The prophenoloxidase-activating system in invertebrates

Characterising phagocytes and measuring phagocytosis from live Galleria mellonella larvae

Over the last 20 years, the larva of the greater waxmoth, Galleria mellonella, has rapidly increased in popularity as an in vivo mammalian replacement model organism for the study of human pathogens. Experimental readouts of response to infection are most often limited to observing the melanization cascade and quantifying larval death and, whilst transcriptomic and proteomic approaches, and methods to determine microbial load are also used, a more comprehensive toolkit of profiling infection over time could transform the applicability of this model. As an invertebrate, Galleria harbour an innate immune system comprised of both humoral components and a repertoire of innate immune cells - termed haemocytes. Although information on subtypes of haemocytes exists, there are conflicting reports on their exact number and function. Flow cytometry has previously been used to assay Galleria haemocytes, but protocols include both centrifugation and fixation - physical methods which have the potential to affect haemocyte morphology prior to analysis. Here, we present a method for live haemocyte analysis by flow cytometry, revealing that Galleria haemocytes constitute only a single resolvable population, based on relative size or internal complexity. Using fluorescent zymosan particles, we extend our method to show that up to 80% of the Galleria haemocyte population display phagocytic capability. Finally, we demonstrate that the developed assay reliably replicates in vitro data, showing that cell wall β-1,3-glucan masking by Candida albicans subverts phagocytic responses. As such, our method provides a new tool with which to rapidly assess phagocytosis and understand live infection dynamics in Galleria.

Cytokine-like-Vago-mediated antiviral response in Penaeus monodon via IKK-NF-κB signaling pathway

Interferon (IFN) system is the primary mechanism of innate antiviral defense in immune response. To date, limited studies of IFN system were conducted in crustaceans. Previous report in Penaeus monodon demonstrated the interconnection of cytokine-like molecule Vago and inhibitor of kappa B kinase-nuclear factor κB (IKK-NF-κB) cascade against white spot syndrome virus (WSSV). This study further identified five different PmVago isoforms. Upon immune stimulation, PmVagos expressed against shrimp pathogens. PmVago1, PmVago4, and PmVago5 highly responded to WSSV, whereas, PmVago1 and PmVago4 RNAi exhibited a rapid mortality with elevated WSSV replication. Suppression of PmVago1 and PmVago4 negatively affected proPO system, genes in signal transduction, and AMPs. WSSV infection additionally induced PmVaog4 granule accumulation and cellular translocation to the area of cell membrane. More importantly, PmVago1 and PmVago4 promoters were stimulated by PmIKK overexpression; meanwhile, they further activated Dorsal and Relish promoter activities. These results suggested the possible roles of the cytokine-like PmVago via IKK-NF-κB cascade against WSSV infection.

Pest management facing warming and chemical stresses: Multi-stress effects on the biological agent Trichogramma oleae

Global change is affecting plant-insect interactions in agroecosystems and can have dramatic consequences on yields when causing non-targeted pest outbreaks and threatening the use of pest natural enemies for biocontrol. The vineyard agroecosystem is an interesting system to study multi-stress conditions: on the one hand, agricultural intensification comes with high inputs of copper-based fungicides and, on the other hand, temperatures are rising due to climate change. We investigated interactive and bottom-up effects of both temperature increase and copper-based fungicides exposure on the important Lepidopteran vineyard pest Lobesia botrana and its natural enemy, the oophagous parasitoid Trichogramma oleae. We exposed L. botrana larvae to three increasing copper sulfate concentrations under two fluctuating thermal regimes, one current and one future. Eggs produced by L. botrana were then exposed to T. oleae. Our results showed that the survival of L. botrana, was only reduced by the highest copper sulfate concentration and improved under the warmer regime. The development time of L. botrana was strongly reduced by the warmer regime but increased with increasing copper sulfate concentrations, whereas pupal mass was reduced by both thermal regime and copper sulfate. T. oleae F1 emergence rate was reduced and their development time increased by combined effects of the warmer regime and increasing copper sulfate concentrations. Size, longevity and fecundity of T. oleae F1 decreased with high copper sulfate concentrations. These effects on the moth pest and its natural enemy are probably the result of trade-offs between the survival and the development of L. botrana facing multi-stress conditions and implicate potential consequences for future biological pest control. Our study supplies valuable data on how the interaction between pests and biological control agents is affected by multi-stress conditions.

The first report of a C-type lectin contains a CLIP domain involved in antibacterial defense in Macrobrachium nipponense

We identified a novel C-type lectin (CTL) from Macrobrachium nipponense, designated as Mn-clip-Lec. It consists of 1315 bp with an open reading frame of 1098 bp, encoding a polypeptide of 365 amino acids. Mn-clip-Lec contains 6 exons and 5 introns. Mn-clip-Lec possessed a CLIP domain at the N-terminal and two carbohydrate recognition domains at the C-terminal. Interaction between Mn-clip-Lec and MnLec was found by Yeast two-hybrid analysis. The expressions of Mn-clip-Lec, MnLec, prophenoloxidase (proPO)-activating system-associated genes (MnPPAF, MnPPAE, and MnPO), and antimicrobial peptides (AMPs) (MnALF and MnCRU) were up-regulated after the challenge with Staphylococcus aureus. RNA interference (RNAi)-mediated suppression of the Mn-clip-Lec and MnLec genes in S. aureus-challenged prawns reduced the transcripts of MnPPAF, MnPPAE, MnPO, MnALF and MnCRU. Knockdown of Mn-clip-Lec and MnLec resulted in decrease in PO activity in M. nipponense infected with S. aureus. The recombinant Mn-clip-Lec (rMn-clip-Lec) protein bound all tested bacteria and agglutinated S. aureus. A sugar-binding assay revealed that rMn-clip-Lec could bind to LPS or PGN. rMn-clip-Lec accelerated the clearance of S. aureus in vivo. Our findings suggest that Mn-clip-Lec and its interacting MnLec play important roles in the induction of the proPO system and AMPs expression in M. nipponense during bacterial infection.

Inhibitors of LAMP used to detect Tenacibaculum sp. strain Pbs-1 associated with black-spot shell disease in Akoya pearl oysters, and additives to reduce the effect of the inhibitors

Black-spot shell disease is an unresolved disease that decreases pearl quality and threatens pearl oyster survival. In previous studies, the bacterium Tenacibaculum sp. strain Pbs-1 was isolated from diseased Akoya pearl oysters Pinctada fucata, and a rapid, specific, and sensitive loop-mediated isothermal amplification (LAMP) assay for detecting this pathogen was established. This technology has considerable potential for routine diagnosis of strain Pbs-1 in oyster hatcheries and/or pearl farms; therefore, it is vital to identify substances in environmental samples that might inhibit LAMP and to find additives that can reduce the inhibition. In this study, we investigated the effects of six chemicals or proteins, otherwise known as conventional PCR inhibitors, on LAMP, using the DNA of strain Pbs-1 as template: humic acid, urea, iron (III) chloride hexahydrate, melanin, myoglobin, and Ethylenediamine-N,N,N',N'-tetraacetic acid, disodium salt, dihydrate (EDTA; pH 6.5). Next, to reduce the effects of identified inhibitors, we tested the addition of bovine serum albumin (BSA) or T4 gene 32 protein (gp32) to the LAMP assay. When 50 ng of DNA template was used, 4 ng/μL of humic acid, 0.05% melanin, and 10 mM of EDTA (pH 6.5) inhibited the LAMP reaction, whereas myoglobin, urea, and FeCl3 had no effect. When 50 pg of DNA template was used, 4 ng/μL of humic acid, 0.05% melanin, 4 μg/μL of myoglobin, 10 μg/μL of urea, and 10 mM of EDTA inhibited the LAMP reaction. Thus, it was shown that the gene-amplification inhibitory effect of melanin, humic acid, and urea could be reduced by adding BSA or gp32 to the LAMP reaction mixture. This technique could be applied as part of a protocol to prevent mass mortalities of pearl oysters; moreover, the results enhance our knowledge about substances that inhibit LAMP and methods to reduce the inhibition, which have rarely been reported.

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.

A comprehensive review on hemocyanin from marine products: Structure, functions, its implications for the food industry and beyond

Hemocyanin, an oxygen-transport protein, is widely distributed in the hemolymph of marine arthropods and mollusks, playing an important role in their physiological processes. Recently, hemocyanin has been recognized as a multifunctional glycoprotein involved in the immunological responses of aquatic invertebrates. Consequently, the link between hemocyanin functions and their potential applications has garnered increased attention. This review offers an integrated overview of hemocyanin's structure, physicochemical characteristics, and bioactivities to further promote the utilization of hemocyanin derived from marine products. Specifically, we review its implication in two aspects of food and aquaculture industries: quality and health. Hemocyanin's inducible phenoloxidase activity is thought to be an inducer of melanosis in crustaceans. New anti-melanosis agents targeted to hemocyanin need to be explored. The red-color change observed in shrimp shells is related to hemocyanin, affecting consumer preferences. Hemocyanin's adaptive modification in response to the aquatic environment is available as a biomarker. Additionally, hemocyanin is endowed with bioactivities encompassing anti-microbial, antiviral, and therapeutic activities. Hemocyanin is also a novel allergen and its allergenic features remain incompletely characterized.

Next-generation neonicotinoid: The impact of cycloxaprid on the crustacean decapod Penaeus vannamei

Cycloxaprid, a new neonicotinoid pesticide, poses ecological risks, particularly in aquatic environments, due to its unique action and environmental dispersal. This study investigated the ecotoxicological effects of various concentrations of cycloxaprid on Penaeus vannamei over 28 days. High cycloxaprid levels significantly altered shrimp physiology, as shown by changes in the hepatosomatic index and fattening. Indicators of oxidative stress, such as increased serum hemocyanin, respiratory burst, and nitric oxide, as well as decreased phenol oxidase activity, were observed. Additionally, elevated activities of lactate dehydrogenase, succinate dehydrogenase, and isocitrate dehydrogenase indicated disrupted energy metabolism in the hepatopancreas. Notably, analyses of the nervous system revealed marked disturbances in neural signaling, as evidenced by elevated acetylcholine, octopamine, and acetylcholinesterase levels. Transcriptomic analysis highlighted significant effects on gene expression and metabolic processes in the hepatopancreas and nervous system. This study demonstrated that cycloxaprid disrupts neural signaling and oxidative balance in P. vannamei, potentially affecting its growth, and provides key insights into its biochemical and transcriptomic toxicity in aquatic systems.

Effects of Dietary Melatonin on Antioxidant Capacity, Immune Defense, and Intestinal Microbiota in Red Swamp Crayfish (Procambarus clarkii)

The aim of this study was to investigate the effects of melatonin (MT) feed supplementation on the antioxidant capacity, immune defense, and intestinal flora in Procambarus clarkii (P. clarkii). Six groups of P. clarkii were fed test feeds containing different levels of MT: 0 mg/kg (control), 22.5, 41.2, 82.7, 165.1, and 329.2 mg/kg for a duration of 2 months. The specific growth rate, hepatosomatic index, and condition factor were recorded highest in the test group of shrimp fed an MT concentration of 165.1 mg/kg. Compared to the control group, the rate of apoptosis was lower in hepatopancreas cells of P. clarkii supplemented with high concentrations of MT. Analyses of antioxidant capacity and immune-response-related enzymes in the hepatopancreas indicated that dietary supplementation of MT significantly augmented both the antioxidant system and immune responses. Dietary MT supplementation significantly increased the expression levels of antioxidant-immunity-related genes and decreased the expression levels of genes linked to apoptosis. Dietary MT was associated with an elevation in the abundance of the Firmicutes and a reduction in the abundance of the Proteobacteria in the intestines; besides, resulting in an increase in the abundance of beneficial bacteria, such as Lactobacilli. The broken-line model indicated that the suitable MT concentration was 154.09-157.09 mg/kg. MT supplementation enhanced the growth performance of P. clarkii, exerting a positive influence on the intestinal microbiota, and bolstered both immune response and disease resistance. Thus, this study offered novel perspectives regarding the application of dietary MT supplementation within the aquaculture field.

Comprehensive Proteomics Analysis of the Hemolymph Composition of Sugar-Fed Aedes aegypti Female and Male Mosquitoes

In arthropods, hemolymph carries immune cells and solubilizes and transports nutrients, hormones, and other molecules that are involved in diverse physiological processes including immunity, metabolism, and reproduction. However, despite such physiological importance, little is known about its composition. We applied mass spectrometry-based label-free quantification approaches to study the proteome of hemolymph perfused from sugar-fed female and male Aedes aegypti mosquitoes. A total of 1403 proteins were identified, out of which 447 of them were predicted to be extracellular. In both sexes, almost half of these extracellular proteins were predicted to be involved in defense/immune response, and their relative abundances (based on their intensity-based absolute quantification, iBAQ) were 37.9 and 33.2%, respectively. Interestingly, among them, 102 serine proteases/serine protease-homologues were identified, with almost half of them containing CLIP regulatory domains. Moreover, proteins belonging to families classically described as chemoreceptors, such as odorant-binding proteins (OBPs) and chemosensory proteins (CSPs), were also highly abundant in the hemolymph of both sexes. Our data provide a comprehensive catalogue of A. aegypti hemolymph basal protein content, revealing numerous unexplored targets for future research on mosquito physiology and disease transmission. It also provides a reference for future studies on the effect of blood meal and infection on hemolymph composition.

The identification of a serpin with immune defense role in oriental river prawn Macrobrachium nipponense

Serpins are a protein superfamily of serine protease inhibitors. One of their functions is to participate in immune responses by inhibiting the activation of prophenoloxidase. To elucidate the immune role of serpin in Macrobrachium nipponense, a serpin gene (Mnserpin) was cloned from M. nipponense in this study. Mnserpin protein has an N-terminal signal peptide and a serpin domain that contains a hinge region, a signature sequence of serpin and a P1(arginine)-P1' scissile bond, and evolutionally closely related to the crustacean serpins. Mnserpin highly expressed in the hepatopancreas and gill. Mnserpin expression increased first and then decreased after Vibrio parahaemolyticus and Aeromonas hydrophila infection, and was knocked down by dsMnserpin injection with a maximum knockdown efficiency of 92 %. Mnserpin knockdown increased the expression of the clip domain serine protease and prophenoloxidase genes and phenoloxidase activity of M. nipponense as well as its mortality rate after V. parahaemolyticus and A. hydrophila infection. The recombinant Mnserpin (rMnserpin) showed bacteria-binding and bacteriostatic activity in vitro. Moreover, rMnserpin injection decreased the bacterial number and the mortality rate of M. nipponense post V. parahaemolyticus and A. hydrophila infection. These results suggested that Mnserpin plays a major role in the innate immune response of M. nipponense.

Antagonistic effect of the beneficial bacterium Enterobacter hormaechei against the heavy metal Cu2+ in housefly larvae

Vermicomposting via housefly larvae can be used to efficiently treat manure and regenerate biofertilizer; however, the uptake of heavy metals could negatively influence the growth and development of larvae. Intestinal bacteria play an important role in the development of houseflies, but their effects on resistance to heavy metal damage in houseflies are still poorly understood. In this study, the life history traits and gut microbiota of housefly larvae were evaluated after exposure to an environment with Cu2+ -Enterobacter hormaechei. The data showed that exposure to 300 μg/mL Cu2+ significantly inhibited larval development and locomotor activity and reduced immune capacity. However, dietary supplementation with a Cu2+ -Enterobacter hormaechei mixture resulted in increased body weight and length, and the immune capacity of the larvae returned to normal levels. The abundances of Providencia and Klebsiella increased when larvae were fed Cu2+ -contaminated diets, while the abundances of Enterobacter and Bacillus increased when larvae were exposed to a Cu2+ -Enterobacter hormaechei mixture-contaminated environment. In vitro scanning electron microscopy analysis revealed that Enterobacter hormaechei exhibited obvious adsorption of Cu2+ when cultured in the presence of Cu2+, which reduced the damage caused by Cu2+ to other bacteria in the intestine and protected the larvae from Cu2+ injury. Overall, our results showed that Enterobacter hormaechei can absorb Cu2+ and increase the abundance of beneficial bacteria, thus protecting housefly larvae from damage caused by Cu2+. These results may fill the gaps in our understanding of the interactions between heavy metals and beneficial intestinal bacteria, offering valuable insights into the interplay between housefly larvae and metal contaminants in the environment. This approach could enhance the efficiency of converting manure contaminated with heavy metals to resources using houseflies.

Toxic effect of chromium on nonspecific immune, bioaccumulation, and tissue structure of Urechis unicinctus

The contamination of toxic heavy metals in aquatic environments has garnered significant global attention due to its detrimental effects on marine organisms and human health. Hexavalent chromium is a typical environmental and occupational heavy metal pollutant, identified as carcinogenic heavy metal. This study aimed to assess the impact of different Cr (VI) concentrations (0.05-2.5 mg/L) on Urechis unicinctus (U. unicinctus) by investigating bioaccumulation, antioxidant defense system, expression of resistance-related genes, and histological issues. A clear concentration-effect relationship was observed in the bioaccumulation of Cr (VI) in muscle tissues of U. unicinctus. Moreover, exposure to Cr (VI) can alter the activities of lysozyme (LSZ), catalase (CAT), and superoxide dismutase (SOD) to enhance cellular defense mechanisms in U. unicinctus. Likewise, maintained the normal protein structure and functional stability by regulating protein folding. The heat shock cognitive protein (HSC70) gene showed an upward and then downward trend after Cr (VI) exposure. At 12 h, the HSC70 gene expression reached the maximum values of 4.75 and 4.61-fold in the 0.1 and 1.5 mg/L groups, respectively. The organism produced a large number of free radicals, and elevated level of metallothionein (MT) was used to scavenge free radicals and alleviate oxidative stress. Additionally, histopathological examination revealed disorganization in the midgut, atrophic changes in intestinal connective tissue, uneven distribution in respiratory tissues, and irregular shape with a significant reduction in epithelial cells within the gastric cavity. These findings can serve as a valuable reference for elucidating the toxicity mechanisms of heavy metals towards marine benthic organisms and enhancing water environment monitoring strategies.

Variation in Paramarteilia canceri infections in velvet crab Necora puber

Sustainable management of crustacean populations requires an understanding of the range of factors affecting different crustacean species. Recently, a high prevalence of a paramyxid parasite, Paramarteilia canceri, was reported in velvet crabs Necora puber in Ireland. Similar parasites have been known to cause mass mortalities in bivalves and, as velvet crabs are an important commercial species, these parasite infections are cause for concern. The main objective of this study was to examine variation in P. canceri infections in relation to host biology and season over a 2 yr period. In addition, we tested a range of host tissues and organs to gain more information on the host-parasite interaction. The parasite was present in all tissues and organs investigated, including the gonad and eggs of a berried female. Parasite prevalence was highest in the cuticular epithelium and hepatopancreas. Both annual and seasonal variation was found in parasite prevalence and parasite load. No difference was found in parasite prevalence or parasite load with either crab size or crab sex. Granulomas as a response to infection were significantly more abundant in infected velvet crab individuals. The results of this study provide important information on the host-parasite interaction between P. canceri and the velvet crab and highlight the importance of including parasite monitoring in the management of crustacean fisheries.

The evolutionary adaptation of shrimp hemocyanin subtypes and the consequences on their structure and functions

Hemocyanin is the main respiratory protein of arthropods and is formed by hexameric and/or oligomeric subunits. Due to changes in the living environment and gene rearrangement, various hemocyanin subtypes and subunits evolved in crustaceans. This paper reviews the various hemocyanin subtypes and isoforms in shrimp and analyses published genomic data of sixteen hemocyanin family genes from Litopenaeus vannamei to explore the evolution of hemocyanin genes, subunits, and protein structure. Analysis of hemocyanin subtypes distribution and structure in various tissues was also performed and related to multiple and tissue-specific functions, i.e., immunological activity, immune signaling, phenoloxidase activity, modulation of microbiota homeostasis, and energy metabolism. The functional diversity of shrimp hemocyanin due to molecular polymorphism, transcriptional regulation, alternative splicing, degradation into functional peptides, interaction with other proteins or genes, and structural differences will also be highlighted for future research. Inferences would be drawn from other crustaceans to explain how evolution has changed the structure-function of hemocyanin and its implication for evolutionary research into the multifunctionality of hemocyanin and other related proteins in shrimp.

Infection with a non-lethal fungal parasite is associated with increased immune investment in the ant Myrmica scabrinodis

Social insects, such as ants, are preferred host organisms of pathogens and parasites because colonies are densely populated, and the number of potential hosts is high in the same place and time. Within a colony, individuals are exposed differentially to risks according to their function and age. Thus, older individuals forage and are therefore the most exposed to infection, predation, or physical stress, while young workers mostly stay inside the sheltered nest being less exposed. Immune investment is considered to be dependent on an individual's age and pathogen pressure. Long-term exposure to a parasite could affect the immune activity of individuals in an intriguing way that interferes with the age-dependent decline in immunocompetence. However, there are only few cases in which such interferences can be studied. The myrmecopathogenic fungus Rickia wasmannii, which infects entire colonies without killing the workers, is a suitable candidate for such studies. We investigated the general immunocompetence of Myrmica scabrinodis ant workers associated with non-lethal fungal infection by measuring the levels of active phenoloxidase (PO) and total PO (PPO) (reflecting the amount of both active and inactive forms of the enzyme) in two age classes. The level of PO proved to be higher in infected workers than in uninfected ones, while the level of PPO increased with age but was not affected by infection. Overall, these results indicate that a long-term infection could go hand in hand with increased immune activity of ant workers, conferring them higher level of protection.

Identification of an essential role against shrimp pathogens of prophenoloxidase activating enzyme 1 (PPAE1) from Fenneropenaeus merguiensis hemocytes

Prophenoloxidase (proPO) activating enzymes, known as PPAEs, are pivotal in activating the proPO system within invertebrate immunity. A cDNA encoding a PPAE derived from the hemocytes of banana shrimp, Fenneropenaeus merguiensis have cloned and analyzed, referred to as FmPPAE1. The open reading frame of FmPPAE1 encompasses 1392 base pairs, encoding a 464-amino acid peptide featuring a presumed 19-amino acid signal peptide. The projected molecular mass and isoelectric point of this protein stand at 50.5 kDa and 7.82, respectively. Structure of FmPPAE1 consists of an N-terminal clip domain and a C-terminal serine proteinase domain, housing a catalytic triad (His272, Asp321, Ser414) and a substrate binding site (Asp408, Ser435, Gly437). Expression of the FmPPAE1 transcript is specific to hemocytes and is heightened upon encountering pathogens like Vibrio parahaemolyticus, Vibrio harveyi, and white spot syndrome virus (WSSV). Using RNA interference to silence the FmPPAE1 gene resulted in reduced hemolymph phenoloxidase (PO) activity and decreased survival rates in shrimp co-injected with pathogenic agents. These findings strongly indicate that FmPPAE1 plays a vital role in regulating the proPO system in shrimp. Furthermore, upon successful production of recombinant FmPPAE1 protein (rFmPPAE1), it became evident that this protein exhibited remarkable abilities in both agglutinating and binding to a wide range of bacterial strains. These interactions were primarily facilitated through the recognition of bacterial lipopolysaccharides (LPS) or peptidoglycans (PGN) found in the cell wall. This agglutination process subsequently triggered melanization, a critical immune response. Furthermore, rFmPPAE1 exhibited the ability to actively impede the growth of pathogenic bacteria harmful to shrimp, including V. harveyi and V. parahaemolyticus. These findings strongly suggest that FmPPAE1 not only plays a pivotal role in activating the proPO system but also possesses inherent antibacterial properties, actively contributing to the suppression of bacterial proliferation. In summary, these results underscore the substantial involvement of FmPPAE1 in activating the proPO system in F. merguiensis and emphasize its crucial role in the shrimp's immune defense against invading pathogens.

Tick innate immune responses to hematophagy and Ehrlichia infection at single-cell resolution

Introduction

Ticks rely on robust cellular and humoral responses to control microbial infection. However, several aspects of the tick's innate immune system remain uncharacterized, most notably that of the immune cells (called hemocytes), which are known to play a significant role in cellular and humoral responses. Despite the importance of hemocytes in regulating microbial infection, our understanding of their basic biology and molecular mechanisms remains limited. Therefore, we believe that a more detailed understanding of the role of hemocytes in the interactions between ticks and tick-borne microbes is crucial to illuminating their function in vector competence and to help identify novel targets for developing new strategies to block tick-borne pathogen transmission.

Methods

This study examined hemocytes from the lone star tick (Amblyomma americanum) at the transcriptomic level using the 10X genomics single-cell RNA sequencing platform to analyze hemocyte populations from unfed, partially blood-fed, and Ehrlichia chaffeensis-infected ticks. The functional role of differentially expressed hemocyte markers in hemocyte proliferation and Ehrlichia dissemination was determined using an RNA interference approach.

Results and discussion

Our data exhibit the identification of fourteen distinct hemocyte populations. Our results uncover seven distinct lineages present in uninfected and Ehrlichia-infected hemocyte clusters. The functional characterization of hemocytin, cystatin, fibronectin, and lipocalin demonstrate their role in hemocyte population changes, proliferation, and Ehrlichia dissemination.

Conclusion

Our results uncover the tick immune responses to Ehrlichia infection and hematophagy at a single-cell resolution. This work opens a new field of tick innate immunobiology to understand the role of hemocytes, particularly in response to prolonged blood-feeding (hematophagy), and tick-microbial interactions.

Valorization of biomass polyphenols as potential tyrosinase inhibitors

Tyrosinases (TYRs; EC 1.14.18.1) catalyze two sequential oxidative reactions of the melanin biosynthesis pathway and play an important role in mammalian pigmentation and enzymatic browning of fruit and vegetables. Inhibition of TYR activity is therefore an attractive target for new drugs and/or food ingredients. In addition, increasing evidence suggests that TYR regulation could be a novel target for treatments of cancer and Parkinson's disease. Biomasses, notably industrial byproducts and biowaste, are good sustainable sources of phytochemicals that may be valorized into bioactive compounds including TYR inhibitors. This review presents potential applications of biomass-derived polyphenols targeting TYR inhibition. Insights into structure-activity relationships of several polyphenols and their glycosides are highlighted. Finally, some remarks and perspectives on research into new TYR inhibitors from biomass waste are provided.

Role of prophenoloxidase 1 from the beetle Octodonta nipae in melanized encapsulation of a wasp egg

Exploring the function of the host immune system can help to understand the host-parasitoid interaction. Prophenoloxidase (PPO) is crucial in defensive melanization during the encapsulation of wasp eggs. However, the existence of multiple PPO sequences increases the difficulty of exploring the specific functions of individual PPOs. We previously identified three PPOs in the nipa palm hispid beetle, Octodonta nipae. Our current work showed that OnPPO1 and OnPPO2 possessed the typical characteristics of the type III copper family, but OnPPO3 lacked the conserved histidine residues, and its active sites were substituted with Gln. OnPPOs showed the highest expression in hemocytes, but OnPPO3 presented extremely low abundance compared with that of OnPPO1 and OnPPO2, and only OnPPO1 showed a quick response after wasp infection. OnPPO1 knockdown decreased the encapsulation index and inhibited melanization, whereas silencing of OnPPO3 appeared to have no adverse effect on encapsulation and melanization, and silencing of OnPPO2 presented low RNAi efficiency. Moreover, the cleavage of recombinant OnPPO1 produced a 62 kDa fragment with high PO activity. OnPPO1 could be produced by oenocytoids, granulocytes and plasmatocytes, and was distributed around wasp eggs during capsule formation. Overall, our results indicate that proteolytic cleavage of OnPPO1 plays key roles in the melanized encapsulation of wasp eggs. This finding illuminates the mechanism of PPO activation in this invasive beetle and provides guidance for its biological control.

A Galleria Model of Cryptococcus neoformans Infection

Galleria mellonella larvae are a popular and simple model organism for infectious disease research. Last instar larvae can be purchased inexpensively from commercial suppliers and infected with Cryptococcus. Injection into the proleg of larvae results in systemic infections. Larvae may then be monitored for survival or homogenized to determine fungal burden. Fixation of infected larvae produces samples suitable for histological staining and analysis.

The immune response of the whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) when parasitized by Eretmocerus eremicus (Hymenoptera: Aphelinidae)

In insects, the innate immune system is subdivided into cellular and humoral defenses. When parasitoids attack insects, both reactions can be activated and notably, the phenoloxidase (PO) cascade and lytic activity are part of both cellular and humoral defenses. However, to our knowledge, no study has characterized any immune response of the whitefly Trialeurodes vaporariorum (Hemiptera: Aleyrodidae) to the attack of Eretmocerus eremicus (Hymenoptera: Aphelinidae). Therefore, the first objective of the present study was to determine whether whitefly nymphs recently parasitized by E. eremicus exhibit any immune response. For this, we estimate the level of prophenoloxidase (proPO), phenoloxidase (PO), and lytic activity by colorimetric assays. A second objective was to assess whether the observed whitefly immune response could be related to a previously reported preference of the predator Geocoris punctipes (Hemiptera: Lygaeidae) for non-parasitized nymphs. We therefore offered non-parasitized and recently parasitized nymphs to the predator. Our results show that parasitism of whitefly nymphs by E. eremicus induced a highly estimated level of proPO and PO, and a lower level of lytic activity. In addition, we found that G. punctipes did not show a preference for non-parasitized over recently parasitized nymphs. The nymphs of T. vaporariorum activated the PO pathway against E. eremicus; however, the increase in proPO and PO levels was traded-off with decreased lytic activity. In addition, the previously reported preference for non-parasitized nymphs was not seen in our experiments, indicating that the induced immune response did not affect predator behavior by G. punctipes.

Functional and genomic characterization of a novel probiotic Lactobacillus johnsonii KD1 against shrimp WSSV infection

White Spot syndrome virus (WSSV) causes rapid shrimp mortality and production loss worldwide. This study demonstrates potential use of Lactobacillus johnsonii KD1 as an anti-WSSV agent for post larva shrimp cultivation and explores some potential mechanisms behind the anti-WSSV properties. Treatment of Penaeus vannamei shrimps with L. johnsonii KD1 prior to oral challenge with WSSV-infected tissues showed a significantly reduced mortality. In addition, WSSV copy numbers were not detected and shrimp immune genes were upregulated. Genomic analysis of L. johnsonii KD1 based on Illumina and Nanopore platforms revealed a 1.87 Mb chromosome and one 15.4 Kb plasmid. Only one antimicrobial resistance gene (ermB) in the chromosome was identified. Phylogenetic analysis comparing L. johnsonii KD1 to other L. johnsonii isolates revealed that L. johnsonii KD1 is closely related to L. johnsonii GHZ10a isolated from wild pigs. Interestingly, L. johnsonii KD1 contains isolate-specific genes such as genes involved in a type I restriction-modification system and CAZymes belonging to the GT8 family. Furthermore, genes coding for probiotic survival and potential antimicrobial/anti-viral metabolites such as a homolog of the bacteriocin helveticin-J were found. Protein-protein docking modelling suggests the helveticin-J homolog may be able to block VP28-PmRab7 interactions and interrupt WSSV infection.

The immune response of Locusta migratoria manilensis at different times of infection with Paranosema locustae

Paranosema locustae is an entomopathogenic microsporidia with promising potential for controlling agricultural pests, including Locusta migratoria manilensis. However, it has the disadvantage of having a slow insecticidal rate, and how P. locustae infection impacts the host immune response is currently unknown. The present study investigated the effect of P. locustae on the natural immune response of L. migratoria and the activities of enzymes that protect against oxidative stress. Infection with P. locustae increased the hemocytes and nodulation number of L. migratoria at the initial stage of infection. The hemocyte-mediated modulation of immune response was also affected by a decrease in the number of hemocytes 12 days postinfection. Superoxide dismutase activity in locusts increased in the early stages of infection but decreased in the later stages, whereas the activities of peroxidase (POD) and catalase (CAT) showed opposite trends may be due to their different mechanisms of action. Furthermore, the transcription levels of mRNA of antimicrobial peptide-related genes and phenoloxidase activity in hemolymph in L. migratoria were suppressed within 15 days of P. locustae infection. Overall, our data suggest that P. locustae create a conducive environment for its own proliferation in the host by disrupting the immune defense against it. These findings provide useful information for the potential application of P. locustae as a biocontrol agent.

Saccharomyces cerevisiae additions normalized hemocyte differential genes expression and regulated crayfish (Procambarus clarkii) oxidative damage under cadmium stress

Because China produces the most crayfish in the world, safe solutions must be improved to mitigate the risks of ongoing heavy metal stressors accumulation. This study aimed to use Saccharomyces cerevisiae as a bioremediation agent to counteract the harmful effect of cadmium (Cd) on crayfish (Procambarus clarkia). Our study used three concentrations of S. cerevisiae on crayfish feed to assess their Cd toxicity remediation effect by measuring total antioxidant capacity (TAC) and the biomarkers related to oxidative stress like malondialdehyde (MDA), protein carbonyl derivates (PCO), and DNA-protein crosslink (DPC). A graphite furnace atomic absorption spectroscopy device was used to determine Cd contents in crayfish. Furthermore, the mRNA expression levels of lysozyme (LSZ), metallothionein (MT), and prophenoloxidase (proPO) were evaluated before and following the addition of S. cerevisiae. The results indicated that S. cerevisae at 5% supplemented in fundamental feed exhibited the best removal effect, and Cd removal rates at days 4th, 8th, 12th, and 21st were 12, 19, 29.7, and 66.45%, respectively, which were significantly higher than the basal diet of crayfish. The addition of S. cerevisiae increased TAC levels. On the other hand, it decreased MDA, PCO, and DPC, which had risen due to Cd exposure. Furthermore, it increased the expression of proPO, which was reduced by Cd exposure, and decreased the expression of LSZ and MT, acting in the opposite direction of Cd exposure alone. These findings demonstrated that feeding S. cerevisiae effectively reduces the Cd from crayfish and could be used to develop Cd-free crayfish-based foods.

Transcriptomic variations associated with salinity stress in Penaeus indicus

BACKGROUND

The Indian white shrimp, Penaeus indicus a native species of India, is important brackishwater aquaculture species. Shrimps are euryhaline in nature and they regulate osmotic and ionic concentrations by osmoregulatory process. However, variations in abiotic factors such as salinity result in stress to the shrimps during culture period affecting their growth and immunity.

METHODS AND RESULTS

To understand the adaptive mechanism to stress in low salinity conditions, RNA-seq was used to compare the transcriptomic response of P. indicus upto 3 weeks. De novo assembly using Trinity assembler generated a total of 173,582 transcripts. The assembly had a mean length of 854 bp, N50 value of 1243 bp and GC content of 42.33%. Differential gene expression analysis, resulted in identification of 2130, 3090, and 5351 DEGs in 7 days, 14 days and 21 days respectively of salinity stress period. The pathway prediction of the assembled trinity transcripts using KEGG database showed total number of 329 pathways linking 12,430 transcripts. KEGG pathway enrichment analyses led to the identification of several enriched pathways related to lipid metabolism, amino acid metabolism, glycolysis, signalling pathways etc. Selected genes involved in osmoregulatory process and immune response in shrimps were validated and analysed for the gene expression levels by quantitative real-time PCR (qPCR).

CONCLUSION

This study on the adaptive transcriptomic response of P. indicus to low salinity, will further help in our understanding of the molecular mechanisms underlying osmoregulation mechanism in shrimps.

Insights into molecular aspects of pathogenesis and disease management in acute hepatopancreatic necrosis disease (AHPND): An updated review

Shrimp aquaculture is a rapidly growing sector that makes a significant economic contribution. However, the aquaculture industry is confronted with significant challenges, and infectious diseases, notably Acute Hepatopancreatic Necrosis Disease (AHPND), have emerged as severe threat. AHPND is caused by pathogens carrying the pVA-1 plasmid, which expresses the PirAB toxin, and it has wreaked havoc in shrimp aquaculture, imposing substantial economic burdens. To address this issue, it is crucial to delve into shrimp's immune responses. Therefore, this comprehensive review offers an in-depth examination of AHPND outbreaks, encompassing various facets such as environmental factors, host susceptibility, and the mechanisms employed by the pathogens. Traditional approaches to combat AHPND, primarily relying on chemicals and antibiotics, have raised concerns related to antibiotic resistance and have demonstrated limited success in disease control. Hence this review spotlights recent advancements in molecular diagnostics, therapeutic agents, and research related to shrimp immunity. Understanding these developments is crucial in the ongoing battle against AHPND. In conclusion, this review underscores the pressing need to comprehend the underlying mechanisms of AHPND pathogenesis and emphasizes the importance of developing comprehensive and effective solutions to combat this devastating disease, which continues to threaten the sustainability of shrimp farming.

A review of the toxic effects of ammonia on invertebrates in aquatic environments

Aquatic invertebrates are the organisms most susceptible to ammonia toxicity. However, the toxic effects of ammonia on invertebrates are still poorly understood. This study reviews the research progress in ammonia toxicology for the period from 1986 to 2023, focusing on the effects on invertebrates. Through examining the toxic effects of ammonia at different levels of organization (community, individual, tissue and physiology, and molecular) as well as the results from omics studies, we determined that the most significant effects were on the reproductive capacity of invertebrates and the growth of offspring, although different populations show variation in their tolerance to ammonia, and tissues have varied potential to respond to ammonia stress. A multicomponent analysis is an in-depth technique employed in toxicological studies, as it can be used to explore the enrichment pathways and functional genes expressed under ammonia stress. This study comprehensively discusses ammonia toxicity from multiple aspects in order to provide new insights into the toxic effects of ammonia on aquatic invertebrates.

Evaluation and Characterization of the Insecticidal Activity and Synergistic Effects of Different GroEL Proteins from Bacteria Associated with Entomopathogenic Nematodes on Galleria mellonella

GroEL is a chaperonin that helps other proteins fold correctly. However, alternative activities, such as acting as an insect toxin, have also been discovered. This work evaluates the chaperonin and insecticidal activity of different GroEL proteins from entomopathogenic nematodes on G. mellonella. The ability to synergize with the ExoA toxin of Pseudomonas aeruginosa was also investigated. The GroELXn protein showed the highest insecticidal activity among the different GroELs. In addition, it was able to significantly activate the phenoloxidase system of the target insects. This could tell us about the mechanism by which it exerts its toxicity on insects. GroEL proteins can enhance the toxic activity of the ExoA toxin, which could be related to its chaperonin activity. However, there is a significant difference in the synergistic effect that is more related to its alternative activity as an insecticidal toxin.

Quantification of proteomic profile changes in the hemolymph of crayfish during in vitro coagulation

Hemolymph is the circulatory fluid that fills the body cavity of crustaceans, analogous to blood in vertebrates. Hemolymph coagulation, similar to blood clotting in vertebrates, plays a crucial role in wound healing and innate immune responses. Despite extensive studies on the clotting process in crustaceans, no comparative quantitative analysis of the protein composition of non-clotted and clotted hemolymph in any decapod has been reported. In this study, we used label-free protein quantification with high-resolution mass spectrometry to identify the proteomic profile of hemolymph in crayfish and quantify significant changes in protein abundances between non-clotted and clotted hemolymph. Our analysis identified a total of two-hundred and nineteen proteins in both hemolymph groups. Furthermore, we discussed the potential functions of the top most high and low-abundant proteins in hemolymph proteomic profile. The quantity of most of the proteins was not significantly changed during coagulation between non-clotted and clotted hemolymph, which may indicate that clotting proteins are likely pre-synthesized, allowing for a swift coagulation response to injury. Four proteins still showed abundance differences (p < 0.05, fold change>2), including C-type lectin domain-containing proteins, Laminin A chain, Tropomyosin, and Reverse transcriptase domain-containing proteins. While the first three proteins were down-regulated, the last one was up-regulated. The down-regulation of structural and cytoskeletal proteins may affect the process of hemocyte degranulation needed for coagulation, while the up-regulation of an immune-related protein might be attributed to the phagocytosis ability of viable hemocytes during coagulation.

Research progress of pattern recognition receptors in red swamp crayfish (Procambarus clarkii)

Though Procambarus clarkii (red swamp crayfish) is a lower invertebrate, it has nonetheless developed a complex innate immune system. The crayfish farming industry has suffered considerable economic losses in recent years as a consequence of bacterial and viral diseases. Hence, perhaps the most effective ways to prevent microbial infections in P. clarkii are to examine and elucidate its innate immunity. The first step in the immune response is to recognize pathogen-associated molecular patterns (PAMPs) through pattern recognition receptors (PRRs). PRRs are expressed mainly on immune cell surfaces and recognize at least one PAMP. Thence, downstream immune responses are activated and pathogens are phagocytosed. To date, the PRRs identified in P. clarkii include Toll-like receptors (TLRs), lectins, fibrinogen-related proteins (FREPs), and β-1,3-glucan-binding proteins (BGRPs). The present review addresses recent progress in research on PRRs and aims to provide guidance for improving immunity and preventing and treating infectious diseases in P. clarkii.

Selective protein self-deprivation by Mormon crickets following fungal attack

Immune responses to infection result in behavioral changes that affect resource acquisition, such as general starvation and compensatory feeding to offset changes in resource allocation. Mormon crickets aggregate and march in bands containing millions of insects. Some bands are comprised of insects seeking proteins. They are also low in circulating phenoloxidase (PO) and more susceptible to fungal attack, as we have demonstrated in the lab. Here, we ask: Do Mormon crickets elevate PO and consume protein in response to infection by the pathogenic fungus Beauveria bassiana? B. bassiana was applied topically (day 0), and mortality began on day 5. Total protein, PO, and prophenoloxidase (proPO) were assayed in hemolymph on day 1 and 4. On day 1, PO titers were not different between inoculated and control insects, whereas by day 4, PO was greater in the inoculated group. proPO activity was unchanged. Circulating protein declined in inoculated insects relative to controls. As predicted, PO titers were elevated as a result of fungal infection, and hemolymph protein was reduced, but the insects did not compensate behaviorally. Indeed, during the first three days post-infection, infected insects reduced protein consumption while maintaining carbohydrate consumption similar to the controls. Following day 3, a more general reduction in protein and carbohydrate intake was evident in infected insects. Survivorship to infection was associated with the amount of protein consumed and unrelated to carbohydrate consumption. Selective protein deprivation by the host seems counterintuitive, but it might limit growth and toxin production by the invading fungus. Alternatively, the fungus might control the host diet to compromise host immunity to infection. Abrupt changes in allocation resulting from an infection can lead to changes in acquisition that are not always intuitive. Because protein acquisition drives aggression between members of the migratory band, B. bassiana application may reduce cannibalism and slow band movement.

Functionality of probiotics on the resistance capacity of shrimp against white spot syndrome virus (WSSV)

Shrimp aquaculture is currently regarded as a significant commercial and food production sector due to its growing importance as a source of human-consumable protein, As shrimp farming has become more intensive, disease outbreaks have become more common, necessitating the overuse of antimicrobial drugs, which has had a number of unintended consequences. The white spot syndrome virus (WSSV) is now recognized as one of the world's most pervasive and potentially fatal diseases affecting shrimp. However, there is currently no cure to prevent the disease's uncontrolled incidence and spread. Probiotics are currently favoured over these antimicrobial substances because of their ability to stimulate disease resilience in shrimp farms by strengthening the immune systems naturally. Probiotics for bacterial infections such as vibriosis are well documented, whereas research is still required to identify the legitimate strains for viral diseases. The utilization of these probiotics as a therapy for and preventative measure against WSSV in shrimp farming is a cutting-edge method that has proven to be effective. Some probiotic strains, such as Bacillus spp, Lactobacillus, and Pediococcus pentosaceus, have been displayed to enhance the innate immunity of shrimp against WSSV, reduce viral load, increase digestibility and growth, and support the gut microbiome of the host in multiple investigations. The present review explores recent developments regarding the function of probiotics in shrimp, with a focus on their anti-WSSV activity.

Retrospective analysis of histologic lesions in captive arachnids

Invertebrates, including arachnids, are a common taxon in zoological collections. Invertebrate medicine and pathology are emerging subspecialties, but there is limited reference material or published resources describing histologic lesions in arachnids. Histopathology of 26 captive arachnids (20 spiders and 6 scorpions) from institutional collections was reviewed. Most animals were found dead with limited clinical signs. Tissues evaluated included body wall (cuticle and epidermis), skeletal muscle, book lungs, digestive tract (pharynx, esophagus, sucking stomach, midgut tube, midgut diverticula, and stercoral pocket), central and peripheral nervous system, heart, hemolymph vessels and sinuses, Malpighian tubules, coxal glands, and gonads. Inflammation was frequent (24/26, 92%), and seen in multiple organs (18/24, 75%) with the midgut diverticulum most commonly affected (14/24, 58%) followed by the book lungs (13/24 arachnids, 54%), and body wall (8/24 arachnids, 33%). Inflammation comprised hemocyte accumulation, hemocytic coagula, melanization, and nodulation. Infectious agents, including bacteria (11/26, 42%), fungi (10/26, 38%), and parasites (2/26, 8%), were seen within inflammatory aggregates. Coinfection with multiple infectious agents was common (6/24, 25%). No etiologic agent was identified in 7/24 (29%) cases with inflammatory lesions. Lesions suggestive of decreased nutritional status or increased metabolic rate included midgut diverticula atrophy in 11/26 (42%) animals and skeletal muscle atrophy in 6/26 (23%) animals. Atrophic lesions were seen in combination with infection (8/11, 73%), pregnancy (2/11, 18%), male sex (2/11, 18%), or without other lesions (1/11, 9%). Other suspected contributors to death included dysecdysis-associated trauma (2/26, 8%) and uterine intussusception (1/26, 4%). No animals had neoplasia.

Trade-offs between immunity and competitive ability in fighting ant males

BACKGROUND

Fighting disease while fighting rivals exposes males to constraints and trade-offs during male-male competition. We here tested how both the stage and intensity of infection with the fungal pathogen Metarhizium robertsii interfere with fighting success in Cardiocondyla obscurior ant males. Males of this species have evolved long lifespans during which they can gain many matings with the young queens of the colony, if successful in male-male competition. Since male fights occur inside the colony, the outcome of male-male competition can further be biased by interference of the colony's worker force.

RESULTS

We found that severe, but not yet mild, infection strongly impaired male fighting success. In late-stage infection, this could be attributed to worker aggression directed towards the infected rather than the healthy male and an already very high male morbidity even in the absence of fighting. Shortly after pathogen exposure, however, male mortality was particularly increased during combat. Since these males mounted a strong immune response, their reduced fighting success suggests a trade-off between immune investment and competitive ability already early in the infection. Even if the males themselves showed no difference in the number of attacks they raised against their healthy rivals across infection stages and levels, severely infected males were thus losing in male-male competition from an early stage of infection on.

CONCLUSIONS

Males of the ant C. obscurior have a well-developed immune system that raises a strong immune response very fast after fungal exposure. This allows them to cope with mild pathogen exposures without compromising their success in male-male competition, and hence to gain multiple mating opportunities with the emerging virgin queens of the colony. Under severe infection, however, they are weak fighters and rarely survive a combat already at early infection when raising an immune response, as well as at progressed infection, when they are morbid and preferentially targeted by worker aggression. Workers thereby remove males that pose a future disease threat by biasing male-male competition. Our study thus reveals a novel social immunity mechanism how social insect workers protect the colony against disease risk.

Immune and Reproductive Biomarkers in Female Sea Urchins Paracentrotus lividus under Heat Stress

The functioning of the immune and reproductive systems is crucial for the fitness and survival of species and is strongly influenced by the environment. To evaluate the effects of short-term heat stress (HS) on these systems, confirming and deepening previous studies, female sea urchin Paracentrotus lividus were exposed for 7 days to 17 °C, 23 and 28 °C. Several biomarkers were detected such as the ferric reducing power (FRAP), ABTS-based total antioxidant capacity (TAC-ABTS), nitric oxide metabolites (NOx), total thiol levels (TTL), myeloperoxidase (MPO) and protease (PA) activities in the coelomic fluid (CF) and mitochondrial membrane potential (MMP), H2O2 content and intracellular pH (pHi) in eggs and coelomocytes, in which TAC-ABTS and reactive nitrogen species (RNS) were also analyzed. In the sea urchins exposed to HS, CF analysis showed a decrease in FRAP levels and an increase in TAC-ABTS, TTL, MPO and PA levels; in coelomocytes, RNS, MMP and H2O2 content increased, whereas pHi decreased; in eggs, increases in MMP, H2O2 content and pHi were found. In conclusion, short-term HS leads to changes in five out of the six CF biomarkers analyzed and functional alterations in the cells involved in either reproductive or immune activities.

Recognition of Arboviruses by the Mosquito Immune System

Arthropod-borne viruses (arboviruses) pose a significant threat to both human and animal health worldwide. These viruses are transmitted through the bites of mosquitoes, ticks, sandflies, or biting midges to humans or animals. In humans, arbovirus infection often results in mild flu-like symptoms, but severe disease and death also occur. There are few vaccines available, so control efforts focus on the mosquito population and virus transmission control. One area of research that may enable the development of new strategies to control arbovirus transmission is the field of vector immunology. Arthropod vectors, such as mosquitoes, have coevolved with arboviruses, resulting in a balance of virus replication and vector immune responses. If this balance were disrupted, virus transmission would likely be reduced, either through reduced replication, or even through enhanced replication, resulting in mosquito mortality. The first step in mounting any immune response is to recognize the presence of an invading pathogen. Recent research advances have been made to tease apart the mechanisms of arbovirus detection by mosquitoes. Here, we summarize what is known about arbovirus recognition by the mosquito immune system, try to generate a comprehensive picture, and highlight where there are still gaps in our current understanding.

Microplastics in feed cause sublethal changes in the intestinal microbiota and a non-specific immune response indicator of the freshwater crayfish Procambarus clarkii (Decapoda: Cambaridae)

Microplastics (MP) are a hazardous pollutant of global concern that threatens aquatic ecosystems and public health. We used the invasive, cosmopolitan, and environmentally versatile red swamp crayfish Procambarus clarkii as a model to study the effects of MP on the intestinal microbiome. Crayfish collected from the environment were compared with specimens exposed to recycled Polyethylene terephthalate (rPET) MP in feed (30%) for 96 h in the laboratory and a control group. We analyzed the 16S rRNA of the intestinal bacteria by PCR-DGGE and high-throughput sequencing. MP exposure caused dysbiosis of the intestinal microbiota, with an increase in Alphaproteobacteria and Actinobacteria. We detected higher abundance of opportunistic genera such as Klebsiella, Acinetobacter, Hydromonas, Pseudomonas, Gemmobacter, and Enterobacter on MP fed organisms. Moreover, MP exposure reduced the abundance of Clostridia and Bateroidetes, which are important for immune system development and pathogen prevention. Furthermore, MP exposure decreased the phenoloxidase (PO) immune response in crayfish. There was a significant difference in the richness of intestinal bacterial communities after consumption of food contaminated with MP, likely increasing the abundance of opportunistic bacteria in the intestinal microbiota. Our results suggest that MP alter the gut microbial composition and impair the health of P. clarkii.

Oxytetracycline-induced inflammatory process without oxidative stress in blue mussels Mytilus trossulus

Potentially harmful compounds including pharmaceuticals are commonly found in marine waters and sediments. Amongst those, antibiotics and their metabolites are detected worldwide in various abiotic (at concentrations as high as µg/L) and biotic matrices at ng/gram of tissue, posing a risk to non-target species exposed to them such as blue mussels. Amongst those, oxytetracycline (OTC) belongs to the most detected antibiotics in the marine environment. In this work, we concentrated on studying the potential induction of oxidative stress, activation of cellular detoxification processes (including Phase I and Phase II xenobiotic biotransformation enzymes) and multixenobiotic resistance pumps (Phase III) as well as changes in the aromatisation efficiency in Mytilus trossulus exposed to 100 μg/L OTC. Our results show that 100 µg/L OTC concentration did not provoke cellular oxidative stress and did not affect the expression of genes involved in detoxification processes in our model. Moreover, no effect of OTC on aromatisation efficiency was found. Instead, phenoloxidase activity measured in haemolymph was significantly higher in OTC exposed mussels than in those from the control (30.95 ± 3.33 U/L and 17.95 ± 2.75 U/L, respectively). OTC exposed mussels were also characterised by a tissue-dependant activation of major vault protein (MVP) gene expression (1.5 times higher in gills and 2.4 times higher in the digestive system) and a decreased expression of the nuclear factor kappa B-a (NF-κB) gene (3.4 times lower in the digestive system) when compared to those from the control. Additionally, an elevated number of regressive changes and inflammatory responses in tissues such as gills, digestive system and mantle (gonads) was observed underlining the worsening of bivalves' general health. Therefore, instead of a free-radical effect of OTC, we for the first time describe the occurrence of typical changes resulting from antibiotic therapy in non-target organisms like M. trossulus exposed to antibiotics such as OTC.

SDS-PAGE-Based Quantitative Assay of Hemolymph Proteins in Honeybees: Progress and Prospects for Field Application

In human and veterinary medicine, serum proteins are considered to be useful biomarkers for assessing the health and nutritional status of the organism. Honeybee hemolymph has a unique proteome that could represent a source of valuable biomarkers. Therefore, the aims of this study were to separate and identify the most abundant proteins in the hemolymph of worker honeybees to suggest a panel of these proteins that could represent useful biomarkers for assessing the nutritional and health status of the colonies and, finally, to analyze them in different periods of the year. Four apiaries were selected in the province of Bologna, and the bees were analyzed in April, May, July, and November. Thirty specimens from three hives of each apiary were sampled and their hemolymph was collected. The most represented bands obtained after 1D sodium-dodecyl-sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were cut from the gel, and the proteins were identified using an LC-ESI-Q-MS/MS System. A total of twelve proteins were unmistakably identified; the two most abundant proteins were apolipophorin and vitellogenin, which are known biomarkers of bee trophic and health status. The two other proteins identified were transferrin and hexamerin 70a, the first being involved in iron homeostasis and the second being a storage protein. Most of these proteins showed an increase from April to November, mirroring the physiological changes of honeybees during the productive season. The current study suggests a panel of biomarkers from honeybee hemolymph worth testing under different physiological and pathological field conditions.

Scutellaria polysaccharide mediates the immunity and antioxidant capacity of giant freshwater prawn (Macrobrachium rosenbergii)

The giant freshwater prawn (Macrobrachium rosenbergii) is a commercially valuable freshwater crustacean species that frequently appears a death affected by various diseases, resulting in substantial economic losses. Improving the survival rate of M. rosenbergii is a hot and essential issue for feeding the prawns. Scutellaria polysaccharide (SPS) extracted from Scutellaria baicalensis (a Chinese medicinal herb) is conducive to the survival rate of organisms by enhancing immunity and antioxidant ability. In this study, M. rosenbergii was fed 50, 100, and 150 mg/kg of SPS. The immunity and antioxidant capacity of M. rosenbergii were tested by mRNA levels and enzyme activities of related genes. The mRNA expressions of NF-κB, Toll-R, and proPO (participating in the immune response) in the heart, muscle, and hepatopancreas were decreased after four weeks of SPS feeding (P < 0.05). This indicated that long-term feeding of SPS could regulate the immune responses of M. rosenbergii tissues. The activity levels of antioxidant biomarkers, alkaline phosphatase (AKP), and acid phosphatase (ACP) had significant increases in hemocytes (P < 0.05). Moreover, catalase (CAT) activities in the muscle and hepatopancreas, as well as superoxide dismutase (SOD) activities in all tissues, significantly decreased after four weeks of culture (P < 0.05). The results demonstrated that long-term feeding of SPS could improve the antioxidant capacity of M. rosenbergii. In summary, SPS was conducive to regulating the immune capacity and enhancing the antioxidant capacity of M. rosenbergii. These results provide a theoretical basis for supporting SPS addition to the feed of M. rosenbergii.

Extracellular vesicles secreted by Brugia malayi microfilariae modulate the melanization pathway in the mosquito host

Vector-borne, filarial nematode diseases cause significant disease burdens in humans and domestic animals worldwide. Although there is strong direct evidence of parasite-driven immunomodulation of mammalian host responses, there is less evidence of parasite immunomodulation of the vector host. We have previously reported that all life stages of Brugia malayi, a filarial nematode and causative agent of Lymphatic filariasis, secrete extracellular vesicles (EVs). Here we investigate the immunomodulatory effects of microfilariae-derived EVs on the vector host Aedes aegypti. RNA-seq analysis of an Ae. aegypti cell line treated with B. malayi microfilariae EVs showed differential expression of both mRNAs and miRNAs. AAEL002590, an Ae. aegypti gene encoding a serine protease, was shown to be downregulated when cells were treated with biologically relevant EV concentrations in vitro. Injection of adult female mosquitoes with biologically relevant concentrations of EVs validated these results in vivo, recapitulating the downregulation of AAEL002590 transcript. This gene was predicted to be involved in the mosquito phenoloxidase (PO) cascade leading to the canonical melanization response and correspondingly, both suppression of this gene using RNAi and parasite EV treatment reduced PO activity in vivo. Our data indicate that parasite-derived EVs interfere with critical immune responses in the vector host, including melanization.

The tracheal immune system of insects - A blueprint for understanding epithelial immunity

The unique design of respiratory organs in multicellular organisms makes them prone to infection by pathogens. To cope with this vulnerability, highly effective local immune systems evolved that are also operative in the tracheal system of insects. Many pathogens and parasites (including viruses, bacteria, fungi, and metazoan parasites) colonize the trachea or invade the host via this route. Currently, only two modules of the tracheal immune system have been characterized in depth: 1) Immune deficiency pathway-mediated activation of antimicrobial peptide gene expression and 2) local melanization processes that protect the structure from wounding. There is an urgent need to increase our understanding of the architecture of tracheal immune systems, especially regarding those mechanisms that enable the maintenance of immune homeostasis. This need for new studies is particularly exigent for species other than Drosophila.

Clip-SP1 cleavage activates downstream prophenoloxidase activating protease (PAP) in Plutella xylostella

Melanization is a component of the humoral immune defense of insects and is induced by serine protease-mediated phenoloxidase (PO) catalysis. Prophenoloxidase (PPO) in the midgut of Plutella xylostella is activated by the CLIP domain serine protease (clip-SP) in response to Bacillus thuringiensis (Bt) infection, but the detailed signaling cascade following this activation is unknown. Here, we report that activation of clip-SP enhances PO activity in the P. xylostella midgut by cleaving three downstream PPO-activating proteases (PAPs). First, the expression level of clip-SP1 was increased in the midgut after Bt8010 infection of P. xylostella. Then, purified recombinant clip-SP1 was able to activate three PAPs - PAPa, PAPb and PAP3 - which in turn enhanced their PO activity in the hemolymph. Furthermore, clip-SP1 showed a dominant effect on PO activity compared to the individual PAPs. Our results indicate that Bt infection induces the expression of clip-SP1, which is upstream of a signaling cascade, to efficiently activate PO catalysis and mediate melanization in the midgut of P. xylostella. And it provides a basis for studying the complex PPO regulatory system in the midgut during Bt infection.

Two Secretory T2 RNases Act as Cytotoxic Factors Contributing to the Virulence of an Insect Fungal Pathogen

RNase T2 members are secreted by several pathogens or parasites during infection, playing various roles in pathogen-host interaction. However, functions of those members in biocontrol microbes targeting their hosts are still unknown. Here, we report that an insect fungal pathogen, Beauveria bassiana, produces two secretory RNase T2 members that act as cytotoxic factors, which were examined by insect bioassays using the targeted gene(s) disruption and overexpression strains. Overexpression strains displayed dramatically increased virulence, which was concurrent with few fungal cells and hemocytes in hemocoel, suggesting a cytotoxicity of the overexpressed gene products. In vitro assays using yeast-expressed proteins verified the cytotoxicity of the two members against insect cells, to which the cytotoxic effect was dependent on their RNases enzyme activities and glycosylation modification. Moreover, the excessive humoral immune responses triggered by the two ribonucleases were examined. These results suggested prospects of these two T2 ribonucleases for improvement of biocontrol agents.

Enhanced resistance to Bacillus thuringiensis Cry1Ac toxin mediated by the activation of prophenoloxidase in a cosmopolitan pest

Plutella xylostella has evolved resistance to Bacillus thuringiensis Cry1Ac toxin over a long evolutionary period. Enhanced immune response is an important factor in insect resistance to a variety of insecticides, and whether phenoloxidase (PO), an immune protein, is involved in resistance to Cry1Ac toxin in P. xylostella remains unclear. Here, spatial and temporal expression patterns showed that prophenoloxidase (PxPPO1 and PxPPO2) in the Cry1S1000-resistant strain was more highly expressed in eggs, 4th instar, head, and hemolymph than those in G88-susceptible strain. The results of PO activity analysis showed that after treatment with Cry1Ac toxin PO activity was about 3 times higher than that before treatment. Furthermore, knockout of PxPPO1 and PxPPO2 significantly increased the susceptibility to Cry1Ac toxin. These findings were further supported by the knockdown of Clip-SPH2, a negative regulator of PO, which resulted in increased PxPPO1 and PxPPO2 expression and Cry1Ac susceptibility in the Cry1S1000-resistant strain. Finally, the synergistic effect of quercetin showed that larval survival decreased from 100 % to <20 % compared to the control group. This study will provide a theoretical basis for the analysis of immune-related genes (PO) genes involved in the resistance mechanism and pest control of P. xylostella.

Role of hemocytin from Litopenaeus vannamei in immune response against microsporidian, Enterocytozoon hepatopenaei

Hemocytin, a multidomain hemostasis-related protein, is a homologous protein of hemolectin in Drosophila melanogaster and von Willebrand factor (vWF) in humans. The vWF type D (VWD) domain in hemocytin is thought to be a major mediator of hemocyte aggregation and the prophenoloxidase (proPO) activation system. Here, we report for the first time the role of hemocytin from Litopenaeus vannamei (LvHCT) against Enterocytozoon hepatopenaei (EHP), the pathogenic microsporidian causing hepatopancreatic microsporidiosis in Pacific white shrimp (L. vannamei). The LvHCT gene contains 58,366 base pairs consisting of 84 exons encoding for 4267 amino acids. Multiple sequence alignment and phylogenetic analysis revealed that LvHCT was clustered with crustacean hemocytins. Gene expression analysis by quantitative real-time RT-PCR showed that LvHCT in hemocytes was significantly upregulated at 9 and 11 days post-EHP cohabitation, which was consistent with EHP copy numbers in the infected shrimp. To further investigate the biological function of LvHCT in EHP infection, a recombinant protein containing an LvHCT-specific VWD domain (rLvVWD) was expressed in Escherichia coli. In vitro agglutination assays showed that rLvVWD was functionally representative of LvHCT and induced aggregation of pathogens, including Gram-negative and -positive bacteria, fungi, and EHP spore. LvHCT suppression resulted in higher EHP copy numbers and proliferation due to the lack of hemocytin-mediated EHP spore aggregation in LvHCT-silenced shrimp. Moreover, immune-related genes in the proPO-activating cascade and Toll, IMD and JAK/STAT signaling pathways were upregulated to eliminate the over-controlled EHP in LvHCT-silenced shrimp. Furthermore, the impaired phenoloxidase activity due to LvLGBP suppression was recovered after rLvVWD injection, suggesting that LvHCT may be directly involved in phenoloxidase activation. In conclusion, a novel LvHCT is involved in shrimp immunity against EHP via EHP spore aggregation and possible activation of the proPO-activating cascade.

Shell disease syndromes of decapod crustaceans

The term shell disease subsumes a number of debilitating conditions affecting the outer integument (the carapace) of decapod crustaceans, such as lobsters and crabs. Herein, we seek to find commonality in the aetiology and pathology of such conditions, and those cases that result in the progressive erosion of the cuticle through to the visceral tissues by a cocktail of microbial-derived enzymes including lipases, proteases and chitinases. Aquimarina spp. are involved in shell disease in many different crustaceans across a wide geographical area, but the overall view is that the condition is polymicrobial in nature leading to dysbiosis within the microbial consortium of the damaged cuticle. The role of environment, decapod behaviour and physiology in triggering this disease is also reviewed. Finally, we provide a conceptual model for disease aetiology and suggest several avenues for future research that could improve our understanding of how such factors trigger, or exacerbate, this condition.

Impact of Beauveria bassiana on antioxidant enzyme activities and metabolomic profiles of Spodoptera frugiperda

Spodoptera frugiperda is a pest that poses serious threat to the production of food and crops. Entopathogenic fungi, represented by Beauveria bassiana, has shown potential for S. frugiperda control. However, the mechanism of this biological control of pathogens is not fully understood, such as how antioxidant enzyme activities and metabolic profiles in S. frugiperda larvae are affected when infected by entomopathogenic fungi. This study assessed the antioxidant enzyme activities and shift in metabolomic profile in the S. frugiperda larvae infected with B.bassiana. The results indicate a pattern of initial increase and subsequent decrease in the activities of superoxide dismutase, catalase, and peroxidase in the B.bassiana-infected larvae. And the enzyme activities at 60 h of infection ended significantly lower than those of the uninfected larvae. A total of 93 differential metabolites were identified in the B.bassiana-infected larvae, of which 41 metabolites were up-regulated and 52 were down-regulated. These metabolites mainly included amino acids, nucleotides, lipids, carbohydrates, and their derivatives. Among the changed metabolites, cystathionine, L-tyrosine, L-dopa, arginine, alpha-ketoglutaric acid, D-sedoheptulose-7-phosphate and citric acid were significantly decreased in B. bassiana-infected larvae. This indicated that the fungal infection might impair the ability of S. frugiperda larvae to cope with oxidative stress, leading to a negative impact of organism fitness. Further analyses of key metabolic pathways reveal that B. bassiana infection might affect purine metabolism, arginine biosynthesis, butanoate metabolism, and phenylalanine metabolism of S. frugiperda larvae. The findings from this study will contribute to our understanding of oxidative stress on immune defense in insects, and offer fundamental support for the biological control of S. frugiperda.

M. Moustafa M, Fónagy A, Farag SM. Co-application of entomopathogenic fungi with chemical insecticides against Culex pipiens

Culex pipiens (Diptera: Culicidae) is a vector of many human and animal diseases. Its control is regarded as a preventative approach that is focused on effectively managing such diseases. In this context, dose response assays of two insecticides, bendiocarb and diflubenzuron were performed with two entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae against 3^rd instar C. pipiens larvae. The most effective agents, combination experiments as well as enzymatic activities of phenoloxidase (PO) and chitinase (CHI) were also assessed. The results showed that diflubenzuron was more effective at low concentrations (LC₅₀: 0.001 ppm) than bendiocarb (LC₅₀: 0.174 ppm), whereas M. anisopliae was more effective (LC₅₀: 5.2x10⁵ conidia/mL) than B. bassiana (LC₅₀: 7.5x10⁷ conidia/mL). Synergistic interactions were observed when diflubenzuron was applied at 2- and 4-days post- exposure to M. anisopliae, with the highest degree of synergism observed when diflubenzuron was applied 2 days post-fungal exposure (χ2 = 5.77). In contrast, additive interactions were recorded with all other insecticide-fungal combinations. PO activities significantly (p ≤ 0.05) increased during 24 h after a single diflubenzuron treatment as well as when diflubenzuron was applied prior to M. anisopliae, whereas suppressed after 24 h when M. anisopliae applied prior to diflubenzuron as well as after 48 h from single and combined treatments. CHI activity increased 24 h after both single and combined treatments, the activity remained elevated 48 h after a single diflubenzuron treatment and when diflubenzuron was applied after M. anisopliae. Histological study of the cuticle by transmission electron microscopy revealed abnormalities following single and combined treatments. Germination of the conidia and production of the mycelium that colonizes the lysing cuticle was obvious when diflubenzuron was applied 48 h after M. anisopliae exposure. Overall, these results demonstrate that M. anisopliae is compatible with diflubenzuron at lower concentrations and that combined applications can improve C. pipiens management.