment of fungal infections, especially in immunocompromised patients. The development of novel antifungal drugs with different modes of action is urgent. In 2016, we developed a groundbreaking new medium-throughput method to distinguish the effects of antibacterial agents. Using small-angle X-ray scattering for biological samples (BioSAXS), it is now possible to screen hundreds of new antibacterial compounds and select those with the highest probability for a novel mode of action. However, yeast (eukaryotic) cells are highly structured compared to bacteria. The fundamental question to answer was if the ultrastructural changes induced by the action of an antifungal drug can be detected even when most structures in the cell stay unchanged. In this exploratory work, BioSAXS was used to measure the ultrastructural changes of C. albicans that were directly or indirectly induced by antifungal compounds. For this, the well-characterized antifungal drug Flucytosine was used. BioSAXS measurements were performed on the synchrotron P12 BioSAXS beamline, EMBL (DESY, Hamburg) on treated and untreated yeast C. albicans. BioSAXS curves were analysed using principal component analysis (PCA). The PCA showed that Flucytosine-treated and untreated yeast were separated. Based on that success further measurements were performed on five antifungal peptides {1. Cecropin A-melittin hybrid [CA (1-7) M (2-9)], KWKLFKKIGAVLKVL; 2. Lasioglossin LL-III, VNWKKILGKIIKVVK; 3. Mastoparan M, INLKAIAALAKKLL; 4. Bmkn2, FIGAIARLLSKIFGKR; and 5. optP7, KRRVRWIIW}. The ultrastructural changes of C. albicans indicate that the peptides may have different modes of action compared to Flucytosine as well as to each other, except for the Cecropin A-melittin hybrid [CA (1-7) M (2-9)] and optP7, showing very similar effects on C. albicans. This very first study demonstrates that BioSAXS shows promise to be used for antifungal drug development. However, this first study has limitations and further experiments are necessary to establish this application.

Insect Meals and Insect Antimicrobial Peptides as an Alternative for Antibiotics and Growth Promoters in Livestock Production

The extensive use of antibiotics in animal production has led to the development of antibiotic-resistant microorganisms and the search for alternative antimicrobial agents in animal production. One such compound may be antimicrobial peptides (AMPs), which are characterized by, among others, a wide range of biocidal activity. According to scientific data, insects produce the largest number of antimicrobial peptides, and the changing EU legislation has allowed processed animal protein derived from insects to be used in feed for farm animals, which, in addition to a protein supplement, may prove to be an alternative to antibiotics and antibiotic growth promoters due to their documented beneficial impact on livestock health. In animals that were fed feeds with the addition of insect meals, changes in their intestinal microbiota, strengthened immunity, and increased antibacterial activity were confirmed to be positive effects obtained thanks to the insect diet. This paper reviews the literature on sources of antibacterial peptides and the mechanism of action of these compounds, with particular emphasis on insect antibacterial peptides and their potential impact on animal health, and legal regulations related to the use of insect meals in animal nutrition.

Insect Antimicrobial Peptides: Advancements, Enhancements and New Challenges

Several insects are known as vectors of a wide range of animal and human pathogens causing various diseases. However, they are also a source of different substances, such as the Antimicrobial Peptides (AMPs), which can be employed in the development of natural bioactive compounds for medical, veterinary and agricultural applications. It is well known that AMP activity, in contrast to most classical antibiotics, does not lead to the development of natural bacterial resistance, or at least the frequency of resistance is considered to be low. Therefore, there is a strong interest in assessing the efficacy of the various peptides known to date, identifying new compounds and evaluating possible solutions in order to increase their production. Moreover, implementing AMP modulation in insect rearing could preserve insect health in large-scale production. This review describes the current knowledge on insect AMPs, presenting the validated ones for the different insect orders. A brief description of their mechanism of action is reported with focus on proposed applications. The possible effects of insect diet on AMP translation and synthesis have been discussed.

Local Immune Biomarker Expression Depending on the Uterine Microbiota in Patients with Idiopathic Infertility

The endometrium has traditionally been considered sterile. Nowadays, active studies are performed on the female upper genital tract microbiota. Bacteria and/or viruses colonizing the endometrium are known to alter its functional properties, including receptivity and embryo implantation. Uterine cavity inflammation caused by microorganisms leads to disrupted cytokine expression, which, in turn, is mandatory for the successful implantation of the embryo. The present study assessed the vaginal and endometrial microbiota composition and its relation to the levels of cytokines produced by the endometrium in reproductive-aged women complaining of secondary infertility of unknown origin. The multiplex real-time PCR assay was applied for vaginal and endometrial microbiota analysis. The quantitative measurement of endometrial α-defensin (DEFa1), transforming growth factor (TGFβ1), and basic fibroblast growth factor (bFGF2) was carried out using the ELISA (Cloud-Clone Corporation (Katy, TX, USA; manufactured in Wuhan, China). A reliable decline in endometrial TGFβ1 and bFGF2 and an increase in DEFa1 were demonstrated in women with idiopathic infertility when compared to fertile patients. However, TGFβ1, bFGF2, and DEFa1 expression correlated reliably only with the presence of Peptostreptococcus spp. and HPV in the uterine cavity. The obtained results highlight the importance of local immune biomarker determination in the assessment of certain bacteria and viruses' significance as causative agents of infertility.

Intestinal mucus components and secretion mechanisms: what we do and do not know

Damage to the colon mucus barrier, the first line of defense against microorganisms, is an important determinant of intestinal diseases such as inflammatory bowel disease and colorectal cancer, and disorder in extraintestinal organs. The mucus layer has attracted the attention of the scientific community in recent years, and with the discovery of new mucosal components, it has become increasingly clear that the mucosal barrier is a complex system composed of many components. Moreover, certain components are jointly involved in regulating the structure and function of the mucus barrier. Therefore, a comprehensive and systematic understanding of the functional components of the mucus layer is clearly warranted. In this review, we summarize the various functional components of the mucus layer identified thus far and describe their unique roles in shaping mucosal structure and function. Furthermore, we detail the mechanisms underlying mucus secretion, including baseline and stimulated secretion. In our opinion, baseline secretion can be categorized into spontaneous Ca²⁺ oscillation-mediated slow and continuous secretion and stimulated secretion, which is mediated by massive Ca²⁺ influx induced by exogenous stimuli. This review extends the current understanding of the intestinal mucus barrier, with an emphasis on host defense strategies based on fortification of the mucus layer.

Structure-activity relationships of antibacterial peptides

Antimicrobial peptides play a crucial role in innate immunity, whose components are mainly peptide-based molecules with antibacterial properties. Indeed, the exploration of the immune system over the past 40 years has revealed a number of natural peptides playing a pivotal role in the defence mechanisms of vertebrates and invertebrates, including amphibians, insects, and mammalians. This review provides a discussion regarding the antibacterial mechanisms of peptide-based agents and their structure-activity relationships (SARs) with the aim of describing a topic that is not yet fully explored. Some growing evidence suggests that innate immunity should be strongly considered for the development of novel antibiotic peptide-based libraries. Also, due to the constantly rising concern of antibiotic resistance, the development of new antibiotic drugs is becoming a priority of global importance. Hence, the study and the understanding of defence phenomena occurring in the immune system may inspire the development of novel antibiotic compound libraries and set the stage to overcome drug-resistant pathogens. Here, we provide an overview of the importance of peptide-based antibacterial sources, focusing on accurately selected molecular structures, their SARs including recently introduced modifications, their latest biotechnology applications, and their potential against multi-drug resistant pathogens. Last, we provide cues to describe how antibacterial peptides show a better scope of action selectivity than several anti-infective agents, which are characterized by non-selective activities and non-targeted actions toward pathogens.

Recent Advances on Peptide-Based Biosensors and Electronic Noses for Foodborne Pathogen Detection

Foodborne pathogens present a serious issue around the world due to the remarkably high number of illnesses they cause every year. In an effort to narrow the gap between monitoring needs and currently implemented classical detection methodologies, the last decades have seen an increased development of highly accurate and reliable biosensors. Peptides as recognition biomolecules have been explored to develop biosensors that combine simple sample preparation and enhanced detection of bacterial pathogens in food. This review first focuses on the selection strategies for the design and screening of sensitive peptide bioreceptors, such as the isolation of natural antimicrobial peptides (AMPs) from living organisms, the screening of peptides by phage display and the use of in silico tools. Subsequently, an overview on the state-of-the-art techniques in the development of peptide-based biosensors for foodborne pathogen detection based on various transduction systems was given. Additionally, limitations in classical detection strategies have led to the development of innovative approaches for food monitoring, such as electronic noses, as promising alternatives. The use of peptide receptors in electronic noses is a growing field and the recent advances of such systems for foodborne pathogen detection are presented. All these biosensors and electronic noses are promising alternatives for the pathogen detection with high sensitivity, low cost and rapid response, and some of them are potential portable devices for on-site analyses.

Hyaluronan-cecropin B interactions studied by ultrasound velocimetry and isothermal titration calorimetry

Interactions between hyaluronan and the antimicrobial peptide cecropin B were studied in water and PBS using high-resolution ultrasonic spectroscopy and isothermal titration calorimetry. Although each technique is fundamentally different, they both gave identical results. It was found that the molecular weight of hyaluronan plays an important role in the interactions - in particular, the transition between the rod conformation and the random coil conformation. In water, interactions were saturated in a molar charge ratio of 1.5 and not 1.0 as expected. The later saturation of the interaction probably occurred either for steric reasons or due to the interaction between functional groups in the cecropin structure, which allowed complete dissociation of the antimicrobial peptide. In PBS, in contrast to water, no interactions were observed, irrespective of the molecular weight of hyaluronan. Thus, at a sufficiently high ionic strength, the interactions were suppressed.

Four antimicrobial peptides of Asian gypsy moth respond to infection of its viral pathogen, nucleopolyhedrovirus (LdMNPV)

Antimicrobial peptides (AMPs) play essential roles in defending against various invading pathogens. Although antibacterial or antifungal properties of AMPs have been well characterized, the contribution of AMPs to immune defenses against viruses especially baculoviruses is still unclear. In this study, four full-length AMP genes (Ldcec, Ldatt, Ldglo and Ldmor) that encode the cecropin, attacin, gloverin and moricin, respectively, were characterized in Lymantria dispar (Asian gypsy moth). All four AMPs were cationic peptides and exhibited hydrophilicity. Structural analysis showed that the Ldcec and Ldmor were α-helical peptides. Tissue-specific Ldcec expression was the highest in fat body, while expression of Ldatt, Ldglo and Ldmor was the highest in epidermis. All four AMP genes were expressed during all developmental stages with the highest expression in the pupa and adult. Compared to mock infection, expression of these four AMP genes were significantly induced following Lymantria dispar multiple nucleopolyhedrovirus (LdMNPV) challenge and sharply increased at 72 h post infection. After Ldglo gene silencing, the DNA replication levels of LdMNPV in L. dispar larvae significantly increased at 48 and 72 h post infection, indicating that the Ldglo could suppress the DNA replication of LdMNPV. Our results suggest that four AMPs of L. dispar may play important roles in antiviral immunity against LdMNPV.

Bioactive Peptide Discovery from Edible Insects for Potential Applications in Human Health and Agriculture

In the past decade, there has been fast-growing interest among researchers to discover bioactive peptides from edible insects and to evaluate their potential applications in the management of human, livestock, and plant health. This review summarizes current knowledge of insect-derived peptides and their potential role in tackling human health issues and solving agriculture problems by protecting crops and livestock against their pathogens. Numerous bioactive peptides have been identified from edible insect species, including peptides that were enzymatically liberated from insect proteins and endogenous peptides that occur naturally in insects. The peptides exhibited diverse bioactivities, encompassing antioxidant, anti-angiotensin-converting enzyme, anti-dipeptidyl peptidase-IV, anti-glucosidase, anti-lipase, anti-lipoxygenase, anti-cyclooxygenase, anti-obesity, and hepatoprotective activities. Such findings point to their potential contribution to solving human health problems related to inflammation, free radical damage, diabetes, hypertension, and liver damage, among others. Although most of the experiments were performed in vitro, evidence for the in vivo efficacy of some peptides is emerging. Evidence of the protective effects of insect-derived endogenous antimicrobial peptides in combating farm animal and plant pathogens is available. The ability of insect-derived endogenous neuropeptides to protect plants against herbivorous insects has been demonstrated as well. Nevertheless, the potency of peptides identified from insect protein hydrolysates in modulating livestock and plant health remains a knowledge gap to be filled.

Dietary leucine requirement of fingerling Channa punctatus (Bloch) based on growth, feed conversion and leucine retention efficiency, hematological parameters, antioxidant and intestinal enzyme activities

To find out the dietary leucine requirement of fingerling Channa punctatus (5.24 ± 0.07 g), six purified experimental diets (45% CP and 14.73 kJ/g DE) with various leucine concentrations (0.5, 1.0,1.5, 2.0, 2.5 and 3.0% diet) were fed to apparent satiation to triplicate groups for 12 weeks (714/02/a/CPCSEA). Absolute weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, protein and leucine retention efficiency, and RNA/DNA ratio improved up to 2.0% leucine in the diet. Carcass protein and fat increased significantly with increasing leucine levels up to a 2.0% dry diet. Moisture content showed a reverse pattern. Red blood corpuscles hemoglobin and hematocrit increased with incremental levels of leucine up to 2.0% diet. Significant changes were also noted in serum total protein, superoxide dismutase, aspartate aminotransferase, alanine aminotransferase, and lysozyme activity. Serum protein, superoxide dismutase and lysozyme activity were positively correlated with increasing leucine levels up to 2.0% diet, whereas aspartate aminotransferase and alanine aminotransferase showed the opposite trend. Based on the quadratic regression analysis of absolute weight gain, specific growth rate, feed conversion ratio, protein, and leucine retention efficiency, inclusion of 2.0% leucine is recommended for optimum growth of fingerling C. punctatus.

Study on the toxic effects of sodium pentachlorophenol (PCP-Na) on razor clam (Sinonovacula constricta)

Currently, research on toxic effects of PCP Na is greatly insufficient. The aim of this study is to explore the toxic effects of PCP-Na for better conducting future work on PCP-Na toxicology. For this purpose, S. constricta adults were exposed to PCP-Na for toxicity testing. The results showed that PCP-Na could easily bioaccumulate in S. constricta and significantly affected both phrase I and II metabolism enzymes. Meanwhile, PCP-Na strongly activated antioxidant system and caused PC, LPO and DNA damage. In addition, neurotoxicity and immunotoxicity of PCP-Na was demonstrated in this study. Interestingly, we observed that PCP-Na significantly affected the expression of genes of electron transport chain and induced key enzymes of glycolysis, indicating that PCP-Na may act as an uncoupler of oxidative phosphorylation, interfering with energy supply and causing energy compensation. This study is the first to fully analyze and provide a new perspective on the toxicity of PCP-Na.

Dietary supplementations modulate the physiological parameters, fatty acids profile and the growth of red claw crayfish (Cherax quadricarinatus)

An optimal diet is an important factor for the proper growth and health of crustaceans. However, the regulation of antioxidant activity and non-specific immunity related to the consumption of feed additives has not been studied in RC-crayfish. Triplicate groups of 20 crayfish/tank (36.72 ± 0.70 g) fed with a basal diet and sixteen experimental diets that contained five feed additives with four grade levels (40, 160, 240 and 320 mg/kg vitamin E, 2, 4, 6 and 8 g/kg nucleotides, 2, 4, 6 and 8 g/kg Haematococcus pluvialis, 5, 10, 15 and 20 g/kg arachidonic acid and 2.5, 5, 10 and 15 g/kg yeast extract) on physiological parameters, fatty acids profile and growth of Cherax quadricarinatus for a period of 70 days by using orthogonal array method (L16 4⁵ ). The results showed that the antioxidants activity in the haemolymph and hepatopancreas were both higher in crayfish fed with diets NO. 9 to 12 than others. Also, all the diets except diets NO. 13 to 16 showed lower free radicals contents than the control group. Similarly, significantly higher non-specific immune parameters were observed in the hepatopancreas of crayfish supplementations than those fed a control diet. Biochemical parameters related to protein profile in haemolymph increased in diets NO. 9 to 12 and then decreased in control and diets NO. 13 to 16, while the highest biochemical parameters related to lipid profile except HDL-c contents in haemolymph were observed in crayfish fed the control diet. Fatty acid composition in the hepatopancreas, muscle and ovary of RC-crayfish was significantly influenced by using the combination of Vit E, NT, H. pluvialis and YP compared to the control group. Compared to all treatments, RC-crayfish fed with diets NO. 2 and 12 had significantly stimulated higher growth performance and feed utilisation. Overall, our results suggest that diets supplemented with Vit E level of 240 mg/kg, in combination with 8 g/kg NT, 4 g/kg, H. pluvialis, 5 g/kg ARA and 10 g/kg YP are the promising treatments to increase antioxidants activity, non-specific immune response, fatty acids composition and growth of RC-crayfish. However, high dietary supplementations level can reduce antioxidants activity, immunity and inhibit growth.

Dietary Riboflavin Requirement of Pacific White Shrimp (Litopenaeus vannamei)

This study was conducted to determine the dietary riboflavin requirement and its effects on growth performance, feed utilization, innate immunity, and diet digestibility of Litopenaeus vannamei. A riboflavin-free basal diet (R0) was formulated as a control, and six other diets were prepared by adding riboflavin of 10, 20, 30, 40, 50, and 60 mg/kg to the basal diet (designated as R10, R20, R30, R40, R50, and R60, respectively). Quadruplicate groups of shrimp (initial average weight 0.17 ± 0.00 g) were fed the diets six times a day for 8 weeks. Weight gain, specific growth rate, and protein efficiency ratio were significantly increased by riboflavin (p < 0.05). The maximum values were observed in shrimp fed R40 diet. The highest activities of phenoloxidase, nitro blue tetrazolium, superoxide dismutase, and glutathione peroxidase were observed in shrimp fed R40 diet. Lysozyme activity was significantly higher in shrimp fed R30 and R40 diets than that of shrimp fed R60 diet (p < 0.05). Intestinal villi were significantly longer in shrimp fed R50 and R60 diets compared to those of all other groups while the shortest villi were observed in R0 group (p < 0.05). Intestinal villi were clearly distinguished in shrimp fed higher levels of riboflavin compared to those of shrimp fed R0 and R10 diets. Apparent digestibility coefficients of dry matter and protein in diets were not significantly affected by riboflavin levels (p < 0.05). Whole-body proximate composition and hemolymph biochemical parameters were not significantly altered by dietary riboflavin (p < 0.05). Therefore, the results of this study indicate that riboflavin is essential to enhance growth performance, feed utilization, nonspecific immunity, and intestine morphology of shrimp. An optimal riboflavin requirement for the maximum growth of L. vannamei seems to be approximately 40.9 mg/kg diet.

Protective Effects of Combined Utilization of Quercetin and Florfenicol on Acute Hepatopancreatic Necrosis Syndrome Infected Litopenaeus vannamei

This study aimed to determine the immunity, survival rate, and disease resistance of Litopenaeus vannamei treated using quercetin and florfenicol alone or in combination, after infection with acute hepatopancreatic necrosis syndrome caused by Vibrio parahaemolyticus (VPAHPND). After infection with VPAHPND, different types of feed were given to the shrimp for 5 days, including a control diet (drug-free), florfenicol only diet (15 mg/kg), quercetin only diet (400 mg/kg), a low-dose florfenicol/quercetin combined diet (200 mg/kg quercetin + 7.0 mg/kg florfenicol), a moderate-dose florfenicol/quercetin combined diet (400 mg/kg quercetin + 15 mg/kg florfenicol), and a high-dose florfenicol/quercetin combined diet (800 mg/kg quercetin + 30 mg/kg florfenicol). The cumulative mortality of shrimp was significantly reduced in the drug combination groups compared with either drug used alone (p < 0.05). The density of Vibrio was significantly lower and the immune parameters were significantly increased in the drug combination groups compared with either drug used alone (p < 0.05). Moreover, in the drug combination groups, the hepatopancreas tubules showed better integrity and structure compared with those when either drug was used alone. Therefore, compared with single drug treatment, the florfenicol and quercetin combination enhanced disease resistance, survival, and immune activity of VPAHPND-infected shrimp. When the combination treatment is used, the dosage of florfenicol can be reduced and a better therapeutic effect is obtained.

Hydrophobic-hydrophilic Alternation: An effective Pattern to de novo Designed Antimicrobial Peptides

The antimicrobial peptide (AMP) is a class of molecules that are active against a variety of microorganisms, from bacterial and cancer cells to fungi. Most AMPs are natural products, as part of an organism's own defense system against harmful microbes. However, the growing prevalence of drug resistance has forced researchers to design more promising engineered antimicrobial agents. Inspired by the amphiphilic detergents, the hydrophobic-hydrophilic alternation pattern was considered to be a simple but effective way to de novo design AMPs. In this model, hydrophobic amino acids (leucine, isoleucine etc.) and hydrophilic amino acids (arginine, lysine etc.) were arranged in an alternating way in the peptide sequence. The majority of this type of peptides have a clear hydrophilic-hydrophobic interface, which allows the molecules to have good solubility in both water and organic solvents. When they come into contact with hydrophobic membranes, many peptides undergo a conformational transformation, facilitating themself to insert into the cellular envelope. Moreover, positive-charged peptide amphiphiles tended to have an affinity with negatively-charged membrane interfaces and further led to envelope damage and cell death. Herein, several typical design patterns have been reviewed. Though varying in amino acid sequence, they all basically follow the rule of alternating arrangement of hydrophilic and hydrophobic residues. Based on that, researchers synthesized some lead compounds with favorable antimicrobial activities and preliminarily investigated their possible mode of action. Besides membrane disruption, these AMPs are proven to kill microbes in multiple mechanisms. These results deepened our understanding of AMPs' design and provided a theoretical basis for constructing peptide candidates with better biocompatibility and therapeutic potential.

Evaluation of dietary fermented tuna by-product meal as partial replacement for unprocessed tuna by-product meal in fishmeal-based diets for juvenile olive flounder Paralichthys olivaceus

This study examined the effects of feeding fermented tuna by-product (FTBP) on the growth, non-specific immune response, liver and intestinal morphology, and disease resistance of olive flounder Paralichthys olivaceus. Olive flounders (n = 20; 2 g) were randomly assigned into four dietary groups in triplicates. Fish were fed four test diets (50% crude protein; 10% crude lipid) for 10 weeks in which unprocessed tuna by-product (TBP) meal was replaced (on a protein basis) with 0% (FTBP0 as the control diet), 15% (FTBP15), 30% (FTBP30), and 60% (FTBP60) of FTBP protein. Results showed that growth performance, blood parameters, and proximate composition were not influenced by FTBP inclusion. Non-specific immune parameters such as superoxide dismutase activity in the FTBP30 and FTBP60 groups were significantly higher than in the FTBP15 and the control groups, whereas lysozyme and myeloperoxidase activities were not different. Liver histopathology revealed normal architecture in groups fed FTBP0 and FTBP15 diets although mild alterations were noted in the FTBP30- and FTBP60-fed groups. Intestinal villi height and muscular thickness were not significantly altered with FTBP inclusion. Moreover, higher cumulative survival rate was observed in the FTBP60-fed group than fish fed with the other diets following the 13-day challenge with E. tarda. Together, these results demonstrate that fermented tuna by-product meal could be included at 60% in olive flounder diets.

Engineering of lysin by fusion of antimicrobial peptide (cecropin A) enhances its antibacterial properties against multidrug-resistant Acinetobacter baumannii

Most clinical isolates of Acinetobacter baumannii, a nosocomial pathogen, are multidrug-resistant (MDR), fueling the search for alternative therapies. Bacteriophage-derived endolysins have potent antibacterial activities and are considered as alternatives to antibiotics against A. baumannii infection. Gram-negative bacteria possess outer lipid membrane that prevents direct contact between the endolysins and the cell wall. We hypothesized that the fusion of antimicrobial peptide (AMP) with endolysin could help to reduce bacterial endolysin resistance and increase antimicrobial activity by membrane permeability action. Accordingly, we fused cecropin A, a commonly used AMP, with the N-terminus of AbEndolysin, which enhances the bactericidal activity of the chimeric endolysin. The bactericidal activity of cecropin A-fused AbEndolysin increased by at least 2–8 fold for various MDR A. baumannii clinical isolates. The in vitro bactericidal activity results also showed higher bacterial lysis by the chimeric endolysin than that by the parental lysin. The engineered AbEndolysin (eAbEndolysin) showed synergistic effects with the beta-lactam antibiotics cefotaxime, ceftazidime, and aztreonam, and an additive effect with meropenem and imipenem. eAbEndolysin had no cytotoxic effect on A549 cell line and rescued mice (40% survival rate) from systemic A. baumannii infection. Together, these findings suggest the potential of lysin therapy and may prompt its use as an alternative to antibiotics.

The effect of a polystyrene nanoplastic on the intestinal microbes and oxidative stress defense of the freshwater crayfish, Procambarus clarkii

The widespread generation and accumulation of plastic waste has become a globally recognized problem. However, there are limited reports on the adverse effects of nanomaterials on freshwater crustaceans. This study tested the acute effects of different concentrations (0, 5, 10, and 20 mg/L) after 48 h exposure of 75 nm polystyrene nanoplastic on intestinal microbes, and oxidative stress parameters of freshwater crayfish, Procambarus clarkii. High-throughput sequencing analysis revealed the richness, diversity, and composition of intestinal microbiota in P. clarkii exposed to polystyrene nanoplastic. At the genus level, abundances of Lactobacillus, Faecalibaculum, Niveibacterium, and Candidatus Bacilloplasma were significantly different. The reduced abundance of Lactobacillus could affect the balance of intestinal microbes through quantitative disadvantage, which may lead to reduced immunity of P. clarkii. Streptococcus salivarius, Clostridium butyricum and Lachnospiraceae bacterium10-1 in intestinal tract reached maximum abundance at a polystyrene concentration of 20 mg/L. The increase in the number of some pathogenic bacteria may upset the balance of intestinal microorganisms through the number of dominance, and the decrease in the relative abundance of lactic acid bacteria. Probiotics, such as Lactobacillus salivarius, Lactobacillus murinus, Lactobacillus gasseri, Lactobacillus reuteri, Lactobacillus iners AB-1, and Lactobacillus crispatus in the intestinal tract reached the lowest value at a concentration of 10 mg/L. The reduced abundance of Lactobacillus can affect the balance of intestinal microbes through quantitative disadvantage, which may lead to reduced immunity in P. clarkii. At nanoplastic 10 mg/L, the relative abundance of intestinal pathogens increased, while the relative abundance of lactic acid bacteria and other probiotics decreased. With increases in nanoplastic concentrations, the values of glutathione (GSH), superoxide dismutase (SOD), acid phosphatase (ACP), lysozyme (LZM), alkaline phosphatase (AKP), peroxidase (POD), glutathione peroxidase (GPX), and protein carbonylation were significantly changed. Our data suggested that Lactobacillus may play an adjunctive role in the treatment of oxidative stress in P. clarkii exposed to 75 nm polystyrene. This study represents an important step towards a better understanding of the toxic effects of nanoplastics on aquatic crustaceans.

In vitro immunotoxicity and possible mechanisms of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on Ruditapes philippinarum hemocytes

Marine bivalves can accumulate large amounts of pollutants from sea water, sediments and microalgae due to their filter-feeding habits. BDE-47 is often the most highly concentrated congener in bivalves. BDE-47 has been found to have toxic effects on bivalves, however, the immunotoxicity and the underlying mechanisms of BDE-47 on bivalves are not well understood yet. In this study, isolated hemocytes of Manila clam Ruditapes philippinarum were exposed to five concentrations of BDE-47 (6.25 μM, 12.5 μM, 25 μM, 50 μM, 100 μM), the effects of BDE-47 on hemocyte survival rate, cell viability, granulocyte ratio, phagocytosis, bacteriolytic activity, reactive oxygen species (ROS), lysosomal membrane permeability (LMP), superoxide dismutase (SOD), and phosphorylation state of extracellular regulated protein kinase (ERK) and p38 at 2 h, 6 h and 12 h were studied. The results indicated that BDE-47 exposure declined the hemocyte cell viability, reduced the granulocyte ratio, hampered the hemocyte phagocytosis and bacteriolytic activity, elevated the ROS levels, increased the LMP, significantly changed SOD expression and depressed the phosphorylation levels of ERK and p38. Taken together, the results demonstrated that BDE-47 had significant toxic effects on the immune function, and the immunotoxicity may partly via the overproduction of ROS and the alteration of MAPK signaling pathways.

Suppression of yolk formation, oviposition and egg quality of locust (Locusta migratoria manilensis) infected by Paranosema locustae

Locusta migratoria manilensis is one of the most important agricultural pests in China. The locust has high fecundity and consumes large quantities of food, causing severe damage to diverse crops such as corn, sorghum, and rice. Immunity against pathogens and reproductive success are two important components of individual fitness, and many insects have a trade-off between reproduction and immunity when resources are limited, which may be an important target for pest control. In this study, adult females L. migratoria manilensis were treated with different concentrations (5 × 106 spores/mL or 2 × 107 spores/mL) of the entomopathogenic fungus Paranosema locustae. Effects of input to immunity on reproduction were studied by measuring feeding amount, enzyme activity, vitellogenin (Vg) and vitellogenin receptor (VgR) production, ovary development, and oviposition amount. When infected by P. locustae, feeding rate and phenol oxidase and lysozyme activities increased, mRNA expression of Vg and VgR genes decreased, and yolk deposition was blocked. Weight of ovaries decreased, with significant decreases in egg, length and weight.Thus, locusts used nutritive input required for reproduction to resist invasion by microsporidia. This leads to a decrease in expression of Vg and VgR genes inhibited ovarian development, and greatly decreased total fecundity. P. locustae at 2 × 107 spores/mL had a more obvious inhibitory effect on the ovarian development in migratory locusts. This study provides a detailed trade-off between reproduction and immune input of the female, which provides a reliable basis to find pest targets for biological control from those trade-off processes.

Antibacterial Peptide NP-6 Affects Staphylococcus aureus by Multiple Modes of Action

Our previous study extracted and identified an antibacterial peptide that was named NP-6. Herein, we investigated the physicochemical properties of NP-6, and elucidated the mechanisms underlying its antimicrobial activity against Staphylococcus aureus. The results showed that the hemolysis activity of NP-6 was 2.39 ± 0.13%, lower than Nisin A (3.91 ± 0.43%) at the same concentration (512 µg/mL). Negligible cytotoxicity towards RAW264.7 cells was found when the concentration of NP-6 was lower than 512 µg/mL. In addition, it could keep most of its activity in fetal bovine serum. Moreover, transmission electron microscopy, confocal laser scanning microscopy, and flow cytometry results showed that NP-6 can destroy the integrity of the bacterial cell membrane and increase the membrane permeability. Meanwhile, NP-6 had binding activity with bacterial DNA and RNA in vitro and strongly inhibited the intracellular β-galactosidase activity of S. aureus. Our findings suggest that NP-6 could be a promising candidate against S. aureus.

Response of cecropin transgenesis to challenge with Edwardsiella ictaluri in channel catfish Ictalurus punctatus

Constructs bearing the cecropin B gene from the moth Hyalophora cecropia, driven by the cytomegalovirus (CMV) promoter, or the common carp beta-actin (β-actin) promoter were transferred to channel catfish, Ictalurus punctatus via electroporation. One F₃ channel catfish family transgenic for cecropin transgene driven by the CMV promoter, and one F₁ channel catfish family transgenic for cecropin transgene driven by the common carp β-actin promoter were produced. F₃ and F₁ individuals exhibited enhanced disease resistance when challenged in tanks with Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish (ESC). Inheritance of the transgene by the F₁ and F₃ generation was 15% and 60%, respectively. Growth rates of the cecropin transgenic and non-transgenic full siblings (controls) channel catfish were not different (P > 0.05). All transgenic fish showed significant resistance to infection by ESC at day 3 and day 4 post exposure (P = 0.005). No correlation was detected between body weight and time to death for all genetic groups (P = 0.34). Results of our study confirmed that genetic enhancement of E. ictaluri resistance can be achieved by cecropin transgenesis in channel catfish. In addition to survival rate, improving survival time is essential because the extension of survival time gives a better chance to apply treatments to stop the bacterial infection.

Replacement of Fish Oil With Groundnut Oil for Developing Sustainable Feeds for Labeo rohita Fingerling

Groundnut oil (GO) is one of the most widely available vegetable oils (VOs) in India and throughout the world, with a global production of 6.12 million metric tons in the year 2020–2021. GO contains phytochemicals and antioxidants with a longer shelf life. Because of these benefits, GO can produce durable, low-cost, and sustainable aquaculture feeds. To evaluate the nutritional efficacy and possibility of replacing fish oil (FO) with GO, this experiment was carried out to test the effects of partial or total substitution of dietary FO by GO on the growth performance, carcass composition, antioxidant capacity, lysozyme activity, muscle fatty acid composition, and filet nutritional quality in Labeo rohita fingerling. Induced bred healthy rohu fingerlings (4.84 ± 0.13 g) were fed six isonitrogenous (400 g kg−1) and isolipidic (97 g kg−1) casein- and gelatin-containing purified diets, wherein the FO was gradually replaced by 0, 20, 40, 60, 80, and 100% GO. Fishes were stocked randomly in triplicate groups of 30 fish per tank and fed at 08:00, 12:00, and 16:00 h to apparent satiety for 8 weeks. The results showed that FO replacement with GO did not affect the growth but decreased the eicosapentaenoic (EPA), docosahexaenoic acid (DHA) levels, and n-3/n-6 ratio in the muscle of rohu fingerlings. The antioxidant capacity and lysozyme activity improved up to 60% replacement of FO with GO in diet and then declined (P &gt; 0.05) upon further inclusion of GO in diets. Although the atherogenicity, thrombogenicity indices, and hypocholesterolemic/hypercholesterolemic (H/H) ratio did not change significantly among all the muscle samples, the highest filet lipid quality (FLQ) value was found in fish receiving a 100% FO diet. Further inclusion of dietary GO decreased the filet H/H ratio and FLQ value. In summary, replacing FO with GO at a higher level had negative consequences on the filet nutritional quality of rohu fingerlings. Therefore, FO can be replaced by GO in formulated feeds to a level of 60% without hampering the growth, antioxidant capacity, and lysozyme activity and to avoid degrading the nutritional quality of fish filet.