Co-interactive DNA-binding between a novel, immunophilin-like shrimp protein and VP15 nucleocapsid protein of white spot syndrome virus

Toxic effects of ammonia and thermal stress on the intestinal microbiota and transcriptomic and metabolomic responses of Litopenaeus vannamei

Ammonia and thermal stress frequently have harmful effects on aquatic animals. The intestine is an important barrier allowing the body to defend against stress. In this study, we investigated the intestinal microbiota and transcriptomic and metabolomic responses of Litopenaeus vannamei subjected to individual and combined ammonia and thermal stress. The results showed that obvious variation in the intestinal microbiota was observed after stress exposure, with increased levels of Firmicutes and decreased levels of Bacteroidetes and Planctomycetes. Several genera of putatively beneficial bacteria (Demequina, Weissella and Bacteroides) were abundant, while Formosa, Kriegella, Ruegeria, Rhodopirellula and Lutimonas were decreased; pathogenic bacteria of the genus Vibrio were increased under individual stress but decreased under combined stress. The intestinal transcriptome revealed several immune-related differentially expressed genes associated with the peritrophic membrane and antimicrobial processes in contrasting accessions. Haemolymph metabolomic analysis showed that stress exposure disturbed the metabolic processes of the shrimp, especially amino acid metabolism. This study provides insight into the underlying mechanisms associated with the intestinal microbiota, immunity and metabolism of L.vannamei in response to ammonia and thermal stress; ten stress-related metabolite markers were identified, including L-lactic acid, gulonic acid, docosahexaenoic acid, l-lysine, gamma-aminobutyric acid, methylmalonic acid, trans-cinnamate, N-acetylserotonin, adenine, and dihydrouracil.

Antigenic properties of VP15 from white spot syndrome virus in kuruma shrimp Marsupenaeus japonicus

White spot syndrome virus (WSSV) is known as one of the most lethal pathogenic viruses in shrimp causing massive damage to shrimp aquaculture industries. To date, no effective treatment or prevention has been found. In this study, five recombinant viral proteins VP15, VP19, VP24, VP26, and VP28 were expressed and purified in E. coli, which were employed as candidates against WSSV in Kuruma shrimp Marsupenaeus japonicus. In vivo antiviral assay in this study newly revealed that VP15 of major nucleocapsid protein, being known as a DNA-binding protein provided the substantial protection against the viral infection when pre-injected into shrimps. Furthermore, we also verified the immunogenic effects of purified VP15 and VP19 proteins produced in a silkworm-bacmid expression system. Taken together, our study identified VP15 as an effective candidate against WSSV infection in the Kuruma shrimp. It is interesting to uncover why and how VP15 is involved in the immune memory in shrimp in the future study.

Proteomic profiling of the white shrimp Litopenaeus vannamei (Boone, 1931) hemocytes infected with white spot syndrome virus reveals the induction of allergy-related proteins

To elucidate the proteomic responses of shrimp hemocytes to white spot syndrome virus (WSSV) infection at the proteome level, a quantitative shotgun proteomic analysis was performed to detect differentially synthesized proteins in infected hemocytes of white shrimp (Litopenaeus vannamei). We identified 1528 proteins associated to 203 gene ontology (GO) categories. The most representative GO categories were regulation of cellular processes, organic substance metabolic processes and nitrogen compound metabolic processes. Most of the 83 detected up-regulated proteins are involved in DNA regulation and organization and cell signaling. In contrast, most of the 40 down-regulated proteins were related to immune defense processes, protein folding, and development. Differentially induced proteins were further analyzed at the transcript level by RT-qPCR to validate the results. This work provides new insights into the alterations of L. vannamei hemocytes at the protein level at 12 h post-infection with WSSV. Interestingly, several of the up-regulated proteins are allergy-related proteins in humans. Based on our results, we suggest a deeper analysis of the effects of this interaction on the regulation of allergy related-proteins as their up-regulation during WSSV could represent a threat to human health.

Molecular determinants of Drosophila immunophilin FKBP39 nuclear localization

FK506-binding proteins (FKBPs) belong to a distinct class of immunophilins that interact with immunosuppressants. They use their peptidyl-prolyl isomerase (PPIase) activity to catalyze the cis-trans conversion of prolyl bonds in proteins during protein-folding events. FKBPs also act as a unique group of chaperones. The Drosophila melanogaster peptidyl-prolyl cis-trans isomerase FK506-binding protein of 39 kDa (FKBP39) is thought to act as a transcriptional modulator of gene expression in 20-hydroxyecdysone and juvenile hormone signal transduction. The aim of this study was to analyze the molecular determinants responsible for the subcellular distribution of an FKBP39-yellow fluorescent protein (YFP) fusion construct (YFP-FKBP39). We found that YFP-FKBP39 was predominantly nucleolar. To identify the nuclear localization signal (NLS), a series of YFP-tagged FKBP39 deletion mutants were prepared and examined in vivo. The identified NLS signal is located in a basic domain. Detailed mutagenesis studies revealed that residues K188 and K191 are crucial for the nuclear targeting of FKBP39 and its nucleoplasmin-like (NPL) domain contains the sequence that controls the nucleolar-specific translocation of the protein. These results show that FKBP39 possesses a specific NLS in close proximity to a putative helix-turn-helix (HTH) motif and FKBP39 may bind DNA in vivo and in vitro.

Antiviral action of the antimicrobial peptide ALFPm3 from Penaeus monodon against white spot syndrome virus

The anti-lipopolysaccharide factor isoform 3 (ALFPm3), the antimicrobial peptide from Penaeus monodon, possesses antibacterial and antiviral activities. Although the mechanism of action of ALFPm3 against bacteria has been revealed but its antiviral mechanism is still unclear. To further study how the ALFPm3 exhibits antiviral activity against the enveloped virus, white spot syndrome virus (WSSV), the ALFPm3-interacting proteins from WSSV were sought and identified five ALFPm3-interacting proteins, WSSV186, WSSV189, WSSV395, WSSV458, and WSSV471. Only the interaction between ALFPm3 and WSSV189, however, has been confirmed to be involved in anti-WSSV activity of ALFPm3. Herein, the interactions between ALFPm3 and rWSSV186, rWSSV395, rWSSV458, or rWSSV471 were further analyzed and confirmed by in vitro pull-down assay. Western blot analysis and immunoelectron microscopy showed that the uncharacterized proteins, WSSV186 and WSSV471, were nucleocapsid and envelope proteins, respectively. The decrease of shrimp survival after injection the shrimp with mixtures of each rWSSV protein, rALFPm3 and WSSV as compared to those injected with rALFPm3-neutralizing WSSV was clearly observed indicating that all rWSSV proteins could interfere with the neutralization effect of rALFPm3 on WSSV similar to that reported previously for WSSV189. Morphological change on WSSV after incubation with rALFPm3 was observed by TEM. The lysed WSSV virions were clearly observed where both viral envelope and nucleocapsid were dismantled. The results lead to the conclusion that the ALFPm3 displays direct effect on the viral structural proteins resulting in destabilization and breaking up of WSSV virions.

WSV399, a viral tegument protein, interacts with the shrimp protein PmVRP15 to facilitate viral trafficking and assembly

Viral responsive protein 15 (PmVRP15) has been identified as a highly up-regulated gene in the hemocyte of white spot syndrome virus (WSSV)-infected shrimp Penaeus monodon. However, the function of PmVRP15 in host-viral interaction was still unclear. To elucidate PmVRP15 function, the interacting partner of PmVRP15 from WSSV was screened by yeast two-hybrid assay and then confirmed by co-immunoprecipitation (Co-IP). Only WSV399 protein was identified as a PmVRP15 binding protein; however, the function of WSV399 has not been characterized. Localization of WSV399 on the WSSV virion was revealed by immunoblotting analysis (in vitro) and immunoelectron microscopy (in vivo). The results showed that WSV399 is a structural protein of the WSSV virion and is particularly located on the tegument. Gene silencing of wsv399 in WSSV-infected shrimp reduced the percentage of cumulative mortality by 74%, although the expression level of a viral replication marker gene, vp28, was not changed suggesting that WSV399 might not involved in viral replication but viral assembly. Because it has already been known that tegument proteins function in capsid transport during viral trafficking and assembly, interaction between PmVRP15 on hemocyte nuclear membrane and the WSV399 viral tegument protein suggests that PmVRP15 might be required for trafficking and assembly of WSSV during infection.

Molecular Mechanisms of White Spot Syndrome Virus Infection and Perspectives on Treatments

Since its emergence in the 1990s, White Spot Disease (WSD) has had major economic and societal impact in the crustacean aquaculture sector. Over the years shrimp farming alone has experienced billion dollar losses through WSD. The disease is caused by the White Spot Syndrome Virus (WSSV), a large dsDNA virus and the only member of the Nimaviridae family. Susceptibility to WSSV in a wide range of crustacean hosts makes it a major risk factor in the translocation of live animals and in commodity products. Currently there are no effective treatments for this disease. Understanding the molecular basis of disease processes has contributed significantly to the treatment of many human and animal pathogens, and with a similar aim considerable efforts have been directed towards understanding host-pathogen molecular interactions for WSD. Work on the molecular mechanisms of pathogenesis in aquatic crustaceans has been restricted by a lack of sequenced and annotated genomes for host species. Nevertheless, some of the key host-pathogen interactions have been established: between viral envelope proteins and host cell receptors at initiation of infection, involvement of various immune system pathways in response to WSSV, and the roles of various host and virus miRNAs in mitigation or progression of disease. Despite these advances, many fundamental knowledge gaps remain; for example, the roles of the majority of WSSV proteins are still unknown. In this review we assess current knowledge of how WSSV infects and replicates in its host, and critique strategies for WSD treatment.

Recent insights into host-pathogen interaction in white spot syndrome virus infected penaeid shrimp

Viral disease outbreaks are a major concern impeding the development of the shrimp aquaculture industry. The viral disease due to white spot syndrome virus (WSSV) observed in early 1990s still continues unabated affecting the shrimp farms and cause huge economic loss to the shrimp aquaculture industry. In the absence of effective therapeutics to control WSSV, it is important to understand viral pathogenesis and shrimp response to WSSV at the molecular level. Identification and molecular characterization of WSSV proteins and receptors may facilitate in designing and development of novel therapeutics and antiviral drugs that may inhibit viral replication. Investigations into host-pathogen interactions might give new insights to viral infectivity, tissue tropism and defence mechanism elicited in response to WSSV infection. However, due to the limited information on WSSV gene function and host immune response, the signalling pathways which are associated in shrimp pathogen interaction have also not been elucidated completely. In the present review, the focus is on those shrimp proteins and receptors that are potentially involved in virus infection or in the defence mechanism against WSSV. In addition, the major signalling pathways involved in the innate immune response and the role of apoptosis in host-pathogen interaction is discussed.

White spot syndrome virus VP51 interact with ribosomal protein L7 of Litopenaeus vannamei

The interaction between viral structural proteins and host plays key functions in viral infection. In previous studies, most research have been undertaken to explore the interaction of envelope structural proteins with host molecules. However, how the nucleocapsid proteins of WSSV interacted with host molecules remained largely unknown. In this study, the interaction of nucleocapsid protein VP51 and ribosomal protein L7 of Litopenaeus vannamei (LvRPL7) was reported. Furthermore, the mRNA transcriptional response of LvRPL7 to WSSV was investigated. The results showed that LvRPL7 was widely distributed in all analyzed tissues of L. vannamei. The high expression levels of LvRPL7 were found in the tissues of muscle and gills. The temporal expression of LvRPL7 in WSSV-challenged shrimp showed that LvRPL7 was up-regulated (P < 0.5) in the muscle at 8 h and 24 h post WSSV challenge and then restored to the normal levels. But the LvRPL7 expression was up-regulated (P < 0.5) in the hepatopancreas at 8 h post WSSV challenge and down-regulated at 12 h and 24 h post WSSV challenge. Indirect immunofluorescence assay indicated that LvRPL7 was mainly located on the surface and cytoplasm of hemocytes. Far-Western blotting showed that VP51 bound with LvRPL7. Moreover, ELISA results appeared that LvRPL7 interacted with VP51 in concentration dependent manner. Neutralization assay in vivo showed that anti-LvRPL7 antibody significantly delayed WSSV infection. Our results reveal that LvRPL7 was involved in WSSV infection.

Proteomic analysis of differentially expressed proteins in Fenneropenaeus chinensis hemocytes upon white spot syndrome virus infection

To elucidate molecular responses of shrimp hemocytes to white spot syndrome virus (WSSV) infection, two-dimensional gel electrophoresis was applied to investigate differentially expressed proteins in hemocytes of Chinese shrimp (Fenneropenaeus chinensis) at 24 h post infection (hpi). Approximately 580 protein spots were detected in hemocytes of healthy and WSSV-infected shrimps. Quantitative intensity analysis revealed 26 protein spots were significantly up-regulated, and 19 spots were significantly down-regulated. By mass spectrometry, small ubiquitin-like modifier (SUMO) 1, cytosolic MnSOD, triosephosphate isomerase, tubulin alpha-1 chain, microtubule-actin cross-linking factor 1, nuclear receptor E75 protein, vacuolar ATP synthase subunit B L form, inositol 1,4,5-trisphosphate receptor, arginine kinase, etc., amounting to 33 differentially modulated proteins were identified successfully. According to Gene Ontology annotation, the identified proteins were classified into nine categories, consisting of immune related proteins, stimulus response proteins, proteins involved in glucose metabolic process, cytoskeleton proteins, DNA or protein binding proteins, proteins involved in steroid hormone mediated signal pathway, ATP synthases, proteins involved in transmembrane transport and ungrouped proteins. Meanwhile, the expression profiles of three up-regulated proteins (SUMO, heat shock protein 70, and arginine kinase) and one down-regulated protein (prophenoloxidase) were further analyzed by real-time RT-PCR at the transcription level after WSSV infection. The results showed that SUMO and heat shock protein 70 were significantly up-regulated at each sampling time point, while arginine kinase was significantly up-regulated at 12 and 24 hpi. In contrast, prophenoloxidase was significantly down-regulated at each sampling time point. The results of this work provided preliminary data on proteins in shrimp hemocytes involved in WSSV infection.

Discovery of immune molecules and their crucial functions in shrimp immunity

Several immune-related molecules in penaeid shrimps have been discovered, most of these via the analysis of expressed sequence tag libraries, microarray studies and proteomic approaches. These immune molecules include antimicrobial peptides, serine proteinases and inhibitors, phenoloxidases, oxidative enzymes, clottable protein, pattern recognition proteins, lectins, Toll receptors, and other humoral factors that might participate in the innate immune system of shrimps. These molecules have mainly been found in the hemolymph and hemocytes, which are the main sites where immune reactions take place, while some are found in other immune organs/tissues, such as the lymphoid organs, gills and intestines. Although the participation of some of these immune molecules in the shrimp innate immune defense against invading pathogens has been demonstrated, the functions of many molecules remain unclear. This review summarizes the current status of our knowledge concerning the discovery and functional characterization of the immune molecules in penaeid shrimps.

Reprint of: Virus-binding proteins and their roles in shrimp innate immunity

Disease outbreaks caused by viral pathogens constitute a major limitation to development of the shrimp aquaculture industry. Many research have been conducted to better understand how host shrimp respond to viral infections with the aim of using the gained knowledge to develop better strategies for disease management and control. One approach has been to study the interactions between host and viral proteins, and particularly host virus-binding proteins that might play an important role in the viral infection process. Within the past five years, increasing numbers of virus-binding proteins (VBPs) have been reported in shrimp. Characterization of these molecules has emphasized on their potential therapeutic applications by demonstrating their activities in inhibition of viral replication via in vivo neutralization assay. However, signaling to induce innate antiviral immune responses as a consequence of binding between viral proteins and VBPs remain to be fully elucidated.

Virus-binding proteins and their roles in shrimp innate immunity

Disease outbreaks caused by viral pathogens constitute a major limitation to development of the shrimp aquaculture industry. Many research have been conducted to better understand how host shrimp respond to viral infections with the aim of using the gained knowledge to develop better strategies for disease management and control. One approach has been to study the interactions between host and viral proteins, and particularly host virus-binding proteins that might play an important role in the viral infection process. Within the past five years, increasing numbers of virus-binding proteins (VBPs) have been reported in shrimp. Characterization of these molecules has emphasized on their potential therapeutic applications by demonstrating their activities in inhibition of viral replication via in vivo neutralization assay. However, signaling to induce innate antiviral immune responses as a consequence of binding between viral proteins and VBPs remain to be fully elucidated.

Effects of high salinity, high temperature and pH on capsid structure of white spot syndrome virus

The structural stability of white spot syndrome virus (WSSV) capsids at high salinity, high temperature and various pH values was studied. To obtain the viral capsids, the nucleocapsids were treated with high salinity. The results showed that high salinity treatment can cause the dissociation of VP15 and most of VP95 from the nucleocapsid, but there were no noticeable alterations in morphology and ultrastructure of the nucleocapsid and capsid. The capsids retained morphological integrity at temperatures <45°C but became aberrant at >60°C. In addition, the capsids were relatively resistant to strong acid conditions and were tolerant to a broad pH range of 1 to 10. However, morphological change occurred at pH 10.5. The capsids broke up into small pieces at pH 11 and completely degraded in 0.1 and 1.0 M NaOH. These results indicated that the WSSV capsid is acid-stable and alkali-labile.

Host and virus protein interaction studies in understanding shrimp virus gene function

Protein-protein interaction studies have been widely used in several fields to characterize an unknown protein. This in turn helps to find out several pathways to understand a complex mechanism or discover a drug for treatment. Among the methods, yeast two-hybrid has widely been used in human, animal and plant research studies. This aspect of research has also been found useful in understanding the shrimp virus gene function. With respect to White spot syndrome virus, interaction studies have been applied to elucidate virus structure, understand the mode of entry of the virus, mechanism of virus replication and also to discover some of the host anti-viral proteins. Interaction studies on other shrimp viruses are scanty and only few reports available on Yellow head virus and Taura syndrome virus. All these findings are still in preliminary stage and lot more studies are necessary to have the clear picture. Protein interaction research on other shrimp viruses are still lacking. Considering all these, it appears that this field of research has a wide scope to understand the virulence mechanism of shrimp viruses where very little information is available till date.