Carboxyl terminus truncated human papillomavirus type 58 L1 protein maintains its bioactivity and ability to form virus-like particles

Summary: To prepare carboxyl terminus truncated human papillomavirus type 58 L1 ( HPV581.1 )protein and evaluate its ability to form virus-like particles, the baculovirus and Sf-9 insect cells was used to express HPV581.1 protein, and pFastBac-Htb containing HPV58L1 gene sequence of carboxyl terminus truncation was generated. Then Sf-9 cells were infected with recombinant baculovirus. After being cultured, the post-infected cells expressing - HPV58L1 protein were harvested and analyzed by SDS-PAGE and Western blot. The ProBond^TM purification system was used for protein purification. The bio-activity of purified protein was identified by mouse erythrocyte hemagglutination assay, and the VLP formation was examined with transmission electron microscope.Our results showed that the recombinant baculovirus was generated and the Sf-9 cells was infected with the recombinant baculovirus, and after collecting, total cellular proteins were extracted. Truncared HPV581.1 protein with MW 58KD was revealed by SDS-PAGE and confirmed by Western blot. The purified L1 proteins under native condition could cause mouse erythrocytes to agglutinate and form VLP. It is concluded that HPV58L1 protein with carboxyl terminus truncation could be efficiently expressed. In baculovirus Sf-9 cells expression system, the purified protein could self-assemble into virions in vitro, and induce agglutination of mouse erythrocytes, indicating that carboxyl terminus truncation does not interfere with the bioactivity of HPV58L1 protein.     

Expression and self-assembly of HCV structural proteins into virus-like particles and their immunogenicity

Background The synthesis of virus-like particles (VLPs) provides an important tool to determine the structural requirements for viral particle assembly and virus-host interactions. Our purpose was to express simultaneously all three structural proteins of hepatitis C virus (HCV) in insect cells to investigate the proteins assembly into VLPs and the imrnunogenicity of these particles. Methods HCV gene sequences encoding the structural proteins C, E1, and E2 were amplified with PCR, and recombinant baculoviruses were constructed using recombinant DNA techniques. The expression of HCV structural proteins in insect cells was analyzed by immunofluoresceoce and SDS-PAGE. The interaction of expressed structural proteins was investigated by immunoprecipitation and immunoblotting. The VLPs in the insect cells were visualized by electron microscopy (EM). VLPs were then purified by sucrose gradient centrifugation and used to immunize BALB/c mice. Antibodies against HCV were tested for in mouse serum samples by an ELISA assay. Results The recombinant baculoviruses reBV/C and reBV/E1-E2 were constructed successfully. Insect cells co-infected with reBV/C and reBV/E1 -E2 expressed HCV C, E1, and E2 proteins with the expected molecular weights of 20kD, 35kD, and 66kD, respectively. The results of immunoprecipitation and immunoblotting assays revealed the coimmunoprecipitation of C, E1, and E2 proteins, indicating association of the three structural proteins. Electron microscopy of insect cells coinfected with reBV/C and reBV/E1-E2 demonstrated spherical particles (40 to 60 nm in diameter) similar to the HCV virions from serum samples or hepatic tissue samples of HCV infected humans. The VLPs were partially purified. Antibodies to HCV were detectable in the serum of mice immunizedwith VLPs. Conclusion HCV structural proteins simultaneously expressed in insect cells can interact with each other and assemble into HCV-like particles, which are shown to be immunogenic in mice.     

Recombinant human heparin- binding neurite- promoting factor express ed with yeast stimulates neurites outgrowth .

Objectives Heparin- binding neurite- promoting factor (HBNF) is a heparin- binding protein primarily found in the brain, which can stimulate neurite outgrowth in vitro.We expressed recombinant human heparin- binding neurite- promoting factor (hrHBNF) using a yeast system, and observed its activity in stimulating neurite outgrowth in vitro.Methods cDNA encoding mature human HBNF was amplified from total RNA isolated from an 18- week aborted human fetal brain by RT- PCR method.After amplification, the HBNF cDNA gene was cloned into pPIC9K, a shuttle expression vector for yeast system.The positive clone of expression vector bearing HBNF cDNA gene was obtained by screening.Verified recombinant vector was then used to transform Pichia strain GS115 by electroporation.His+ transformants were selected on minimal dextrose medium (MD) plates which were histidine free.His+ yeast recombinants with multi- copy inserts were screened in vivo by their resistance to G418.PCR analysis was used to confirm the integration of the HBNF cDNA gene into the Pichia genome.Secreted expression of hrHBNF protein in culture medium was obtained when the positive clone containing the HBNF cDNA gene was induced by methanol. The hrHBNF product purified by gel chromatography was added to cultured rat pheochromocytoma (PC12) cells to observe its ability to stimulate neurite outgrowth.Results In the recombinant expression vector, the insert was sequenced to show exactly the sequence encoding human HBNF according to Genbank data.The HBNF cDNA gene was cloned downstream to the α- factor, and its open reading frame was in frame with the α- factor signal sequence in pPIC9K.SDS- PAGE showed that the molecular weight of the induced expression product was about 18 kDa, consistent with that of human HBNF reported in the literature.The protein product did promote neurite outgrowth in cultured rat pheochromocytoma (PC12) cells.Conclusion Recombinant human heparin- binding neurite- promoting factor can be expressed with a yeast system, and its product possesses the biological activity to promote neurite outgrowth.     

Cloning of the Eukaryotic Expression Vector with Nerve Growth Factor in Rats and Its Effects on Proliferation and Differentiation of Mesencephal Neural Stem Cells of Fetal Rats

The eukaryotic expression vector containing full-length cDNA sequence of rate nerve growth factor （NGF） β subunit was constructed and its effects on proliferation and differentiation of neural stem cells were observed. By using PCR, full-length cDNA sequence of NGF β subunit in rats was cloned and ligated into the eukaryotic expression vector pEGFP-N1-NGF. The recombinant plasmid pEGFP-N1-NGF was transfected into the mesencephal neural stem cells of embryonic rats by Lipofectamin and transiently expressed. MTT method was used to determine the effects of NGF on proliferation of neural stem cells, and under phase-contrast microscopy, the effects of NGF on growth of nervous processes following differentiation of neural stem cells were observed. Sequence analysis indicated that the cloned full-length cDNA sequence of rat NGF β was identical to that of published sequence encoding NGF in gene GeneBank. The transfection of recombinant plasmid pEGFP-N1-NGF into mesencephal neural stem cells of embryonic rats could obviously promote proliferation of neural stem cells and faciliate the growth of neural stem cells-derived nerve cells. It was suggested that neural stem cells could be used as a vehicle of gene transfer, and the expression of NGF β subunit in the neural stem cells could promote the growth of nerve cells derived from neural stem cells.     

Expression of Hantaan virus 26 kD fragment of nucleocapsid protein in insect cells and prelimimary study on its immunogenicity

Objective: To express the 26 kD fragment of Hantaan virus nucleocapsid protein that contains the major an-tigenic epitopes in insect cells, and make a preliminary analysis of its immunological characteristics. Methods: The re-combinant baculovirus bat-S0. 7 with the 700 bp fragment of S gene 5‘ terminal of Hantaan virus was constructed, and the anfigenicity of the expression product was tested. Mice were injected with Sf9 cells infected by the recombinant bac-ulovirus. The humoral and cellular immunological effects were identified by indirectassay, micro-cell culture neutralization test and T lymphocytes stimulation test. Results: Immunized by bac-S0. 7 infecting insect cells, specific antibody with the highest titer of 1:1 600 was observed. The stimulation indexes of splenocytes of immu-nized mice to nucleocapsid protein of Hantaan virus was higher than the negative control. Conclusion: The expression product of SO. 7 gene fragment in insect cells is immunogenic.     

A cell-based high-throughput screening assay for Farnesoid X receptor agonists

Objective To develop a high-throughput screening assay for Farnesoid X receptor （FXR） agonists based on mammalian one-hybrid system （a chimera receptor gene system） for the purpose of identifying new lead compounds for dyslipidaemia drug from the chemical library. Methods cDNA encoding the human FXR ligand binding domain （LBD） was amplified by RT-PCR from a human liver total mRNA and fused to the DNA binding domain （DBD） of yeast GAL4 of pBIND to construct a GAL4-FXR （LBD） chimera expression plasmid. Five copies of the GAL4 DNA binding site were synthesized and inserted into upstream of the SV40 promoter of pGL3-promoter vector to construct a reporter plasmid pG5-SV40 Luc. The assay was developed by transient co-transfection with pG5-SV40 Luc reporter plasmid and pBIND-FXR-LBD （189-472） chimera expression plasmid. Results After optimization, CDCA, a FXR natural agonist, could induce expression of the luciferase gene in a dose-dependent manner, and had a signal/noise ratio of 10 and Z＇ factor value of 0.65, Conclusion A stable and sensitive cell-based high-throughput screening model can be used in high-throughput screening for FXR agonists from the synthetic and natural compound library.     

Heterologous Expression of Rat Testis GABAA Receptor β3t Splicing Variant in CHO Cells

Objective To characterize a possible retention function of unique sequence in the 5＇end of rat testis GABAA receptor β3t splicing variant Methods Rat testis GABAA receptor β3t splicing variant cDNA was cloned and two eukaryotic expression recombinant plasmids of pEGFP-N1 and pEGFP-C1 were constructed respectively by fusing green fluorescent protein to the N or C-terminus of β3t isoform. The recombinant plasmids were transfected into CHO cells by calcium phosphate co-precipitation method Fluorescence microscope and laser confocal microscope were used to analyze localization of β3t in the transfected cells. ConA-Texas-Red was used to label cell ER and the localization of rat testis β3t splicing variant in CHO cells was determined. Results When rat testis β3t splicing variant was expressed in CHO cells, two expression patterns were delineated, the distributions of uniform and mainly discrete intracellular compartments respectively, The chimera product failed to be translocated into the cell surface when expressed in ClIO cells; whereas the β3 subunit of rat brain was incorporated into the plasma membrane. Conclusion The inability of β3t to target into the ER may be a consequence of the unique 25 specific amino acid segments in the N terminus.     

Differentiation of NIH3T3 fibroblasts into adipocytes induced by peroxisome proliferator activated receptor γ2 expression

Objective To express mouse peroxisome proliferator activated receptor γ2 (mPPARγ2) in NIH3T3 fibroblasts mediated by the recombinant retrovirus and study its function. Methods The mPPARγ2 gene was subcloned into retrovirus vector pGCEN to generate the recombinant pGCEN/mPPARγ2. Then it was packaged into PA317 cells and selected with G418. Viral supernatants were harvested and then used to infect NIH3T3 fibroblasts. PPARγ activator 5,8,11,14-eicosatetraynoic acid (ETYA) was used to induce the mPPARγ2-expressing NIH3T3 cells into adipocyte differentiation.Results The recombinant retrovirus pGCEN/mPPARγ2 was constructed, and the higher titers of the viral supernatants were obtained. mPPARγ2 was expressed in NIH3T3 cells mediated by the recombinant retrovirus. Lipid accumulation obviously existed in these induced adipocytes which morphologically resembled mature adipocytes in vivo and expressed tissue specific adipocyte P2 (AP2) and Leptin genes.Conclusions An adipocyte differentiation model in vitro was successfully established. The work is the basis for further research on the molecular mechanism of adipocyte differentiation induced by PPARγ2.     

The protein X4 of severe acute respiratory syndrome-associated coronavirus is expressed on both virus-infected cells and lung tissue of severe acute respiratory syndrome patients and inhibits growth of Balb/c 3T3 cell line

BackgroundThe genome of the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) includes sequences encoding the putative protein X4 (ORF8, ORF7a), consisting of 122 amino acids. The deduced sequence contains a probable cleaved signal peptide sequence and a C-terminal transmembrane helix,indicating that protein X4 is likely to be a type I membrane protein. This study was conducted to demonstrate whether the protein X4 was expressed and its essential function in the process of SARS-CoV infection.MethodsThe prokaryotic and eukaryotic protein X4-expressing plasmids were constructed. Recombinant soluble protein X4 was purified from E. coli using ion exchange chromatography, and the preparation was injected into chicken for rising specific polyclonal antibodies. The expression of protein X4 in SARS-CoVinfected Vero E6 cells and lung tissues from patients with SARS was performed using immunofluorescence assay and immunohistochemistry technique. The preliminary function of protein X4 was evaluated by treatment with and over-expression of protein X4 in cell lines. Western blot was employed to evaluate the expression of protein X4 in SARS-CoV particles.Results We expressed and purified soluble recombinant protein X4 from E. coli, and generated specific antibodies against protein X4. Western blot proved that the protein X4 was not assembled in the SARS-CoV particles. Indirect immunofluorescence assays revealed that the expression of protein X4 was detected at 8 hours after infection in SARS-CoV-infeeted Vero E6 cells.It was also detected in the lung tissues from patients with SARS. Treatment with and overexpression of protein X4 inhibited the growth of Balb/c 333 cells as determined by cell counting and MTI““““““““ assays.Conclusion The results provide the evidence of protein X4 expression following SARS-CoV infection,and may facilitate further investigation of the immunopathological mechanism of SARS.     

High Expression of Insulin-like Growth Factor H (IGF-Ⅱ) Using Bac-to-Bac Expression System

Objective In order to obtain mature insulin-like growth factor- Ⅱ ( IGF- Ⅱ ), we used Bac-to-Bac baculovirus expression system. Methods Firstly the IGF- Ⅱ cDNA was cloned into a donor plasmid pFastBac1 and the recombinant pFastBac1 was then introduced into competent cells DH 10Bac. Recombinant bacmids were constructed by transposing a mini-Tn7 element from a donor plasmid pFastBac1 to the mini-attTn7 attachment site on the bacmid where the Tn7 transposition functions were provided in trans by a helper plasmid, and then used to transfect Sf9 insect cells to get recombinant baculovirus. The recombinant baculovirus was used to infect insect cells. Results Agarose gel analysis showed that recombinant donor plasmid pFastBac1 was constructed successfully; Agarose gel analysis of PCR products confirmed recombinant bacmid ; SDS-PAGE and Western Blotting showed that a 7KD protein band appeared. Conclusion The mature IGF- Ⅱ with immunogenecity has been expressed and produced by using Bac-to-Bac expression system.     

High Expression of Insulin-like Growth Factor H (IGF-Ⅱ) Using Bac-to-Bac Expression System

Objective In order to obtain mature insulin-like growth factor- Ⅱ ( IGF- Ⅱ ), we used Bac-to-Bac baculovirus expression system. Methods Firstly the IGF- Ⅱ cDNA was cloned into a donor plasmid pFastBac1 and the recombinant pFastBac1 was then introduced into competent cells DH 10Bac. Recombinant bacmids were constructed by transposing a mini-Tn7 element from a donor plasmid pFastBac1 to the mini-attTn7 attachment site on the bacmid where the Tn7 transposition functions were provided in trans by a helper plasmid, and then used to transfect Sf9 insect cells to get recombinant baculovirus. The recombinant baculovirus was used to infect insect cells. Results Agarose gel analysis showed that recombinant donor plasmid pFastBac1 was constructed successfully; Agarose gel analysis of PCR products confirmed recombinant bacmid ; SDS-PAGE and Western Blotting showed that a 7KD protein band appeared. Conclusion The mature IGF- Ⅱ with immunogenecity has been expressed and produced by using Bac-to-Bac expression system.     

重组人Versican G1蛋白在昆虫细胞中的表达

目的：利用杆状病毒．昆虫细胞表达系统制备人蛋白聚糖Versican G1区(VG1)的重组蛋白。方法：将编码人VG1蛋白343个氨基酸的基因插入pFastBacl载体，转化大肠杆菌DH10Bac，提取重组Bacmids转染Sf9昆虫细胞，获取含重组人VG1蛋白的杆状病毒进一步感染昆虫细胞进行蛋白表达。通过Ni—NTA层析柱对重组蛋白进行纯化。免疫印迹方法对昆虫细胞培养上清中的蛋白成分进行鉴定，采用透明质酸结合实验确定重组人VG1蛋白的生物活性。结果：人VG1基因在昆虫细胞中获得高水平表达，重组人VG1蛋白具免疫原性和与透明质酸结合的生物活性。结论：昆虫细胞表达的重组人VG1蛋白具有良好的免疫原性和生物活性。     

利用杆状病毒表达载体系统表达重组乙型肝炎病毒核心蛋白

目的利用杆状病毒表达载体系统制备重组乙型肝炎病毒核心蛋白。方法构建含有HBVC基因的杆状病毒转移载体pFastBac Dual—HBV core，转化大肠埃希菌DH10Bac进行转座，提取重组Bacmid DNA转染昆虫细胞Sf9，获得含有HBVC基因的重组杆状病毒。用重组杆状病毒感染Sf9细胞进行乙型肝炎病毒核心蛋白表达，然后通过SDS-PAGE电泳和Western blot分析表达情况。结果成功构建了含HBVC基因的重组杆状病毒，而且在昆虫细胞Sf9中表达了乙型肝炎病毒核心蛋白。结论利用Bac to Bac杆状病毒表达系统，成功地表达了乙型肝炎病毒核心蛋白，为进一步研究奠定了基础。     

EBV-LMP1基因杆状病毒表达载体的构建及其在昆虫细胞中的表达

目的：构建EBV-LMP1基因的杆状病毒重组供体质粒，包装重组LMP1的杆状病毒，感染昆虫细胞进行表达。方法：先将已克隆的LMP1 cDNA与线性化的pFastBACHTb进行连接，使pFASTBACHTb-LMP1与DHl0BAC感受菌进行转座重组，利用抗性及蓝白斑筛选重组Bacmid／LMPl克隆，提取Bacmid／LMP1转染昆虫细胞Sf9包装杆状病毒，利用病毒感染Sf9细胞进行蛋白表达，通过免疫荧光、SDS-PAGE和Western-blot检测表达情况。结果:获得了重组LMP1的杆状病毒，细胞能表达出与LMP1单抗结合的蛋白，分子量为63kDa左右，细胞可直接分泌LMP1蛋白至上清。结论:LMPl能在昆虫细胞中获得良好表达，为研究肿瘤疫苗及LMPl在EBV致瘤分子机理中的作用奠定了基础。     

庚型肝炎病毒NS3蛋白在杆状病毒载体中的表达及其抗原性研究

目的：利用Ｂａｃ－ｔｏ－Ｂａｃ ＨＴ杆状病毒系统在Ｓｆ９昆虫细胞中表达庚型肝炎病毒（ＨＧＶ）ＮＳ３蛋白,并对表达产物的免疫原性进行研究。方法：将ＨＧＶ ＮＳ３基因片段定向克隆至转座载体ｐＥａｓｔＢｓｃ ＨＴａ,转化ＤＨ１０Ｂａｃ感受态细胞,３７℃振荡培养４ｈ使发生转座,用抗生素平皿筛选重组ｂａｃｍｉｄ。脂质体介导转染Ｓｆ９昆虫细胞,待细胞形态明显改变后收获细胞和培养上清液,将上清液再次感染Ｓｆ９细     

利用细菌/杆状病毒系统在昆虫细胞中表达人CYP2E1

目的获得人CYP2E1重组酶,并用该重组酶的特征性探针底物对其进行代谢活性研究.方法以人肝组织RNA为模板,通过RT-PCR得到CYP2E1 cDNA片断,然后与pFastBac质粒连接,得到pFastBac-CYP2E1重组质粒,将其转化E.coli DH 10Bac大肠杆菌,通过转座作用,获得重组Bacmid-CYP2E1,将其转染草地夜蛾细胞(Sf9) 后,产生重组杆状病毒.将该病毒以及分别含有人CYPOR和人CYPb5的病毒共同感染Sf9细胞,收集共表达蛋白,以氯唑沙宗为底物鉴定重组酶的活性.结果利用细菌/杆状病毒系统得到重组人CYP2E1的表达,其对氯唑沙宗的Km值为(72.4±8.7)μmol·L-1,Vmax值为(2.41±0.10)μmol·min-11·g-1蛋白.结论利用杆状病毒系统成功表达了有催化活性的人CYP2E1重组酶,其活性与文献报道值相似.     

人碱性成纤维细胞生长因子在昆虫细胞sf9中的表达

将人碱性成纤维细胞生长因子 (basicfibroblastgrowthfactor,bFGF)基因cDNA克隆到pFastBacI转移载体中 ,重组质粒转化到感受态细胞DH1 0Bac中 ,使目的基因转座入BacmidDNA中 ,纯化DNA后 ,利用病毒噬斑实验筛选重组的杆状病毒。重组杆状病毒感染Sf9细胞 ,在Sf9细胞中进行表达。Western印迹结果表明 :表达产物为相对分子质量约 1 70 0 0的蛋白 ,与预计的重组蛋白相对分子质量相同 ,并具有较好的免疫学活性。MTT检测证实表达产物能明显促进人脐静脉内皮细胞 (HUVEC)的分裂增生 ,具有hbFGF的生物学活性     

人IL-12在昆虫细胞中的表达及其体外生物活性的检测

目的：建立表达具有生物活性的人IL-12 的杆状病毒/昆虫细胞表达系统。方法：将p40和p35 cDNA一起构建入杆状病毒转移载体pAcUW42,然后与杆状病毒AcUW1.lacZ DNA共同转染昆虫细胞Sf9,使两者产生同源重组;随后利用病毒空斑实验筛选重组的杆状病毒,再由ELISA筛选及鉴定表达IL-12的重组病毒,并进行Western Blotting和体外生物活性的检测。结果：经病毒空斑试验、ELISA和Western Blotting逐步阳性选择的IL-12重组杆状病毒,其感染Sf9细胞的上清与IL-12标准品一样具备刺激正常人外周血T淋巴细胞增生的生物活性。结论：本研究建立了能表达具有体外生物活性的人重组IL-12的杆状病毒/昆虫表达系统。