Involvement of interaction between viral VP466 and host tropomyosin proteins in virus infection in shrimp

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

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

Proteomic Polyphenism in Color Morphotypes of Diaphorina citri, Insect Vector of Citrus Greening Disease

Diaphorina citri is a vector of "Candidatus Liberibacter asiaticus" (CLas), associated with citrus greening disease. D. citri exhibit at least two color morphotypes, blue and non-blue, the latter including gray and yellow morphs. Blue morphs have a greater capacity for long-distance flight and transmit CLas less efficiently as compared to non-blue morphs. Differences in physiology and immunity between color morphs of the insect vector may influence disease epidemiology and biological control strategies. We evaluated the effect of CLas infection on color morph and sex-specific proteomic profiles of D. citri. Immunity-associated proteins were more abundant in blue morphs as compared to non-blue morphs but were upregulated at a higher magnitude in response to CLas infection in non-blue insects. To test for differences in color morph immunity, we measured two phenotypes: (1) survival of D. citri when challenged with the entomopathogenic fungus Beauveria bassiana and (2) microbial load of the surface and internal microbial communities. Non-blue color morphs showed higher mortality at four doses of B. bassinana, but no differences in microbial load were observed. Thus, color morph polyphenism is associated with two distinct proteomic immunity phenotypes in D. citri that may impact transmission of CLas and resistance to B. bassiana under some conditions.

Screening for the Proteins That Can Interact with Grouper Nervous Necrosis Virus Capsid Protein

Nervous necrosis virus (NNV) can infect many species of fish and has an 80-100% mortality rate. NNV capsid protein (NNVCP) is the only structural protein of NNV, but there are few studies on the protein-protein interaction between NNVCP and the host cell. To investigate NNV morphogenesis, native NNV capsid protein (NNVCP) was used to screen for protein-protein interactions in this study. The results identified that 49 grouper optic nerve proteins can interact with NNVCP and may function as putative receptor or co-receptor, cytoskeleton, glucose metabolism and ATP generation, immunity, mitochondrial ion regulation, and ribosomal proteins. Creatine kinase B-type (CKB) is one of those 49 optic nerve proteins. CKB, a kind of enzyme of ATP generation, was confirmed to interact with NNVCP by far-Western blot and showed to colocalize with NNVCP in GF-1 cells. Compared to the control, the expression of CKB was significantly induced in the brain and eyes infected with NNV. Moreover, the amount of replication of NNV is relatively high in cells expressing CKB. In addition to providing the database of proteins that can interact with NNVCP for subsequent analysis, the results of this research also verified that CKB plays an important role in the morphogenesis of NNV.

Potential roles of insect Tropomyosin1-X1 isoform in the process of Candidatus Liberibacter asiaticus infection of Diaphorina citri

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is the transmitting vector of Candidatus Liberibacter asiaticus (CLas), which causes citrus disease Huanglongbing (HLB). In recent years, control of HLB has been achieved by reducing the vector population. In the present study, we identified an isoform of D. citri tropomyosin (herein designated as DcTm1-X1). DcTm1-X1 was down-regulated in CLas-infected ACPs compared with uninfected ACPs. Bioinformatics analysis revealed that the full-length DcTm1-X1 is 2955 bp and encodes a protein of 284 amino acids with a deduced molecular weight of 32.15 kDa. Phylogenetic tree analysis suggested that DcTm1-X1 shares a high amino acid identity with its homolog in Acyrthosiphon pisum. Higher DcTm1-X1 expression levels were found in the leg of the psyllid by reverse transcription quantitative PCR (RT-qPCR). According to Blue Native PAGE analysis and mass spectrometric analysis, DcTm1-X1 interacts with citrate synthase (CS) and V-type proton ATPase subunit B-like (VAT). In addition, knockdown of DcTm1-X1 by RNA interference (RNAi) significantly increased the mortality rate of nymphs and the infection rate of CLas at different time points. Taken together, our results show that DcTm1-X1 might play an important role in response to CLas, but also lay a foundation for further research on the functions of DcTm1-X1.

Identification of Litopenaeus vannamei BiP as a novel cellular attachment protein for white spot syndrome virus by using a biotinylation based affinity chromatography method

White spot syndrome virus (WSSV) is a dangerous threat to shrimp farming that also attacks a wide range of crustaceans. Knowledge of the surface protein-protein interactions between the pathogen and host is very crucial to unraveling the molecular pathogenesis mechanisms of WSSV. In this study, LvBiP (Litopenaeus vannamei immunoglobulin heavy-chain-binding protein) was identified as a novel WSSV binding protein of L. vannamei by a biotinylation based affinity chromatography method. By using pull-down and ELISA assays, the binding of recombinant LvBiP to WSSV was proved to be specific and ATP- dependent. The interaction was also confirmed by the result of co-immunoprecipitation assay. Immunofluorescence studies revealed the co-localization of LvBiP with WSSV on the cell surface of shrimp haemocytes. Additionally, LvBiP is likely to play an important role in WSSV infection. Treatment of gill cellular membrane proteins (CMPs) with purified rLvBiP and antibody that specifically recognizes LvBiP, led to a significant reduction in the binding of WSSV to gill CMPs. In the in vivo neutralization assay, rLvBiP and anti-LvBiP polyclonal antibody partially blocked the infection of WSSV. Taken together, the results indicate that LvBiP, a molecular chaperon of the HSP70 family, is a novel host factor involved at the step of attachment of the WSSV to the host cells and a potential candidate of therapeutic target.

The interaction of Rotavirus A pig/China/NMTL/2008/G9P[23] VP6 with cellular beta-actin is required for optimal RV replication and infectivity

VP6 forms the intermediate layer of the rotavirus (RV) capsid, and it plays important roles after RV penetration and uncoating. These functions rely on its ability to interact with host cell proteins. To gain further insights into the role of VP6 in porcine RV (PoRV) infection, a glutathione S-transferase pull-down assay was utilized to find unknown cellular factors that interact with VP6. In this study, beta-actin, tropomyosin 1, and 40S ribosomal protein S16 were identified as interaction partners of VP6 by mass spectrometry and co-immunoprecipitation. The interaction with beta-actin was further studied. By immunoelectron microscopy, we observed VP6 proteins that labeled with colloidal gold localized on the actin microfilaments at the early stage of PoRV infection, we also found VP6 distributed in the ribosome, mitochondria, endoplasmic reticulum and nucleus in the infected cells. Actin binding protein spin-down assays verified PoRV double-layered particles (DLPs) bound to F-actin in vitro, but didn't have actin polymerization enhancement activity. After a small interfering RNA (siACTB) was used to knock down beta-actin expression, PoRV VP6 expression and the infection rates of newly synthesized virions releasing into culture supernatants decreased dramatically. Our results confirm and extend previous reports indicating that the interaction between PoRV VP6 and beta-actin plays vital roles in the PoRV lifecycle.

The promotion of cytoskeleton integration and redox in the haemocyte of shrimp Litopenaeus vannamei after the successive stimulation of recombinant VP28

VP28 protein has been reported to work as a "vaccine" to protect the host from white spot syndrome, but the detailed mechanism of vaccination with VP28 protein in shrimp is still far from well understood. In the present study, whole transcriptomes of shrimp haemocytes were sequenced using the SOLiD4 platform after the successive VP28 stimulation. Eight single-end fragment libraries were constructed and sequenced in the four groups including the VP28-VP28, PBS-VP28, PBS-PBS and BLANK group, and there were 243,949,667 single-end reads with length of 50bp obtained totally, with 14,800 genes further identified. After reads mapping and transcript assembling, 1027, 1539, 1158, 1091 and 1300 genes in five differentially expressed gene lists were obtained in the comparison of VP28-VP28 versus PBS-VP28, VP28-VP28 versus PBS-PBS, VP28-VP28 versus BLANK, PBS-VP28 versus PBS-PBS and PBS-VP28 versus BLANK, respectively. There were 555 differentially expressed genes responsive to the single VP28 stimulation after grouping the PBS-VP28_BLANK and PBS-VP28_PBS-PBS gene lists, and 269 ones responsive to the successive VP28 stimulation after grouping the VP28-VP28_BLANK, VP28-VP28_PBS-PBS and VP28-VP28_PBS-VP28 gene lists. In the GO enrichment analysis of the genes responsive to the single VP28 stimulation, five immune-related GO terms were observed among 14 increased terms, which included defense response to bacterium, response to stimulus, disruption of cells of other organism, killing of cells of other organism and response to bacterium. It was worth noting that the GO terms, response to stimulus and response to stress, were the most common annotation ones which accounted 28.7% and 18.8% of the total differently expressed genes, respectively. For the genes responsive to the successive VP28 stimulation, terms including actin filament-based movement and myosin heavy chain binding were mostly enriched in the Biological Process and Molecular Function category, respectively. In the Cellular Component category, the enriched GO terms were myosin VII complex, myosin V complex, myosin VI complex and myosin II complex. Furthermore, the most abundant GO term was oxidation-reduction process, followed by single-organism transport, neurogenesis and translation for 214 genes only responsive to successive VP28 stimulation. These results collectively indicated that the successive VP28 stimulation could modulate cytoskeleton integration and redox to promote the phagocytosis activity of shrimp haemocytes, which might protect effectively for shrimp against WSSV infection.

Antiviral defense in shrimp: from innate immunity to viral infection

The culture of penaeid shrimp is rapidly developing as a major business endeavor worldwide. However, viral diseases have caused huge economic loss in penaeid shrimp culture industries. Knowledge of shrimp innate immunity and antiviral responses has made important progress in recent years, allowing the design of better strategies for the prevention and control of shrimp diseases. In this study, we have updated information on shrimp antiviral immunity and interactions between shrimp hosts and viral pathogens. Current knowledge and recent progress in immune signaling pathways (e.g., Toll/IMD-NF-κB and JAK-STAT signaling pathways), RNAi, phagocytosis, and apoptosis in shrimp antiviral immunity are discussed. The mechanism of viral infection in shrimp hosts and the interactions between viruses and shrimp innate immune systems are also analyzed.

Characterization and interactome study of white spot syndrome virus envelope protein VP11

White spot syndrome virus (WSSV) is a large enveloped virus. The WSSV viral particle consists of three structural layers that surround its core DNA: an outer envelope, a tegument and a nucleocapsid. Here we characterize the WSSV structural protein VP11 (WSSV394, GenBank accession number AF440570), and use an interactome approach to analyze the possible associations between this protein and an array of other WSSV and host proteins. Temporal transcription analysis showed that vp11 is an early gene. Western blot hybridization of the intact viral particles and fractionation of the viral components, and immunoelectron microscopy showed that VP11 is an envelope protein. Membrane topology software predicted VP11 to be a type of transmembrane protein with a highly hydrophobic transmembrane domain at its N-terminal. Based on an immunofluorescence assay performed on VP11-transfected Sf9 cells and a trypsin digestion analysis of the virion, we conclude that, contrary to topology software prediction, the C-terminal of this protein is in fact inside the virion. Yeast two-hybrid screening combined with co-immunoprecipitation assays found that VP11 directly interacted with at least 12 other WSSV structural proteins as well as itself. An oligomerization assay further showed that VP11 could form dimers. VP11 is also the first reported WSSV structural protein to interact with the major nucleocapsid protein VP664.