黄热病毒NS1蛋白的制备及免疫原性鉴定

目的 原核系统克隆表达黄热病毒(yellow fever virus, YFV)非结构蛋白1(nonstructural protein 1,NS1),鉴定其免疫原性。方法 以YFV-17D疫苗株为模板,常规分子生物学方法构建pQE30-YFV NS1表达载体,原核表达纯化YFVNS1重组蛋白;免疫印记、免疫荧光和酶联免疫吸附实验验证其免疫原性。结果 成功构建重组质粒pQE30-YFV NS1,制备纯化可溶性YFV NS1蛋白;该重组YFV NS1蛋白与登革病毒、黄热病毒、乙脑病毒、西尼罗河病毒免疫小鼠腹水及寨卡病毒NS1、YFV NS1蛋白免疫小鼠血清均发生反应,重组YFV NS1蛋白免疫小鼠血清与YFV感染细胞超声上清也发生反应。结论 获得高纯度YFV NS1重组蛋白,且具有较好的免疫原性,含天然NS1蛋白表位,为基于NS1黄热病毒早期抗原诊断方法和蛋白功能研究奠定基础。     

Ⅰ型登革病毒ns1基因克隆及其表达产物的免疫原性研究

目的克隆并表达Ⅰ型登革病毒非结构蛋白1(NS1)基因,初步鉴定其免疫原性。方法登革热Ⅰ型病毒标准株感染C6/36细胞后,抽提病毒RNA,经RT-PCR方法扩增出NS1全长基因片段,经T-A克隆后,在QIA表达系统中表达,表达产物用Ni柱亲和层析纯化后,用兔抗Ⅰ型登革病毒免疫血清及登革热患者血清对重组蛋白进行Western Blot及ELISA鉴定。结果构建的重组质粒pQE-30/DV1NS1经IPTG诱导,重组蛋白NS1高效表达并纯化成功,经Western Blot及ELISA证实重组蛋白NS1可以被免疫血清和病人血清特异识别。结论Ⅰ型登革病毒非结构蛋白NS1表达载体在大肠杆菌M15中高效表达。纯化产物具有较强的免疫原性,为进一步研究NS1的生物学特性和血清学检测奠定了基础。     

Ⅱ型登革病毒NS1基因的克隆及其在昆虫细胞中的表达

目的获得II型登革热病毒NS1基因并在昆虫细胞中表达,为进一步研发登革热血清学检测试剂盒提供抗原。方法RT-PCR扩增II型登革热病毒NS1基因并测序列,并定向克隆入杆状病毒转移载体pFastBac-HTA,获得重组转移载体pFastBac-NS1。并将pFastBac-NS1转化到DH10Bac感受态细胞中,筛选到重组转座子rBacmid-NS1。在脂质体介导下将rBacmid-NS1转染Sf9昆虫细胞获得重组杆状病毒rBV-NS1。rBV-NS1感染Sf9细胞后,通过SDS-PAG和Western blot检测NS1重组蛋白。结果成功克隆II型登革病毒NS1基因,SDS-PAGE、间接免疫荧光和Western blot检测表明NS1基因在昆虫细胞得到表达,能与登革患者血清发生特异性免疫反应,具有免疫原性。结论II型登革病毒非结构蛋白NS1在昆虫中表达,为进一步研究NS1的生物学特性和血清学检测奠定基础。     

II型登革病毒NS1基因的克隆及其在昆虫细胞中的表达

目的获得II型登革热病毒NS1基因并在昆虫细胞中表达,为进一步研发登革热血清学检测试剂盒提供抗原。方法RT-PCR扩增II型登革热病毒NS1基因并测序列,并定向克隆入杆状病毒转移载体pFastBac-HTA,获得重组转移载体pFastBac-NS1。并将pFastBac-NS1转化到DH10Bac感受态细胞中,筛选到重组转座子rBacmid-NS1。在脂质体介导下将rBacmid-NS1转染Sf9昆虫细胞获得重组杆状病毒rBV-NS1。rBV-NS1感染Sf9细胞后,通过SDS-PAG和Western blot检测NS1重组蛋白。结果成功克隆II型登革病毒NS1基因,SDS-PAGE、间接免疫荧光和Western blot检测表明NS1基因在昆虫细胞得到表达,能与登革患者血清发生特异性免疫反应,具有免疫原性。结论II型登革病毒非结构蛋白NS1在昆虫中表达,为进一步研究NS1的生物学特性和血清学检测奠定基础。     

Ⅱ型登革病毒非结构蛋白NS1血清型特异性单克隆抗体的制备与鉴定

目的制备并鉴定Ⅱ型登革病毒非结构蛋白NS1(DV2-NS1)的血清型特异性单克隆抗体。方法以具有良好抗原性的重组DV2-NS1蛋白与灭活的Ⅱ型登革病毒(DV2)混合免疫Balb/c小鼠,取其脾细胞与小鼠骨髓瘤细胞融合,杂交瘤细胞经间接ELISA法、IFA法筛选,ELISA、IFA及WesternBlot对mAbs的类型及亚类、交叉实验及特异性等进行鉴定。结果免疫的Balb/c小鼠经多次融合筛选,共获得14株血清型特异性抗DV2-NS1蛋白的mAbs,其亚类测定两株为IgG2b,余均为IgG1。ELISA和免疫印迹显示这些mAbs与重组DV2-NS1蛋白和DV2抗原均特异性结合,IFA结果显示这14株单抗特异结合Ⅱ型登革病毒,与其它3型登革病毒无交叉。结论成功获得了特异性针对DV2-NS1蛋白的mAb,为进一步研究NS1蛋白的结构和功能以及研制早期诊断试剂奠定基础。     

西尼罗河病毒E蛋白结构域Ⅲ的原核表达及间接ELISA方法的建立

目的 建立西尼罗河病毒(West Nile Virus, WNV)抗体检测方法。方法 人工合成了WNV NY99株E蛋白结构域Ⅲ(DⅢ)基因序列,构建了重组表达载体PET-28a-DⅢ。结果 重组质粒转化BL21宿主菌后诱导表达,SDS-PAGE分析表明,表达产物相对分子量17 kD,以包涵体形式存在。对表达产物作变性和复性及纯化处理,Western-blot鉴定结果表明,纯化产物可被WNV血清识别。将纯化重组蛋白包被酶标板,优化间接ELISA反应条件,抗原最佳包被浓度为3.75 μg/mL、血清最佳稀释度为1∶1 600、酶标二抗最佳稀释度1∶6 000、阴阳血清临界值为0.148。特异性、敏感性及重复性试验结果表明,本方法特异性强、敏感性高、重复性良好。结论 本研究为WNV感染的血清学诊断提供了技术储备。     

4种血清型登革病毒多表位重组抗原的表达及血清学初步评价

目的在原核表达系统中对登革病毒包膜蛋白(E蛋白)和非结构蛋白1(NS1)融合的B细胞抗原表位进行表达、纯化及血清学评价。方法将B细胞抗原表位用形成α螺旋的连接肽(EAAAK)2作为接头,串联合成1条全新的多表位融合重组基因rE,将其克隆到原核表达载体pET-28a(+)中,转化大肠杆菌BL21(DE3)后经IPTG诱导表达融合蛋白,用镍柱对重组蛋白纯化,并用SDS-PAGE和Western blot方法鉴定表达产物。以融合蛋白为抗原,用间接ELISA检测登革热病人血清IgM抗体。结果重组表达载体pET28a-rE构建成功,并在大肠杆菌BL21(DE3)中成功表达。融合蛋白主要以包涵体形式存在,用镍柱纯化获得高纯度的目的蛋白,SDS-PAGE和Western blot检测结果显示蛋白分子量大小与预期结果相符,建立的间接ELISA具有较高的准确性。结论原核表达的登革病毒多表位融合蛋白具有良好的血清学检测价值。     

流行性乙型脑炎病毒NS5蛋白的表达

目的 在大肠杆菌中表达并纯化流行性乙型脑炎病毒NS5蛋白,为进一步研究乙脑病毒NS5蛋白的结构与功能奠定基础。方法 根据乙脑病毒NS5蛋白的基础序列,设计两对PCR引物,采用RT-PCR法分别扩增乙脑病毒JaOH0566株部分及全长NS5基因。将扩增产物分别克隆到表达载体pQE30。筛选重组质粒,转化大肠杆菌表达重组蛋白。重组蛋白经金属柱亲和层析纯化。结果与结论 获得了含部分及全长乙脑病毒NS5基因的重组质粒,重组质粒经限制性酶双酶切、DNA序列分析及PCR扩增筛选证实。在大肠杆菌中表现出了带6个组氨酸头的部分及全长的重组乙脑病毒NS5蛋白。经SDS-PAGE及Western-blot分析证实表达蛋白确定是重组乙脑病毒NS5蛋白。     

肺炎支原体热休克蛋白HSP70的表达、纯化及其免疫原性分析北大核心CSCD

目的构建肺炎支原体(MP)热休克蛋白HSP70重组原核表达质粒,纯化并鉴定其免疫原性。方法以肺炎支原体ATCC 29342为模板,利用搭桥PCR扩增HSP70全序列,胶回收纯化后测序验证。使用BamH1和Xho1双酶切PCR产物,构建重组表达质粒pGEX-4T-1-HSP70,转入大肠埃希菌BL21中,经IPTG诱导目的蛋白表达,对表达产物进行12.5%SDS-PAGE和质谱鉴定。利用AKTA explore 100蛋白纯化仪纯化重组HSP70,以此为抗原与MP感染者血清进行Western blot,检测其免疫反应性。结果搭桥PCR成功完成HSP70基因A1728G突变,重组质粒pGEX-4T-1-HSP70构建正确,转化BL21后经IPTG诱导表达分子质量单位92 ku含GST标签的重组HSP70,纯化蛋白经Western blot检测能与感染Ⅰ型和Ⅱ型MP菌株患儿血清发生特异性反应。结论获得重组HSP70完整蛋白,纯化产物具有免疫反应性,为制备高效防治肺炎支原体感染的基因工程疫苗及研究HSP70蛋白的免疫学功能奠定了基础。     

A型口蹄疫病毒型特异性抗原的可溶性原核表达及多克隆抗体的制备

目的可溶性表达A型口蹄疫病毒型特异性结构蛋白VP1,制备型特异性的兔抗A型FMDV VP1多克隆抗体。方法以A型口蹄疫病毒结构蛋白VP1基因重组克隆载体pGEM-AVP1为模板,设计表达引物,经PCR扩增获得上游带有OmpT信号肽编码序列的VP1基因编码区,将其克隆至该表达载体pET-30a(+)中,构建可溶性原核表达载体pET-30a-OmpT-AVP1。将该重组质粒转化大肠杆菌工程菌株BL21-(DE3)-plysS,经IPTG诱导表达,以金属离子螯合层析法对可溶性表达的VP1融合蛋白进行纯化,然后用纯化的蛋白免疫新西兰大耳白兔制备其多克隆抗体,以ELISA、Western blot和间接免疫荧光法分别对多克隆抗体进行鉴定。结果 SDS-PAGE电泳分析显示pET-30a-OmpT-AVP1重组菌经诱导后表达一Mr约为33 000的VP1融合蛋白,与预期结果相符。目的蛋白纯化后,在电泳图片上显示较为清晰的单一条带。Western blot分析结果显示,VP1蛋白可与豚鼠抗A型口蹄疫病毒阳性血清反应。用纯化VP1蛋白免疫新西兰大耳白兔制备的多克隆抗体效价达1∶12 800以上,具有较高的型特异性,并且可与同型FMDV细胞培养物中的病毒抗原发生反应。结论制备了具有高亲和性和特异性的兔抗A型FMDV结构蛋白VP1多克隆抗体,为A型FMDV易感动物的抗体筛查及病原鉴定奠定了基础。     

Isolation and partial characterization of dengue virus type 2 and 4 strains from dengue fever and dengue haemorrhagic fever patients from Mindanao, Republic of the Philippines

OBJECTIVE: Isolation of dengue virus from dengue fever and dengue haemorrhagic fever cases from Mindanao, Republic of the Philippines. METHODS: 12 patients with clinically suspected dengue fever (DF) or dengue haemorrhagic fever (DHF) presenting in four regional hospitals between August and September 1995 on Minadano were enrolled in the study. Dengue virus was isolated by inoculation of Vero/E6 or C6/36 cells with patient serum. IgM antibodies were measured using a commercial test system. Up to 454 bp of the capsid region and 240 bp of the E/NS1 gene junction of different viral isolates were sequenced and phylogenetically analyzed. RESULTS: Virus could be isolated from seven patients, five isolates were typed as dengue virus type 2 and two as dengue virus type 4 by immunostaining with monoclonal antibodies or by RT/PCR. Phylogenetic analysis confirmed a close relationship of the dengue virus type 2 isolates with viruses isolated in the Philippines in 1983 and 1988. CONCLUSION: As observed in studies from other parts of South East Asia, dengue virus type 2 was readily isolated from dengue haemorrhagic fever cases. Dengue virus type 2 and 4 circulate in Mindanao, Philippines, with dengue type 2 being responsible for most of our severe DF or DHF cases.     

Dengue outbreak in Swat and Mansehra,Pakistan 2013;an epidemiological and diagnostic perspective

Objective:To High light some epidemiological,clinical and diagnostic features of dengue fever during an outbreak and the role of different diagnostic techniques to achieve the highest level of accuracy in results.Methods:Blood samples(n=323) were collected along with epidemiological and clinical data from suspected dengue patients who visited different hospitals in Swat and Mansehra district of Pakistan between May-November 2013 during a dengue outbreak.Samples were tested for the detection of viral nucleic acid by real-lime PCR.non structural protein-1(NS1antigen and IgM antibodies by ELISA.Results:Out of 323 cases with clinical dengue infection,304 were positive by one or more diagnostic parameter:201 samples were positive by real-time PCR,209 were positive by NS1 ELISA and 190 were positive by IgM antibodies.Sensitivities of real-time PCR and NS1 F.LISA were comparable for early diagnosis of dengue virus infection.IgM antibody detection assay was found useful for the diagnosis in the samples collected later than day 5 of onset.Conclusions:The use of real-lime PCR or detection of non stnictural protein NS 1 by ELISA followed by IgM antibodies detection can be recommended for early diagnosis of dengue virus infection with a high level of accuracy.     

Differentiation of West Nile virus-infected animals from vaccinated animals by competitive ELISA using monoclonal antibodies against non-structural protein 1

Antibodies against non-structural protein 1 (NS1) are considered to be the most reliable indicator of a present or past infection by West Nile virus (WNV) in animals. In this study, an in-house competitive enzyme-linked immunosorbent assay (NS1-cELISA) utilizing baculovirus-expressed NS1 and monoclonal antibodies against NS1 was established for the detection of antibody responses to NS1 in WNV-infected animals. The assay was validated by the simultaneous detection of early antibody responses to NS1 and the structural envelope protein in animals infected with WNV, or inoculated with inactivated WNV. NS1-cELISA detected WNV antibodies at 6 days post-infection (dpi) in a WNV-infected rabbit (percent inhibition [PI] value of 84.0), and at 10 dpi in a WNV-infected chicken (PI value of 67.0). The NS1-cELISA was able to detect WNV antibodies in sera from all WNV-infected rabbits at 10 dpi (PI value of 79.2±18.0), and from three of four WNV-infected chickens at 14 dpi (PI value of 73.7±22.8). The results of this study demonstrate that the antibody response to NS1 is similar to that against envelope protein in WNV-infected rabbits and chickens, whereas animals inoculated with inactivated WNV develop antibody responses only to the envelope protein but not to NS1. The NS1-cELISA developed here has the potential to be a useful tool for monitoring WNV circulation (i.e., the prevalence of specific antibodies against WNV NS1), by assaying serum samples from regions in which an inactivated vaccine control strategy has been implemented.     

Immune response in rabbits to dengue viral proteins

Antisera to all types of dengue and Japanese encephalitis (JE) viruses were raised in rabbits. The first set of rabbits was immunized with crude antigens prepared by a sucrose acetone extraction. The first generation of antisera demonstrated antibody activity towards the group specific flaviviruses, without unwanted antibody activity towards the mouse brain material. Antibody activity towards E, NS3, NS5 and NS1 could be observed by western blot/immunoenzymatic assay. Another set of rabbits was immunized with the precipitin complexes formed between antisera raised against each type of dengue, or JE viruses, and their homologous antigens. Each rabbit serum was screened again by the western blot/immunoenzymatic method, and was absorbed with other types of dengue viruses until the specific activity towards the immunized viral antigen was obtained. The last 2 bands detected on the viral antigen strip were the doublet of protein bands at Mr 67 and 71 kDa, which are the NS3 protein. The specific polyclonal antisera obtained can be used with other tests as well as the monoclonal antibody. Since absorption can lead to type specific antisera, this NS3 protein must be quite unique, it processes a type specific determinant (s) and deserves further study as a target molecule at the polypeptide level as well as at the RNA level.     

Facilitation of cell adhesion by immobilized dengue viral nonstructural protein 1 (NS1): arginine-glycine-aspartic acid structural mimicry within the dengue viral NS1 antigen

Dengue virus infection causes life-threatening hemorrhagic fever. Increasing evidence implies that dengue viral nonstructural protein 1 (NS1) exhibits a tendency to elicit potentially hazardous autoantibodies, which show a wide spectrum of specificity against extracellular matrix and platelet antigens. How NS1 elicits autoantibodies remains unclear. To address the hypothesis that NS1 and matrix proteins may have structural and functional similarity, cell-matrix and cell-NS1 interactions were evaluated using a cell-adhesion assay. The present study showed that dengue NS1 immobilized on coverslips resulted in more cell adhesion than did the control proteins. This cell adhesion was inhibited by peptides containing arginine-glycine-aspartic acid (RGD), a motif important for integrin-mediated cell adhesion. In addition, anti-NS1 antibodies blocked RGD-mediated cell adhesion. Although there is no RGD motif in the NS1 protein sequence, these data indicate that RGD structural mimicry exists within the NS1 antigen.     

Induction of neutralizing antibodies specific to dengue virus serotypes 2 and 4 by a bivalent antigen composed of linked envelope domains III of these two serotypes

There is no vaccine to prevent dengue fever, a mosquito-borne viral disease, caused by four serotypes of dengue viruses. In this study, which has been prompted by the emergence of dengue virus envelope domain III as a promising sub-unit vaccine candidate, we have examined the possibility of developing a chimeric bivalent antigen with the potential to elicit neutralizing antibodies against two serotypes simultaneously. We created a chimeric dengue antigen by splicing envelope domain IIIs of serotypes 2 and 4. It was expressed in Escherichia coli and purified to near homogeneity. This protein retains the antigenic identities of both its precursors. It elicited antibodies that could efficiently block host cell binding of both serotypes 2 and 4 of dengue virus and neutralize their infectivity (neutralizing antibody titers approximately 1:40 and ~1:80 for dengue virus serotypes 2 and 4, respectively). This work could be a forerunner to the development of a single envelope domain III-based tetravalent antigen.     

登革3型病毒义乌流行株免疫原性研究

目的对2009年浙江省义乌市暴发流行的登革3型病毒进行系统进化分析并初步研究其E蛋白的免疫原性。方法 RT-PCR扩增义乌分离株全基因组,利用MEGA 4分别构建E及NS1区域核苷酸及氨基酸系统发生树,进行系统进化分析。构建重组质粒JESS-ywD3prM/E397JEV-pcDNA5,IFA及Western Blot检测E蛋白在293T细胞中的表达及分泌情况。将纯化后的分泌性E蛋白免疫BALB/c小鼠,通过ELISA、中和试验等方法对体液免疫进行测定。结果登革3型病毒义乌分离株与广州GZ1D3株及印度GWL-25株核苷酸及氨基酸序列同源性均达到99%以上;其分泌性E蛋白可以刺激小鼠产生登革特异性IgG抗体及针对同型病毒的中和抗体。结论义乌分离株属于登革3型病毒亚型Ⅲ,其分泌性E蛋白具有一定的免疫原性。