Yi-Yang Lien

Development and evaluation of a loop-mediated isothermal amplification assay for rapid detection of chicken anaemia virus.

Aim:  Chicken anaemia virus (CAV) causes an economically important viral disease in chickens worldwide. The main aim of this study was to establish a rapid, sensitive and specific loop‐mediated isothermal amplification (LAMP) assay for detecting CAV infection.

High yield expression in a recombinant E. coli of a codon optimized chicken anemia virus capsid protein VP1 useful for vaccine development

BackgroundChicken anemia virus (CAV), the causative agent chicken anemia, is the only member of the genus Gyrovirus of the Circoviridae family. CAV is an immune suppressive virus and causes anemia, lymph organ atrophy and immunodeficiency. The production and biochemical characterization of VP1 protein and its use in a subunit vaccine or as part of a diagnostic kit would be useful to CAV infection prevention.ResultsSignificantly increased expression of the recombinant full-length VP1 capsid protein from chicken anemia virus was demonstrated using an E. coli expression system. The VP1 gene was cloned into various different expression vectors and then these were expressed in a number of different E. coli strains. The expression of CAV VP1 in E. coli was significantly increased when VP1 was fused with GST protein rather than a His-tag. By optimizing the various rare amino acid codons within the N-terminus of the VP1 protein, the expression level of the VP1 protein in E. coli BL21(DE3)-pLysS was further increased significantly. The highest protein expression level obtained was 17.5 g/L per liter of bacterial culture after induction with 0.1 mM IPTG for 2 h. After purification by GST affinity chromatography, the purified full-length VP1 protein produced in this way was demonstrated to have good antigenicity and was able to be recognized by CAV-positive chicken serum in an ELISA assay.ConclusionsPurified recombinant VP1 protein with the genes codons optimized in the N-terminal region has potential as chimeric protein that, when expressed in E. coli, may be useful in the future for the development of subunit vaccines and diagnostic tests.

Efficient Production of an Engineered Apoptin from Chicken Anemia Virus in a Recombinant E. coli for Tumor Therapeutic Applications

BackgroundApoptin, a nonstructural protein encoded by the VP3 gene of chicken anemia virus (CAV), has been shown to not only induce apoptosis when introduced into the precursors of chicken thymocytes, but has been found to specifically kill human cancer cells, tumor cell and transformed cells without affecting the proliferation of normal cells. This tumor-specific apoptotic characteristic of the protein potentially may allow the development of a protein drug that has applications in tumor therapy. However, several major problems, which include poor expression and poor protein solubility, have hampered the production of apoptin in bacteria.ResultsSignificantly increased expression of recombinant full-length apoptin that originated from chicken anemia virus was demonstrated using an E. coli expression system. The CAV VP3 gene was fused with a synthetic sequence containing a trans-acting activator of transcription (TAT) protein transduction domain (PTD). The resulting construct was cloned into various different expression vectors and these were then expressed in various E. coli strains. The expression of the TAT-Apoptin in E. coli was significantly increased when TAT-Apoptin was fused with GST-tag rather than a His-tag. When the various rare amino acid codons of apoptin were optimized, the expression level of the GST-TAT-Apoptinopt in E. coli BL21(DE3) was significantly further increased. The highest protein expression level obtained was 8.33 g/L per liter of bacterial culture after induction with 0.1 mM IPTG for 4 h at 25 °C. Moreover, approximately 90% of the expressed GST-TAT-Apoptinopt under these conditions was soluble. After purification by GST affinity chromatography, the purified recombinant TAT-Apoptinopt protein was used to evaluate the recombinant protein’s apoptotic activity on tumor cells. The results demonstrated that the E. coli-expressed GST-TAT-apoptinopt showed apoptotic activity and was able to induce human premyelocytic leukemia HL-60 cells to enter apoptosis.ConclusionsOn expression in E. coli, purified recombinant TAT-Apoptinopt that has been fused to a GST tag and had its codons optimized, was found to have great potential. This protein may in the future allow the development of a therapeutic protein that is able to specifically kill tumor cells.

Expression and characterization of highly antigenic domains of chicken anemia virus viral VP2 and VP3 subunit proteins in a recombinant E. coli for sero-diagnostic applications

BackgroundChicken anemia virus (CAV) is an important viral pathogen that causes anemia and severe immunodeficiency syndrome in chickens worldwide. Generally, CAV infection occurs via vertical transmission in young chicks that are less than two weeks old, which are very susceptible to the disease. Therefore, epidemiological investigations of CAV infection and/or the evaluation of the immunization status of chickens is necessary for disease control. Up to the present, systematically assessing viral protein antigenicity and/or determining the immunorelevant domain(s) of viral proteins during serological testing for CAV infection has never been performed. The expression, production and antigenic characterization of CAV viral proteins such as VP1, VP2 and VP3, and their use in the development of diagnostic kit would be useful for CAV infection prevention.ResultsThree CAV viral proteins VP1, VP2 and VP3 was separately cloned and expressed in recombinant E. coli. The purified recombinant CAV VP1, VP2 and VP3 proteins were then used as antigens in order to evaluate their reactivity against chicken sera using indirect ELISA. The results indicated that VP2 and VP3 show good immunoreactivity with CAV-positive chicken sera, whereas VP1 was found to show less immunoreactivity than VP2 and VP3. To carry out the further antigenic characterization of the immunorelevant domains of the VP2 and VP3 proteins, five recombinant VP2 subunit proteins (VP2-435N, VP2-396N, VP2-345N, VP2-171C and VP2-318C) and three recombinant VP3 subunit proteins (VP3-123N, VP3-246M, VP3-366C), spanning the defined regions of VP2 and VP3 were separately produced by an E. coli expression system. These peptides were then used as antigens in indirect ELISAs against chicken sera. The results of these ELISAs using truncated recombinant VP2 and VP3 subunit proteins as coating antigen showed that VP2-345N, VP2-396N and VP3-246M gave good immunoreactivity with CAV-positive chicken sera compared to the other subunit proteins. Moreover, the VP2-396N and VP2-345 based ELISAs had better sensitivity (97.5%) and excellent specificity (100%) during serodiagnosis testing using a mean plus three standard deviations cut-off. The VP3-246M based ELISA showed a sensitivity of 85% and a specificity of 100% at the same cut-off value.ConclusionsThis is the first report to systematically assess the antigenic characteristics of CAV viral proteins for sero-diagnosis purposes. Purified recombinant VP2-396N and VP2-345N subunit proteins, which span defined regions of VP2, were demonstrated to have good antigenicity and higher sensitivities than VP3-246M and were able to recognize CAV-positive chicken serum using an ELISA assay. The defined antigenicity potential of these chimeric subunit proteins produced by expression in E. coli seem to have potential and could be useful in the future for the development of the CAV diagnostic tests based on a subunit protein ELISA system.

Immunomodulating Activity of Nymphaea rubra Roxb. Extracts: Activation of Rat Dendritic Cells and Improvement of the TH1 Immune Response

Polysaccharides play a key role in enhancing immune function and facilitating cellular communication. Here, we purified Nymphaea rubra Roxb. polysaccharides (NR-PS) by treating them with pullulanase. They were then cultured with immature dendritic cells (DCs) derived from rat bone marrow hematopoietic cells (BMHCs). After treatment with bioactive NR-PS with a degree of polymerization (DP) value of 359.8, we found that the DCs underwent morphological changes indicative of activation. CD80/86 (87.16% ± 8.49%) and MHC class II (52.01% ± 10.11%) expression levels were significantly up-regulated by this treatment compared to the controls (65.45% ± 0.97% and 34.87% ± 1.96%). In parallel, endocytosis was also reduced (167.94% ± 60.59%) after treatment with 25 μg/mL of NR-PS as measured by the medium fluorescence intensity compared to the control (261.67% ± 47.26%). Furthermore, the DCs after treatment with 25 μg/mL NR-PS showed increased IL-12 (102.09 ± 10.16 to 258.78 ± 25.26 pg/mL) and IFN-γ (11.76 ± 0.11 to 15.51 ± 1.66 pg/mL) secretion together with reduced IL-10 secretion (30.75 ± 3.35 to 15.37 ± 2.35 pg/mL), which indicates a TH1 immune response. In conclusion, NR-PS exhibits stimulatory effects on rat DCs and promotes the secretion of TH1 cytokines. Taken together, our studies are the first to show that NR-PS is an immunomodulator affecting the maturation and functioning of DCs.

Production and Diagnostic Application of a Purified, E. coli‐Expressed, Serological‐Specific Chicken Anaemia Virus Antigen VP3

The aim of this study was to evaluate the production of chicken anaemia virus VP3 protein in different Escherichia coli strains and to address the diagnostic application of purified E. coli-expressed VP3 protein for the detection of chicken anaemia virus (CAV) infection and the development of an ELISA kit. Three E. coli strains, BL21, BL21 codonplus RP and BL21 pLysS, each harbouring a VP3 protein expressing plasmid, were investigated after induction to produce recombinant VP3 protein. After isopropyl-β-D-thiogalactoside (IPTG) induction, VP3 protein was successfully expressed in all three E. coli strains. The BL21 pLysS strain gave the best performance in terms of protein productivity and growth profile. In addition, the optimal culture temperature and IPTG concentration were found to be 0.25 mM and 20 °C, respectively. Using Ni-NTA-purified VP3 protein as an ELISA coating antigen, the purified VP3 was shown to be highly antigenic and able to discriminate sera from chickens infected with CAV from those that were uninfected during an evaluation of CAV infection serodiagnosis. A VP3-based ELISA demonstrated 100% (6/6 x 100%) specificity and sensitivities of 91.3% (21/23 x 100%) and 82.6% (19/23 x 100%) using cut-off values of the mean plus 2 SD and the mean plus 3 SD, respectively.

Identification of the NLS and NES motifs of VP2 from chicken anemia virus and the interaction of VP2 with mini-chromosome maintenance protein 3

BackgroundVP2 of chicken anemia virus (CAV) is a dual-specificity phosphatase required for virus infection, assembly and replication. The functions of the nuclear localization signal (NLS) and nuclear export signal (NES) of VP2 in the cell, however, are poorly understood. Our study identified the presence of a NLS in VP2 and showed that the protein interacted significantly with mini-chromosome maintenance protein 3 (MCM3) in the cell.ResultsAn arginine-lysine rich NLS could be predicted by software and spanned from amino acids 133 to 138 of VP2. The critical amino acids residues between positions 136 and 138, and either residue 133 or 134 are important for nuclear import in mammalian cells based on systematic mutagenesis. A NES is also predicted in VP2; however the results suggest that no functional NES is present and that this protein is CRM1 independent. It was also shown that VP2 is a chromatin binding protein and, notably, using a co-immunoprecipitation assay, it was found that VP2 association with MCM3 and that this interaction does not require DSP activity.ConclusionsVP2 contains a NLS that span from amino acids 133 to 138. VP2 is a CRM1 independent protein during nuclear export and associates with MCM3 in cells.

The development of loop-mediated isothermal amplification (LAMP) assays for the rapid authentication of five forbidden vegetables in strict vegetarian diets

Plant-based food ingredients such as garlic, Chinese leek, Chinese onion, green onion and onion are widely used in many cuisines around the world. However, these ingredients known as the “five forbidden vegetables” (FFVs) are not allowed in some vegetarian diets. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for the detection of FFVs using five respective LAMP primer sets. The specific primers targeted the ITS1-5.8S-ITS2 nuclear ribosomal DNA sequence regions among the five vegetables. The results demonstrated that the identification of FFVs using the newly developed LAMP assay is more sensitive than the traditional PCR method. Using pepper, basil, parsley, chili and ginger as references, established LAMP primer sets showed high specificity for the identification of the FFV species. Moreover, when FFVs were mixed with other plant ingredients at different ratios (100:0, 50:50, 20:80, 10:90, 5:95, 2:98, and 1:99), no cross-reactivity was evident using LAMP. Finally, genomic DNAs extracted from boiled and steamed FFVs in processed foods were used as templates; the performance of the LAMP reaction was not influenced using validated LAMP primers. Not only can FFV ingredients be identified but commercial foods containing FFVs can also be authenticated. This LAMP method will be useful for the authentication of FFVs in practical food markets in the future.

Development and characterization of a potential diagnostic monoclonal antibody against capsid protein VP1 of the chicken anemia virus

Chicken anemia virus (CAV) is an important viral pathogen that causes anemia and severe immunodeficiency syndrome in chickens worldwide. In this study, a potential diagnostic monoclonal antibody against the CAV VP1 protein was developed which can precisely recognize the CAV antigen for diagnostic and virus recovery purposes. The VP1 gene of CAV encoding the N-terminus-deleted VP1 protein, VP1Nd129, was cloned into an Escherichia (E.) coli expression vector. After isopropyl-β-D-thiogalactopyronoside induction, VP1Nd129 protein was shown to be successfully expressed in the E. coli. By performing an enzyme-linked immunoabsorbent assay using two coating antigens, purified VP1Nd129 and CAV-infected liver tissue lysate, E3 monoclonal antibody (mAb) was found to have higher reactivity against VP1 protein than the other positive clones according to the result of limiting dilution method from 64 clones. Using immunohistochemistry, the presence of the VP1-specific mAb, E3, was confirmed using CAV-infected liver and thymus tissues as positive-infected samples. Additionally, CAV particle purification was also performed using an immunoaffinity column containing E3 mAb. The monoclonal E3 mAb developed in this study will not only be very useful for detecting CAV infection and performing histopathology studies of infected chickens, but may also be used to purify CAV particles in the future.

VP2 of Chicken Anaemia Virus Interacts with Apoptin for Down-regulation of Apoptosis through De-phosphorylated Threonine 108 on Apoptin

Chicken anaemia virus (CAV) is an important contagious agent that causes immunosuppressive disease in chickens. CAV Apoptin is a nucleoplasmic shuffling protein that induces apoptosis in chicken lymphoblastoid cells. In the present study, confocal microscopy revealed co-localisation of expressed CAV non-structural protein VP2 with Apoptin in the nucleus of MDCC-MSB1 cells and the nucleoplasmic compartment of CHO-K1 cells. In vitro pull-down and ex vivo biomolecular fluorescent complementation (BiFC) assays further showed that the VP2 protein directly interacts with Apoptin. Transient co-expression of VP2 and Apoptin in MDCC-MSB1 cells significantly decreased the rate of apoptosis compared with that in cells transfected with the Apoptin gene alone. In addition, the phosphorylation status of threonine 108 (Thr108) of Apoptin was found to decrease upon interaction with VP2. Although dephosphorylated Thr108 did not alter the subcellular distribution of Apoptin in the nucleus of MDCC-MSB1 cells, it did suppress apoptosis. These findings provide the first evidence that VP2 directly interacts with Apoptin in the nucleus to down-regulate apoptosis through alterations in the phosphorylation status of the latter. This information will be useful to further elucidate the underlying mechanism of viral replication in the CAV life cycle.