WSSV-host interaction: Host response and immune evasion

Exploration and Characterization of Antimicrobial Peptides from Shrimp Litopenaeus Vannamei by A Genomic and Transcriptomic Approach

Antimicrobial peptides (AMPs) are crucial in the humoral immunity aspect of invertebrates' innate immune systems. However, studies on AMP discovery in the Pacific white shrimp (Litopenaeus vannamei) using omics data have been limited. Addressing the growing concern of antibiotic resistance in aquaculture, this study focused on the identification and characterization of AMPs in L. vannamei using advanced genomic and transcriptomic techniques. The genome of L. vannamei was performed to predict and identify a total of 754 AMP-derived genes, distributed across most chromosomes and spanning 24 distinct AMP families, and further identified 236 AMP-derived genes at the mRNA level in hemocytes. A subset of 20 chemically synthesized peptides, derived from these genes, exhibited significant antimicrobial activity, with over 85% showing effectiveness against key bacterial strains such as Staphylococcus aureus and Vibrio parahaemolyticus. The expression patterns of these AMPs were also investigated in different shrimp tissues and at various infection stages, revealing dynamic responses to pathogenic challenges. These findings highlight the significant potential of AMPs in L. vannamei as novel, effective alternatives to traditional antibiotics in aquaculture, offering insights into their diverse structural properties and biological functions. Together, this comprehensive characterization of the AMP repertoire in L. vannamei demonstrates the efficacy of using omics data for AMP discovery and lays the groundwork for their potential applications.

Identification of a FOXO gene and its roles in anti-WSSV infection through regulation of Dicers and Argos in Macrobrachium nipponense

Forkhead box O (FOXO) proteins are a subgroup of the forkhead family of transcription factors that play important roles in the immune response. In this study, we cloned and identified a FOXO gene named MnFOXO from Macrobrachium nipponense. The full-length cDNA of MnFOXO is 2086 bp and contains a 1302 bp open reading frame, which encodes 433 amino acids. MnFOXO consists of five low-complexity regions and a conserved DNA-binding domain (forkhead domain). Evolutionary analyses indicate that MnFOXO proteins cluster with FOXO proteins from crustaceans. Tissue distribution analysis showed that MnFOXO was expressed in all detected tissues, with relatively higher expression levels in the intestine, eyestalks, stomach, and hemocytes than in the hepatopancreas, gills, and heart. The expression levels of MnFOXO in the hepatopancreas and intestine were significantly up-regulated in M. nipponense infected with white spot syndrome virus (WSSV) at 24 and 48 h. Furthermore, knockdown of MnFOXO increased the expression of WSSV envelope protein VP28 during WSSV infection. Further studies showed that knockdown of the MnFOXO gene in M. nipponense inhibited the synthesis of Dicers (MnDicer1, MnDicer2) and Argonautes (MnArgo1, MnArgo2) during WSSV invasion. These findings suggest that MnFOXO positively regulates the expression of Dicers and Argos, and inhibits the expression of VP28. This study provides new evidence for understanding the role of FOXO in antiviral innate immunity in crustaceans.

Transcriptome analysis of Scylla paramamosain hepatopancreas response to mud crab dicistrovirus-1 infection

Scylla paramamosain, an economically significant crab, is widely cultivated worldwide. In recent years, S. paramamosain has faced a serious threat from viral diseases due to the expansion of culture scale and increased culture density. Among these, mud crab dicistrovirus-1 (MCDV-1) stands out as highly pathogenic, presenting substantial challenges to the healthy development of mud crab aquaculture. Therefore, a comprehensive understanding of the mud crab immune response to MCDV-1 infection is imperative for devising effective disease prevention strategies. In this study, transcriptomic analyses were conducted on the hepatopancreas of mud crabs infected with MCDV-1. The findings revealed a total of 5139 differentially expressed genes (DEGs) between healthy and MCDV-1 infected mud crabs, including 3327 upregulated and 1812 downregulated DEGs. Further analysis showed that mud crabs resist MCDV-1 infection by activating humoral immune-related pathways, including the MAPK signaling pathway, MAPK signaling pathway-fly, and Toll and Imd signaling pathway. In contrast, MCDV-1 infection triggers host metabolic disorders. Several immune-related vitamin metabolism pathways (ascorbate and aldarate metabolism, retinol metabolism, and nicotinate and nicotinamide metabolism) were significantly inhibited, which may create favorable conditions for the virus's self-replication. Notably, endocytosis emerged as significantly upregulated both in GO terms and KEGG pathways, with several viral endocytosis-related pathways showing significant activation. PPI network analysis identified 9 hub genes associated with viral endocytosis within the endocytosis. Subsequent GeneMANIA analysis confirmed the association of these hub genes with viral endocytosis. Both transcriptome data and qPCR analysis revealed a significant upregulation of these hub genes post MCDV-1 infection, suggesting MCDV-1 may use viral endocytosis to enter cells and facilitate replication. This study represents the first comprehensive report on the transcriptomic profile of mud crab hepatopancreas response to MCDV-1 infection. Future investigations should focus on elucidating the mechanisms through which MCDV-1 enters cells via endocytosis, as this may holds critical implications for the development of vaccine targets.

Complete genome of the new bacilliform virus that causes Milky Hemolymph Syndrome in Chionoecetes bairdi (Rathbun, 1924)

The genome of a new member of the Nimaviridae family has been sequenced. The Chionoecetes bairdi bacilliform virus (CbBV) causes Milky Hemolymph Syndrome (MHS) in Chionoecetes bairdi populations of the Pacific coast of Kamchatka. The CbBV genome is represented by double-stranded DNA with a length of 245,567 nucleotides containing 120 ORFs. Of these, 85 proteins had significant matches in the NCBI database, and 57 genes encoded capsid, envelope, tegument and nonstructural proteins. Comparative analysis of the genomes of CbBV and a number of representatives of the class nuclear arthropod large DNA viruses (NALDVs) made it possible to isolate 49 evolutionarily conserved orthologue core genes. Among them, 5 were multicopy genes, and 44 were single-copy genes. There were ancestral genes characteristic of all Naldaviricetes - per os infectivity complex genes, one DNA polymerase gene and one thymidylate synthase gene. Phylogenetic analysis of representatives of the Nimaviridae family revealed that the CbBV and Chionoecetes opilio bacilliform virus (CoBV) form an independent clade within the family separate from the clade containing WSSV strains. This is supported by data on the order and arrangement of genes in the genomes of nimaviruses that were identical within each clade but differed between them. In addition, a high identity of the genomes and proteomes of CbBV and CoBV (approximately 99%) was shown, and their identity with WSSV strains was no more than 33%. The data on the structure of the genome of the new virus that causes MHS in C. bairdi indicate that it belongs to the family Nimaviridae, genus Whispovirus. Thus, the CbBV infecting the commercially important species of Tanner crab in populations of the Pacific coast of Kamchatka is the second "wild" representative of replicating nimaviruses whose genome has been characterized after the CoBV that causes MHS in C. opilio in populations of the Sea of Japan. The discovery of a new member of the family that infects decapods indicates the prevalence of nimaviruses in marine ecosystems. The information obtained is important for understanding the evolution of representatives of the class of nuclear arthropod large DNA viruses. The discovery of a new nimavirus that causes MHS in Chionoecetes crabs, in contrast to the white spot syndrome (WSS) caused by WSSV strains, makes it relevant to identify two variants and possibly species within the family, namely, WSSV and Milky Hemolymph Syndrome virus (MHSV).

Characterization of DmToll and DmToll7 homologue in Litopenaeus vannamei based on structure analysis

Toll-like receptors (TLRs) are a family of pattern recognition receptors (PRRs) that recognize invading pathogens and activate downstream signaling pathways. The number of 10 Tolls is found in Litopenaeus vannamei but have not yet been identified as the corresponding Toll homologue of model animal. In this study, we predicted the three-dimensional (3D) structures of 10 LvTolls (LvToll1-10) with AlphaFold2 program. The per-residue local distance difference test (pLDDT) scores of LvTolls showed the predicted structure of LvTolls had high accuracy (pLDDT>70). By structural analysis, 3D structures of LvToll2 and LvToll3 had high similarity with Drosophila melanogaster Toll and Toll7, respectively. 3D structure of LvToll7 and LvToll10 were not similar to that of other LvTolls. Moreover, we also predicted that LvSpätzle4 had high structural similarity to DmSpätzle. There were 9 potential hydrogen bonds in LvToll2-LvSpätzle4 complex. Importantly, co-immunoprecipitation assay showed that LvToll2 could bind with LvSpätzle4. Collectively, this study provides new insight for researching invertebrate immunity by identifying the protein of model animal homologue.

A Negative Regulatory Feedback Loop within the JAK-STAT Pathway Mediated by the Protein Tyrosine Phosphatase DUSP14 in Shrimp

The JAK-STAT pathway is a central communication node for various biological processes. Its activation is characterized by phosphorylation and nuclear translocation of the transcription factor STAT. The regulatory balance of JAK-STAT signaling is important for maintenance of immune homeostasis. Protein tyrosine phosphatases (PTPs) induce dephosphorylation of tyrosine residues in intracellular proteins and generally function as negative regulators in cell signaling. However, the roles of PTPs in JAK-STAT signaling, especially in invertebrates, remain largely unknown. Pacific white shrimp Penaeus vannamei is currently an important model for studying invertebrate immunity. This study identified a novel member of the dual-specificity phosphatase (DUSP) subclass of the PTP superfamily in P. vannamei, named PvDUSP14. By interacting with and dephosphorylating STAT, PvDUSP14 inhibits the excessive activation of the JAK-STAT pathway, and silencing of PvDUSP14 significantly enhances humoral and cellular immunity in shrimp. The promoter of PvDUSP14 contains a STAT-binding motif and can be directly activated by STAT, suggesting that PvDUSP14 is a regulatory target gene of the JAK-STAT pathway and mediates a negative feedback regulatory loop. This feedback loop plays a role in maintaining homeostasis of JAK-STAT signaling and is involved in antibacterial and antiviral immune responses in shrimp. Therefore, the current study revealed a novel inhibitory mechanism of JAK-STAT signaling, which is of significance for studying the regulatory mechanisms of immune homeostasis in invertebrates.

Glycosaminoglycan lyase: A new competition between bacteria and the pacific white shrimp Litopenaeus vannamei

Horizontal gene transfer (HGT) is an important evolutionary force in the formation of prokaryotic and eukaryotic genomes. In recent years, many HGT genes horizontally transferred from prokaryotes to eukaryotes have been reported, and most of them are present in arthropods. The Pacific white shrimp Litopenaeus vannamei, an important economic species of arthropod, has close relationships with bacteria, providing a platform for horizontal gene transfer (HGT). In this study, we analyzed bacteria-derived HGT based on a high-quality genome of L. vannamei via a homology search and phylogenetic analysis, and six HGT genes were identified. Among these six horizontally transferred genes, we found one gene (LOC113799989) that contains a bacterial chondroitinase AC structural domain and encodes an unknown glycosaminoglycan (GAG) lyase in L. vannamei. The real-time quantitative PCR results showed that the mRNA expression level of LOC113799989 was highest in the hepatopancreas and heart, and after stimulation by Vibrio parahaemolyticus, its mRNA expression level was rapidly up-regulated within 12 h. Furthermore, after injecting si-RNA and stimulation by V. parahaemolyticus, we found that the experimental group had a higher cumulative mortality rate in 48 h than the control group, indicating that the bacteria-derived GAG lyase can reduce the mortality of shrimp with respect to infection by V. parahaemolyticus and might be related to the resistance of shrimp to bacterial diseases. Our findings contribute to the study of the function of GAGs and provide new insights into GAG-related microbial pathogenesis and host defense mechanisms in arthropods.

Estimation of Genetic Parameters for Growth and WSSV Resistance Traits in Litopenaeus vannamei

The current study aimed to provide a precise assessment of the genetic parameters associated with growth and white spot syndrome virus (WSSV) resistance traits in Pacific white shrimp (Litopenaeus vannamei). This was achieved through a controlled WSSV challenge assay and the analysis of phenotypic values of five traits: body weight (BW), overall length (OL), body length (BL), tail length (TL), and survival hour post-infection (HPI). The analysis included test data from a total of 1017 individuals belonging to 20 families, of which 293 individuals underwent whole-genome resequencing, resulting in 18,137,179 high-quality SNP loci being obtained. Three methods, including pedigree-based best linear unbiased prediction (pBLUP), genomic best linear unbiased prediction (GBLUP), and single-step genomic BLUP (ssGBLUP) were utilized. Compared to the pBLUP model, the heritability of growth-related traits obtained from GBLUP and ssGBLUP was lower, whereas the heritability of WSSV resistance was higher. Both the GBLUP and ssGBLUP models significantly enhanced prediction accuracy. Specifically, the GBLUP model improved the prediction accuracy of BW, OL, BL, TL, and HPI by 4.77%, 21.93%, 19.73%, 19.34%, and 63.44%, respectively. Similarly, the ssGBLUP model improved prediction accuracy by 10.07%, 25.44%, 25.72%, 19.34%, and 122.58%, respectively. The WSSV resistance trait demonstrated the most substantial enhancement using both genomic prediction models, followed by body size traits (e.g., OL, BL, and TL), with BW showing the least improvement. Furthermore, the choice of models minimally impacted the assessment of genetic and phenotypic correlations. Genetic correlations among growth traits ranged from 0.767 to 0.999 across models, indicating high levels of positive correlations. Genetic correlations between growth and WSSV resistance traits ranged from (-0.198) to (-0.019), indicating low levels of negative correlations. This study assured significant advantages of the GBLUP and ssGBLUP models over the pBLUP model in the genetic parameter estimation of growth and WSSV resistance in L. vannamei, providing a foundation for further breeding programs.

Immunological lectins in shrimp Penaeus vannamei challenged with infectious myonecrosis virus (IMNV) under low-salinity conditions

Lectins are proteins capable of recognizing and binding to glycan in a specific way. In invertebrates, lectins are a crucial group of Pattern Recognition Proteins (PRRs), activating cellular and humoral responses in the innate immune system. The shrimp Penaeus vannamei is the main crustacean cultivated worldwide, however, the productivity of cultures is strongly affected by diseases, mainly viral ones, such as Infectious Myonecrosis (IMN). Thus, we investigated the participation of five lectins (LvAV, LvCTL4, LvCTL5, LvCTLU, and LvLdlrCTL) in IMNV-challenged shrimp. We verified upregulation gene profiles of lectins after IMNV-challenge, especially in hepatopancreas and gills, in addition to an increase in total hemocytes count (THC) after to 12 h post-infection (hpi). The bioinformatics characterization also revealed several sites of post-translational modification (PTM), such as phosphorylation and glycosylation, which possibly influence the action and stabilization of these lectins. We conclude that LvLdlrCTL and LvCTL5 are the lectins with greater participation in the activation of the immune system against IMNV, showing the greatest potential for PTM, higher upregulation levels, and overlapping with the THC and IMNV viral load.

Bacterial and viral co-infections in aquaculture under climate warming: co-evolutionary implications, diagnosis, and treatment

Climate change and the associated environmental temperature fluctuations are contributing to increases in the frequency and severity of disease outbreaks in both wild and farmed aquatic species. This has a significant impact on biodiversity and also puts global food production systems, such as aquaculture, at risk. Most infections are the result of complex interactions between multiple pathogens, and understanding these interactions and their co-evolutionary mechanisms is crucial for developing effective diagnosis and control strategies. In this review, we discuss current knowledge on bacteria-bacteria, virus-virus, and bacterial and viral co-infections in aquaculture as well as their co-evolution in the context of global warming. We also propose a framework and different novel methods (e.g. advanced molecular tools such as digital PCR and next-generation sequencing) to (1) precisely identify overlooked co-infections, (2) gain an understanding of the co-infection dynamics and mechanisms by knowing species interactions, and (3) facilitate the development multi-pathogen preventive measures such as polyvalent vaccines. As aquaculture disease outbreaks are forecasted to increase both due to the intensification of practices to meet the protein demand of the increasing global population and as a result of global warming, understanding and treating co-infections in aquatic species has important implications for global food security and the economy.

Single-cell RNA-seq revealed heterogeneous responses and functional differentiation of hemocytes against white spot syndrome virus infection in Litopenaeus vannamei

Shrimp hemocytes are the vital immune cells participating in innate immune response to defend against viruses. However, the lack of specific molecular markers for shrimp hemocyte hindered the insightful understanding of their functional clusters and differential roles in combating microbial infections. In this study, we used single-cell RNA sequencing to map the transcriptomic landscape of hemocytes from the white spot syndrome virus (WSSV)-infected Litopenaeus vannamei and conjointly analyzed with our previous published single-cell RNA sequencing technology data from the healthy hemocytes. A total of 16 transcriptionally distinct cell clusters were identified, which occupied different proportions in healthy and WSSV-infected hemocytes and exerted differential roles in antiviral immune response. Following mapping of the sequencing data to the WSSV genome, we found that all types of hemocytes could be invaded by WSSV virions, especially the cluster 8, which showed the highest transcriptional levels of WSSV genes and exhibited a cell type-specific antiviral response to the viral infection. Further evaluation of the cell clusters revealed the delicate dynamic balance between hemocyte immune response and viral infestation. Unsupervised pseudo-time analysis of hemocytes showed that the hemocytes in immune-resting state could be significantly activated upon WSSV infection and then functionally differentiated to different hemocyte subsets. Collectively, our results revealed the differential responses of shrimp hemocytes and the process of immune-functional differentiation post-WSSV infection, providing essential resource for the systematic insight into the synergistic immune response mechanism against viral infection among hemocyte subtypes.

IMPORTANCE

Current knowledge of shrimp hemocyte classification mainly comes from morphology, which hinder in-depth characterization of cell lineage development, functional differentiation, and different immune response of hemocyte types during pathogenic infections. Here, single-cell RNA sequencing was used for mapping hemocytes during white spot syndrome virus (WSSV) infection in Litopenaeus vannamei, identifying 16 cell clusters and evaluating their potential antiviral functional characteristics. We have described the dynamic balance between viral infestation and hemocyte immunity. And the functional differentiation of hemocytes under WSSV stimulation was further characterized. Our results provided a comprehensive transcriptional landscape and revealed the heterogeneous immune response in shrimp hemocytes during WSSV infection.

MicroRNA sequencing analysis reveals immune responses in hepatopancreas of Fenneropenaeus penicillatus under white spot syndrome virus infection

White Spot Disease is one of the most harmful diseases of the red tail shrimp, which can cause devastating economic losses due to the highest mortality up to 100% within a few days. MicroRNAs (miRNAs) are large class of small noncoding RNAs with the ability to post-transcriptionally repress the translation of target mRNAs. MiRNAs are considered to have a significant role in the innate immune response of crustaceans, particularly in relation to antiviral defense mechanisms. Numerous crustacean miRNAs have been verified to be required in host immune defense against viral infection, however, till present, the miRNAs functions of F. penicillatus defense WSSV infection have not been studied yet. Here in this study, for the first time, miRNAs involved in the F. penicillatus immune defense against WSSV infection were identified using high-throughput sequencing platform. A total of 432 miRNAs were obtained including 402 conserved miRNAs and 30 novel predicted miRNAs. Comparative analysis between the WSSV-challenged group and the control group revealed differential expression of 159 microRNAs in response to WSSV infection. Among these, 48 were up-regulated and 111 were down-regulated. Ten candidate MicroRNAs associated with immune activities were randomly selected for qRT-PCR analysis, which confirming the expression profiling observed in the MicroRNA sequencing data. As a result, most differentially expressed miRNAs were down-regulated lead to increase the expression of various target genes that mediated immune reaction defense WSSV infection, including genes related to signal transduction, Complement and coagulation cascade, Phagocytosis, and Apoptosis. Furthermore, the genes expression of the key members in Toll and Imd signaling pathways and apoptotic signaling were mediated by microRNAs to activate host immune responses including apoptosis against WSSV infection. These results will help to understand molecular defense mechanism against WSSV infection in F. penicillatus and to develop an effective WSSV defensive strategy in shrimp farming.

Effects of geniposide on innate immunity and antiviral activity of Scyllaparamamosain

In this study, we examined the impact of geniposide on the innate immunity of the mud crab Scylla paramamosain, specifically in relation to WSSV infection. Through the use of in vitro cell culture experiments, we assessed the effects of geniposide on various parameters of hemocyte activity in S. paramamosain. Our findings revealed that high doses of geniposide inhibited hemocyte growth, with an optimal dose of 100 mg/kg determined. Additionally, we observed that geniposide increased the total hemocyte counts in S. paramamosain following WSSV infection. Geniposide also enhanced the enzymatic activities in hemolymph following treatment. The enzymes affected by geniposide encompassed ACP (acid phosphatase), POD (phenol oxidase catalase), PO (phenoloxidase), SOD (superoxide dismutase), CAT (catalase), and LZM (lysozyme). Furthermore, the activities of ACP, POD, PO, and LZM were also observed to increase subsequent to infection with WSSV. Notably, geniposide was found to enhance the phagocytosis of V. alginolyticus within the hemocytes. Geniposide can reduce hemocyte apoptosis rates after treatment, as well as hemocytes infected with WSSV. Furthermore, geniposide treatment significantly up-regulated the expression level of Myosin, but expression levels of Astakine, C-type lectin (CTL), STAT, JAK, proPO, minichromosome maintenance protein (MCM7), caspase-3 and crustin were down-regulated in the hemocytes. Additionally, geniposide treatment inhibited WSSV replication in hemocytes of S. paramamosain, and enhanced the survival rates of mud crabs following WSSV infection. These experimental results provide evidence that geniposide can improve the immune response by regulating humoral immunity and cellular immunity, and enhance pathogen resistance in S. paramamosain.

White spot syndrome virus hijacks host PP2A-FOXO axes to promote its propagation

Viruses have developed superior strategies to escape host defenses or exploit host components and enable their infection. The forkhead box transcription factor O family proteins (FOXOs) are reportedly utilized by human cytomegalovirus during their reactivation in mammals, but if FOXOs are exploited by viruses during their infection remains unclear. In the present study, we found that the FOXO of kuruma shrimp (Marsupenaeus japonicus) was hijacked by white spot syndrome virus (WSSV) during infection. Mechanistically, the expression of leucine carboxyl methyl transferase 1 (LCMT1) was up-regulated during the early stages of WSSV infection, which activated the protein phosphatase 2A (PP2A) by methylation, leading to dephosphorylation of FOXO and translocation into the nucleus. The FOXO directly promoted transcription of the immediate early gene, wsv079 of WSSV, which functioned as a transcriptional activator to initiate the expression of viral early and late genes. Thus, WSSV utilized the host LCMT1-PP2A-FOXO axis to promote its replication during the early infection stage. We also found that, during the late stages of WSSV infection, the envelope protein of WSSV (VP26) promoted PP2A activity by directly binding to FOXO and the regulatory subunit of PP2A (B55), which further facilitated FOXO dephosphorylation and WSSV replication via the VP26-PP2A-FOXO axis in shrimp. Overall, this study reveals novel viral strategies by which WSSV hijacks host LCMT1-PP2A-FOXO or VP26-PP2A-FOXO axes to promote its propagation, and provides clinical targets for WSSV control in shrimp aquaculture.

Identification of an Ortholog of MALT1 from Shrimp That Induces NF-κB-Mediated Antiviral Immunity

MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) serves as a pivotal mediator for NF-κB activation in response to a wide spectrum of transmembrane receptor stimuli. In the present study, a homolog of MALT1, named LvMALT1, is cloned from the Pacific white shrimp (Litopenaeus vannamei) and its potential function in shrimp innate immunity is explored. The open reading frame of LvMALT1 is 2364 bp that encodes 787 amino acids. The predicted LvMALT1 protein structure comprises a death domain, three immunoglobulin domains, and a caspase-like domain, exhibiting remarkable similarity to other homologs. LvMALT1 is a cytoplasmic-localized protein and could interact with LvTRAF6. Overexpression of LvMALT1 induces the activation of promoter elements governing the expression of several key antimicrobial peptides (AMPs), including penaeidins (PENs) and crustins (CRUs). Conversely, silencing of LvMALT1 leads to a reduction in the phosphorylation levels of Dorsal and Relish, along with a concomitant decline in the in vivo expression levels of multiple AMPs. Furthermore, LvMALT1 is prominently upregulated in response to a challenge by the white spot syndrome virus (WSSV), facilitating the NF-κB-mediated expression of AMPs as a defense against viral infection. Taken together, we identified a MALT1 homolog from the shrimp L. vannamei, which plays a positive role in the TRAF6/NF-κB/AMPs axis-mediated innate immunity.

SARS-COV-2 protein NSP9 promotes cytokine production by targeting TBK1

SARS-COV-2 infection-induced excessive or uncontrolled cytokine storm may cause injury of host tissue or even death. However, the mechanism by which SARS-COV-2 causes the cytokine storm is unknown. Here, we demonstrated that SARS-COV-2 protein NSP9 promoted cytokine production by interacting with and activating TANK-binding kinase-1 (TBK1). With an rVSV-NSP9 virus infection model, we discovered that an NSP9-induced cytokine storm exacerbated tissue damage and death in mice. Mechanistically, NSP9 promoted the K63-linked ubiquitination and phosphorylation of TBK1, which induced the activation and translocation of IRF3, thereby increasing downstream cytokine production. Moreover, the E3 ubiquitin ligase Midline 1 (MID1) facilitated the K48-linked ubiquitination and degradation of NSP9, whereas virus infection inhibited the interaction between MID1 and NSP9, thereby inhibiting NSP9 degradation. Additionally, we identified Lys59 of NSP9 as a critical ubiquitin site involved in the degradation. These findings elucidate a previously unknown mechanism by which a SARS-COV-2 protein promotes cytokine storm and identifies a novel target for COVID-19 treatment.

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.

Identification of an AnnexinB9 involve in white spot syndrome virus infection in red claw crayfish Cherax quadricarinatus

Annexin (Anx) family protein is a highly conserved protein family that plays important roles in immune defense of vertebrates and invertebrates against invading pathogens. In this study, a novel Anx was cloned and characterized from the red claw crayfish, Cherax quadricarinatus. The Open Reading Frame of CqAnxB9 consisted of 930 nucleotide bases pair and encoded 309 amino acids. The CqAnxB9 protein contained three repeat Anx domains and a typical KGLGT sequence. Tissue expression analysis showed that the expression levels of CqAnxB9 were mainly expressed in the intestine, hepatopancreas and hemocytes. After WSSV challenge, CqAnxB9 expression was up-regulated in the hematopoietic tissue (Hpt) cells. Moreover, knockdown of CqAnxB9 inhibited WSSV replication and VP28 expression, suggesting that CqAnxB9 plays a positive role in WSSV infection. Further studies revealed that recombinant CqAnxB9 protein was found to bind to the viral envelop protein VP28. All these findings indicate that new-found CqAnxB9 is likely to promote WSSV infection in crustaceans, which provides a better understanding of the pathogenesis of WSSV.

Integrated analysis of a miRNA-mRNA network related to immunity and autophagy in Macrobrachium rosenbergii infected with Aeromonas hydrophila

MicroRNAs (miRNAs) are a group of RNAs that regulate gene expression in the post-transcriptionally. miRNAs can regulate numerous processes, such as the immune response, due to their dynamic expression patterns. The giant freshwater prawn Macrobrachium rosenbergii is a major freshwater aquaculture prawn that is attacked by various bacteria, including Aeromonas hydrophila. For this study, we performed an analysis of the miRNA and mRNA transcriptome analysis of M. rosenbergii which was infected with A. hydrophila. We identified 56 differentially expressed miRNAs (DEMs) and 1542 differentially expressed mRNAs. Furthermore, an integrated analysis of miRNA-mRNA expression led to the identification of 729 differentially predicted target genes (DETGs) of the DEMs. Multiple functional categories related to immunity, apoptosis, and autophagy were found to be enriched in the DETGs. During the infection of M. rosenbergii by A. hydrophila, an elaborate regulatory network involving Toll and immune deficiency (IMD) signaling, mitogen-activated protein kinase (MAPK) signaling, lysosome, and cell apoptosis was formed by a complex interplay of 40 crucial DEMs and 22 DETGs, all associated with the immune and autophagy pathway. The findings suggest that infection with A. hydrophila triggers intricate responses in both miRNA and mRNA, significantly impacting immune and autophagy processes in M. rosenbergii.

MicroRNA sequencing analysis reveals injury-induced immune responses of Scylla paramamosain against cheliped autotomy

During pond culture or intensive culture system of crabs (mainly Eriocheir sinensis, Portunus trituberculatus and Scylla paramamosain), high-density farming has typically contributed to a higher limb autotomy level in juvenile animals, especially in S. paramamosain which has a high level of cannibalism. Due to the high limb autotomy level, the survival and growth rates in S. paramamosain farming are restricted, which limit the growth of the mud crab farming industry. MicroRNAs (miRNAs) are small noncoding RNAs that regulate a series of biological processes including innate immune responses by post-transcriptional suppression of their target genes. MiRNAs are believed to be crucial for innate immune process of host wound healing. Many miRNAs have been verified to be required in host immune responses to repair wound and to defense pathogen after tissue damage. However, to our best knowledge, the miRNAs functions of crustacean innate immune reactions against injury induced by limb autotomy have not been studied yet. Here in this study, for the first time, miRNAs involved in the S. paramamosain immune reactions against injury induced by cheliped autotomy were obtained by high-throughput sequencing. A total of 575 miRNAs (518 known miRNAs and 57 novel predicted miRNAs) were obtained, of which 141 differentially expressed microRNAs (93 up-regulated microRNAs and 48 down-regulated microRNAs) were revealed to be modified against cheliped autotomy, and the qPCR results of randomly selected miRNAs confirmed the expression patterns in the miRNAs sequencing data. Numerous immune-related target genes associated with innate immune system were mediated by miRNAs to induce host humoral immune and cellular immune defense to minimize acute physical damage. Furthermore, the genes expression in hemolymph coagulation and melanization pathways, as well as Toll and Imd signaling pathways were mediated by miRNAs to activate host immune responses including melanization and antimicrobial peptides for rapid wound healing and killing invaded pathogens. These results will help to understand injury-induced immune responses in crabs and to develop an effective control strategy of autotomy rate in crabs farming.

Resilience and probiotic interventions to prevent and recover from shrimp gut dysbiosis

To counter the recurrent outbreaks of bacterial (acute hepatopancreatic necrosis disease; AHPND) and viral (white spot disease; WSD) shrimp diseases, which still remain a threat to the global industry, shrimp gut microbiota research has been gaining more attention in recent years, and the use of probiotics in aquaculture has had promising results in improving shrimp gut health and immunity. In this review based on our studies on AHPND and WSD, we summarize our current understanding of the shrimp gastrointestinal tract and the role of the microbiota in disease, as well as effects of probiotics. We focus particularly on the concept of microbiota resilience, and consider strategies that can be used to restore shrimp gut health by probiotic intervention at a crucial time during gut microbiota dysbiosis. Based on the available scientific evidence, we argue that the use of probiotics potentially has an important role in controlling disease in shrimp aquaculture.

A simple sequence repeats marker of disease resistance in shrimp Litopenaeus vannamei and its application in selective breeding

The polymorphism of the simple sequence repeat (SSR) in the 5' untranslated coding region (5'-UTR) of the antiviral gene IRF (LvIRF) has been shown to be implicated in the resistance to viral pathogens in shrimp Litopenaeus vannamei (L. vannamei). In this study, we explored the potential of this (CT)n-SSR marker in disease resistance breeding and the hereditary property of disease resistance traits in offspring. From 2018 to 2021, eight populations were generated through crossbreeding by selecting individuals according to microsatellite genotyping. Our results demonstrated that shrimp with the shorter (CT)n repeat exhibited higher resistance to white spot syndrome virus (WSSV) or Decapod iridescent virus 1 (DIV1); meanwhile, these resistance traits could be inherited in offspring. Interestingly, we observed that the longer (CT)n repeats were associated with bacterial resistance traits. Accordingly, shrimp with longer (CT)n repeats exhibited higher tolerance to Vibrio parahaemolyticus infection. Taken together, these results indicate that the single (CT)n-SSR marker could be used to selective breeding for both resistance to virus and bacteria in shrimps.

Activity of bovine lactoferrin in resistance to white spot syndrome virus infection in shrimp

White spot syndrome virus (WSSV) is a notorious pathogen that has plagued shrimp farming worldwide for decades. To date, there are no known treatments that are effective against this virus. Lactoferrin (LF) is a protein with many bioactivities, including antiviral properties. In this study, the activities and mechanisms of bovine LF (bLF) against WSSV were analyzed. Our results showed that bLF treatment significantly reduced shrimp mortalities caused by WSSV infection. bLF was found to have the ability to bind to surfaces of both host cells and WSSV virions. These bindings may have been a result of bLF interactions with the host cellular chitin binding protein and F1 ATP synthase β subunit protein and the WSSV structural proteins VP28, VP110, VP150 and VP160B. bLF demonstrated potential for development as an anti-WSSV agent in shrimp culture. Furthermore, these reactionary proteins may play a role in WSSV infection.

Single von Willebrand factor C-domain protein confers host defense against white spot syndrome virus by functioning as a pattern recognition receptor in Macrobrachium nipponense

The single von Willebrand factor C-domain proteins (SVWCs), also known as Vago, are primarily found in arthropods. Their expression was induced by nutritional status, bacterial and viral infections. Despite the prominence of SVWCs in antiviral immunity, the detailed molecular mechanisms remain poorly explained. SVWC has been proposed to elicit antiviral activities through its function as an interferon analog. In contrast, herein, we illustrate that an SVWC homolog from Macrobrachium nipponense (MnSVWC) confers host defense against white spot syndrome virus (WSSV) and covert mortality nodavirus (CMNV) as a pattern recognition receptor (PRR). qRT-PCR analyses demonstrated that the expression of MnSVWC was enhanced upon WSSV infection in all detected tissues, including gills, nerve cords, and hemocytes. Coating WSSV with recombinant MnSVWC (rMnSVWC) promoted the phagocytic activity of hemocytes and subsequent clearance of invasive WSSV from the prawn. On the other hand, the knockdown of MnSVWC with RNAi improved the proliferation ability of WSSV and CMNV in the prawn. Analysis of ELISA and Co-immunoprecipitation (Co-IP) showed that rMnSVWC could bind WSSV by interacting with the vesicle proteins VP26 and VP28. Co-IP analysis verified the interaction between MnSVWC and calmodulin, which implies a vesicle protein-SVWC-calmodulin-clathrin-dependent mechanism underlying the hemocyte-mediated phagocytosis against WSSV. Subsequently, MnSVWC was recognized to activate the expression of transcription factor STAT and an interferon-stimulating gene Viperin, illustrating its involvement in modulating humoral immunity via activation of the JAK/STAT pathway after WSSV infection. These findings indicate that MnSVWC could bind to WSSV as a PRR and participate in the promotion of hemocyte-mediated phagocytosis and the activation of the JAK/STAT pathway in prawns.

WSSV exploits AMPK to activate mTORC2 signaling for proliferation by enhancing aerobic glycolysis

AMPK plays significant roles in the modulation of metabolic reprogramming and viral infection. However, the detailed mechanism by which AMPK affects viral infection is unclear. The present study aims to determine how AMPK influences white spot syndrome virus (WSSV) infection in shrimp (Marsupenaeus japonicus). Here, we find that AMPK expression and phosphorylation are significantly upregulated in WSSV-infected shrimp. WSSV replication decreases remarkably after knockdown of Ampkα and the shrimp survival rate of AMPK-inhibitor injection shrimp increases significantly, suggesting that AMPK is beneficial for WSSV proliferation. Mechanistically, WSSV infection increases intracellular Ca2+ level, and activates CaMKK, which result in AMPK phosphorylation and partial nuclear translocation. AMPK directly activates mTORC2-AKT signaling pathway to phosphorylate key enzymes of glycolysis in the cytosol and promotes expression of Hif1α to mediate transcription of key glycolytic enzyme genes, both of which lead to increased glycolysis to provide energy for WSSV proliferation. Our findings reveal a novel mechanism by which WSSV exploits the host CaMKK-AMPK-mTORC2 pathway for its proliferation, and suggest that AMPK might be a target for WSSV control in shrimp aquaculture.

Current Disease Threats for Cultivated Crab Eriocheir sinensis in China

The Chinese mitten crab, Eriocheir sinensis, is a commercially important crustacean in China due to its great commercial value and compatibility in a variety of aquaculture systems. However, increases in its production have been accompanied by the emergence of various diseases affecting yield, profit, and trading potential. In this study, we review the pathogenic agents associated with E. sinensis since the start of its commercial culture. The history of crab cultivation implies that increased pathogen transfer can occur as E. sinensis aquaculture grows because polyculture of E. sinensis with other aquaculture species is a prevalent practice. With this in mind, a special focus of this review is placed on pathogens that were initially discovered in other crustacean species but have since been demonstrated to infect and cause disease in E. sinensis. We expect that this review will not only offer recommendations for disease management in the E. sinensis aquaculture sector but will also advance other crustacean cultivation.

The first description of the blue swimming crab (Portunus pelagicus) transcriptome and immunological defense mechanism in response to white spot syndrome virus (WSSV)

In the global shellfish farming industry, white spot syndrome virus (WSSV) is a major cause of mortality and a significant factor in economic losses. However, information on molecular immune responses to WSSV in blue swimming crabs (Portunus pelagicus) has never been reported. First, viral loads were measured in the gills, hepatopancreas, intestines, subcuticular epithelium and hemocytes of blue swimming crabs (50 ± 10 g) (n = 4) after WSSV induction at 0, 24, 48 and 96 h post injection (hpi). A significant increase in WSSV particles was observed in gills at 48 and 96 hpi, as supported by histopathology. To further investigate the acute immune response to WSSV, total RNA from the same gill tissues at 0, 24, and 96 hpi was used to construct 16 high-quality RNA-seq cDNA libraries. In summary, 162,740 unigenes were discovered in these transcriptomic libraries analyzed with the GO, KO, KOG, NR, NT, PFAM and SwissProt databases. Intensive sequence analysis against control crabs using three major categories of gene oncology (GO) of DEGs, biological processes (BPs), molecular functions (MFs), and cellular components (CCs), indicated that induction of WSSV in blue swimming crabs strongly affected the immune responses of the target animals significantly during the early stages of infection from 24 to 96 hpi. Furthermore, KEGG identified approximately twenty biological pathways of gene expression that were both downregulated and upregulated. Interestingly, at 24 and 96 hpi, several immune-related genes involved in virus defense in the blue swimming crab, particularly crustin 2, chitinase, anti-lipopolysaccharide, proteinase inhibitor, and lysozyme, were highly expressed during the WSSV early infection stages. At the same time, viral mRNA transcripts, including WSV289, WSV343, WSV306, deoxyuridine 5' triphosphate nucleohydrolase, RING finger containing E3 ubiquitin-protein ligase WSV403 and WSV404, were recorded in the top twenty upregulated genes. Moreover, some immune-responsive genes related to growth development, such as chitinase, tubulin alpha and beta chains, trypsin, and the cathepsin family, were also differentially expressed during these periods. Expression validation of 20 upregulated and 11 downregulated immune-related genes using qRT‒PCR showed similar patterns with transcriptome information. Overall, the data showed that during WSSV infection, a number of immune-, metabolism-, and growth-related pathways were activated, and several of the pathways involved differed depending on the stage of virus invasion. These findings could effectively help us better understand the impact of WSSV on the physiology of blue swimming crabs and serve as a valuable reference for future research on the immune system and disease control in this target species.

Ring-stacked capsids of white spot syndrome virus and structural transitions with genome ejection

White spot syndrome virus (WSSV) is one of the largest DNA viruses and the major pathogen responsible for white spot syndrome in crustaceans. The WSSV capsid is critical for genome encapsulation and ejection and exhibits the rod-shaped and oval-shaped structures during the viral life cycle. However, the detailed architecture of the capsid and the structural transition mechanism remain unclear. Here, using cryo-electron microscopy (cryo-EM), we obtained a cryo-EM model of the rod-shaped WSSV capsid and were able to characterize its ring-stacked assembly mechanism. Furthermore, we identified an oval-shaped WSSV capsid from intact WSSV virions and analyzed the structural transition mechanism from the oval-shaped to rod-shaped capsids induced by high salinity. These transitions, which decrease internal capsid pressure, always accompany DNA release and mostly eliminate the infection of the host cells. Our results demonstrate an unusual assembly mechanism of the WSSV capsid and offer structural insights into the pressure-driven genome release.

Effects of length and sequence of long double-stranded RNAs targeting ribonucleotide reductase 2 of white spot syndrome virus (WSSV) on protective efficacy against WSSV

Long double-stranded RNA (dsRNA)-mediated RNA interference (RNAi) has been a well-known mechanism against white spot syndrome virus (WSSV) in cultured shrimp. In the present study, we investigated the protective efficacy of dsRNAs targeting the ribonucleotide reductase 2 (rr2) gene of WSSV according to length and target sequence location. To produce different lengths of dsRNAs, the 640 bp rr2 fragment (fragment I) was split into two equal 320 bp fragments (fragment II and III), then each 320 bp fragment was redivided into two 160 bp fragments (fragment IV, V, VI, and VII). After the synthesis of seven kinds of dsRNA fragments, dsRNAs with the same length were mixed with each other, then used for the evaluation of dsRNA's length effect in Penaeus vannamei. The result showed that 160 bp long dsRNAs were as effective as 320 and 640 bp long dsRNAs in the protection of shrimp against WSSV infection, suggesting that the dsRNA length of 160 bp would be enough to be used as RNAi-mediated WSSV suppression in P. vannamei. However, as the 160 bp long dsRNAs used in the length effect experiment were not a single dsRNA population but a mixture of 160 bp dsRNA fragments covering the parent 640 bp long dsRNA, the sequence effect was not included in this RNAi efficacy. In the experiments to know the effect of not only length but also sequence of rr2-targeting long dsRNAs on the protective efficacy against WSSV, dsRNAs with a length of 640 bp (fragment I) and 320 bp (fragment II, III) showed a constant high defense ability, but the protection degree of long dsRNAs with a length of 160 bp was different depending on the kinds of the fragment, suggesting that the RNAi efficacy of some rr2-targeting long dsRNAs with a length of 160 bp might have sequences that are variable according to experimental conditions. In conclusion, this study showed that the protective ability of long dsRNAs in shrimp against WSSV infection can be affected by the length and sequence of the long dsRNAs.

Heterologous Expression of Toxic White Spot Syndrome Virus (WSSV) Protein in Eengineered Escherichia coli Strains

Aquacultural shrimps suffer economic lost due to the white spot syndrome virus (WSSV) that is the most notorious virus for its fatality and contagion, leading to a 100% death rate on infected shrimps within 7 days. However, the infection of mechanism remains a mystery and crucial problem. To elucidate the pathogenesis of WSSV, a high abundance of protein is required to identify and characterize its functions. Therefore, the optimal WSSV355 overexpression was explored in engineered Escherichia coli strains, in particular C43(DE3) as a toxic tolerance strain remedied 40% of cell growth from BL21(DE3). Meanwhile, a trace amount of WSSV355 was observed in both strains. To optimize the codon of WSSV355 using codon adaption index (CAI), an overexpression was observed with 1.32 mg/mL in C43(DE3), while the biomass was decreased by 35%. Subsequently, the co-expression with pRARE boosted the target protein up to 1.93 mg/mL. Finally, by scaling up production of WSSV355 in the fermenter with sufficient oxygen supplied, the biomass and total and soluble protein were enhanced 67.6%, 44.9%, and 7.8% compared with that in flask condition. Herein, the current approach provides efficacious solutions to produce toxic proteins via codon usage, strain selection, and processing optimization by alleviating the burden and boosting protein production in E. coli.

Nuclear factor interleukin 3 (NFIL3) participates in regulation of the NF-κB-mediated inflammation and antioxidant system in Litopenaeus vannamei under ammonia-N stress

Nuclear factor interleukin 3 (NFIL3) is a critical upstream regulator of the NF-κB pathway. Nevertheless, the detailed molecular mechanism of NFIL3 and its function in shrimp have not been well characterized. In the present study, NFIL3 was identified and characterized from Litopenaeus vannamei. Molecular feature analysis revealed that the open reading frame (ORF) of LvNFIL3 was 2963 bp, which codes for a polypeptide of 516 amino acids with a conserved basic region leucine zipper (bZIP) domain. Sequence alignments and phylogenetic tree analysis showed that the amino acid sequence of LvNFIL3 shared 18.82%-98.07% identity with that of NFIL3 in other species, and was closely related to Penaeus monodon NFIL3. A core promoter in the 5' flanking region of LvNFIL3 was essential for regulation of transcription. LvNFIL3 mRNA was highly expressed in gills and hepatopancreas. Subcellular localization of the protein was observed almost exclusively in the nucleus. Amplification of mRNA by RT-qPCR showed that LvNFIL3 was induced in shrimp gills, hepatopancreas, and muscle after ammonia-N stress. Moreover, silencing of LvNFIL3 increased the mortality of shrimp exposed to ammonia-N. Furthermore, dual-luciferase reporter assay data suggested that LvNFIL3 was capable of activating the NF-κB pathway. Conversely, knockdown of LvNFIL3 decreased NF-κB homolog (Dorsal and Relish) and IkB homolog (Cactus) expression, as well as expression of anti-inflammatory cytokine (IL-16) and five antioxidant-related genes (HO-1, Mn-SOD, CAT, GPx, and GST), whereas NF-κB repressing factor (NKRF) and inflammation-related genes (TNFα and Spz) were upregulated. More importantly, LvNFIL3 knockdown exacerbated the pathology in hepatopancreas exposed to ammonia-N, and the total antioxidant capacity (T-AOC) and superoxide dismutase (T-SOD) were significantly decreased, resulting in a significant increased lipid peroxidation and protein carbonization. Taken together, these data suggest that LvNFIL3 was involved in ammonia-N tolerance in L. vannamei by regulating the inflammation and antioxidant system through the NF-κB pathway.

Dietary supplementation with Pediococcus pentosaceus enhances the innate immune response in and promotes growth of Litopenaeus vannamei shrimp

To reach the sustainable development goals on health management in Litopenaeus vannamei shrimp culture, Pediococcus pentosaceus AB01 was supplemented in shrimp diet. In this study, the control diet and three experimental diets containing P. pentosaceus AB01 (10⁸ , 10⁹ , 10¹⁰  CFU/g) were separately introduced to L. vannamei for a 28 days feeding trial. After the feeding trial, percent weight gain, feeding efficiency, and feed conversion ratio (FCR) were significantly elevated in L. vannamei administered with P. pentosaceus AB01 at 10⁹ and 10¹⁰ colony-forming unit (CFU)/g. Protease, amylase, and trypsin were found at higher levels in the probiotic-supplied groups. The feeding of shrimps with P. pentosaceus AB01 significantly increased innate immune response and levels of related biochemical parameters in the haemolymph. After the white spot syndrome virus (WSSV) challenge, supplementation of P. pentosaceus AB01 had significant positive effects (p < .05) on survival rate, compared to that of the control diet. The higher resistance of L. vannamei to WSSV might have been due to alterations in the gut microbiome composition and upregulation of the Toll-Like Receptor (TLR) signalling pathway. Hence, P. pentosaceus AB01 may be a promising alternative feed to promote growth rate, modulate microbiota composition, and enhance immunity in L. vannamei shrimp.

A TRIM-like protein restricts WSSV replication in the oriental river prawn, Macrobrachium nipponense

Tripartite motif (TRIM) proteins are a multifunctional family of ubiquitin E3 ligases involved in multiple biological processes. Studies have shown that many TRIM proteins in mammals play vital roles in the host defense against viral pathogens. In the present study, we identified a novel TRIM gene (MnTrim-like) from the oriental river prawn, Macrobrachium nipponense. Predicted MnTrim-like protein contains the characteristic RING finger domain. MnTrim-like was abundantly distributed in hepatopancreas, intestine, stomach, and gills. Upon white spot syndrome virus (WSSV) challenge, transcripts of MnTrim-like in the stomach were significantly up-regulated. Knockdown of MnTrim-like increased the expression of VP28 and decreased the synthesis of several antimicrobial peptides, including two crustins and one anti-lipopolysaccharide factor. Besides, silencing of these three antimicrobial peptides (AMPs) led to an increase in the expression of VP28 and WSSV copies. Moreover, it was found that injection of recombinant MnTrim-like protein with WSSV could decrease the transcription of VP28 and the number of virus particles. These results suggest that this MnTrim-like may restrict WSSV infection by positively regulating the expression of AMPs with antiviral activities and directly interacting with viral components. This study will broaden our understanding about the function of TRIM in crustacean during viral infection.

Characterization of four spliced isoforms of a transmembrane C-type lectin from Procambarus clarkii and their function in facilitating WSSV infection

C-type lectin (CTL) is an important pattern recognition receptor that play vital functions in the innate immunity. Many soluble CTLs in crustacean participate in the inhibition or promotion of white spot syndrome virus (WSSV) infection. However, whether transmembrane CTLs participate in WSSV infection in crustacean remains unknown. In the present study, four spliced isoforms of a transmembrane CTL (designated as PcTlec) from Procambarus clarkii were identified for the first time. The genome structure of PcTlec contains eight exons, six known introns, and one unknown intron. PcTlec-isoform1 is produced by intron retention, whereas PcTlec-isoform3 and PcTlec-isoform4 are produced by exon skipping. All of them contain the transmembrane domain and characteristic carbohydrate recognition domain (CRD). Four PcTlec isoforms were mainly expressed in the hepatopancreas, stomach, and intestine. After WSSV challenge, the expression levels of PcTlec-isoform1-4 in the intestine were upregulated. The knockdown of the region shared by four PcTlec isoforms evidently decreased the expression of WSSV envelope protein VP28 and the copies of viral particles. A recombinant protein (rPcTlec-CRD) containing the CRD that was shared by four PcTlec isoforms was acquired by procaryotic expression system. The injection of purified rPcTlec-CRD protein evidently increased the VP28 expression and WSSV copies during viral infection. Moreover, rPcTlec-CRD could directly bind to WSSV and interact with VP28 protein. These findings indicate that new-found transmembrane CTL isoforms in P. clarkii may act as viral receptors that facilitate WSSV infection. This study contributes to the recognition and understanding of the functions of transmembrane CTLs in crustacean in the infection of host by WSSV.

The MIP-T3 from shrimp Litopenaeus vannamei restricts white spot syndrome virus infection via regulating NF-κB activation

In vertebrate, MIP-T3 (microtubule-interacting protein associated with TRAF3) functions as a regulator of innate immune response that involves many cellular processes. However, the immune response regulated by shrimp (an arthropod) MIP-T3 remains unrevealed. In the present study, a MIP-T3 homolog from shrimp Litopenaeus vannamei (named as LvMIP-T3) was cloned and identified. LvMIP-T3 had a 2076 bp open reading frame (ORF), encoding a polypeptide of 691 amino acids that contained a classic coiled-coil domain in the C-terminal that showed a high degree of conservation to other homologs. LvMIP-T3 could interact with LvTRAF6, a member of the canonical NF-κB pathway, but not LvTRAF3, which implies that LvMIP-T3 is able to regulate NF-κB activity via its interaction with LvTRAF6. In addition, LvMIP-T3 was substantially inducted in response to white spot syndrome virus (WSSV) challenge, and we demonstrated that LvMIP-T3 facilitated the expression of NF-κB-mediated several Penaeidins (antimicrobial peptides, AMPs) to oppose infection. Taken together, we identified a MIP-T3 homolog from shrimp L. vannamei that played a positive role in the TRAF6/NF-κB/AMPs axis mediated defense response, which will contribute to better understand the regulator relationship among members of the canonical NF-κB pathway in shrimp, and provides some insights into disease resistance breeding.

Comparative Transcriptome Analysis Reveals That WSSV IE1 Protein Plays a Crucial Role in DNA Replication Control

For DNA viruses, the immediate-early (IE) proteins are generally essential regulators that manipulate the host machinery to support viral replication. Recently, IE1, an IE protein encoded by white spot syndrome virus (WSSV), has been demonstrated to function as a transcription factor. However, the target genes of IE1 during viral infection remain poorly understood. Here, we explored the host target genes of IE1 using RNAi coupled with transcriptome sequencing analysis. A total of 429 differentially expressed genes (DEGs) were identified from penaeid shrimp, of which 284 genes were upregulated and 145 genes were downregulated after IE1 knockdown. GO and KEGG pathway enrichment analysis revealed the identified DEGs are significantly enriched in the minichromosome maintenance (MCM) complex and DNA replication, indicating that IE1 plays a critical role in DNA replication control. In addition, it was found that Penaeus vannamei MCM complex genes were remarkably upregulated after WSSV infection, while RNAi-mediated knockdown of PvMCM2 reduced the expression of viral genes and viral loads at the early infection stage. Finally, we demonstrated that overexpression of IE1 promoted the expression of MCM complex genes as well as cellular DNA synthesis in insect High-Five cells. Collectively, our current data suggest that the WSSV IE1 protein is a viral effector that modulates the host DNA replication machinery for viral replication.

The Non-Receptor Protein Tyrosine Phosphatase PTPN6 Mediates a Positive Regulatory Approach From the Interferon Regulatory Factor to the JAK/STAT Pathway in Litopenaeus vannamei

SH2-domain-containing protein tyrosine phosphatases (PTPs), belonging to the class I PTP superfamily, are responsible for the dephosphorylation on the phosphorylated tyrosine residues in some proteins that are involved in multiple biological processes in eukaryotes. The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway transduce signaling responding to interferons and initiate cellular antiviral responses. The activity of the JAK/STAT pathway is generally orchestrated by the de-/phosphorylation of the tyrosine and serine residues of JAKs and STATs, in which the dephosphorylation processes are mainly controlled by PTPs. In the present study, an SH2-domian-contianing PTP, temporally named as LvPTPN6, was identified in Litopenaeus vannamei. LvPTPN6 shares high similarity with PTPN6s from other organisms and was phylogenetically categorized into the clade of arthropods that differs from those of fishes and mammals. LvPTPN6 was constitutively expressed in all detected tissues, located mainly in the cytoplasm, and differentially induced in hemocyte and gill after the challenge of stimulants, indicating its complicated regulatory roles in shrimp immune responses. Intriguingly, the expression of LvPTPN6 was regulated by interferon regulatory factor (IRF), which could directly bind to the LvPTPN6 promoter. Surprisingly, unlike other PTPN6s, LvPTPN6 could promote the dimerization of STAT and facilitate its nuclear localization, which further elevated the expression of STAT-targeting immune effector genes and enhanced the antiviral immunity of shrimp. Therefore, this study suggests a PTPN6-mediated regulatory approach from IRF to the JAK/STAT signaling pathway in shrimp, which provides new insights into the regulatory roles of PTPs in the JAK/STAT signaling pathway and contributes to the further understanding of the mechanisms of antiviral immunity in invertebrates.

Integrative analysis of the miRNA-mRNA regulation network in hemocytes of Penaeus vannamei following Vibrio alginolyticus infection

Penaeus vannamei is an important cultured shrimp that has high commercial value in the worldwide. However, the industry suffers heavy economic losses each year due to disease outbreaks caused by pathogenic bacteria. In the present study, after Vibrio alginolyticus infection, DNA damage in the hemocytes of the shrimp markedly increased, and autophagy and apoptosis increased significantly. Subsequently, hemocytes were sampled from the control and infected shrimp and sequenced for mRNA and microRNA (miRNA) 24 h after V. alginolyticus infection to better understand the response mechanism to bacterial infection in P. vannamei. We identified 1,874 and 263 differentially expressed mRNAs (DEGs) and miRNAs (DEMs) respectively, and predicted that 997 DEGs were targeted by DEMs. These DEGs were involved in the regulation of multiple signalling pathways, such as Toll and IMD signalling, TGF-beta signalling, MAPK signalling, and cell apoptosis, during Vibrio alginolyticus infection of the shrimp. We identified numerous mRNA-miRNA interactions, which provide insight into the defense mechanism that occur during the antimicrobial process of P. vannamei.

Interferon-Induced Protein 6-16 (IFI6-16) from Litopenaeus vannamei Regulate Antiviral Immunity via Apoptosis-Related Genes

A growing number of evidence shows that some invertebrates possess an antiviral immunity parallel to the interferon (IFN) system of higher vertebrates. For example, the IRF (interferon regulatory factor)–Vago–JAK/STAT regulatory axis in an arthropod, shrimp Litopenaeus vannamei (whiteleg shrimp) is functionally similar to the IRF–IFN–JAK/STAT axis of mammals. IFNs perform their cellular immunity by regulating the expression of target genes collectively referred to as IFN-stimulated genes (ISGs). However, the function of invertebrate ISGs in immune responses is almost completely unclear. In this study, a potential ISG gene homologous to the interferon-induced protein 6-16 (IFI6-16) was cloned and identified from L. vannamei, designated as LvIFI6-16. LvIFI6-16 contained a putative signal peptide in the N-terminal, and a classic IFI6-16-superfamily domain in the C-terminal that showed high conservation to other homologs in various species. The mRNA levels of LvIFI6-16 were significantly upregulated after the stimulation of poly (I:C) and challenges of white spot syndrome virus (WSSV). Moreover, silencing of LvIFI6-16 caused a higher mortality rate and heightened virus loads, suggesting that LvIFI6-16 could play a crucial role in defense against WSSV. Interestingly, we found that the transcription levels of several caspases were regulated by LvIFI6-16; meanwhile, the transcription level of LvIFI6-16 self was regulated by the JAK/STAT cascade, suggesting there could be a JAK/STAT–IFI6-16–caspase regulatory axis in shrimp. Taken together, we identified a crustacean IFI6-16 gene (LvIFI6-16) for the first time, and provided evidence that the IFI6-16 participated in antiviral immunity in shrimp.

Complementary Effects of Virus Population Are Required for Efficient Virus Infection

It is believed that the virions of a virus infecting a host may share the identical viral genome and characteristics. However, the role of genomic heterogeneity of the virions of a virus in virus infection has not been extensively explored. To address this issue, white spot syndrome virus (WSSV), a DNA virus infecting crustaceans, was characterized in the current study. In WSSV, differences in two nucleotides of the viral genome generated two types of WSSV, forming a virus population that consisted of Type A WSSV (encoding WSSV lncRNA-24) and Type B WSSV (encoding the wsv195 gene) at a ratio of 1:3. The virus populations in all virus-infected cells and tissues of different hosts exhibited a stable 1:3 structure. WSSV lncRNA-24 in Type A WSSV promoted virus infection by binding to shrimp and WSSV miRNAs, while the wsv195 gene in Type B WSSV played an essential role in virus infection. Loss of Type A WSSV or Type B WSSV in the WSSV population led to a 100-fold decrease in viral copy number in shrimp. Simultaneous loss of both types of WSSV prevented virus infection. These results indicated that the virus infection process was completed by two types of WSSV encoding different functional genes, revealing the complementary effects of WSSV population. Therefore, our study highlights the importance of the complementarity of virus population components in virus infection.

Catalytic and regulatory subunits of casein kinase 2 in Penaeus vannamei: Cloning, identification, expression profiles and functional analysis

As a highly conserved serine/threonine kinase with catalytic and regulatory subunits distributed ubiquitously in eukaryotic organisms, casein kinase 2 (CK2) is involved in multiple cellular functions, including immune regulation. In this study, two variants of the catalytic subunit (designated PvCK2α-1 and PvCK2α-2) and the regulatory subunit homologs (designated PvCK2β-1 and PvCK2β-2) in Penaeus vannamei were cloned and characterised. PvCK2α-1 and PvCK2α-2 shared the same genomic sequence consisting of six exons and five introns and encoded the same protein of 350 amino acids with an S_TKc domain, although there was a sequence deletion in 3'-UTR in PvCK2α-2 when compared with PvCK2α-1. Because of the sequence deletion in the ORF, PvCK2β-1 and PvCK2β-2 encoded different proteins with a CK_II_beta domain. The gene structures of PvCK2β-1 and PvCK2β-2 were identical and consisted of four exons and three introns. Semi-quantitative RT-PCR analyses revealed that PvCK2α and PvCK2β were constitutively expressed in all P. vannamei tissues tested, with higher levels detected in the immune-related tissues including hemocytes, hepatopancreas, gills and intestine. In these four tissue types, all variants of PvCK2α and PvCK2β were induced upon challenge with white spot syndrome virus (WSSV), Vibrio parahaemolyticus and Staphyloccocus aureus. The inhibition of PvCK2α, PvCK2β-1 and PvCK2βComb (the amount of PvCK2β-1 and PvCK2β-2) significantly reduced the survival rates of P. vannamei after WSSV infection and significantly increased the WSSV viral loads. Knockdown of PvCK2 by RNAi could distinctly decrease the expression of NF-κB related genes. All of these results suggest that PvCK2 plays an important role in the innate immune response to pathogen challenges in P. vannamei, with a positive role in anti-WSSV response which may be mediated through regulating the expression of NF-κB drived antimicrobial peptide genes.

The Role of microRNA-133 in Hemocyte Proliferation and Innate Immunity of Scylla paramamosain

MicroRNAs (miRNAs) are important signaling regulators that are involved in regulating the innate immunity of crustacean. However, few studies focus on the role of crustacean miRNAs in the cellular immunity have been reported. In this study, we showed that the expression of miR-133 was significantly up-regulated in the mud crab Scylla paramamosain after infection by white spot syndrome virus (WSSV) or Vibrio parahaemolyticus. The anti-miRNA oligonucleotide AMO-miR-133 was used to knock down miR-133 expression in S. paramamosain. The number of WSSV copies increased significantly in WSSV-infected crabs after miR-133 knockdown. Knockdown of miR-133 also enhanced the mortality rates of WSSV-infected and V. parahaemolyticus-infected mud crabs, and it significantly enhanced the expression of the astakine, which was confirmed by real-time quantitative PCR and western blot analysis. The data also indicate that miR-133 may affect hemocyte proliferation in S. paramamosain by regulating astakine expression. miR-133 Knockdown enhanced the apoptosis or phagocytosis of crab hemocytes, and increased the mortality of mud crabs after WSSV or V. parahaemolyticus infection. These results indicate that miR-133 is involved in the host immune response to WSSV and V. parahaemolyticus infection in mud crabs. Taken together, our research provides new insights for the control of viral or vibrio diseases in S. paramamosain.

Protein phosphorylation in hemocytes of Fenneropenaeus chinensis in response to white spot syndrome virus infection

Protein phosphorylation and dephosphorylation are the most common and important regulatory mechanisms in signal transduction, which play a vital role in immune defense response. Our previous study has found the level of tyrosine phosphorylation was significantly changed in the hemocytes of Fenneropenaeus chinensis upon white spot syndrome virus (WSSV) infection. In order to explore the relationship between protein phosphorylation and WSSV infection, the quantitative phosphoproteomics was employed to identify differential phosphorylated proteins in hemocytes of F. chinensis before and after WSSV infection, and elucidate the role of key differential phosphorylated proteins in WSSV infection process. The results showed that a total of 147 differential phosphorylated proteins were identified in the hemocytes, including 64 phosphorylated proteins and 83 dephosphorylated proteins, which were mostly enriched in pyruvate metabolism, TCA cycle, glycolysis, and ribosomal biosynthesis. Functional analysis of differential phosphorylated proteins showed that they were involved in cell apoptosis, cell phagocytosis, cell metabolism and antiviral infection. A total of 236 differential phosphorylation sites were found, including 91 modified sites in the phosphorylation proteins and 145 modified sites in the dephosphorylation proteins. Motif analysis showed that these phosphorylation sites could activate mitogen-activated protein kinase, P70 S6 kinase and other kinases in hemocytes. Moveover, the phosphorylation levels of eukaryotic protein initiation factor 4E binding proteins and histone H3 were further determined by ELISA and Western blotting, which both exhibited a significant increase post WSSV infection and reach their peak levels at 6 and 12 h, respectively. Moreover, we found that lactate, a metabolite closely related to pyruvate metabolism, TCA cycle and glycolysis, was significantly increased in the hemocytes after WSSV infection. This study revealed the protein phosphorylation response in hemocytes of F. chinensis to WSSV infection, which help to clarify the response characteristics and virus resistance mechanism of hemocytes in F. chinensis, and also facilitate further understanding of the interaction between WSSV and shrimp hemocytes.

Anti-lipopolysaccharide factors regulated by Stat, Dorsal, and Relish are involved in anti-WSSV innate immune defense in Macrobrachium nipponense

Anti-lipopolysaccharide factors (ALF) is an important antimicrobial peptide and critical effector molecule with a broad spectrum of antimicrobial activities in crustaceans. In addition to the previously reported five ALFs (MnALF1-5), another three ALFs [MnALF1, which is different from MnALF1 (ALF02818) that has been reported; MnALF6; and MnALF7] and an isoform of MnALF4 (MnALF4-isoform2) were newly identified from Macrobrachium nipponense in this study. MnALF6 has 134 amino acids and one single nucleotide polymorphism (SNP) in MnALF6 resulted in the change of 107th amino acid from E to D. Intron 1 retention produced longer transcript of MnALF6. The full length of MnALF7 has 691 bp with a 363 bp ORF encoding 120 amino acid protein. Three SNPs in MnALF2 resulted in the conversion of amino acids at positions 70, 73, and 91 from T⁷⁰I⁷³P⁹¹ to K⁷⁰L⁷³S⁹¹. The deletion of 13 bp in MnALF4 resulted in early termination of ORF, resulting in MnALF4-isoform2 with only 98 amino acids. The gDNAs of MnALF1, MnALF2, MnALF5, and MnALF6 contain three exons and two introns, while those of MnALF3 and MnALF7 contain three exons, one known intron, and one unknown intron. The MnALF1-7 in M. nipponense were widely distributed in multiple tissues. After white spot syndrome virus (WSSV) stimulation, the expression levels of MnALF1-7 changed. Knockdown of MnALF1-7 could evidently increase the expression of the envelope protein VP28 and the copy number of WSSV during viral infection. Further studies found that silencing of three transcription factors (Stat, Dorsal, and Relish) in M. nipponense significantly inhibit the synthesis of MnALF1-7 during the process of WSSV challenge. This study adds to the knowledge about the roles of ALFs in the innate immune responses to WSSV infection in M. nipponense.

A glimpse on metazoan ZNFX1 helicases, ancient players of antiviral innate immunity

The human zinc finger NFX1-type containing 1 (ZNFX1) is an interferon-stimulated protein associated to the outer mitochondrial membrane, able to bind dsRNAs and interact with MAVS proteins, promoting type I IFN response in the early stage of viral infection. An N-terminal Armadillo (ARM)-type fold and a large helicase core (P-loop) and zinc fingers confer RNA-binding and ATPase activities to ZNFX1. We studied the phylogenetic distribution of metazoan ZNFX1s, ZNFX1 gene expression trends and genomic and protein signatures during viral infection of invertebrates. Based on 221 ZNFX1 sequences, we obtained a polyphyletic tree with a taxonomy-consistent branching at the phylum-level only. In metazoan genomes, ZNFX1 genes were found either in single copy, with up to some tens of exons in vertebrates, or in multiple copies, with one or a few exons and one of them sometimes encompassing most of the coding sequence, in invertebrates like sponges, sea urchins and mollusks. Structural analyses of selected ZNFX1 proteins showed high conservation of the helicase region (P-loop), an overall conserved region and domain architecture, an ARM-fold mostly traceable, and the presence of intrinsically disordered regions of varying length and position. The remarkable over-expression of ZNFX1 in bivalve and gastropod mollusks infected with dsDNA viruses underscores the antiviral role of ZNFX1, whereas nothing similar was found in virus-infected nematodes and corals. Whether the functional diversification reported in the C. elegans ZNFX1 occurs in other metazoan proteins remains to be established.

Integrated Analysis of mRNA-Seq and MiRNA-Seq Reveals the Molecular Mechanism of the Intestinal Immune Response in Marsupenaeus japonicus Under Decapod Iridescent Virus 1 Infection

The intestine is not only an important digestive organ but also an important immune organ for shrimp; it plays a key role in maintaining homeostasis. Decapod iridescent virus 1 (DIV1) is a new type of shrimp-lethal virus that has received extensive attention in recent years. To date, most studies of the shrimp intestinal immune response under viral infections have relied on single omics analyses; there is a lack of systematic multi-omics research. In the current study, intestinal mRNA-seq and microRNA (miRNA)-seq analyses of Marsupenaeus japonicus under DIV1 infection were performed. A total of 1,976 differentially expressed genes (DEGs) and 32 differentially expressed miRNAs (DEMs) were identified. Among them, 21 DEMs were negatively correlated with 194 DEGs from a total of 223 correlations. Functional annotation analysis revealed that M. japonicus can regulate glycosaminoglycan biosynthesis (chondroitin sulfate, dermatan sulfate, and keratan sulfate), vitamin metabolism (retinol metabolism and ascorbate and aldarate metabolism), immune pathway activation (Toll and IMD signaling pathways, Wnt signaling pathway, IL-17 signaling pathway, and Hippo signaling pathway), immunity enzyme activity promotion (triose-phosphate isomerase), antimicrobial peptide (AMP) expression, reactive oxygen species (ROS) production, and cell apoptosis through miRNAs to participate in the host’s antiviral immune response, while DIV1 can influence Warburg effect-related pathways (pyruvate metabolism, glycolysis/gluconeogenesis, and citrate cycle), glycosphingolipid biosynthesis-related pathways (glycosphingolipid biosynthesis—globo and isoglobo series and glycosphingolipid biosynthesis—lacto and neolacto series), and the tight junction and adhesion junction of the intestinal mucosal epithelium through the host’s miRNAs and mRNA to promote its own invasion and replication. These results indicate that intestinal miRNAs play important roles in the shrimp immune response against DIV1 infection. This study provides a basis for further study of the shrimp intestinal antiviral immune response and for the formulation of effective new strategies for the prevention and treatment of DIV1 infection.

Litopenaeus vannamei peroxiredoxin 2-like is involved in WSSV infection by interaction with wsv089 and VP26

White spot syndrome virus (WSSV) is one of the most dangerous pathogen in shrimp aquaculture, which can cause extremely high mortality of shrimp. A full understanding of virus-host interactions is important to prevent viral infection. In the present study, wsv089-interacting molecule Litopenaeus vannamei peroxiredoxins2-like (LvPrx2-L) was selected by the yeast two-hybrid (Y2H) method. The interaction between wsv089 and LvPrx2-L was confirmed by far-western blotting assay. Interestingly, a further study indicated that LvPrx2-L interacted with VP26, and the molecular docking analysis supported the interaction between LvPrx2-L and VP26. Tissues distribution assay showed that LvPrx2-L was detected in all sampled tissues. The highest expression of LvPrx2-L was appeared in hemocytes. Following WSSV challenge, LvPrx2-L mRNA transcripts were significantly increased in the hemocytes and gill. In addition, the relative expression of IE1 and VP28 were remarkably up-regulated in the hepatopancreas and intestines of LvPrx2-L-knockdown shrimp. Moreover, the cumulative survival rate was significantly lower in the LvPrx2-L- silenced group compared with the control and blank groups. Furthermore, LvPrx2-L could regulate the expression of proPO, crustin, ALF3, and CAT at the mRNA level. These findings would further deepen our understanding of WSSV-host interaction and shrimp antiviral response. All these data might useful for assessing the function of LvPrx2-L in the immune response of crustacean.

Phenylalanine hydroxylase (PAH) plays a positive role during WSSV and Vibrio parahaemolyticus infection in Litopenaeus vannamei

Phenylalanine hydroxylase (PAH) is involved in immune defence reactions by providing the starting material, tyrosine, to synthesise catecholamines and melanin. PAH is an important metabolic enzyme of aromatic amino acids and the rate-limiting enzyme in the hydroxylation of amino acid phenylalanine to tyrosine. In the present study, a PAH gene, LvPAH, was cloned and identified from Litopenaeus vannamei. The open reading frame (ORF) of LvPAH was 1383 bp, encoding a protein of 460 amino acids comprised of an ACT domain and a Biopterin_H domain. LvPAH was constitutively expressed in healthy L. vannamei, with the highest expression levels in the eyestalk and the lowest in the hepatopancreas. Both white spot syndrome virus (WSSV) and Vibrio parahaemolyticus infection upregulated LvPAH expression in hemocytes, hepatopancreas and gills of L. vannamei. Inhibition of LvPAH resulted in a significantly lower survival rate of L. vannamei after WSSV infection than the control group, consistent with the observation that WSSV viral load was significantly higher in LvPAH-silenced L. vannamei. After a V. parahaemolyticus challenge, there was no significant difference between the survival rate of LvPAH-silenced and the control L. vannamei. However, the load of V. parahaemolyticus in LvPAH-silenced L. vannamei was significantly higher than the control population for L. vannamei. The effect of LvPAH on L. vannamei from a neuroendocrinological perspective was assessed by measuring l-DOPA, dopamine (DA) and noradrenaline (NE) levels in the hemocytes after the knockdown of LvPAH. The results showed that phenoloxidase (PO), l-DOPA and DA levels in the hemolymph of LvPAH-silenced L. vannamei were significantly decreased starting from 24hpi. In contrast, the NE levels in the hemolymph of shrimp decreased significantly at first and then increased. The results suggest that LvPAH may play an important role in antiviral and bacterial immunity in L. vannamei.