重组鼠疫菌F1抗原在大肠杆菌中的表达及免疫原性分析

利用基因重组技术,用pET42(b+)质粒在大肠杆菌DE3中表达鼠疫菌F1抗原。经分析rF1抗原基因序列与天然F1抗原结构基因序列完全一致,电泳扫描测其表达量为25%:W estern B lot结果表明,rF1抗原可与F1特异性抗体相互作用,具有天然F1抗原的活性。用镍离子亲和层析纯化rF1抗原免疫BALB/c小鼠,在其血清中可检测到高滴度的抗F1抗体。     

中试规模纯化重组鼠疫rF1-V融合蛋白及其免疫原性分析

重组F1-V融合蛋白(rF1-V)是目前在进行临床研究的鼠疫亚单位疫苗的主要成分。本研究摸索了rF1-V的可溶表达条件,并对条件进行了优化和放大,确定的中试发酵工艺为:在重组菌对数生长期中期加入50μmol/LIPTG,25℃诱导表达5h。通过硫酸铵分级沉淀、离子交换、疏水相互作用层析和凝胶过滤四步纯化,最终得到纯度为99%、回收率大于20%且各项检测指标合格的蛋白。在此基础上,将蛋白使用氢氧化铝佐剂进行吸附,在小鼠体内进行了免疫原性研究。ELISA测定两次皮下免疫后血清的抗体滴度。比较融合蛋白免疫组(rF1-V)与单一抗原免疫组(rF1、rV)以及联合抗原免疫组(rF1+rV)之间体液免疫反应的差异。结果显示:20μgrF1-V免疫剂量组诱导的抗F1抗体滴度明显高于其他组,抗V抗体滴度与其他组相比没有显著差异。表明本工艺制备的rF1-V抗原有望作为鼠疫亚单位疫苗的主要组分。     

鼠疫F1-V重组融合蛋白抗原的制备及其免疫保护效果的研究

为制备鼠疫耶尔森氏菌F1-V重组融合蛋白抗原,观察其免疫原性和免疫保护效果,通过疏水层析、阴离子交换层析、凝胶过滤层析纯化鼠疫F1-V重组融合蛋白抗原.用氢氧化铝凝胶吸附制备试验性鼠疫F1-V重组融合蛋白抗原,皮下接种健康BALB/c小鼠,ELISA检测血清F1-V抗体效价、MTT法测定淋巴细胞增殖能力,进一步用400LD50鼠疫耶尔森氏菌141标准毒株皮下攻毒,观察动物的存活情况.通过三步柱层析纯化获得的鼠疫F1-V重组融合蛋白抗原纯度达到90%以上.氢氧化铝凝胶吸附的鼠疫F1-V重组融合蛋白抗原免疫BALB/c小鼠三次,血清抗F1-V抗体效价为1∶(51200±800),对耶尔森氏菌141强毒株攻击的保护率是90%.上述结果表明,制备的鼠疫F1-V重组融合蛋白抗原具有良好的免疫原性和免疫保护效果,为研制鼠疫F1-V重组融合蛋白疫苗奠定了基础.     

新型鼠疫疫苗F1抗原原液性质的研究

目的新型鼠疫疫苗包含鼠疫减毒菌EV株培养提取的天然F1抗原。研究生理氯化钠溶液中F1抗原的生物与理化性质、结构概况及聚合状态等特性,以期对F1抗原的制备、质量控制及其免疫原性研究提供理论依据。方法①过碘酸-希夫(PAS)染色法、糖蛋白碳水化合物估测试剂盒鉴定F1抗原是否为糖蛋白,蒽酮-硫酸法定量测定F1抗原中多糖含量,基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)技术测定F1抗原单体相对分子质量并与理论值差异比对,间接证明F1抗原是否糖基化;②高效分子排阻色谱法联用多角度激光散射(HPSEC-MALLS)法研究保存于生理氯化钠溶液中F1抗原的天然聚集状态;③搜索GeneBank获得鼠疫菌F1抗原的核苷酸序列,经DNAStar软件翻译出氨基酸序列,并通过肽段覆盖率验证成熟F1抗原的氨基酸序列,以圆二色谱试验结合K2D2软件推测二级结构,MALDI-TOF-MS测定单体相对分子质量。结果①鉴定出F1抗原单体相对分子质量为15 500的蛋白质,不含有多糖成分;②F1抗原的相对分子质量分布范围在10~6～10~7之间,呈现聚集状态;③F1抗原由149个氨基酸组成,单体相对分子质量为15 500,F1抗原的二级结构以β-sheet为主。结论新型鼠疫疫苗中F1抗原为不含多糖成分的蛋白质,天然状态下F1抗原以高分子聚集态存在,F1抗原单体相对分子质量为15 500,抗原结构性质稳定,与理论结果一致。在制造、检定和免疫学研究中应参考F1抗原的这些特性。     

鼠疫耶尔森菌F1-V融合蛋白改构体的构建、原核表达及纯化

目的:通过基于结构的基因突变获得鼠疫耶尔森菌F1抗原突变体(F1mut),克隆、表达并纯化F1mut-V融合蛋白。方法:通过3轮PCR,将编码F1抗原分子N端1~14位氨基酸的基因序列移到3'端,测序无误后将F1mut基因与V基因的5'端连接,构建改构的融合基因F1mut-V,将其克隆到原核表达载体p ET-32a后转化大肠杆菌BL21(DE3),经IPTG诱导后,目的蛋白为可溶性表达,通过硫酸铵分级沉淀、阴离子交换层析、疏水相互作用层析和凝胶过滤层析纯化,用SDS-PAGE和Western印迹分析纯化产物。结果:重组F1mut-V在大肠杆菌中为可溶性表达,表达量占全菌蛋白的25%以上,纯化后目的蛋白的纯度达95%,经Western印迹检测,与抗V、F1抗体均有特异性结合。结论:重组F1mut-V有望成为新一代亚单位疫苗的有效成分。     

应用噬菌体随机肽库技术筛选鼠疫耶尔森菌F1抗原中和性表位

目的:筛选鼠疫耶尔森菌F1抗原的中和性表位,构建基于鞭毛蛋白佐剂的重组表位疫苗。方法:利用鼠疫菌F1抗原的中和抗体F2H5筛选噬菌体随机12肽库,对得到的阳性克隆采用ELISA进行特异性鉴定,采用竞争抑制ELISA确定具有竞争性的噬菌体单克隆并对其DNA测序,重组表达并纯化获得肽序列与截短型鞭毛蛋白Fli Cdel的融合蛋白,并通过Western印迹和ELISA鉴定重组蛋白与F2H5的结合。结果:获得了2株能够与F1抗原竞争结合F2H5的噬菌体单克隆12-1和12-14,其中12-14的竞争能力较强;通过序列比对,并没有发现这2株噬菌体克隆的插入肽序列与F1抗原序列存在一致性,但这2个插入肽序列与Fli Cdel的重组蛋白在Western印迹和ELISA结果中均显示出能够被抗F1的单克隆抗体识别。结论:F1中和性抗体筛选出的肽序列与截短的鞭毛蛋白融合表达后能够被F2H5特异性识别,为进一步对重组表位抗原进行免疫保护评价奠定了基础。     

鼠疫溶菌疫苗免疫小鼠的体液免疫应答

为选择以F1抗原为主要有效成分的鼠疫溶菌疫苗(Whole cell lysate of Yersinia pestis vaccine,WCLY)的免疫程序,设计了这组试验。在37℃培养鼠疫EV菌,通过超声波裂解法制备鼠疫溶菌疫苗。设计(0,2周)、(0,4周)、(0,2,4周)三种免疫程序,以每剂总蛋白量7.9μg、31.5μg和126.0μg三个剂量皮下接种NIH小鼠。分别在第一针免疫后2、4、8、12周采集血清,通过间接ELISA检测抗鼠疫菌F1抗原和总抗原抗体。结果显示:免疫后血清抗体上升很快,2周内即可测出;无论哪种免疫程序,至12周时抗体滴度仍保持高水平;加强免疫后,抗体水平在4周或8周达到较高,可与活疫苗免疫者相比;溶菌疫苗的接种剂量为7.9μg时,动物只出现轻度不良反应。提示鼠疫溶菌疫苗需要两剂免疫,最短可间隔2周,接种剂量应不超过7.9μg,疫苗中应富含F1抗原。     

重组鼠疫菌V抗原的纯化及其豚鼠免疫保护力初探

采用Ni^2 亲和层析方法,对用工程化大肠杆菌BL21(DE3)表达的重组鼠疫菌v抗原进行纯化,目标蛋白纯度达到90％以上。以氢氧化铝凝胶配制吸附疫苗,经二针次肌内注射免疫实验豚鼠后,对皮下注射400个致死剂量(MLD)强毒鼠疫菌攻击有一定保护效力,存活率为20％。结果表明,重组鼠疫菌V抗原有望作为改进的F1 V亚单位疫苗的主要成分。     

猪丹毒丝菌天然SpaA和重组SpaA-N免疫保护效果的评价

【目的】本试验以小鼠为动物模型,评估了猪丹毒丝菌重组表面保护性抗原A的N端保护区域(rSpaA-N)和天然SpaA的免疫保护效果。【方法】将猪丹毒丝菌C43311株SpaA-N以可溶形式表达在大肠杆菌BL21中,用GST Bind Resin纯化试剂盒纯化rSpaA-N,采用电洗脱法从猪丹毒丝菌C43311株NaOH提取抗原中纯化天然SpaA,将rSpaA-N、天然SpaA和NaOH提取抗原制成亚单位疫苗,同时设GST及生理盐水对照组,间隔2周分3次皮下免疫小鼠,第3次免疫后2周用100LD50猪丹毒丝菌C43065株进行腹腔攻毒,采用间接ELISA方法检测免疫组小鼠血清的抗体动态变化。【结果】SDS-PAGE结果显示,采用GST Bind Resin纯化试剂盒和电洗脱法纯化得到了66kDa的rSpaA-N和64kDa的天然SpaA,蛋白含量分别为1.34mg/mL和1.26mg/mL,而Western印迹结果表明rSpaA-N和纯化前后的SpaA具有良好的免疫反应性。保护试验结果表明,不同免疫剂量的rSpaA-N组、天然SpaA组和NaOH提取抗原组均能完全保护小鼠受强毒株C43065的致死性攻击,而GST组和生理盐水组小鼠攻毒后全部死亡。ELISA检测结果表明,在不同免疫剂量的rSpaA-N组、天然SpaA组和NaOH提取抗原组小鼠血清中的抗体效价之间无显著差异(P0.05)。【结论】本研究结果表明rSpaA-N具有良好的免疫保护作用,可以作为猪丹毒亚单位疫苗。     

鼠疫耶尔森氏菌rV270抗原的克隆、表达及其免疫保护作用评价

目的：为研制鼠疫亚单位疫苗,克隆、表达并纯化去除产生免疫抑制作用序列后的鼠疫耶尔森氏菌LcrV抗原（rV270）。方法：依据已知的LcrV的核苷酸序列,避开其产生免疫抑制作用的区段设计引物,扩增rV270基因并克隆到pET24a载体中,在大肠杆菌BL21中表达His-rV270融合蛋白：表达产物先后经Co^2＋亲和层析和Sephacryl S-200HR凝胶柱纯化,并在纯化过程中应用凝血酶切除His标塔;氢氧化铝佐剂吸附重组抗原后免疫BALB／c小鼠,初次免疫后第21天加强免疫1次,第5周使用104CFU鼠疫菌141强毒株攻毒,测定其免疫保护作用。结果：rV270以可溶性方式表达;应用Co^2＋亲和层析柱和Sephacryl S-200HR凝胶柱结合凝血蛋白酶切除His标签的方法可得到不含标签的较高纯度的重组蛋白;攻毒实验中实验组小鼠全部存活,而对照组全部死亡。结论：获得了具有良好免疫保护作用的rV270蛋白,可用于鼠疫亚单位疫苗的研究。     

Effect of culture pH on recombinant antibody production by a new human cell line, F2N78, grown in suspension at 33.0 °C and 37.0 °C

The human host cell line, F2N78, is a new somatic hybrid cell line designed for therapeutic antibody production. To verify its potential as a human host cell line, recombinant F2N78 cells that produce antibody against rabies virus (rF2N78) were cultivated at different culture pH (6.8, 7.0, 7.2, 7.4, and 7.6) and temperatures (33.0 °C and 37.0 °C). Regardless of the culture temperature, the highest specific growth rate was obtained at a pH of 7.0–7.4. Lowering the culture temperature from 37.0 °C to 33.0 °C suppressed cell growth while allowing maintenance of high cell viability for a longer period. However, it did not enhance antibody production because specific antibody productivity did not increase at 33.0 °C. The highest maximum antibody concentration was obtained at 37.0 °C and pH 6.8. The N-linked glycosylation of the antibody was affected by the culture pH rather than the temperature. Nevertheless, G1F was dominant and G2F occupied a larger portion than G0F in all culture conditions. Compared to the same antibody produced from recombinant CHO cells, the antibody produced from rF2N78 cells has more galactose capping and was more similar to human plasma IgG. Taken together, the results obtained here demonstrate the potential of F2N78 as an alternative human host cell line for therapeutic antibody production.     

Probing molecular interactions in intact antibody: antigen complexes, an electrospray time-of-flight mass spectrometry approach.

Using a combination of nanoflow-electrospray ionization and time-of-flight mass spectrometry we have analyzed the oligomeric state of the recombinant V antigen from Yersinia pestis, the causative agent of plague. The mass spectrometry results show that at pH 6.8 the V antigen in solution exists predominantly as a dimer and a weakly associated tetramer. A monoclonal antibody 7.3, raised against the V antigen, gave rise to mass spectra containing a series of well-resolved charge states at m/z 6000. After addition of aliquots of solution containing V antigen in substoichiometric and molar equivalents, the spectra revealed that two molecules of the V antigen bind to the antibody. Collision-induced dissociation of the antibody-antigen complex results in the selective release of the dimer from the complex supporting the proposed 1:2 antibody:antigen stoichiometry. Control experiments with the recombinant F1 antigen, also from Yersinia pestis, establish that the antibody is specific for the V antigen because no complex with F1 was detected even in the presence of a 10-fold molar excess of F1 antigen. More generally this work demonstrates a rapid means of assessing antigen subunit interactions as well as the stoichiometry and specificity of binding in antibody-antigen complexes.     

Effect of glucose feeding on the glycosylation quality of antibody produced by a human cell line,F2N78, in fed-batch culture

The human cell line rF2N78 produces an antibody with a high galactosylation ratio which resembles human IgG. However, it has been observed that the aglycosylated antibody starts to appear when glucose is depleted. To determine whether glucose depletion is a main cause for aglycosylation of the antibody, fed-batch cultures of rF2N78 cells were performed using different feeding cocktails (glucose only, nutrient feeding cocktail without glucose, and nutrient feeding cocktail with glucose). In the fed-batch culture with nutrient feeding cocktail without glucose, aglycosylated antibody was produced in a later phase of culture, when glucose was depleted. Approximately 44 % of antibodies produced were aglycosylated at the end of culture. In contrast, aglycosylated antibody was not produced in cultures with glucose feeding. The expression levels of oligosaccharyl transferases determined by Western blot analysis were similar among the cultures, suggesting that aglycosylation of the antibody was not due to altered expression of oligosaccharyl transferases under glucose-deficient conditions. Thus, it is likely that glucose deficiency led to insufficiency of the precursor for glycosylation and induced aglycosylation of the antibody. Taken together, glucose feeding in fed-batch cultures successfully prevented occurrence of aglycosylated antibody during the cultures, confirming that glucose depletion is a main cause for aglycosylation of antibody.     

Purification, cloning, and heterologous expression of a catalytically efficient flavonol 3-O-galactosyltransferase expressed in the male gametophyte of Petunia hybrida

Flavonols are plant-specific molecules that are required for pollen germination in maize and petunia. They exist in planta as both the aglycone and glycosyl conjugates. We identified a flavonol 3-O-galactosyltransferase (F3GalTase) that is expressed exclusively in the male gametophyte and controls the formation of a pollen-specific class of glycosylated flavonols. Thus an essential step to understanding flavonol-induced germination is the characterization of F3GalTase. Amino acid sequences of three peptide fragments of F3GalTase purified from petunia pollen were used to isolate a full-length cDNA clone. RNA gel blot analysis and enzyme assays confirmed that F3GalTase expression is restricted to pollen. Heterologous expression of the F3GalTase cDNA in Escherichia coli yielded active recombinant enzyme (rF3GalTase) which had the identical substrate specificity as the native enzyme. Unlike the relatively nonspecific substrate usage of flavonoid glycosyltransferases from sporophytic tissues, F3GalTase uses only UDP-galactose and flavonols to catalyze the formation of flavonol 3-O-galactosides. Kinetic analysis showed that the k(cat)/K(m) values of rF3GalTase, using kaempferol and quercetin as substrates, approaches that of a catalytically perfect enzyme. rF3GalTase catalyzes the reverse reaction, generation of flavonols from UDP and flavonol 3-O-galactosides, almost as efficiently as the forward reaction. The biochemical characteristics of F3GalTase are discussed in the context of a role in flavonol-induced pollen germination.     

An anti-carbohydrate monoclonal antibody inhibits cell-substratum adhesion of F9 embryonal carcinoma cells

A monoclonal rat IgM antibody (4C9) raised against F9 embryonal carcinoma cells reacted with fucosyl residues in poly-N-acetyllactosamine-type large carbohydrates of these cells (embryoglycan). The chemical properties and distribution of the antigen resembled those of SSEA-1. The monoclonal antibody was found to inhibit cell-substratum adhesion of F9 cells: in the presence of the antibody, cells grew as spherical cell aggregates on plastic dishes. When the antibody was added to the already spread cells, they displayed the initial sign of rounding up within 3 h; the rounding process was largely completed within 6 h. After removal of the antibody, cells resumed their normal morphology. The antibody could act in the presence of 2,4-dinitrophenol. In serum-free medium, F9 cells spread on plastic dishes coated with fibronectin or with laminin, and the process was also inhibited by the antibody. Immuno-electronmicroscopy revealed that 4C9 antigen was diffusely distributed over the cell surface of F9 cells. The distribution of the antigen was not altered generally after culturing with the antibody for 6 h. Another monoclonal rat IgM antibody, which did not react with embryoglycan and resembled anti-Forssman, did not inhibit cell-substratum adhesion of F9 cells, in spite of its reactivity to the cells. Thus, a glycoprotein with fucosyl (poly)-N-acetyllactosamine structure appears to be involved in cell-substratum adhesion of F9 cells.     

Purification and characterization of E. histolytica antigen for diagnosis of amoebiasis

Entamoeba histolytica soluble crude antigen was fractionated by gel filtration on Sephacryl S-300 into four fractions, viz. F1(669 kDa); F2(51.2 kDa); F3(25.1 kDa) and F4(10.5 kDa). F1 fraction was observed to be more sensitive and specific for the detection of antibody in amoebiasis than the crude and other fractions of purified antigens employing IHAT and ELISA. ELISA was found to be better than IHAT since it could detect antibody in the sera (3/6) of asymptomatic cyst passers. The cross reaction of crude antigen with toxocariasis (1/4) and toxoplasmosis (2/5) sera were associated with F4 fraction. F3 and F4 were having low molecular weight and were not sensitive in detection of antibody in amoebiasis. Biochemical characterization revealed glycoprotein nature of the specific (F1) antigen fraction.     

鼠疫菌F1抗体/抗原酶联免疫诊断试剂盒的应用评价

目的对兰州生物制品研究所有限责任公司研制的鼠疫菌F1抗体酶联免疫诊断试剂盒和鼠疫菌F1抗原酶联免疫诊断试剂盒进行临床应用评价。方法采用双抗原/抗体夹心酶联免疫吸附试验(ELISA)、间接血球凝集试验(IHA)、胶体金免疫层析试验(GICA)3种方法的诊断试剂对比检测云南省地方病防治所中心实验室保藏的和现场采集的血清样品和脏器样品,对血清样品做鼠疫菌F1抗体检测,对脏器样品做鼠疫菌F1抗原检测。结果在358份血清样品中,ELISA试剂检出F1抗体阳性52份(14.52%),IHA试剂检出阳性37份(10.34%),GICA试剂检出阳性45份(12.57%)。ELISA与IHA试剂的符合率为95.23%,与GICA试剂的符合率为96.92%。经统计学χ2检验,ELISA试剂检出F1抗体阳性率高于IHA试剂(χ2=11.53,P=0.000 7),与GICA试剂检出的差异无统计学意义(χ2=3.27,P=0.070 4)。进一步分析滴度差值频数,ELISA试剂检测人血清的敏感性高于IHA试剂的样品占87.5%。在117份脏器样品中,3种试剂均检出F1抗原阳性15份(12.82%),符合率100%。滴度差值频数比较,ELISA试剂检测敏感性高于反向间接血球凝集试验(RIHA)试剂的样品为78.57%。结论兰州生物制品研究所有限责任公司研制的鼠疫菌F1抗体酶联免疫诊断试剂盒和鼠疫菌F1抗原酶联免疫诊断试剂盒性质特异,其敏感性优于IHA试剂盒和GICA试剂条,值得在鼠疫的监测和快速诊断中推广应用。     

Major histocompatibility complex-restricted augmenting T cells induced by in vitro cultivation of antigen-primed T cells. A new parallelism between suppressor and augmenting circuits

In vitro cultivation of primed T cells with antigen resulted in the induction of a regulatory T cell that nonspecifically augmented the in vitro antibody responses of H-2-compatible T and B cells. This T cell, designated as the augmenting T cell (Ta), was unable to help B cells by itself but enhanced the antibody response of B cells to several multitudes only when conventional helper T (Th) cells or cloned Th cells from the same H-2 haplotype coexisted. Ta was radioresistant and belonged to Lyt-1+, 2-, L3T4+, I-J- T cell lineage. Ta exhibited interesting H-2-restricted activities: when primed T cells from (A X B) F1 were cultured with the antigen in the presence of parent A type antigen-presenting cells, the induced Ta was able to augment the antibody response of (A x B) F1 B cells in the presence of Th cells from F1----A but not from F1----B radiation bone marrow chimeras. This indicates that the induction of Ta in an F1 T cell population is dependent on the H-2 haplotype of antigen-presenting cells during in vitro cultivation. The restriction specificity of the established Ta is, however, not directed to the class II antigen itself but to the restriction specificity of Th cells that recognize class II antigen. In support of this is the fact that the elimination of A-restricted Th cells during cultivation by treatment with anti-I-J mAb, which is known to react with H-2-restricted Th cells, resulted in failure of induction of Ta cells having the augmenting activity for the A-restricted response.