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

Antimicrobial Peptides and Copper(II) Ions: Novel Therapeutic Opportunities

The emergence of new pathogens and multidrug resistant bacteria is an important public health issue that requires the development of novel classes of antibiotics. Antimicrobial peptides (AMPs) are a promising platform with great potential for the identification of new lead compounds that can combat the aforementioned pathogens due to their broad-spectrum antimicrobial activity and relatively low rate of resistance emergence. AMPs of multicellular organisms made their debut four decades ago thanks to ingenious researchers who asked simple questions about the resistance to bacterial infections of insects. Questions such as "Do fruit flies ever get sick?", combined with pioneering studies, have led to an understanding of AMPs as universal weapons of the immune system. This review focuses on a subclass of AMPs that feature a metal binding motif known as the amino terminal copper and nickel (ATCUN) motif. One of the metal-based strategies of hosts facing a pathogen, it includes wielding the inherent toxicity of copper and deliberately trafficking this metal ion into sites of infection. The sudden increase in the concentration of copper ions in the presence of ATCUN-containing AMPs (ATCUN-AMPs) likely results in a synergistic interaction. Herein, we examine common structural features in ATCUN-AMPs that exist across species, and we highlight unique features that deserve additional attention. We also present the current state of knowledge about the molecular mechanisms behind their antimicrobial activity and the methods available to study this promising class of AMPs.

Physiological Tradeoffs of Immune Response Differs by Infection Type in Pieris napi

Understanding the tradeoffs that result from successful infection responses is central to understanding how life histories evolve. Gaining such insights, however, can be challenging, as they may be pathogen specific and confounded with experimental design. Here, we investigated whether infection from gram positive or negative bacteria results in different physiological tradeoffs, and whether these infections impact life history later in life (post-diapause development), in the butterfly Pieris napi. During the first 24 h after infection (3, 6, 12, and 24 h), after removing effects due to injection, larvae infected with Micrococcus luteus showed a strong suppression of all non-immunity related processes while several types of immune responses were upregulated. In contrast, this tradeoff between homeostasis and immune response was much less pronounced in Escherichia coli infections. These differences were also visible long after infection, via weight loss and slower development, as well as an increased mortality at higher infection levels during later stages of development. Individuals infected with M. luteus, compared to E. coli, had a higher mortality rate, and a lower pupal weight, developmental rate and adult weight. Further, males exhibited a more negative impact of infection than females. Thus, immune responses come at a cost even when the initial infection has been overcome, and these costs are likely to affect later life history parameters with fitness consequences.

Computational studies of membrane pore formation induced by Pin2

Understanding, at the molecular level, the effect of AMPs on biological membranes is of crucial importance given the increasing number of multidrug-resistant bacteria. Being part of an ancient type of innate immunity system, AMPs have emerged as a potential solution for which bacteria have not developed resistance. Traditional antibiotics specifically act on biosynthetic pathways, while AMPs may directly destabilize the lipid membrane, but it is unclear how AMPs affect the membrane's stability. We performed multiscale molecular dynamics simulations to investigate the structural features leading to membrane pores formation on zwitterionic and anionic membranes by the antimicrobial peptide (AMP) Pandinin 2 (Pin2). Some experimental reports propose that Pin2 could form barrel-stave pores, while others suggest that it could form toroidal pores. Since there is no conclusive evidence of which type of pore is formed by Pin2 on bilayers, performing molecular dynamics simulations on these systems could shed some light on whether or not or what type of pore Pin2 forms on model membranes. Our results are focused on a detailed description of the pore formation by Pin2 in POPC and POPE:POPG membranes., which strongly suggest that Pin2 forms a toroidal pore and not a barrel-shaped pore; this type of pore also affects the membrane properties. In the process, a phospholipid remodeling in the POPE:POPG membrane takes place. Moreover, the pores formed by Pin2 indicate that they are selective for the chlorine ion. There are no previous ion selectivity reports for other AMPs with similar physicochemical properties, such as melittin and magainin.Communicated by Ramaswamy H. Sarma.

In vitro and in vivo immunologic potentiation of herb extracts on shrimp (Litopenaeus vannamei)

In vitro and in vivo effects of Astragalus polysaccharide (APS), chlorogenic acid (CGA) and berberine (BBR) on shrimp (Litopenaeus vannamei) were studied. In vitro test showed that the combination of APS and BBR and the combination of APS and CGA have strong immune enhancement effects and no lysosomal membrane damage on hemocyte. Then, feeding experiment was proceeded to optimize the concentrations of compound herbal extracts. Four diets containing G1-G4(0.5 g kg ^-1 APS + 0.5 g kg ^-1 BBR, 1.0 g kg ^-1 APS +1.0 g kg ^-1 BBR, 0.5 g kg ^-1 APS +0.5 g kg ^-1 CGA, 1.0 g kg ^-1 APS + 1.0 g kg ^-1 CGA) associated with the control group (common diet) were compared and determined their biomolecule damage to hepatopancreas including DNA damage, lipid peroxidation and protein carbonyl. The results indicated that G3 (0.5 g kg ^-1 APS +0.5 g kg ^-1 CGA) showed higher total hemocyte counts, phagocytic activities, antibacterial activities and bacteriolytic activities during 6 days feeding, and without biomolecule damages after 6 days post-withdrawal. Therefore, the appropriate immunostimulants formula in this study was the combination of 0.5 g kg ^-1 APS and 0.5 g kg^-1 CGA, which was used for 6 days followed by 6 days post-withdrawal. Additionally, our study provides new support for screening composite immunostimulants formula by using primary shrimp hemocyte culture.

A C-type lectin with dual-CRD from Tribolium castaneum is induced in response to bacterial challenge

BACKGROUND

C-type lectins (CTLs), a group of pattern recognition receptors, are involved in regulating the immune response of insects and could be used as potential targets for pest control. However, information about roles of CTLs in the innate immunity of Tribolium castaneum, a serious, worldwide pest that damages stored grain products, is relatively scarce.

RESULTS

Here, a CTL with dual carbohydrate recognition domains (CRDs) containing a highly conserved WHD (Trp⁵³ -His⁵⁴ -Asp⁵⁵ ) motif was identified in T. castaneum and named as TcCTL3. Spatiotemporal analysis showed that TcCTL3 was highly expressed in all developmental stages except early eggs, and mainly distributed in central nervous system and hemolymph. The transcript levels of TcCTL3 were significantly increased after lipopolysaccharide (LPS) and peptidoglycan (PGN) stimulation. Recombinant TcCTL3 was able to bind directly to LPS, PGN and all tested bacteria and induce a broad spectrum of microbial agglutination in the presence of Ca²⁺ . The binding was shown mainly through CRD1 domain of TcCTL3. When TcCTL3 was knocked down by RNA interference, expression of nine antimicrobial peptides (AMPs) (attacin1, attacin2, attacin3, defensins1, defensins2, coleoptericin1, coleoptericin2, cecropins2 and cecropins3) and four transcription factors (TFs) (dif1, dif2, relish and jnk) were significantly decreased under LPS and PGN stimulation, leading to increased mortality of T. castaneum when infected with Gram-positive Staphylococcus aureus or Gram-negative Escherichia coli infection.

CONCLUSION

TcCTL3 could mediate the immune response in T. castaneum via the pattern recognition, agglutination and AMP expression. These findings indicate a potential mechanism of TcCTL3 in resisting bacteria and provide an alternative molecular target for pest control. © 2020 Society of Chemical Industry.

Utilization of a recombinant defensin from Maize (Zea mays L.) as a potential antimicrobial peptide

The search for effective and bioactive antimicrobial molecules to  encounter the medical need for new antibiotics is an encouraging area of research. Plant defensins are small cationic, cysteine-rich peptides with a stabilized tertiary structure by disulfide-bridges and characterized by a wide range of biological functions. The heterologous expression of Egyptian maize defensin (MzDef) in Escherichia coli and subsequent purification by glutathione affinity chromatography yielded 2 mg/L of recombinant defensin peptide. The glutathione-S-transferase (GST)-tagged MzDef of approximately 30 kDa in size (26 KDa GST +  ~ 4 KDa MzDef peptide) was immunodetected with anti-GST antibodies. The GST-tag was successfully cleaved from the MzDef peptide by thrombin, and the removal was validated by the Tris-Tricine gel electrophoresis. The MzDef induced strong growth inhibition of Rhizoctonia solani, Fusarium verticillioides, and Aspergillus niger by 94.23%, 93.34%, and 86.25%, respectively, whereas relatively weak growth inhibitory activity of 35.42% against Fusarium solani was recorded. Moreover, strong antibacterial activities were demonstrated against E. coli and Bacillus cereus and the moderate activities against Salmonella enterica and Staphylococcus aureus at all tested concentrations (0.1, 0.2, 0.4, 0.8, 1.6, and 3.2 µM). Furthermore, the in vitro MTT assay exhibited promising anticancer activity against all tested cell lines (hepatocellular carcinoma, mammary gland breast cancer, and colorectal carcinoma colon cancer) with IC50 values ranging from 14.85 to 29.85 µg/mL. These results suggest that the recombinant peptide MzDef may serve as a potential alternative antimicrobial and anticancer agent to be used in medicinal application.

Antimicrobial peptides (AMPs): a patent review (2015-2020)

Introduction: Antimicrobial peptides are a large class of compounds that are part of innate immune response found among all classes of life and are considered promising compounds to deal with antimicrobial resistance. These AMPs have been demonstrated to have some advantages over the traditional antibiotics with a broad spectrum of antimicrobial activities and even overcome bacterial drug-resistance. Areas covered: The present review represents a comprehensive analysis of patents and patent applications available on Espacenet, from the year 2015 to 2020 referring to the therapeutic use of AMPs. Expert opinion: There are important examples about the use of antimicrobial peptides in clinical practice (e.g. polimixin b, colistin, etc.). AMPs are usually inspired by nature being produced by different living organisms as defensive and/or competition mechanisms. Despite limitations related to their development in classical drug discovery pipeline, they are endowed with relevant advantages, such as an unlimited reservoir of organisms able to produce new AMPs and they represent good starting point upon which to develop new antimicrobials.

A Review on the Use of Antimicrobial Peptides to Combat Porcine Viruses

Viral infectious diseases pose a serious threat to animal husbandry, especially in the pig industry. With the rapid, continuous variation of viruses, a series of therapeutic measures, including vaccines, have quickly lost their efficacy, leading to great losses for animal husbandry. Therefore, it is urgent to find new drugs with more stable and effective antiviral activity. Recently, it has been reported that antimicrobial peptides (AMPs) have great potential for development and application in animal husbandry because of their significant antibacterial and antiviral activity, and the antiviral ability of AMPs has become a research hotspot. This article aims to review the research situation of AMPs used to combat viruses in swine production of animal husbandry, clarify the mechanism of action of AMPs on viruses and raise some questions, and explore the future potential of AMPs in animal husbandry.

Effects of nanoplastics on antioxidant and immune enzyme activities and related gene expression in juvenile Macrobrachium nipponense

Nanoplastics are widely distributed in aquatic environments, and nanoplastic pollution has become a global concern. However, few studies have evaluated the toxicity of nanoplastics to freshwater crustaceans. In this study, by adding different concentrations of nanoplastics to water, we explored the effects of nanoplastics on the survival, antioxidant activity, immune enzyme activity, and related gene expression levels in juvenile Macrobrachium nipponense. The results showed that the 96 -h half-lethal concentration of nanoplastics to juvenile shrimp was 396.391 mg/L. As the concentration of nanoplastics increased, the activities of antioxidant enzymes generally decreased, while the contents of hydrogen peroxide and lipid peroxidation products increased. The activities of non-specific immune enzymes first increased and then decreased with increasing nanoplastic concentration. The trends in the expressions of antioxidant-related genes were generally consistent with those in the activities of antioxidant enzymes. As the nanoplastic concentration increased, the expressions of immune-related genes generally increased at first and then decreased. These results indicate that low concentrations of nanoplastics (5 mg/L) may enhance the viability of juvenile shrimp, whereas high concentrations (10,20, 40 mg/L) have inhibitory and/or toxic effects. The findings provide basic information on the toxic effects of nanoplastics in juvenile shrimp.

Effects of Yu-Ping-Feng polysaccharides (YPS) on the immune response, intestinal microbiota, disease resistance and growth performance of Litopenaeus vannamei

A 28-day feeding trial was conducted to investigate the effects of Yu-Ping-Feng polysaccharides (YPS) containing Astragalus polysaccharides (APS), Atractylodes macrocephala polysaccharides (AMP) and Saposhnikoviae polysaccharides (SPS) on the immune response, intestinal microbiota, disease resistance and growth performance of Litopenaeus vannamei. Seven hundred and twenty shrimp (3.04 ± 0.33 g) were fed the following diets: Control, YPS1 (0.13% APS + 0.0325% AMP + 0.0325% SPS), YPS2 (0.13% APS + 0.0325% AMP + 0.065% SPS) and YPS3 (0.13% APS + 0.0325% AMP+0.0975% SPS). After 14 and 28 days of feeding, the immune responses of hemocytes and intestine were measured. Intestinal microbiota and growth performance were measured after 28 days of feeding, after that, a 7-day challenge test against Vibrio harveyi was conducted. A significant (P < 0.05) increase of the total haemocyte count (THC), phagocytic activity, antibacterial activity and phenoloxidase (PO) activity was observed in shrimp fed YPS diets compared to the control. Also, dietary YPS supplementation particularly YPS3 group significantly increased the expressions of immune-related genes in the hemocytes and intestine. Regarding the intestinal microbiota, the microbial diversity and richness decreased and functional genes associated with short-chain fatty acids metabolism increased in YPS groups. After Vibrio harveyi challenge, the cumulative mortality in YPS groups was significantly lower than that of the control. Besides, dietary YPS had no significant effect on growth performance of shrimp (P > 0.05). The present results suggested that YPS could be considered as potential prebiotics for aquaculture farmed shrimp.

Characterization of novel antigenic vaccine candidates for nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae infection

Streptococcus agalactiae is one of the important pathogens responsible for high mortality and economic losses of the tilapia industry worldwide. Based on ten serovars of S. agalactiae infection, subunit vaccine with conserved antigens is promising strategy corresponding stimulated long-term immunity and provides protection for animals against different serotypes of S. agalactiae. In the present study, eight proteins (AP, AL, LivK, ESAT6, essA, essB, essC and esaA) were selected from the S. agalactiae serotype Ia genome as immunogenic antigens with bioinformation and immune experiment assays. These recombinant proteins were successfully obtained through expression in Escherichia coli and the immunogenicity was assessed in tilapia challenge model. The results showed that the recombinant proteins caused high-level-specific antibodies production and high lysozyme activities, suggesting that the recombinant proteins induced specific humoral immune response and innate immune response of tilapia. The signficant increase were observed in the cytokines levels of TNF-α, IL-1β, IFN-γ, cc1, cc2 and immune-related genes levels of CD8α and MHC factors in the spleen and head kidney tissues, suggesting that the recombinant proteins induced immune response of tilapia through cytokines signal pathway and activated high cytotoxic T-lymphocyte (CTL) activity of tilapia. Furthermore, vaccinated tilapia conferred high levels of protection against challenge with a lethal dose of highly virulent serovar Ⅰa (highest RPS was 91.60% in AL and essC protein groups). Our results indicated that the eight recombinant proteins induced high level of immune responses and offered protection against S. agalactiae infection, could be potential subunit vaccine candidates.

Antimicrobial Effect of Zophobas morio Hemolymph against Bovine Mastitis Pathogens

Coliforms and Staphylococcus spp. infections are the leading causes of bovine mastitis. Despite extensive research and development in antibiotics, they have remained inadequately effective in treating bovine mastitis induced by multiple pathogen infection. In the present study, we showed the protective effect of Zophobas morio (Z. morio) hemolymph on bovine mammary epithelial cells against bacterial infection. Z. morio hemolymph directly kills both Gram-positive and Gram-negative bacteria through membrane permeation and prevents the adhesion of E. coli or the clinically isolated S. simulans strain to bovine mammary epithelial (MAC-T) cells. In addition, Z. morio hemolymph downregulates the expression of nucleotide-binding oligomerization domain (NOD)-like receptor family member pyrin domain-containing protein 3 (NLRP3), caspase-1, and NLRP6, as well as inhibits the secretion of interleukin-1β (IL-1β) and IL-18, which attenuates E. coli or S. simulans-induced pyroptosis. Overall, our results suggest the potential role of Z. morio hemolymph as a novel therapeutic candidate for bovine mastitis.

Anti-Inflammatory Activity of Antimicrobial Peptide Periplanetasin-5 Derived from the Cockroach Periplaneta americana

Previously, we performed an in silico analysis of the Periplaneta americana transcriptome. Antimicrobial peptide candidates were selected using an in silico antimicrobial peptide prediction method. It was found that periplanetasin-5 had antimicrobial activity against yeast and grampositive and gram-negative bacteria. In the present study, we demonstrated the anti-inflammatory activities of periplanetasin-5 in mouse macrophage Raw264.7 cells. No cytotoxicity was observed at 60 μg/ml periplanetasin-5, and treatment decreased nitric oxide production in Raw264.7 cells exposed to lipopolysaccharide (LPS). In addition, quantitative RT-PCR and enzyme-linked immunosorbent assay revealed that periplanetasin-5 reduced cytokine (tumor necrosis factor-α, interleukin-6) expression levels in the Raw264.7 cells. Periplanetasin-5 controlled inflammation by inhibiting phosphorylation of MAPKs, an inflammatory signaling element, and reducing the degradation of IκB. Through LAL assay, LPS toxicity was found to decrease in a periplanetasin-5 dose-dependent manner. Collectively, these data showed that periplanetasin-5 had antiinflammatory activities, exemplified in LPS-exposed Raw264.7 cells. Thus, we have provided a potentially useful antibacterial peptide candidate with anti-inflammatory activities.

Preserved antibacterial activity of ribosomal protein S15 during evolution

Conventional role of ribosomal proteins is ribosome assembly and protein translation, but some ribosomal proteins also show antimicrobial peptide (AMP) activity, though their mode of action remains ill-defined. Here we demonstrated for the first time that amphioxus RPS15, BjRPS15, was a previously uncharacterized AMP, which was not only capable of identifying Gram-negative and -positive bacteria via interaction with LPS and LTA but also capable of killing the bacteria. We also showed that both the sequence and 3D structure of RPS15 and its prokaryotic homologs were highly conserved, suggesting its antibacterial activity is universal across widely separated taxa. Actually this was supported by the facts that the residues positioned at 45-67 formed the core region for the antimicrobial activity of BjRPS15, and its prokaryotic counterparts, including Nitrospirae RPS19_33-55, Aquificae RPS19_33-55 and P. syringae RPS19_50-72, similarly displayed antibacterial activities. BjRPS15 functioned by both interaction with bacterial surface via LPS and LTA and membrane depolarization as well as induction of intracellular ROS. Moreover, we showed that RPS15 existed extracellularly in amphioxus, shrimp, zebrafish and mice, hinting it may play a critical role in systematic immunity in different animals. In addition, we found that neither BjRPS15 nor its truncated form BjRPS15_45-67 were toxic to mammalian cells, making them promising lead molecules for the design of novel AMPs against bacteria. Collectively, these indicate that RPS15 is a new member of AMP with ancient origin and high conservation throughout evolution.

Cationic Amphiphilic Peptides: Synthetic Antimicrobial Agents Inspired by Nature

Antimicrobial peptides are ubiquitous in multicellular organisms and have served as defense mechanisms for their successful evolution and throughout their life cycle. These peptides are short cationic amphiphilic polypeptides of fewer than 50 amino acids containing either a few disulfide-linked cysteine residues with a characteristic β-sheet-rich structure or linear α-helical conformations with hydrophilic side chains at one side of the helix and hydrophobic side chains on the other side. Antimicrobial peptides cause bacterial cell lysis either by direct cell-surface damage via electrostatic interactions between the cationic side chains of the peptide and the negatively charged cell surface, or by indirect modulation of the host defense systems. Electrostatic interactions lead to bacterial cell membrane disruption followed by leakage of cellular components and finally bacterial cell death. Because of their unusual mechanism of cell damage, antimicrobial peptides are effective against drug-resistant bacteria and may therefore prove more effective than classical antibiotics in certain cases. Currently, around 3000 natural antimicrobial peptides from six kingdoms (bacteria, archaea, protists, fungi, plants, and animals) have been isolated and sequenced. However, only a few of them are under clinical trials and/or in the commercial development stage for the treatment of bacterial infections caused by antibiotic-resistant bacteria. Moreover, high structural complexity, poor pharmacokinetic properties, and low antibacterial activity of natural antimicrobial peptides hinder their progress in drug development. To overcome these hurdles, researchers have become increasingly interested in modification and nature-inspired synthetic antimicrobial peptides. This review discusses some of the recent studies reported on antimicrobial peptides.

Antimicrobial Peptides as Potential Antiviral Factors in Insect Antiviral Immune Response

Antimicrobial peptides (AMPs) with antiviral activity (antiviral peptides: AVPs) have become a research hotspot and already show immense potential to become pharmaceutically available antiviral drugs. AVPs have exhibited huge potential in inhibiting viruses by targeting various stages of their life cycle. Insects are the most speciose group of animals that inhabit almost all ecosystems and habitats on the land and are a rich source of natural AMPs. However, insect AVP mining, functional research, and drug development are still in their infancy. This review aims to summarize the currently validated insect AVPs, explore potential new insect AVPs and to discuss their possible mechanism of synthesis and action, with a view to providing clues to unravel the mechanisms of insect antiviral immunity and to develop insect AVP-derived antiviral drugs.

The Dual Role of Antimicrobial Peptides in Autoimmunity

Autoimmune diseases (AiDs) are characterized by the destruction of host tissues by the host immune system. The etiology of AiDs is complex, with the implication of multiple genetic defects and various environmental factors (pathogens, antibiotic use, pollutants, stress, and diet). The interaction between these two compartments results in the rupture of tolerance against self-antigens and the unwanted activation of the immune system. Thanks to animal models, the immunopathology of many AiDs is well described, with the implication of both the innate and adaptive immune systems. This progress toward the understanding of AiDs led to several therapies tested in patients. However, the results from these clinical trials have not been satisfactory, from reversing the course of AiDs to preventing them. The need for a cure has prompted many investigators to explore alternative aspects in the immunopathology of these diseases. Among these new aspects, the role of antimicrobial host defense peptides (AMPs) is growing. Indeed, beyond their antimicrobial activity, AMPs are potent immunomodulatory molecules and consequently are implicated in the development of numerous AiDs. Importantly, according to the disease considered, AMPs appear to play a dual role in autoimmunity with either anti- or pro-inflammatory abilities. Here, we aimed to summarize the current knowledge about the role of AMPs in the development of AiDs and attempt to provide some hypotheses explaining their dual role. Definitely, a complete understanding of this aspect is mandatory before the design of AMP-based therapies against AiDs.

Identification and functional characterization of ribosomal protein S23 as a new member of antimicrobial protein

Previous studies show that some ribosomal proteins possess antimicrobial peptide (AMP) activity. However, information as such remains rather fragmentary and rather limited. We showed here for the first time that amphioxus RPS23, BjRPS23, was a previously uncharacterized AMP. It not only acted as a pattern recognition receptor, capable of identifying LPS, LTA and PGN, but also an effector, capable of killing the Gram-negative and -positive bacteria. We also showed that the residues positioned at 67-84 formed the core region for the antimicrobial activity of BjRPS23, and its orthologues Verrucomicrobia RPS12_68-85 and Thermotoga RPS12_65-82 similarly displayed some antibacterial activities. BjRPS23 functioned by a combined action of membranolytic mechanisms including interaction with bacterial membrane via LPS, LTA and PGN, and membrane depolarization. BjRPS23 also stimulated production of intracellular ROS in bacteria. Moreover, we demonstrated that RPS23 existed across widely separated taxa, and might play a universal role in protection against bacterial infection in different animals. In addition, we found that neither BjRPS23 nor its truncated form BjRPS23_67-84 were cytotoxic to mammalian cells, making them promising lead molecules for the design of novel peptide antibiotics against bacteria. Collectively, these indicate that RPS23 is a new member of AMP with ancient origin and high conservation.

De novo transcriptome of the whole-body of the gastropod mollusk Philomycus bilineatus, a pest with medical potential in China

Philomycus bilineatus is a highly common gastropod mollusk pest in China and is also utilized to treat infectious diseases. However, no genomic resources are available for this non-model species. In the present study, the transcriptomic analysis of P. bilineatus was completed. After sequencing using the next generation sequencing technology, 9.11 Gb of clean reads were obtained, which led to the assembly and annotation of 145,523 transcripts and 125,690 unigenes. Unigenes were functionally classified using Gene Ontology (GO), euKaryotic Ortholog Groups of proteins (KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG). A total of 27,554 unigenes were assigned into 55 GO terms, 13,989 unigenes were differentiated into 26 KOG categories, and 16,368 unigenes were assigned to 229 KEGG pathways. Furthermore, 16,614 simple sequence repeats (SSRs), 38 olfactory genes, and 40 antimicrobial peptide/protein genes were identified. The transcriptome profile of P. bilineatus will provide a valuable genomic resource for further study, will promote the development of new pest management strategies through interference of chemosensory communication, and will support potential medicinal uses of this species.

Antimicrobial Resistance in ESKAPE Pathogens

Antimicrobial-resistant ESKAPE ( Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens represent a global threat to human health. The acquisition of antimicrobial resistance genes by ESKAPE pathogens has reduced the treatment options for serious infections, increased the burden of disease, and increased death rates due to treatment failure and requires a coordinated global response for antimicrobial resistance surveillance. This looming health threat has restimulated interest in the development of new antimicrobial therapies, has demanded the need for better patient care, and has facilitated heightened governance over stewardship practices.

Acute ammonia poisoning in dolly varden char (Salvelinus malma) and effect of methionine sulfoximine

Ammonia is toxic to most bony fishes. However, little information is available on the toxicology mechanisms induced by ammonia and the means to mitigate the effects by various fishes. In this study, four groups of experiments were designed and carried out to test the response of dolly varden char to ammonia toxicity and their mitigation through methionine sulfoximine (MSO). NaCl group was injected with NaCl, NH₃ group was injected with ammonium acetate, NH₃+MSO group was injected with ammonium acetate and MSO, MSO group was injected with MSO. Results showed that ammonia toxicity could lead to blood deterioration (elevation in white blood cell and blood ammonia), free amino acid imbalance (elevation in glutamine, glutamate, arginine and ornithine, coupled with reduction of citrulline and aspartate), ammonia metabolism enzyme activity inhibition (reduction in carbamyl phosphate synthetase, ornithine transcarbamylase and arginase), oxidative stress (reduction in superoxide dismutase, catalase and glutathione peroxidase) and immunosuppression (reduction in lysozyme, 50% hemolytic complement, total immunoglobulin and phagocytic index), but the MSO can eliminate fatal effect of oxidative damage. In addition, ammonia poisoning could induce down-regulation of antioxidant enzymes coding genes (SOD, CAT and GPx) and up-regulation of inflammatory cytokine genes (TNFα, IL-1β and IL-8) transcription, suggesting that immunosuppression and inflammation may relate to oxidative stress in fish.

Antiviral Peptides: Identification and Validation

Despite rapid advances in the human healthcare, the infection caused by certain viruses results in high morbidity and mortality accentuate the importance for development of new antivirals. The existing antiviral drugs are limited, due to their inadequate response, increased rate of resistance and several adverse side effects. Therefore, one of the newly emerging field “peptide-based therapeutics” against viruses is being explored and seems promising. Over the last few years, a lot of scientific effort has been made for the identification of novel and potential peptide-based therapeutics using various advanced technologies. Consequently, there are more than 60 approved peptide drugs available for sale in the market of United States, Europe, Japan, and some Asian countries. Moreover, the number of peptide drugs undergoing the clinical trials is rising gradually year by year. The peptide-based antiviral therapeutics have been approved for the Human immunodeficiency virus (HIV), Influenza virus and Hepatitis virus (B and C). This review enlightens the various peptide sources and the different approaches that have contributed to the search of potential antiviral peptides. These include computational approaches, natural and biological sources (library based high throughput screening) for the identification of lead peptide molecules against their target. Further the applications of few advanced techniques based on combinatorial chemistry and molecular biology have been illustrated to measure the binding parameters such as affinity and kinetics of the screened interacting partners. The employment of these advanced techniques can contribute to investigate antiviral peptide therapeutics for emerging infections.

Effects of dietary non-viable Bacillus sp. SJ-10, Lactobacillus plantarum, and their combination on growth, humoral and cellular immunity, and streptococcosis resistance in olive flounder (Paralichthys olivaceus)

Heat-killed (HK) Bacillus sp. SJ-10 (B), HK Lactobacillus plantarum (P), and their combination were dietary supplemented to olive flounder (Paralichthys olivaceus) to quantify the effects on growth, innate immunity, and disease resistance. Four test diets were supplied: a control feed free of HK probiotics, 1 × 10⁸ CFUs g^-1 single treatments of each of HK B (HKB) and HK P (HKP), and an equal proportion of (0.5 HKB + 0.5 HKP) × 10⁸ CFUs g^-1 (HKB_0.5 HKP_0.5). At 8 weeks of completion feeding trail, HKB_0.5 HKP_0.5 significantly (P < .05) improved growth, feed utilization, and nonspecific immune parameters (respiratory burst and superoxide dismutase) compared to the control group. Similarly, serum lysozyme and myeloperoxidase activities were higher in both HKB and HKB_0.5HKP_0.5 groups. The levels of pro-inflammatory cytokine IL-6 in the liver and IL-1β in the liver, kidney, and spleen were also improved in the treatments, but microvilli length was only increased in HKB_0.5HKP_0.5. After Streptococcus iniae 1 × 10⁸ CFUs mL^-1 challenged; HKB and HKB_0.5HKP_0.5 had a higher survival than control and HKP. Overall, dietary administration of synergy HK probiotics elevated growth, cellular and humoral immunity, and streptococcosis resistance in olive flounder.

Probiotic effects of mixture of Groenewaldozyma salmanticensis and Gluconacetobacter liquefaciens on growth and immune responses in Paralichthys olivaceus

This study was performed to evaluate the effects of dietary probiotics on growth, non-specific immune responses and disease resistance in olive flounder, Paralichthys olivaceus. During 8 weeks, the fish were fed the five experimental diets such as a basal commercial diet (CON), oxytetracycline (OTC) and three basal diets containing Bacillus subtilis (BS), a commercial microbial product (CES) and a mixture of yeast and bacterium (PI), respectively. Fish fed all the probiotics diets and OTC showed a significantly higher growth than fish-fed CON (P < 0·05). Fish-fed PI had a significantly higher nitroblue tetrazolium activity, whereas fish-fed CES showed a higher lysozyme level (P < 0·05). A 7-day challenge test also showed that fish-fed PI had a cumulative survival rate equivalent to that of fish-fed OTC (P < 0·05). Moreover, the diet (PI) appeared to increase the diversity of microbial community in the fish. All these results suggest that the probiotics diet could function as a potential antibiotic replacer in the olive flounder. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique in revealing that a diet mixture of yeast, Groenewaldozyma salmanticensis and bacterium Gluconacetobacter liquefaciens can enhance growth, innate immunity and diversity of microbial community including dominant species in the olive flounder. All these indicate that the diet mixture could function as a potential antibiotic replacer in one of the most commercially important fisheries in South Korea.

Effects of partial replacement of dietary fish meal by bioprocessed plant protein concentrates on growth performance, hematology, nutrient digestibility and digestive enzyme activities in juvenile Pacific white shrimp, Litopenaeus vannamei

BACKGROUND

Bioprocessing of plant feedstuff can be a novel approach for reducing the overwhelming dependence on fish meal in aquaculture. The objective of this study was to evaluate the performance of Pacific white shrimp Litopenaeus vannamei fed solid-state fermented protein concentrates in order to replace fish meal in the diet.

RESULTS

In the first trial, a group of 15 shrimp (average 3.88 g) were randomly distributed into aquaria in triplicate according to the experimental diets. Ten isonitrogenous (400 g kg-1 CP) and isolipidic (90 g kg-1 CL) diets were formulated to contain high-protein fish meal (HFM) and low-protein fish meal (LFM), and four types of bioprocessed protein concentrates (BPCs) as a replacement of fish meal (BPC-A, -B, -C and -D) each at 30% and 50% FM replacement levels. BPC-A was a solid-state fermented mixture of soybean and corn gluten meals; BPC-B was pre-treated acid-hydrolyzed BPC-A; BPC-C and BPC-D were BPC-A + 2% shrimp soluble extract (SSE) and BPC-B + 2% SSE, respectively. After 8 weeks, shrimp fed the HFM, BPC-B, BPC-C and BPC-D diets showed significantly higher growth performance at 30% FM replacement than those of shrimp fed the BPC diets at 50% FM replacement. Interestingly, shrimp fed the BPC-D diet could replace up to 50% FM replacement. In the second trial, the results show that apparent digestibility coefficients of feeds and apparent digestibility coefficients of ingredients for crude protein were significantly higher in fish fed the BPC-B, BPC-C and BPC-D diets.

CONCLUSIONS

The results demonstrated successful partial replacement of high-protein fish meal using high-quality fermented protein concentrates from plant sources. © 2019 Society of Chemical Industry.

Bombardier Enables Delivery of Short-Form Bomanins in the Drosophila Toll Response

Toll mediates a robust and effective innate immune response across vertebrates and invertebrates. In Drosophila melanogaster, activation of Toll by systemic infection drives the accumulation of a rich repertoire of immune effectors in hemolymph, including the recently characterized Bomanins, as well as the classical antimicrobial peptides (AMPs). Here we report the functional characterization of a Toll-induced hemolymph protein encoded by the bombardier (CG18067) gene. Using the CRISPR/Cas9 system to generate a precise deletion of the bombardier transcriptional unit, we found that Bombardier is required for Toll-mediated defense against fungi and Gram-positive bacteria. Assaying cell-free hemolymph, we found that the Bomanin-dependent candidacidal activity is also dependent on Bombardier, but is independent of the antifungal AMPs Drosomycin and Metchnikowin. Using mass spectrometry, we demonstrated that deletion of bombardier results in the specific absence of short-form Bomanins from hemolymph. In addition, flies lacking Bombardier exhibited a defect in pathogen tolerance that we trace to an aberrant condition triggered by Toll activation. These results lead us to a model in which the presence of Bombardier in wild-type flies enables the proper folding, secretion, or intermolecular associations of short-form Bomanins, and the absence of Bombardier disrupts one or more of these steps, resulting in defects in both immune resistance and tolerance.

A serine protease-associated lectin in the cytolytic system of blowfly (Chrysomya megacephala) larvae: Evidence and characterization

Cytolytic activity against invading microorganisms is one of the innate forms of immunity in invertebrates. A serine protease-associated sialic acid-specific cytolytic lectin was purified using glutaraldehyde-fixed ox erythrocytes from the larval extract of blowfly (Chrysomya megacephala). The purified lectin lysed vertebrate erythrocytes with effective haemolysis of ox red blood cells (RBCs) in an isotonic medium. The degree of haemolytic (HL) activity of the purified cytolytic lectin depended on its concentration, pH, temperature, and calcium ions. It was sensitive to ethylenediaminetetraacetic acid. The native molecular mass of the C-type lectin was 260 ± 26 kDa, comprising four different polypeptide subunits of 75 kDa (pI ~8), 69 kDa (pI ~7.0), 61 kDa (pI ~5.3), and 55 kDa (pI ~4.6). The association between the C-type lectin and serine protease was confirmed by MALDI-TOF-MS analysis that revealed its homology in the same spectral peak as well as the proteases and phenylmethylsulphonyl fluoride inhibition of HL activity. Haemolysis inhibition by N-acetylneuraminic acid and other sugars revealed the properties of the lectin. The purified lectin distorted the integrity of ox RBCs and Paenalcaligenes hermetiae. This in vitro study documents the presence of a cytolytic system in blowfly (C. megacephala) larvae for the clearance of invading microbial pathogens in their feeding niche.

Insect Cecropins, Antimicrobial Peptides with Potential Therapeutic Applications

The alarming escalation of infectious diseases resistant to conventional antibiotics requires urgent global actions, including the development of new therapeutics. Antimicrobial peptides (AMPs) represent potential alternatives in the treatment of multi-drug resistant (MDR) infections. Here, we focus on Cecropins (Cecs), a group of naturally occurring AMPs in insects, and on synthetic Cec-analogs. We describe their action mechanisms and antimicrobial activity against MDR bacteria and other pathogens. We report several data suggesting that Cec and Cec-analog peptides are promising antibacterial therapeutic candidates, including their low toxicity against mammalian cells, and anti-inflammatory activity. We highlight limitations linked to the use of peptides as therapeutics and discuss methods overcoming these constraints, particularly regarding the introduction of nanotechnologies. New formulations based on natural Cecs would allow the development of drugs active against Gram-negative bacteria, and those based on Cec-analogs would give rise to therapeutics effective against both Gram-positive and Gram-negative pathogens. Cecs and Cec-analogs might be also employed to coat biomaterials for medical devices as an approach to prevent biomaterial-associated infections. The cost of large-scale production is discussed in comparison with the economic and social burden resulting from the progressive diffusion of MDR infectious diseases.

Antimicrobial functional divergence of the cecropin antibacterial peptide gene family in Musca domestica

BACKGROUND

It has been reported that there are more than ten antimicrobial peptides (AMPs) belonging to the cecropin family in Musca domestica; however, few of them have been identified, and the functions of the other molecules are poorly understood.

METHODS

Sequences of the M. domestica cecropin family of genes were cloned from cDNA template, which was reverse-transcribed from total mRNA isolated from third-instar larvae of M. domestica that were challenged with pathogens. Sequence analysis was performed using DNAMAN comprehensive analysis software, and a molecular phylogenetic tree of the cecropin family was constructed using the Neighbour-Joining method in MEGA v.5.0 according to the mature peptide sequences. Antibacterial activity of the synthetic M. domestica cecropin protein was detected and the minimum inhibitory concentration (MIC) values were determined using broth microdilution techniques. Time-killing assays were performed on the Gram-negative bacteria, Acinetobacter baumannii, at the logarithmic or stabilizing stages of growth, and its morphological changes when treated with Cec4 were assessed by scanning electron microscopy (SEM) and detection of leakage of 260 nm absorbing material.

RESULTS

Eleven cecropin family genes, namely Cec01, Cec02 and Cec1-9, show homology to the Cec form in a multigene family on the Scaffold18749 of M. domestica. In comparing the encoded cecropin protein sequences, most of them have the basic characteristics of the cecropin family, containing 19 conservative amino acid residues. To our knowledge, this is the first experimental demonstration that most genes in the Cec family are functional. Cec02, Cec1, Cec2, Cec5 and Cec7 have similar antibacterial spectra and antibacterial effects against Gram-negative bacteria, while Cec4 displays a more broad-spectrum of antimicrobial activity and has a very strong effect on A. baumannii. Cec4 eliminated A. baumannii in a rapid and concentration-dependent manner, with antibacterial effects within 24 h at 1× MIC and 2× MIC. Furthermore, SEM analysis and the leakage of 260 nm absorbing material detection indicated that Cec4 sterilized the bacteria through the disruption of cell membrane integrity.

CONCLUSIONS

Although there are more than ten cecropin genes related to M. domestica, some of them have no preferred antibacterial activity other than Cec4 against A. baumannii.

Characterization, expression profiling, and functional analysis of a Populus trichocarpa defensin gene and its potential as an anti-Agrobacterium rooting medium additive

The diverse antimicrobial properties of defensins have attracted wide scientific interest in recent years. Also, antimicrobial peptides (AMPs), including cecropins, histatins, defensins, and cathelicidins, have recently become an antimicrobial research hotspot for their broad-spectrum antibacterial and antifungal activities. In addition, defensins play important roles in plant growth, development, and physiological metabolism, and demonstrate tissue specificity and regulation in response to pathogen attack or abiotic stress. In this study, we performed molecular cloning, characterization, expression profiling, and functional analysis of a defensin from Populus trichocarpa. The PtDef protein was highly expressed in the prokaryotic Escherichia coli system as a fusion protein (TrxA–PtDef). The purified protein exhibited strong antibacterial and antifungal functions. We then applied PtDef to rooting culture medium as an alternative exogenous additive to cefotaxime. PtDef expression levels increased significantly following both biotic and abiotic treatment. The degree of leaf damage observed in wild-type (WT) and transgenic poplars indicates that transgenic poplars that overexpress the PtDef gene gain enhanced disease resistance to Septotis populiperda. To further study the salicylic acid (SA) and jasmonic acid (JA) signal transduction pathways, SA- and JA-related and pathogenesis-related genes were analyzed using quantitative reverse-transcription polymerase chain reaction; there were significant differences in these pathways between transgenic and WT poplars. The defensin from Populus trichocarpa showed significant activity of anti-bacteria and anti-fungi. According to the results of qRT-PCR and physiological relevant indicators, the applied PtDef to rooting culture medium was chosen as an alternative exogenous additive to cefotaxime. Overexpressing the PtDef gene in poplar improve the disease resistance to Septotis populiperda.

Effects of Vibro harveyi and Staphyloccocus aureus infection on hemocyanin synthesis and innate immune responses in white shrimp Litopenaeus vannamei

Hemocyanin, a multifunctional oxygen-carrying protein, has critical effects on immune defense in crustaceans. To explore the role of hemocyanin in anti-pathogen mechanism, effects of Vibrio harveyi (V. harvey) and Staphyloccocus aureus (S. aureus) on hemocyanin synthesis and innate immune responses were investigated in Litopenaeus vannamei (L. vannamei) during infection in vivo. Results showed that 10⁵ and 10⁶ cells mL^-1V. harveyi and 10⁶ cells mL^-1S. aureus significantly affected plasma hemocyanin concentration, hepatopancreas hemocyanin mRNA and subunits expressions, plasma phenol oxidase (PO), hemocyanin-derived PO (Hd-PO), antibacterial, and bacteriolytic activities during the experiment under bacterial stress, while these parameters did not change remarkably in control group. The concentration of hemocyanin in plasma fluctuated, with a minimum at 12 h and a maximum at 24 h. Moreover, the expression of hemocyanin mRNA peaked at 12 h, while the level of hemocyanin p75 and p77 subunits reached maximum at 24 h. Besides, plasma PO and Hd-PO activities peaked at 24 h, and antimicrobial and bacteriolytic activities peaked at 12 h and 24 h, respectively. In addition, 10⁵ cells mL^-1S. aureus had no significant effect on the synthesis of hemocyanin and prophenoloxidase activating (pro-PO) system, but significantly increased antimicrobial activity at 12 h and bacteriolytic activity at 24 h. Therefore, these results suggest that the hemocyanin synthesis was initiated after invasion of pathogen, and the newly synthesized hemocyanin, acted as an immune molecule, can exerts PO activity to regulate the immune defense in L. vannamei in vivo.

Effects of dietary multi-strain probiotics supplementation in a low fishmeal diet on growth performance, nutrient utilization, proximate composition, immune parameters, and gut microbiota of juvenile olive flounder (Paralichthys olivaceus)

A 12-week feeding trial was conducted to evaluate the effects of multi-strain probiotics (MSP) in a low fish meal (FM) diet on overall performance, gut microbiota, selected non-specific immune responses and antioxidant enzyme activities of olive flounder (Paralichthys olivaceus) juveniles. A total of 225 healthy olive flounders (initial mean body weight, 13.5 ± 0.01 g) were randomly separated into 3 groups of 75 fish, each group having three replicates of 25 fish; first group was fed with a FM-based control diet (Con), 2nd group was fed with a low-FM diet containing a blend of plant and animal protein meals replacing 30% of the FM protein (FM30), and 3rd group was fed with the FM30 diet supplemented with 10⁸-10⁹ CFU kg^-1 of the MSP (Pro). With the exception of lipid retention, which was significantly lower in fish fed the FM30 diet compared to the other two treatments, no other statistically significant differences were recorded with respect to any of the other growth and nutrient utilization parameters. Myeloperoxidase and lysozyme activities of fish fed the Pro diet were much higher and significantly different than those of fish fed the FM30 diet. Glutathione peroxidase activity was significantly higher in Pro- than in Con-fed fish, which, in turn, was significantly higher than FM30-fed fish. Expression of immune-related genes including IL-1β, IL-6, and TNF-α was markedly upregulated in livers of the fish fed Pro diet compared to those fed the Con and FM30 diets. Furthermore, supplementation of MSP in FM30 diet enriched the Lactobacillus abundance in the fish gut as well as predictive gene functions in relation to lipid and carbohydrate metabolisms. These data suggested that the MSP could reduce the potential adverse effects of the low-FM diet and might be used as a healthy immunostimulant for olive flounder.

The innate immune system of kissing bugs, vectors of chagas disease

Kissing bugs have long served as models to study many aspects of insect physiology. They also serve as vectors for the parasite Trypanosoma cruzi that causes Chagas disease in humans. The overall success of insects is due, in part, to their ability to recognize parasites and pathogens as non-self and to eliminate them using their innate immune system. This immune system comprises physical barriers, cellular responses (phagocytosis, nodulation and encapsulation), and humoral factors (antimicrobial peptides and the prophenoloxidase cascade). Trypanosoma cruzi survives solely in the gastrointestinal (GI) tract of the vector; if it migrates to the hemocoel it is eliminated. Kissing bugs may not mount a vigorous immune response in the GI tract to avoid eliminating obligate symbiotic microbes on which they rely for survival. Here we describe the current knowledge of innate immunity in kissing bugs and new opportunities using genomic and transcriptomic approaches to study the complex triatomine-trypanosome-microbiome interactions.

Antiviral peptides as promising therapeutic drugs

While scientific advances have led to large-scale production and widespread distribution of vaccines and antiviral drugs, viruses still remain a major cause of human diseases today. The ever-increasing reports of viral resistance and the emergence and re-emergence of viral epidemics pressure the health and scientific community to constantly find novel molecules with antiviral potential. This search involves numerous different approaches, and the use of antimicrobial peptides has presented itself as an interesting alternative. Even though the number of antimicrobial peptides with antiviral activity is still low, they already show immense potential to become pharmaceutically available antiviral drugs. Such peptides can originate from natural sources, such as those isolated from mammals and from animal venoms, or from artificial sources, when bioinformatics tools are used. This review aims to shed some light on antimicrobial peptides with antiviral activities against human viruses and update the data about the already well-known peptides that are still undergoing studies, emphasizing the most promising ones that may become medicines for clinical use.

Worms' Antimicrobial Peptides

Antimicrobial peptides (AMPs) are natural antibiotics produced by all living organisms. In metazoans, they act as host defense factors by eliminating microbial pathogens. But they also help to select the colonizing bacterial symbionts while coping with specific environmental challenges. Although many AMPs share common structural characteristics, for example having an overall size between 10-100 amino acids, a net positive charge, a γ-core motif, or a high content of cysteines, they greatly differ in coding sequences as a consequence of multiple parallel evolution in the face of pathogens. The majority of AMPs is specific of certain taxa or even typifying species. This is especially the case of annelids (ringed worms). Even in regions with extreme environmental conditions (polar, hydrothermal, abyssal, polluted, etc.), worms have colonized all habitats on Earth and dominated in biomass most of them while co-occurring with a large number and variety of bacteria. This review surveys the different structures and functions of AMPs that have been so far encountered in annelids and nematodes. It highlights the wide diversity of AMP primary structures and their originality that presumably mimics the highly diverse life styles and ecology of worms. From the unique system that represents marine annelids, we have studied the effect of abiotic pressures on the selection of AMPs and demonstrated the promising sources of antibiotics that they could constitute.

Enhanced Silkworm Cecropin B Antimicrobial Activity against Pseudomonas aeruginosa from Single Amino Acid Variation

Pseudomonas aeruginosa is an opportunistic bacterial pathogen causing severe infections in hospitalized and immunosuppressed patients, particularly individuals affected by cystic fibrosis. Several clinically isolated P. aeruginosa strains were found to be resistant to three or more antimicrobial classes indicating the importance of identifying new antimicrobials active against this pathogen. Here, we characterized the antimicrobial activity and the action mechanisms against P. aeruginosa of two natural isoforms of the antimicrobial peptide cecropin B, both isolated from the silkworm Bombyx mori. These cecropin B isoforms differ in a single amino acid substitution within the active portion of the peptide, so that the glutamic acid of the E53 CecB variant is replaced by a glutamine in the Q53 CecB isoform. Both peptides showed a high antimicrobial and membranolytic activity against P. aeruginosa, with Q53 CecB displaying greater activity compared with the E53 CecB isoform. Biophysical analyses, live-cell NMR, and molecular-dynamic-simulation studies indicated that both peptides might act as membrane-interacting elements, which can disrupt outer-membrane organization, facilitating their translocation toward the inner membrane of the bacterial cell. Our data also suggest that the amino acid variation of the Q53 CecB isoform represents a critical factor in stabilizing the hydrophobic segment that interacts with the bacterial membrane, determining the highest antimicrobial activity of the whole peptide. Its high stability to pH and temperature variations, tolerance to high salt concentrations, and low toxicity against human cells make Q53 CecB a promising candidate in the development of CecB-derived compounds against P. aeruginosa.

Crustacean hyperglycemic hormone (CHH) affects hemocyte intracellular signaling pathways to regulate exocytosis and immune response in white shrimp Litopenaeus vannamei

Recombinant Litopenaeus vannamei CHH (rLvCHH) was obtained from a bacterial expression system and the intracellular signaling pathways involved in exocytosis and immune response after rLvCHH injection (0.2 and 2 μg/shrimp) was investigated in this study. The results showed that CHH contents increased 51.4%-110.2% (0.2 μg/shrimp) and 65.0%-211.3% (2 μg/shrimp) of the control level. And the contents of three biogenic amines in hemolymph presented a similar variation pattern after rLvCHH injection, but reached the highest level at different time points. Furthermore, the mRNA expression levels of membrane-bound guanylyl cyclase (mGC) (1.20-1.93 fold) and biogenic amine receptors, including type 2 dopamine receptor (DA2R) (0.72-0.89 fold), α2 adrenergic receptor (α2-AR) (0.72-0.91 fold) and 5-HT7 receptor (5-HT7R) (1.37-3.49 fold) in hemocytes were changed consistently with their ligands. In addition, the second messenger and protein kinases shared a similar trend and reached the maximum at the same time respectively. The expression levels of nuclear transcription factor (cAMP response element-binding protein, CREB) and exocytosis-related proteins transcripts were basically overexpressed after rLvCHH stimulation, which reached the peaks at 1 h or 3 h. Eventually, the phenoloxidase (PO) activity (37.4%-158.5%) and antibacterial activity (31.8%-122.3%) in hemolymph were dramatically enhanced within 6 h, while the proPO activity in hemocytes significantly decreased (11.2%-62.6%). Collectively, these results indicate that shrimps L. vannamei could carry out a simple but 'smart' NEI regulation by releasing different neuroendocrine factors at different stages after rLvCHH stimulation, which could couple with their receptors and trigger the downstream signaling pathways during the immune responses in hemocytes.

One recombinant C-type lectin (LvLec) from white shrimp Litopenaeus vannamei affected the haemocyte immune response in vitro

C-type lectin has received widespread attention in animal immunomodulation functions since it was discovered, but it is still limited in crustaceans. The present study is to explore effects of one recombinant C-type lectin (LvLec protein) on haemocyte immune response in Litopenaeus vannamei (L. vannamei). The methods of keeping haemocyte immune activity were optimised by the Key Laboratory of Mariculture. The experiment was divided into four groups: control group, recombinant protein group (LvLec protein, 1.0 mg mL^-1), Lipopolysaccharide group (LPS, 1.0 mg mL^-1), and LPS combine with LvLec protein group (LPS + LvLec protein, 1.0 mg mL^-1 + 1.0 mg mL^-1), while each group processes 0, 3, 6, 9, 12, and 24 h respectively. The results showed that the haemocyte count reduced, while the exocytosis PO activity, hemagglutinating activity and phagocytic activity promoted, and the concentration of cGMP and PKA increased after LvLec protein treatment. However, the levels of antibacterial activity and bacteriolytic activity as well as the concentrations of cAMP and PKG did not change significantly after treating with LvLec protein, LPS or LPS + LvLec protein. Therefore, these results suggest that LvLec protein can stimulate the exocytosis PO activity through cGMP-PKA pathway to affect the phagocytic activity and hemagglutinating activity of L. vannamei haemocytes in vitro.

Heat-killed Bacillus sp. SJ-10 probiotic acts as a growth and humoral innate immunity response enhancer in olive flounder (Paralichthys olivaceus)

Investigations were carried out to evaluate and quantify the effects of dietary supplementation with heat-killed (HK) Bacillus sp. SJ-10 (BSJ-10) probiotic (1 × 10⁸ CFU g^-1) on the growth and immunity of olive flounder (Paralichthys olivaceus). Flounder (averagely 9.64 g) were divided into two groups, and fed control and HK BSJ-10 (HKBSJ-10)-inoculated diets for 8 weeks. Investigations were carried out on growth and feed utilizations, innate immunity, serum biochemical parameters, microvilli length, and pro- and anti-inflammatory cytokine gene (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, IL-6, and IL-10) transcriptions. Compared to control, HKBSJ-10 diet significantly (P < 0.05) enhanced weight gain and protein efficiency ratio, 1.17 and 1.11 folds respectively. Humoral innate immune parameters, lysozyme and superoxide dismutase in treatment group were also elevated by 1.34 and 1.16 folds. Similarly, an increased (P < 0.05) relative expressions of TNF-α, IL-1β, IL-6 were recorded in liver (2.71, 3.38, and 4.12 folds respectively), and gill (2.08, 1.98, and 1.81 folds respectively) than that of controls. Moreover, after challenge with Streptococcus iniae (1 × 10⁸ CFU mL^-1), the HKBSJ-10-fed group exhibited significantly higher protection (P < 0.05) against streptococcosis compared to controls, validating the observed changes in immune parameters and induction on the cytokine-encoding genes. Therefore, HKBSJ-10 increases growth, modulates innate immune parameters, and protects olive flounders against streptococcosis.

Effects of stocking density on growth, stress, and immune responses of juvenile Chinese sturgeon (Acipenser sinensis) in a recirculating aquaculture system

The present study was to investigate the effects of stocking density on the welfare of juvenile Chinese sturgeon (Acipenser sinensis) cultured in a recirculating aquaculture system (RAS) for three months. Fish (average weight 760.86 g) were reared in triplicate under three densities: low density (4.80 kg m^-2), medium density (8.99 kg m^-2), and high density (12.68 kg m^-2). The results showed that the 12.68 kg m^-2 treatment significantly suppressed fish growth, gene expression of glutathione-s-transferase (GST), and enhanced serum adrenocorticotropic hormone (ACTH), cortisol, glucose, lactate levels, and the heat shock protein 70 (HSP70) mRNA level (P < 0.05). Additionally, the 12.68 kg m^-2 treatment significantly decreased serum glutathione peroxidase and superoxide dismutase activities, and increased the formation of malondialdehyde (P < 0.05). Serum immunoglobulin M (IgM), lysozyme, alkaline phosphatase, and acid phosphatase activities showed a significant decline in this group (P < 0.05). Transcriptions of immune-related genes, including lysozyme, hepcidin antimicrobial peptide 1 (HAMP1), tumor necrosis factor-ɑ (TNF-ɑ), interleukin 1β, and interleukin 8 significantly reduced in the 12.68 kg m^-2 group (P < 0.05). In the somatotropic axis, both the serum values and gene expressions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) resulted in a down-regulation in the 12.68 kg m^-2 group (P < 0.05). Overall, these results suggest that high stocking density could negatively influence the growth, stress, and immune responses of juvenile Chinese sturgeon. Consequently, the appropriate stocking density recommended for culturing juvenile Chinese sturgeon in an RAS is between 4.80 kg m^-2 and 8.99 kg m^-2.

Effectiveness of traditional Chinese herbal medicine, San-Huang-San, in combination with enrofloxacin to treat AHPND-causing strain of Vibrio parahaemolyticus infection in Litopenaeus vannamei

The effects of oral administration of enrofloxacin (ENR) and San-Huang-San (SHS), singly or in combination, on the survival performance, disease resistance, and immunity of Litopenaeus vannamei were investigated. After challenge with an AHPND-causing strain of Vibrio parahaemolyticus (VP_AHPND), shrimp were immediately fed a drug-free diet, diets containing only ENR (20 mg·kg^-1) or SHS (500 mg·kg^-1) or diets containing low-dose (10 mg·kg^-1 ENR + 250 mg ·kg^-1 SHS), medium-dose (20 mg·kg^-1 ENR + 500 mg ·kg^-1 SHS), and high-dose (40 mg·kg^-1 ENR + 1000 mg ·kg^-1 SHS) drug combinations for 5 days. The cumulative shrimp mortality over 5 days after injection of VP_AHPND in the ENR + SHS combination groups was significantly lower than that in the ENR or SHS alone groups (p < 0.05). Immune parameters, including the vibrio density, total hemocyte counts (THCs), hemocyanin (HEM) concentration, antibacterial activity, activity levels of lysozyme (LZM), acid phosphatase (ACP), alkaline phosphatase (AKP), and phenoloxidase (PO) in cell-free hemolymph, and the expression levels of the immune-related genes anti-lipopolysaccharide factor (ALF), cathepsin B (catB), crustin, lectin (Lec), lysozyme (LZM), and Toll-like receptor (TLR) in hemocytes were determined in the shrimp. The results showed that the shrimp in drug combination groups cleared more VP_AHPND than that in the ENR or SHS group in the same time. The values for other immune parameters in the drug combination groups were higher than those in the ENR or SHS group (p < 0.05). Finally, in the histological examinations, the histological structural alignment and integrity of the hepatopancreatic tubules in the drug combination groups were better than that in the ENR and SHS groups. Under the experimental conditions, compared with ENR or SHS used alone, the combination use of ENR and SHS could improve immunity and disease resistance in shrimp after VP_AHPND infection, and could reduce the use of ENR when the better therapeutic effect was achieved.

Evaluation of combination effects of Astragalus polysaccharides and florfenicol against acute hepatopancreatic necrosis disease-causing strain of Vibrio parahaemolyticus in Litopenaeus vannamei

The effects of oral administration of Astragalus polysaccharides (APS) and florfenicol (FFC), singly or in combination, on the survival performance, disease resistance, and immunity of Litopenaeus vannamei were investigated. After challenge with an AHPND-causing strain of Vibrio parahaemolyticus (VP_AHPND), shrimp were immediately fed a drug-free diet, diets containing only APS (200 mg·kg^-1) or FFC (15 mg·kg^-1), or diets containing low-dose (7.5 mg·kg^-1 FFC + 100 mg·kg^-1 APS), medium-dose (15 mg·kg^-1 FFC + 200 mg·kg^-1 APS), and high-dose (30 mg·kg^-1 FFC+400 mg·kg^-1 APS) drug combinations for 5 days. The cumulative shrimp mortality over 5 days after injection of VP_AHPND in the APS + FFC combination groups was significantly lower than that in the APS or FFC alone groups (p < 0.05). Immune parameters, including the total hemocyte counts (THCs), hemocyanin (HEM) concentration, antibacterial activity, activity levels of lysozyme (LZM), and levels of acid phosphatase (ACP), alkaline phosphatase (AKP), and phenoloxidase (PO) in cell-free hemolymph, and the expression levels of the immune-related genes anti-lipopolysaccharide factor (ALF), cathepsin B (catB), crustin, lectin (Lec), lysozyme (LZM), and Toll-like receptor (TLR) in hemocytes and hepatopancreas were determined in the shrimp. The values for these immune parameters in the drug combination groups were higher than those in the APS or FFC group (p < 0.05). Finally, in the histological examinations, the histological structural alignment and integrity of the hepatopancreatic tubules in the drug combination groups was better than that in the APS and FFC groups. Under the experimental conditions, dietary APS and FFC had a synergistic effect on immunity and disease resistance among shrimp after VP_AHPND infection.

Synergy and remarkable specificity of antimicrobial peptides in vivo using a systematic knockout approach

Antimicrobial peptides (AMPs) are host-encoded antibiotics that combat invading microorganisms. These short, cationic peptides have been implicated in many biological processes, primarily involving innate immunity. In vitro studies have shown AMPs kill bacteria and fungi at physiological concentrations, but little validation has been done in vivo. We utilized CRISPR gene editing to delete all known immune-inducible AMPs of Drosophila, namely: 4 Attacins, 4 Cecropins, 2 Diptericins, Drosocin, Drosomycin, Metchnikowin and Defensin. Using individual and multiple knockouts, including flies lacking all 14 AMP genes, we characterize the in vivo function of individual and groups of AMPs against diverse bacterial and fungal pathogens. We found that Drosophila AMPs act primarily against Gram-negative bacteria and fungi, contributing either additively or synergistically. We also describe remarkable specificity wherein certain AMPs contribute the bulk of microbicidal activity against specific pathogens, providing functional demonstrations of highly specific AMP-pathogen interactions in an in vivo setting.

Independent and simultaneous effect of crustacean hyperglycemic hormone and dopamine on the hemocyte intracellular signaling pathways and immune responses in white shrimp Litopenaeus vannamei

Immune responses and intracellular signaling pathways were examined after hemolymph of Litopenaeus vannamei being incubated in Crustacean hyperglycemic hormone (CHH), dopamine (DA) and DA antagonist (Y). The results showed that the effect CHH and CHH + DA + Y on viability of hemocytes were no significant changes compared to the control group. However, in DA, DA + Y and CHH + DA groups, the viability of hemocytes decreased significantly. The phagocytic activity and the antibacterial activity of CHH group were increased significantly within 12h. Whereas the CHH + DA, DA were significantly lower than the control. PO in haemolymph was up-regulated after CHH and DA incubation. The proPO has the opposite change in all groups. In addition, DA + Y, CHH + DA + Y has a similar trend with the DA and CHH respectively. Furthermore, a significant increase of cAMP, CaM and cGMP were found in treatment groups except for the CaM concentration of the CHH group and the cGMP concentration of DA group. There is no significant change observed in the CHH group about CaM concentration. Whereas the cGMP of DA group decreased within 12h. The results suggest that DA could depress the immune responses by cAMP-, CaM-pathways. However, the CHH is on the contrary, which transduced the signals from cAMP, cGMP to PKA, PKC and PKG to enhance the immune response parameters.