乙肝多表位抗原基因非融合表达载体的构建和表达

目的:研究乙型肝炎病毒(HBV)多表位基因的在原核载体中的克隆、游离表达及其产物的抗原性.方法:设计、并合成HBV多表位抗原基因BPT, 克隆入原核表达载体pBAD/gIIIA, 进而转化Top10大肠杆菌, 阿拉伯糖诱导表达出HBV多表位抗原蛋白(B-BPT), 并用Western blot方法初步检测该抗原蛋白的抗原性.结果:成功构建了原核表达载体pBAD/BPT, 在大肠杆菌中表达出HBV多表位抗原蛋白B-BPT, Western blot 检测显示该蛋白具有良好抗原性.结论:HBV多表位抗原基因的设计是成功的, 其在大肠杆菌中表达的非融合蛋白具有良好的抗原性, 可能是较理想的HBV治疗性疫苗候选物.     

乙型肝炎病毒多表位抗原基因的设计、合成及表达

目的　设计合成乙型肝炎病毒多表位抗原基因并在大肠杆菌中表达 ,以期获得兼具预防和治疗作用的新型乙肝疫苗。方法　设计并合成一条乙型肝炎病毒 (HBV)多表位抗原基因 (P T) ,该基因包括HBV前S2区的核苷酸序列 ,和分别来自乙型肝炎表面抗原、乙型肝炎核心抗原、乙型肝炎DNA聚合酶的其它 4个连续的HLA限制性抗原表位的核苷酸序列。基因合成后克隆入载体质粒pWR4 5 0 1,转化大肠杆菌BL2 1,IPTG诱导P T基因与载体质粒的 β 半乳糖酐酶基因融合表达。结果　成功合成并拼接出乙型肝炎多表位抗原基因P T ,阳性重组子PWR HBV P T构建成功 ,并在大肠杆菌中融合表达出相对分子质量 (Mr)约 75× 10 3的碱性蛋白质。结论　初步设计成功HBV多表位抗原基因 ,在大肠杆菌中可表达出具有良好抗原性的重组融合蛋白 ,可能是较理想的HBV预防、治疗性疫苗候选物。     

HCV多表位抗原融合肽的表达与抗原性的研究

目的观察HCV复合多表位抗原融合肽的抗原性,探讨利用这种抗原融合肽制备的抗体在丙型肝炎抗原检测方面的潜在可行性。方法将人工合成的HCV复合多表位抗原基因B2克隆到表达载体pThioHis A中,并在大肠杆菌中表达融合蛋白(Trx-B2),纯化该蛋白后免疫小鼠及家兔,分析表达产物的免疫特异性及抗原性。结果融合蛋白(Trx-B2)能在原核表达系统中高效表达,并可诱发小鼠及家兔产生高滴度的特异性HCV抗体。结论偶联了融合蛋白的HCV复合多表位抗原具有良好的抗原性,其免疫实验动物后产生的抗体有望用于HCV的抗原检测。     

HCV HLA-A2限制性复合多表位基因的构建、克隆表达及其免疫特性分析

目的:构建丙型肝炎病毒(HCV)HLA-A2限制性复合多表位基因的原核表达载体,表达纯化,并观察其免疫原性。方法:分别合成HCV HLA-A2限制性多表位基因、人泛素基因,串联后得到融合基因Ub-Mep,克隆入原核表达质粒pRSET-A,转化E.coliBL21,IPTG诱导融合蛋白表达,薄层扫描分析表达蛋白组成;可溶性分析后用Ni2+-NTA凝胶亲和层析柱纯化、透析并浓缩融合蛋白;Western blot分析纯化蛋白的特异性和抗原性;免疫小鼠分析其免疫原性。结果:成功构建复合多表位抗原基因的原核表达质粒pRSET-Ub-Mep,目的基因可高效表达,表达产物主要以包涵体形式存在,Ni2+-NTA纯化可获得目的蛋白,纯化蛋白具有良好的抗原性和免疫原性。结论:成功构建HCV HLA-A2限制性复合多表位基因并进行原核表达,表达的多表位基因抗原具良好的免疫原性,为进一步的HCV A2限制性复合多表位诱导的细胞免疫应答研究奠定基础。     

单纯疱疹病毒1型糖蛋白D主要抗原表位区的表达、纯化及鉴定

 目的 原核表达单纯疱疹病毒1型(HSV-1) 糖蛋白D(gD)主要抗原表位区,纯化融合表达蛋白并对其进行鉴定。方法 用Lasergene7.0中Protean软件对HSV-1 gD氨基酸序列进行抗原表位预测和分析,筛选出gD主要抗原表位区(gD MED),人工合成该区域cDNA序列,构建原核表达载体pET-GST-gD MED;将重组质粒转化大肠杆菌(E.coli)BL21(DE3) pLysS,用异丙基-β-D-硫代吡喃半乳糖苷(IPTG)诱导表达,通过GST?Bind 纯化试剂盒对gD MED融合蛋白进行纯化;Western blot对gD MED融合蛋白的免疫活性进行分析。结果 HSV-1 gD在266~394区域富含抗原表位,人工合成了该区域的cDNA序列,并成功构建了原核表达载体pET-GST-gD MED;gD MED融合蛋白主要以可溶形式表达,分子质量约为45 ku,纯度能达95%;Western blot结果显示,gD MED融合蛋白能与感染HSV-1患者的血清发生特异结合。结论 成功表达和纯化了具有良好抗原性的HSV-1 gD MED融合蛋白,为HSV免疫诊断试剂盒和基因工程疫苗的研制奠定了基础。     

乙型肝炎病毒表面抗原基因点突变对HBsAg抗原性的影响

目的 研究乙型肝炎病毒表面抗原(HBsAg)常见基因点突变对HBsAg抗原性的影响,了解我国目前常用的HBsAg检测试剂对HBV S基因突变株的检测灵敏性,减少漏检,有效控制乙肝病毒(HBV)感染的传播.方法 构建HBsAg重组野毒株和重组变异株表达质粒,分别将重组野毒株HBsAg表达质粒pSS1adw2及pSS1adr和重组变异株HBsAg表达质粒pSS1adw2-145Arg、pSS1adr-126 Ser和pSS1adr-126 Asn转染COS-7细胞,进行瞬时转染.采用市售HBsAg ELISA检测试剂盒对细胞上清进行抗原性检测.结果 野毒株HBsAg和两种126位变异株HBsAg具有较好的抗原性;145位点突变后、导致HBsAg的抗原性下降.结论 推测是由于145位点变异影响了"a"抗原决定簇的空间结构,从而降低了其与抗-HBs的结合能力.     

淋球菌LOS 2C7表位筛选及其与HBc融合蛋白的原核表达

目的:将淋球菌脂寡糖的2C7表位插入乙型肝炎病毒核心抗原(HBc)的MIR区,通过原核表达系统进行融合蛋白的表达,以期获得高免疫原性的淋球菌亚单位疫苗的候选靶位。方法:通过间接ELISA法,以CMCC29403菌株的LOS为包被抗原,对7个表位进行筛选;并通过杀菌试验检测肽段免疫动物产生血清的保护力。对已筛选好的肽段基因进行人工合成,通过重叠PCR将肽段基因嵌入HBc基因中,以增强表位的免疫原性,并进行原核表达。结果:初步研究表明了表位PEP1,PEP2,PEP7具有较强的脂寡糖(LOS)的免疫原性,能够模拟脂寡糖的抗原性。这3个肽段可能成为候选疫苗亚单位。通过重叠PCR方法:成功地将PEP1,PEP2,PEP7三个表位基因序列插入乙型肝炎病毒核心抗原(HBc)的刺突(MIR)部位,构建了HBc-PEP1,HBc-PEP2,HBc-PEP7融合基因,通过PET22b(+)载体进行原核表达,为下一步疫苗的研究奠定了基础。结论:2C7表位PEP1,PEP2,PEP7具有较强的脂寡糖(LOS)的免疫原性,能够模拟脂寡糖的抗原性。表位与HBc的融合蛋白可以通过原核表达系统进行可溶性表达,为下一步疫苗的研究奠定基础。     

用于研究人凝血因子Ⅷ重链抗原表位的双色荧光免疫印迹分析法

目的:寻找更简便精确的方法来检测人凝血因子Ⅷ的抗原表位.方法:采用PCR技术从人凝血因子Ⅷ的克隆载体pENTR223.1/FVⅢ上克隆出FⅧ重链(FⅧ-N)的cDNA.将cDNA插入原核载体pET21a构建重组表达载体pET21 a-FⅧ-N,并转化大肠杆菌BL21( DE3),以IPTG诱导表达His-FⅧ-N融合蛋白.以表达产物免疫BALB/c小鼠,制备小鼠抗FVⅢ-N的抗血清.接着在重组表达载体pET21 a-FⅧ-N中引入内参Flagotag.对FⅧ-N进行定点突变,构建两个突变克隆N1和N2,对二者以及原FⅧ-N进行双色荧光免疫印迹分析.用双色红外激光成像系统进行扫描和定量分析,以绿荧光与红荧光的光密度比值表示突变克隆抗原性的大小.结果:双色荧光免疫印迹分析表明,突变克隆N1,N2的抗原性与原FⅧ-N相比均有显著下降(P＜0.05).FⅧ A2区的三个氨基酸残基Arg484,Arg489,Arg593对FⅧ-N 抗原性起着重要的作用.结论:成功建立了人凝血因子Ⅷ重链抗原表位检测的双色荧光免疫印迹分析法.     

乙型肝炎病毒S和前S1基因的融合构建及其在P. pastoris酵母中的表达

目的构建含有乙型肝炎病毒(HBV)S和前S1(preS1,10～50AA)表位的ss1融合基因,并在P.pastoris酵母中表达SS1融合蛋白。方法以HBV全基因组质粒为模板,扩增出目的区段:S(1～222AA)、preS1(10～50AA),以酶切-PCR的方法将其连接为ss1融合基因,然后克隆入表达载体pPIC3.5k;电穿孔转化毕赤酵母菌株GS115,筛选后进行诱导表达并对表达产物进行检测。结果表达产物的相对分子质量为30000左右,与抗HBs抗体和抗preS1抗体均有特异反应。结论ss1融合基因能够在P.pastoris酵母中高效表达,而且表达产物具有HBVS蛋白和preS1蛋白的抗原性,为进一步研究其免疫原性打下基础。     

人源N-末端脂多糖结合蛋白(NH-LBP)的原核表达及抗原性分析

目的 在大肠杆菌表达系统中大量表达、纯化N-末端脂多糖结合蛋白(NH-LBP)并检测其抗原性.方法 构建pET28a-NHLBP质粒,转入大肠杆菌BL21感受态细胞,IPTG诱导表达成功后扩大培养、提取包涵体、亲和层析分离纯化,并将纯化得到的NH-LBP融合蛋白经Western blot鉴定.结果 成功构建pET28a-NH-LBP表达质粒并转入BL21细菌进行诱导表达,目的 蛋白以包涵体形式表达为主;经扩大培养、分离纯化产物大小与NH-LBP融合蛋白理论计算值一致,经Western blot检测具有B细胞表位.结论原核表达人源N-末端脂多糖结合蛋白(NH-LBP)是制备抗原的一种可行方便的方法,为筛选针对NHLBP的人源性小分子抗体提供了材料.     

Chimeric Newcastle disease virus nucleocapsid with parts of viral hemagglutinin-neuraminidase and fusion proteins

The nucleocapsid (NP) protein of Newcastle disease virus (NDV) self-assembled in Escherichia coli as ring-like and herringbone-like particles. Several chimeric NP proteins were constructed in which the antigenic regions of the hemagglutinin-neuraminidase (HN) and fusion (F) proteins of NDV, myc epitope, and six histidines (a hexa-His tag) were linked to the C-terminus of the NP monomer. These chimeric proteins were expressed efficiently in soluble form in E. coli as detected by Western blot analysis. Electron microscopy of the purified products revealed that they self-assembled into ring-like particles. These chimeric particles exhibited antigenicity of the myc epitope, suggesting that the foreign sequences were exposed on the surface of the particles. Chickens inoculated with the chimeric particles mounted an immune response against NDV, suggesting the possibility of use of the ring-like particle as a carrier of immunogens in subunit vaccines and immunological reagents.     

Immunoreactivity of HCV/HBV epitopes displayed in an epitope-presenting system

It has been demonstrated that the immunodominant region of the HCV core protein and the hepatitis B surface antigen (HBsAg) have high degree of reactivity. In order to construct a chimeric protein that carries HCV and HBV epitopes and possesses immunogenicity to both HCV and HBV, four epitopes derived from residues aa2-21 (epitope C1), aa22-40 (epitope C2) of the core protein, residues aa315-328 (epitope E) of E1 protein of HCV, and residues aa124-147 (epitope S) of HBsAg were chosen to be displayed in a conformation-specific manner on the outer surface of the Flock House virus capsid protein and expressed in E. coli cells. The reactivity of these epitopes with antisera from hepatitis C and hepatitis B patients and induction of immune response in guinea pigs were determined. The results showed that when displayed in this system, the chimeric protein carrying only epitope S could react with anti-HBsAg positive human sera, elicit an anti-HBsAg response in guinea pigs. The chimeric protein carrying epitopes C1, C2 and E could react with antibodies to different HCV genotypes, elicit an anti-HCV response in guinea pigs. The chimeric protein carrying epitopes C1, C2, E, and S could react with antibodies against HCV and HBV, elicit anti-HCV and anti-HBsAg responses in guinea pigs. The results suggested that these epitopes displayed in this form could be considered for development of epitope-based vaccines against HCV/HBV infections.     

Asparaginase display of polypeptides in the periplasm of Escherichia coli: potential rapid pepscan technique for antigen epitope mapping

Asparaginase of Escherichia coli, a tetramer of identical subunits, was tested as a vector to display linear peptides on the surface of each enzyme subunit. A recombinant gene encoding a chimeric protein composed of asparaginase, a tetanus toxin peptide (TTP) spacer (831-854 fragment), and the foreign cholesteryl ester transfer protein C-terminal fragment (CETPC) was expressed and targeted to the periplasm of E. coli. The purified chimeric enzyme exhibited approximately 83% activity of the native enzyme, allowing the rapid screening of recombinant clones. In contrast, an asparaginase-CETPC fusion protein without the TTP spacer produced only about 23% activity of the native enzyme. Rats immunized with bacterial cells containing the chimeric enzymes induced CETP-specific immunoresponse. In contrast, rats inoculated with the cells expressing asparaginase only did not generate specific anti-CETP antibodies. Our study showed that asparaginase of E. coli was an effective carrier for displaying foreign peptides or epitopes. Moreover, the use of the TTP spacer appeared to play a critical role in maintaining the catalytic activity of the chimeric enzymes by redirecting the foreign CETPC peptide to the surface of the enzyme. The chimeric enzyme constructs fusing asparaginase with foreign peptides via a TTP spacer could be utilized as a rapid pepscan technique for antigen epitope mapping. The fusion protein of asparaginase-TTP-CETPC could also be useful for the development of a vaccine against atherosclerosis.     

Expression of multiple foreign epitopes presented as synthetic antigens on the surface of Potato virus X particles

Summary. We describe the construction of recombinant Potato virus X (PVX) vectors expressing two different epitopes, ep4 and ep6, from Beet necrotic yellow vein virus (BNYVV). The seven-amino-acid epitopes were expressed as N-terminal coat protein fusions and were displayed on the surface of PVX particles. Particle assembly into full virions was successful even though no wild type coat protein subunits were present, and the epitopes could be detected in crude extracts and purified virus preparations with appropriate antibodies. A construct containing both epitope sequences in tandem was also prepared. The resulting PVX particles could be detected by antibodies against ep4 and ep6, either individually or simultaneously, showing that both epitopes were accessible. In addition mixed infections with PVX vectors containing the individual ep4 and ep6 sequences were carried out. This resulted in the formation of PVX particles displaying ep4 alone, ep6 alone, or both epitopes. These experiments demonstrate for the first time that PVX can be utilized to present multiple epitopes, either tandemly on every coat protein subunit or as heteromultimeric assemblies, both of which could be useful vaccination strategies. The production of epitope-presenting viruses in which every coat protein subunit contains a foreign epitope allows the high-level expression of defined numbers of foreign antigen sites, making such viruses useful standards for immune detection.     

Construction and Immunological Evaluation of Multivalent Hepatitis B Virus (HBV) Core Virus-Like Particles Carrying HBV and HCV Epitopes

A multivalent vaccine candidate against hepatitis B virus (HBV) and hepatitis C virus (HCV) infections was constructed on the basis of HBV core (HBc) virus-like particles (VLPs) as carriers. Chimeric VLPs that carried a virus-neutralizing HBV pre-S1 epitope corresponding to amino acids (aa) 20 to 47 in the major immunodominant region (MIR) and a highly conserved N-terminal HCV core epitope corresponding to aa 1 to 60 at the C terminus of the truncated HBcΔ protein (N-terminal aa 1 to 144 of full-length HBc) were produced in Escherichia coli cells and examined for their antigenicity and immunogenicity. The presence of two different foreign epitopes within the HBc molecule did not interfere with its VLP-forming ability, with the HBV pre-S1 epitope exposed on the surface and the HCV core epitope buried within the VLPs. After immunization of BALB/c mice, specific T-cell activation by both foreign epitopes and a high-titer antibody response against the pre-S1 epitope were found, whereas an antibody response against the HBc carrier was notably suppressed. Both inserted epitopes also induced a specific cytotoxic-T-lymphocyte (CTL) response, as shown by the gamma interferon (IFN-γ) production profile.Genetically engineered virus-like particle (VLP)-based vaccines are one of the most promising tools in modern vaccinology. VLPs from almost all classes of viruses are being evaluated now or have just been adopted to use as carriers for presentation of foreign immunological epitopes (for a review, see references 29 and 31). VLP technologies possess obvious advantages for the generation of safe and efficacious vaccines. First, the repetitive antigenic structure of VLPs makes them highly immunogenic. Second, VLPs lack viral genomes or genes and are noninfectious, although they mimic infectious viruses in their structural and immunological features. Third, VLPs are generated by highly efficient heterologous expression of the cloned viral structural genes with subsequent quantitative in vivo or in vitro self-assembly of their products. Fourth, VLPs can be obtained by simple and efficient purification procedures. VLPs can be used for a broad range of applications, but the generation of vaccines against hepatitis B virus (HBV) and hepatitis C virus (HCV) infections is of special interest.The HBV core (HBc) protein was first reported as a promising VLP carrier in 1986 and was published in 1987 (6, 10, 24). In many ways, HBc occupies a unique position among the VLP carriers because of its high-level synthesis and efficient self-assembly in virtually all known homologous and heterologous expression systems, including bacteria (for a review, see references 29 to 31). The major HBc B-cell epitopes (c and e1) are localized within the major immunodominant region (MIR), whereas the next important epitope, e2, is localized around amino acid position 130, close to the C-terminal histone-like region (for a review, see reference 30).The high-resolution spatial structure of HBc icosahedrons (11, 43) shows that the MIR is located on the tip of the spike, around the most protruding region between amino acids (aa) 78 and 82. For this reason, the MIR is generally accepted as the target site of choice for insertion of foreign epitopes (30). The other widely accepted site for insertions is C-terminal position 144, a short stretch after the e2 epitope. For C-terminal insertions, so-called HBcΔ vectors lacking a 39-aa-long positively charged C-terminal histone-like fragment are preferred for their high insertion capacities (up to 741 amino acid residues) (30).Here, we present the construction and preliminary immunological characterization of a first multivalent HBV and HCV vaccine candidate. As an HBV epitope, we chose the pre-S1 sequence aa 20 to 47, which alone is able to elicit HBV-neutralizing and protective antibodies (23), for insertion into the HBc MIR. Concurrently, we inserted at the C terminus of the HBcΔ vector the N-terminal 60-aa fragment of the HCV core, which is highly conserved among various HCV genotypes with amino acid homology exceeding 95% (12, 14) and therefore is an attractive target for the generation of an HCV vaccine (19, 41). Such a combination of foreign epitopes did not prevent correct self-assembly of chimeric HBc-based particles and provided them with specific HBV and HCV antigenicity and immunogenicity in mice.     

Tomato bushy stunt virus (TBSV), a versatile platform for polyvalent display of antigenic epitopes and vaccine design

Viruses-like particles (VLPs) are frequently being used as platforms for polyvalent display of foreign epitopes of interest on their capsid surface to improve their presentation enhancing the antigenicity and host immune response. In the present study, we used the VLPs of Tomato bushy stunt virus (TBSV), an icosahedral plant virus, as a platform to display 180 copies of 16 amino acid epitopes of ricin toxin fused to the C-terminal end of a modified TBSV capsid protein (NΔ52). Expression of the chimeric recombinant protein in insect cells resulted in spontaneous assembly of VLPs displaying the ricin epitope. Cryo-electron microscopy and image reconstruction of the chimeric VLPs at 22 Å resolution revealed the locations and orientation of the ricin epitope exposed on the TBSV capsid surface. Furthermore, injection of chimeric VLPs into mice generated antisera that detected the native ricin toxin. The ease of fusing of short peptides of 15-20 residues and their ability to form two kinds (T = 1, T = 3) of bio-nanoparticles that result in the display of 60 or 180 copies of less constrained and highly exposed antigenic epitopes makes TBSV an attractive and versatile display platform for vaccine design.     

Induction of T cell response by bluetongue virus core-like particles expressing a T cell epitope of the M1 protein of influenza A virus

A CD4⁺ T cell epitope of the influenza virus matrix protein corresponding to the C terminus (QAYQKRMGVQMQRFK) was inserted into the VP7 gene of bluetongue virus (BTV). The chimeric protein was expressed by a dual recombinant Autographa californica polyhedrosis virus (AcNPV), which encodes the two inner capsid proteins VP3 and VP7 of BTV. When Spodoptera frugiperda cells (Sf9 cells) were infected with this recombinant BTV, core-like particles (CLPs) were formed as demonstrated by electron microscopy. To study the immunogenicity of a foreign epitope deprived of its natural flanking sequences in vitro, purified CLPs expressing the T cell epitope were used to stimulate two different MHC class II-restricted CD4⁺ human T cell clones. One of these T cell clones, ALF 3.7 was specific for the inserted epitope, whereas the other T cell clone ALF 4.4 recognized shorter derivates of the given epitope. CLPs with the inserted epitope were presented as efficiently as purified influenza virus matrix protein to the clone ALF 3.7, whereas clone ALF 4.4 showed no proliferative response. Received: 17 February 1998     

Epitope mapping and affinity purification of monospecific antibodies by Escherichia coli cell surface display of gene-derived random peptide libraries.

We report a method for the precise mapping of linear epitopes by presenting a peptide library on the surface of Escherichia coli cells. A random library of gene fragments derived from the classical swine fever virus (CSFV) envelope protein E(rns) was generated by DNAse I cleavage and cloned into a specially designed bacterial surface display vector. A carboxyterminally truncated intimin, an adhesin from enteropathogenic E. coli, serves as a carrier protein to present foreign peptides on the surface of E. coli K12 cells. Epitope-presenting cells were isolated by immunofluorescence staining of the bacterial cell population with monoclonal anti-E(rns) antibodies followed by fluorescence-activated cell sorting (FACS). Nucleotide sequence analysis of the coding sequence for the cloned target gene fragments of a few FACS-positive clones allowed the identification of the respective epitope sequence. A major linear antigenic determinant of the E(rns) protein could be identified by epitope mapping with a polyclonal anti-E(rns) serum. Furthermore, the high-density surface display of intimin-peptide fusions allowed us to use epitope-presenting bacteria directly as whole cell adsorbants for affinity purification of monospecific antibodies. Monospecific antibodies directed against the carboxyterminal fragment of E(rns) were isolated and used for immunostaining of transfected BHK-21 cells to validate the transient expression of E(rns). This demonstrates that gene-fragment libraries displayed on E. coli cells as fusion proteins with intimin are useful tools for rapid mapping of linear epitopes recognized by monoclonal antibodies (MAbs) and polyclonal sera and for the affinity purification of monospecific antibodies by adsorption to the E. coli surface exposed antigenic peptide.