Expression and evaluation of Chikungunya virus E1 and E2 envelope proteins for serodiagnosis of Chikungunya virus infection

Purpose

Chikungunya virus (CHIKV) causes endemic or epidemic outbreaks of CHIKV fever, which is a mosquitoe-transmitted viral disease in Africa, India, South-East Asia, and recently Southern Europe. Currently, serological diagnostic tests such as hemagglutination inhibition test (HI test), in-house IgM capture enzyme-linked immunosorbent assays (ELISA), and indirect immunofluorescence test were used for diagnosis of chikungunya fever, which are based on whole virus antigens.

Materials and Methods

CHIKV E1, and E2 envelope proteins for the CHIKV-specific serodiagnostic reagents for chikungunya fever were expressed in baculovirus expression system. The seroreactivity of recombinant CHIKV E1 and E2 envelope proteins were evaluated using sera panels of patients from Laboratoire Marcel Merieux by indirect IgM capture ELISA.

Results

The recombinant CHIKV E1 and E2 envelope protein showed sensitivity of 77.5% and 90%, respectively. The specificities of both CHIKV E1 and E2 envelope proteins were 100%.

Conclusion

The recombinant CHIKV E1 and E2 envelope proteins could be a useful diagnostic reagent for CHIKV infection.     

重组风疹病毒外膜蛋白E1的表达及其在血清学中的初步应用

目的 在大肠埃希菌中表达重组风疹病毒外膜蛋白E1,用其作为包被抗原,建立一种用于诊断风疹病毒感染的ELISA检测方法 .方法 通过基因重组的方式构建表达质粒并在大肠埃希菌中表达风疹病毒外膜蛋白E1,蛋白纯化后作为包被抗原,用ELISA的方法 检测世界卫生组织(WHO)的风疹检测质控血清以及来自广西桂林的未知血清样本.结果 采用WHO用于风疹检测的质控血清对所表达的重组抗原的抗原性进行鉴定,通过试验,特异性、敏感性均为100%.用表达的抗原对来自我国广西的200份未知血清样本进行风疹病毒外膜蛋白抗体的检测,阳性率为93%,与文献报道的我国其他地区风疹病毒抗体阳性率基本一致.结论 通过实验我们表达了具有良好抗原性的风疹病毒外膜蛋白E1,为进一步研究风疹病毒感染的实验室诊断技术奠定了基础.     

风疹病毒JR23株糖蛋白E1在毕赤酵母表达系统中的表达和抗原性分析

目的在毕赤酵母表达系统中表达风疹病毒(rubella virus，RV)JR23株包膜糖蛋白E1，为研究E1蛋白的结构功能、开发基因工程疫苗和重组蛋白诊断试剂盒奠定基础。方法E1基因的表达质粒pGAPZαa-E1经AVRⅡ线性化后用LiCl法转化酵母菌，在YPD(含100μg／ml Zeocin^TM)平板上两次筛选，挑出单菌落，于液体YPD中培养，并在不同时间收集培养物，用SDS-PAGE和Western blot进行分析。结果SDS-PAGE显示E1重组蛋白在毕赤酵母中高效稳定表达，在48h时表达量达到最高，之后趋于稳定，上清和细胞中均有蛋白表达。Western blot结果表明，上清中的E1重组蛋白能够分别与抗RV的阳性血清和单克隆抗体反应，而细胞中的E1重组蛋白只能与抗RV的阳性血清反应，不能与单克隆抗体反应。这说明所表达的蛋白一部分在信号肽的引导下分泌出胞，并经过折叠形成了正确的构像，能够与单克隆抗体结合；而另一部分由于蛋白本身的跨膜区连在了细胞膜上没有分泌出去，没有形成能够被单抗识别的构像，不能与单抗结合。结论E1包膜糖蛋白在酵母菌中成功表达，且免疫反应性良好。     

人骨形成蛋白2在昆虫杆状病毒表达系统中的表达及初步鉴定

目的:研究hBMP2在昆虫杆状病毒系统中的表达规律。方法:将编码hBMP2的全长cDNA克隆入转移载体PK8中,重组后的载体与线性化的病毒DNA经脂质体包裹转染昆虫细胞。重组病毒经蓝白筛选后,提取病毒DNA进行PCR扩增,鉴定目的基因。收集重组病毒感染4d的细胞,进行免疫荧光及电子显微镜观察。结果:含有目的基因的重组载体经酶切可切下相应大小的目的基因片段。PCR产物的电泳结果表明,有目的基因片段的扩增。免疫荧光染色呈阳性的颗粒分布在昆虫细胞的胞浆及胞膜。结论:初步证实,hBMP2在此套表达系统中获得了表达。     

The identification and characterization of a monoclonal antibody to the vaccinia virus E3 protein

Monoclonal antibodies with reactivity to vaccinia virus specific proteins are useful reagents to study the proteins as well as to help understand aspects of the poxvirus life cycle. Using a vaccinia virus proteomics microarray, we found a hybridoma (MAb 3015B2) from a vaccinia virus vaccinated mouse that reacted with the product of the E3L gene. The specificity to the E3 protein was confirmed by Western blotting and immunofluorescence of cells infected with either wild-type vaccinia virus or a mutant virus with the E3L gene deleted. Antibody reactivity with E3 was also seen in cells transfected with a plasmid expressing the E3 protein. A panel of mutated vaccinia viruses with truncations in the E3L gene revealed that while MAb 3015B2 reacted with E3 lacking the C-terminal 7 amino acids, it lost reactivity with a mutant E3 lacking the C-terminal 26 amino acids. This indicates that the antigenic site recognized by 3015B2 is on the C-terminus, somewhere between amino acids 164 through 183. The antibody also recognizes the E3 protein encoded by other orthopoxviruses. This antibody will be useful for further investigations of the E3 protein as well as a useful reagent to indicate vaccinia virus early protein expression.     

马乙型脑炎病毒E蛋白的原核表达及间接ELISA的初步应用

目的原核表达马乙型脑炎病毒(Japanese encephalitis virus,JEV)E蛋白,建立JEV间接ELISA诊断方法。方法根据GenBank(AF315119.1)公布的JEVSA14-14-2株E蛋白基因序列设计一对引物,提取病毒RNA经反转录和RT-PCR扩增获得E蛋白编码基因片段,将该片段插入表达载体pET30a(+),转化BL21(DE3)后经IPTG诱导蛋白表达,Western blot检测活性,以表达的E蛋白为包被抗原建立间接ELISA诊断方法。结果获得约1500bp目的片段,与GenBank上的序列同源性100%,其表达产物相对分子质量约为60000,Western blot结果显示该蛋白可与JEV阳性血清结合,具有免疫反应性。建立了间接ELISA检测方法,对不同省份的340份马血清进行检测,其中154份为阳性。结论原核表达JEV的E蛋白具有良好的免疫活性,建立的间接ELISA诊断方法特异性和灵敏性较好,可用于JEV的现地检测。     

乙型脑炎病毒E蛋白在巴斯德毕赤酵母中的表达

目的：用巴斯德毕赤酵母系统表达乙型脑炎病毒(JEV)E蛋白。方法：将JEV E蛋白基因亚克隆人真核表达载体pPIC9K，以电穿孔法转化酵母SMD1168。用MD平板筛选重组子、G418筛选高拷贝转化子，经甲醇诱导表达后，SDS—PAGE和免疫印迹分析表达产物。结果：由于糖基化不同，所表达产物的相对分子质量(Mr)约为113000和78000，表达量约为50mg/L。结论：在巴斯德比赤酵母中成功地表达了JEVE蛋白，为制备JEV的诊断抗原和基因工程重组疫苗打下基础。     

我国登革2型病毒43株包膜E蛋白MBP-B165抗原性的研究

目的 通过对我国登革2型病毒株包膜E蛋白包括B区在内的第267－432氨基酸编码基因片段的表达,研究MBP－B165蛋白的抗原性。方法 首先采用PCR方法扩增了编码B165蛋白的基因片段,并将其插入到pMal－C2核载体进行融合表达。采用蛋白印迹和ELISA法对表达产物进行特异性鉴定。用表达的融合蛋白MBP－B165免疫大白兔,产通过ELISA法检测兔免疫血清中登革2型病毒特异的抗体。结果 表达的融合蛋白MBP－B165可与我国登革2型病毒株抗体特异结合,而且与登革1、3和4型病毒参考株的多克隆抗体均具有较高的反应性。用表达蛋白免疫大白兔可产生针对我国登革2型病毒株E蛋白的特异抗体,并且该抗体与基他3个型病毒参考株有交叉反应。结论 我国登革2型病毒43株E蛋白包括B区在内的第267－432氨基酸序列具有一定的抗原性,而且具有黄病毒亚组特异的反应性表位,即4个型登革病毒的结构保守性表位。     

人促血液血管生成素的原核表达、分离纯化及活性分析

目的利用基因工程技术获得重组的人促血液血管生成素（HAPO）,以探讨其对骨髓细胞的作用。方法提取人胎肝总RNA,利用RT-PCR、克隆HAPO cDNA插入表达载体pET32c,使之在大肠杆菌BL21（DE3）中表达;用DEAE Sephamse Fast Flow阴离子交换柱、Ni-Chelating Sepharose Fast Flow亲和柱以及SP Sepharose Fast Flow阳离子交换柱分离纯化,肠激酶酶切,液体培养小鼠骨髓细胞。结果经IPTG诱导HAPO实现了在大肠杆菌中的可溶性表达,经一系列层析获得融合的rh-HAPO,肠激酶酶切除去N-端融合部分后,获得高纯度的rh-HAPO。液体培养小鼠骨髓实验发现rh-HAPO可促进CD34^＋细胞和flk-1细胞的增殖。结论重组蛋白rh-HAPO可促进造血干／祖细胞的增殖。     

HCV核心蛋白在大肠杆菌中的表达及免疫学特性研究

目的 研究HCV核心蛋白在大肠杆菌中的非融合表达及重组蛋白的免疫学特性。方法 用DNA重组技术在两种表达质粒（pQE3O和pTrcHisA）、4种宿主菌（DH5a,TOP10,BL21和M15）中表达HCV全长及羟基端部分缺失的核心蛋白（aal～191,aal～154和aal～69）,表达蛋白经SDSF-PAGE检测,免疫印亦分析,亲和层析法纯化后免疫BALB/C小鼠,ELISA法检测免疫小鼠血清中抗HCV抗体水平。结果 HCV核心蛋白C154,C191在pQE30/M15中获得了表达,表达量分别占菌体总蛋白的18.2%和9.3%。免疫印迹分析的结果显示在C154和C191相应位置处出现杂交条带。ELISA结果显示C154和C191诱导小鼠产生了抗HCV抗体。结论 表达的重组蛋白具有抗原特异性和免疫原性。“截断”型HCV核心蛋白的抗原性和免疫原性并未因羧端的部分缺失而减弱。     

丙型肝炎病毒H株包膜糖蛋白在昆虫细胞中的表达

目的 利用杆状病毒表达系统,在昆虫细胞中表达了丙型肝炎病毒（HCV）H株的包膜糖蛋白E,并应用表达产物对HCV感染患者血清中抗膜蛋白抗体进行检测。方法 将HCVH株E基因片段克隆到杆状病毒转移载体上,转染昆虫细胞,表达包膜糖蛋白,经免疫杂交法鉴定表达产物,并用细胞间接免疫荧光法检测患者血清抗膜蛋白抗体的水平。结果 Western blot显示,表达产物中有多条分子量不同、可与HCV RNA阳性血甭反应的蛋白,细胞免疫荧光染色表明,HCV包膜糖蛋白在细胞浆中表达,用表达产物分别检测HCV患者血清,发现仅11.4%血清中含有膜抗体。结论 成功利用昆虫细胞表达了HCV包膜糖蛋白,为HCV疫苗的研究奠定了基础。     

人N端脂多糖结合蛋白基因在sf21昆虫细胞中的表达

目的 表达重组人N端脂多糖结合蛋白（truncated lipopolysaccharide binding proten,tIBP）。方法 通过病毒鉴定、SDS-PAGE、western blot、毛细管电泳、体外结合实验、细胞活性实验对重组病毒及重组蛋白tLBP的分子量、纯度和生物学活性进行分析。结果 重组病毒空斑分析确定MOI(multiplicity of infection)为8～10,SDS-PAGE显示感染时间65～72h为最佳表达分析;凝胶扫描显示特异表达蛋白占总产物的9.8%,纯化蛋白的分子量约27000u,纯度达95%以上;毛细管电泳显示表达产物呈单一峰型;Lowry法测定约1L上清液可获9mg纯化蛋白;Western blot间接显示表达产物反应带与预期值相符;酶联体外结合实验证实该蛋白可特异结合LPS。应用U937细胞,经LPS(1ng/mL）刺激与LPS（1mg/mL）刺激加纯化蛋白细胞中获得高效表达,并观察到它在体外具有结合或中和内毒素的活性作用。     

风疹病毒JR23株E1包膜糖蛋白的基因克隆与序列分析

目的：建立风疹病毒包膜糖蛋白E1的克隆载体，研究E1基因变异情况，并对其序列进行系统发生树分析。方法：利用RT－PCR方法扩增并回收风疹病毒JR23株的包膜糖蛋白E1的基因片段，将其与PMD－18T载体连接，经氨苄青霉素筛选，酶切鉴定，以获得风疹病毒E1蛋白基因的克隆，将此基因测序后，利用DNASTAR和WINSTAR软件包绘制系统发生树进行序列之间的比较分析。结果：筛选出含有风疹病毒E1蛋白基因的克隆，序列分析及发生树的绘制表明：JR23株与日本TCRB株及英国THOMAS株差别最小，分别为0．9％和1．2％，与北京BRD2株及香港XG379株差别最大，分别为7．6％和7．3％，与其它各株的差别均小于3％（除NC株为3．7％外），系统发生也与THO－MAS株、TCRB株最近，与BRD2株最远。结论：克隆载体的建立为进一步研究E1基因与糖蛋白功能的关系提供基础。系统发生表明中国不同地区风疹流行株基因序列存在明显差异，这对风疹病毒遗传与变异，分子流行病学研究，以及制备有效的亚单位疫苗提供了资料。     

Expression of the X protein of hepatitis B virus in insect cells using recombinant baculoviruses

The baculovirus system was used to express the X protein of human hepatitis B virus (HBV). The X open reading frames (X ORFs) from cloned viral DNA of the HBV subtypes ayw and adr were introduced into the genome ofAutographa californica nuclear polyhedrosis virus (AcNPV). The HBV-DNA of subtype adr derived from a hepatocellular carcinoma contains an X ORF and a 5 extended preX/X ORF, which were both used to construct X recombinant baculoviruses. Infection of Sf9 insect cells with these recombinant viruses yielded large amounts of the respective X proteins. They were identified by a set of mouse monoclonal antibodies directed against different epitopes of the ayw X protein using immunoblotting techniques. A subpopulation of the X protein expressed is modified, thus raising the molecular weight from the expected size of 17 kD to 21 kD. Indirect immunofluorescence and immunoelectron microscopy was performed to characterize the subcellular distribution of the X protein expressed in Sf9 cells. Data are presented that it accumulates as large globular structures within the cytoplasm and the nucleus of the infected cells.     

Isolation and characterization of human monoclonal antibodies against hepatitis C virus envelope glycoproteins

The isolation and characterization of human monoclonal antibodies (humAbs) against the hepatitis C Virus (HCV) glycoproteins E1 and E2 are described. B-cells from blood donors with anti-HCV were transformed with Epstein-Barr virus. The supernatants of the resulting lymphoblastoid clones were screened by ELISA with an extract of cells infected with a recombinant vaccinia virus RMPA95 expressing the envelope proteins E1 and E2 of an HCV genotype 1a virus (H strain). Positive clones were fused to the heteromyeloma cell line K6H6/B5. Fifteen heterohybridoma cell lines have been established. The specificity of the isolated humAbs was determined both by ELISA and Western blot assays. Several recombinant extracts expressing either the E1 or E2 protein or truncated forms were used in an attempt to map the epitopes on the viral glycoproteins. Some of the humAbs were used successfully for immunofluorescence investigation of transfected cells. Seven specific anti-E2 humAbs, which react with the envelope protein 2 of genotype 1a and 1b isolates, were characterized. J. Med. Virol. 55:28–34, 1998. © 1998 Wiley-Liss, Inc.     

Expression, characterization, and immunoreactivities of a soluble hepatitis E virus putative capsid protein species expressed in insect cells.

The hepatitis E virus (HEV) open reading frame-2 (ORF-2) is predicted to encode a 71-kDa putative capsid protein involved in virus particle formation. When insect Spodoptera frugiperda (Sf9) cells were infected with a recombinant baculovirus containing the entire ORF-2 sequence, two types of recombinant proteins were produced; an insoluble protein of 73 kDa and a soluble protein of 62 kDa. The 62-kDa species was shown to be a proteolytic cleavage product of the 73-kDa protein. N-terminal sequence analysis of the 62-kDa protein indicated that it lacked the first 111 amino acids that are present in the full-length 73-kDa protein. A soluble 62-kDa protein was produced without the proteolytic processing by inserting the coding sequence of amino acids 112 to 660 of ORF-2 in a baculovirus expression vector and using the corresponding virus to infect Sf9 cells. The two recombinant 62-kDa proteins made by different mechanisms displayed immunoreactivities very compatible to each other. The 62-kDa proteins obtained by both proteolytic processing and reengineering demonstrated much higher sensitivities in detecting anti-HEV antibodies in human sera than the antigens made from bacteria, as measured by enzyme-linked immunosorbent assay. The data suggest that the soluble 62-kDa protein made from insect cells contains additional epitopes not present in recombinant proteins made from bacteria. Therefore, the 62-kDa protein may be useful for HEV diagnostic improvement and vaccine development. The reengineered construct allows for the consistent large-scale production of the soluble 62-kDa protein without proteolytic processing.     

登革2型病毒NS3蛋白NTPase/RNA解旋酶结构域的原核表达及活性研究

目的 表达登革病毒非结构蛋白NS3 NTPase／RNA解旋酶结构域（dNS3），纯化表达产物并对其活性作初步研究。方法提取感染登革2型病毒的BHK-21细胞总RNA，RT-PCR扩增目的基因，经NcoⅠ、HindⅢ双酶切后连入表达载体pET28a，转化宿主菌BL21（DE3），优化诱导表达条件，SDS-PAGE和免疫印迹鉴定表达蛋白。表达产物经亲和层析纯化，超滤浓缩脱盐，孔雀绿钼酸铵法检测NTPase活性。结果成功构建重组表达载体pET28a-dNS3并在大肠杆菌中获得可溶性表达，纯化产物经测定具有良好的NTease活性及抗原性。体外条件下证实登革2型病毒非结构蛋白NS5（RDRP）对dNS3的ATPase活性有促进作用，提示在病毒复制时NS3与NS5间的相互作用对NS3的生物活性及对病毒复制过程可能具有调控作用。结论本研究为基于抑制NS3 NTPase／RNA解旋酶活性的抗病毒药物的筛选提供了实验依据。     

Detection of parvovirus B19 NS1-specific antibodies by ELISA and western blotting employing recombinant NS1 protein as antigen

Human parvovirus B19 (B19) encodes a number of nonstructural proteins, including the major protein, NS1, and two structural proteins, VP1 and VP2. The use of denatured NS1 in enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) assay has provided an opportunity to study some of the immunologic properties of NS1, but the results have been equivocal and the diagnostic sensitivity poor, probably because of the absence of conformational epitopes. Various viral isolates and baculovirus vectors were employed to produce recombinant B19 NS1 under nondenaturing conditions for the first time. To assess the antigenicity of purified B19 NS1, the reaction patterns of 252 samples were compared by B19 NS1 and VP2 ELISA. In sera from individuals with past infection (VP2 IgG-positive), the use of this new antigen increased significantly the sensitivity of ELISA compared with WB (78% vs. 33%, P = 0.001), contradicting perpetuated claims that B19 NS1 IgG is detected primarily in patients with arthralgia or chronic infection. Previous reports of the absence of NS1 IgG during the initial phase of infection (< 6 weeks) were proved incorrect by the detection of NS1 IgG in 60% of samples from patients recently infected by B19. Including conformational epitopes in the ELISA increases the diagnostic sensitivity, although immunologically, a temporal (years) attenuation of NS1 antibodies appears to take place. This novel diagnostic tool may be useful as a supplement in case of borderline results by VP2 ELISA and for monitoring the efficacy of future capsid-based B19 vaccines.