乙肝表面抗原结合蛋白SBP在毕赤酵母中的表达纯化及功能鉴定

乙肝表面抗原结合蛋白(HBsAg binding protein,SBP)是本实验室发现的一种人源蛋白,该蛋白与人乙型肝炎病毒HBV表面抗原HBsAg存在特异性的结合能力。此前的研究证实SBP具有增强乙肝疫苗免疫效果的作用。为进一步研究该蛋白的生理功能和作用机制,利用毕赤酵母表达系统进行了SBP的表达菌株构建,筛选得到了SBP的高效表达菌株。发酵产物经过分离纯化,最终得到了大量高纯度的真核来源的目的蛋白。通过SDS-PAGE、高效液相色谱、Western blotting和质谱鉴定,证实所得到的蛋白具有较高的纯度和完整性。通过ELISA方法初步证实了其与乙肝表面抗原具有较好的结合能力。该研究为进一步进行SBP的体内外功能研究及免疫增效研究打下了基础。     

HBsAg/GM-CSF融合蛋白在毕赤酵母中的表达及其免疫原性研究

为探索一种提高乙肝病毒表面抗原免疫原性的新方法,用PCR和基因重组技术构建HBsAg与GM-CSF的融合基因,并在毕赤酵母中分泌表达HBsAg/GM-CSF(S-GM)融合蛋白。表达产物用SDS-PAGE检测,W estern b lot分析,离子交换柱纯化后免疫昆明鼠,ELISA检测免疫小鼠血清中抗HBsAg的抗体水平。结果显示S-GM融合蛋白在毕赤酵母中获得了表达,离子交换柱一步纯化即可得到纯度达90%以上的S-GM。W estern b lot分析S-GM可分别与抗HBsAg及抗GM-CSF的抗体特异结合。ELISA检测发现第一次免疫后4w出现抗HBsAg的抗体,加强免疫后融合蛋白组几乎全部阳转,且抗体水平较HBsAg组(P=0.009<0.05)及HBsAg和GM-CSF的混合物组(P=0.032<0.05)高。HBsAg/GM-CSF融合蛋白能够在毕赤酵母中表达,且可增强HBsAg的免疫原性,为提高乙肝疫苗的免疫效果提供了新的思路与方法。     

毕赤酵母工程菌表达乙肝表面抗原结合蛋白(SBP)的发酵纯化工艺研究

乙肝表面抗原结合蛋白(HBsAg binding protein,SBP)是以HBsAg为探针,通过人肝cDNA噬菌体表达库筛选的一种人源蛋白。SBP可特异性结合乙肝表面抗原(Hepatitis B virus surface antigen, HBsAg),增强乙肝疫苗的免疫效果,是一种潜在快速高效的免疫佐剂。成功构建了分泌型高表达SBP的毕赤酵母工程菌。对该菌株进行了放大规模发酵表达,并对纯化工艺进行了研究。在发酵实时检测过程中,自诱导剂甲醇加入开始,SBP蛋白的分泌表达量随时间推移而逐渐增加,发现于38h达到最佳水平且此时杂蛋白含量最少,是放罐收集菌液的最佳时间。18L发酵液在低温离心除菌体和沉淀物后可得到15L的上清液,再利用截留量为5kDa的超滤膜包将上清液浓缩至2L,将浓缩后的上清液依次通过S200分子筛柱和TDEAE阴离子交换柱进行分离纯化,可得到300ml浓度为1.125mg/ml、纯度达98%的目标蛋白液,发酵液得率为22.5mg/L;最后将蛋白液定量分装冻干低温保存。所获得的放大规模SBP发酵诱导表达条件和SBP蛋白的分离纯化工艺,为SBP蛋白大规模生产奠定了坚实的基础。     

新型佐剂DC-Chol对不同来源HBsAg促细胞免疫比较研究

目的： 筛选治疗性乙肝疫苗的候选抗原。方法： 分别用国产CHO乙肝表面抗原和酵母乙肝表面抗原结合DC-Chol脂质体佐剂免疫BALB/c小鼠,1周后检测其脾细胞产生的IL-2和IFN-γ的水平。ELISPOT法评价铝佐剂和DC-Chol脂质体佐剂结合HBsAg促小鼠细胞免疫反应水平。结果： 酵母乙肝表面抗原结合DC-Chol脂质体所诱导的IL-2和IFN-γ的水平分别为CHO乙肝表面抗原结合DC-Chol脂质体的20倍和119倍。酵母乙肝表面抗原结合DC-Chol脂质体所诱导的IL-4和IFN-γ的斑点数分别为酵母乙肝表面抗原结合铝佐剂的2.8倍和46.3倍。结论： 就DC-Chol脂质体佐剂而言,酵母表达的乙肝表面抗原细胞免疫原性强,是适合用于治疗性乙肝疫苗的候选疫苗。     

一种新的乙型肝炎病毒表面抗原结合蛋白的筛选、表达及其生物学活性的初步研究

为了研究乙肝病毒侵染肝细胞过程中的功能蛋白 ,通过印迹免疫分析技术从人肝cDNA噬菌体表达库中筛选出一株编码乙肝表面抗原结合蛋白 (hepatitisBsurfaceantigenbindingprotein ,HBsAg BP)的cDNA克隆 .基因测序结果表明 ,该cDNA具有独立的开放阅读框架 ,编码 1个由 344个氨基酸残基构成的可溶性蛋白分子 ,属于免疫球蛋白超家族成员 .将该基因克隆到原核表达载体pTriplEx后 ,在E .coliXL1 Blue菌株中获得 4 4kD的重组蛋白 .重组蛋白经Western印迹和ELISA实验证明具有与乙肝表面抗原特异性结合的能力 .进一步经流式细胞仪实验显示 ,在纯化的重组蛋白存在的情况下 ,天然的HBsAg与肝细胞株HepG2的亲和力显著增高 .结果显示 ,该乙肝表面抗原结合蛋白可能是介导乙肝病毒对肝细胞亲和侵染的可溶性辅助受体 .     

新生儿国产重组(酵母)乙型肝炎疫苗免疫效果考核

为了考核新生儿接种国产重组(酵母)乙型肝炎(乙肝)疫苗后的免疫效果,并与血源乙肝疫苗效果比较。对1997年出生并接种重组(酵母)乙肝疫苗的新生儿隔年随访一次,采血检测乙肝病毒表面抗原(HBsAg),乙肝病毒表面抗体(抗-HBs)和乙肝病毒核心抗体(抗-HBc),1998年以后对乙肝免疫人群开展急性乙肝发病监测。显示五年期间3次随访检测HBsAg阳性率平均为1.5%,较免前本底的HBsAg阳性率呈较大幅度下降,疫苗保护率为83%(95%可信区间为76.97%~89.02%),无论母亲HBsAg阳性或阴性,使用不同乙肝疫苗的儿童HBsAg阳性率没有统计学差异。接受重组(酵母)乙肝疫苗免疫的对象中,无一例急性乙肝病例报告。重组(酵母)乙肝疫苗有较好的近期保护效果和免疫原性,与以前使用血源乙肝疫苗效果相当。     

人源性抗HBsAg抗体Fab段在酵母中的表达

通过分步整合的方式,将人源性抗乙肝表面抗原（HBsAg）抗体Fab的轻、重链基因分步整合到巴斯德毕赤（Pichia pastoris）酵母GS115菌株的染色体上,经甲醇诱导,成功地分泌表达出抗HBsAg抗体的Fab片段,表达量达50～80mg/L。ELISA结果显示重组酵母分泌表达出的Fab具有较强的结合HBsAg的能力。通过抗Fab的抗体柱亲和层析,纯化出了纯度较高的Fab产品。     

一条新的柱层析纯化路径对HBsAg免疫原性的影响

摘要目的：建立一条新的毕赤酵母表达乙肝表面抗原（HepatitisBantigen,HBsAg）柱层析纯化方法,保持HBsAg结构完整性和提高免疫原性。方法：毕赤酵母发酵料液经过菌体破碎、聚乙二醇沉淀、疏水层析、超滤和凝胶分子筛精纯,收集HBsAg合格样品液适当稀释后加入铝佐荆吸附,制成乙肝疫苗半成品免疫BALB／c小鼠。结果：纯化产物经SDS-PAGE银染鉴定得单一条带,分子量在23kD左右,凝胶成像软件分析纯度超过95％;该纯化方法得到的HBsAg颗粒电镜观察得平均直径为22nm病毒样颗粒,结构较均一完整;自制疫苗免疫小鼠后,其血清抗体水平高于葛兰素史克生产的Engerix—B（安在时）,存在显著性差异（P〈0．05）。结论：通过该方法纯化的HBsAg结构完整性良好,疫苗免疫效果优于酵母表达的Engerix—B,纯化路径简单高效,易于放大用于工业化生产。     

利用毕赤酵母系统表达重组人生长激素的研究

为了获得重组人生长激素在毕赤酵母中高表达的菌株,按毕赤酵母基因密码子偏爱性,人工合成hGH的全基因序列.该基因被克隆到穿梭质粒pPIC9K中,PEG1000介导转入毕赤酵母GS115细胞,通过G418筛选获得高拷贝转化子.在甲醇的诱导下.实现了hGH在毕赤酵母中的成功表达.通过发酵条件的优化.发酵上清中的表达量达1537 mg/L经过超滤和两步层析,重组蛋白的得率这35%,纯度为97%,相对分子质量测定表明重组蛋白的相对分子质量与理论值相近.N-端氨基酸测序证实hGH基因在毕赤酵母中获得正确的表达.     

两种新型HBsAg基因的毕赤酵母表达载体构建及其表达

目的：从乙肝患者血清中发现2个有突变的乙型肝炎病毒株,从中扩增出HBsAg(乙肝表面抗原)基因,构建酵母表达载体,并在巴斯德毕赤酵母中表达,以鉴定这2个基因表达产物的活性。方法：利用PCR技术从乙肝患者血清中扩增出乙肝表面抗原基因．并将其连接到pPIC3．5K中,转化毕赤酵母,通过甲醇诱导,利用SDS-PAGE和ELISA检测表达的蛋白。结果：通过序列测定结果表明成功地构建了毕赤酵母表达载体,聚丙烯酰胺凝胶电泳(SDS—PAGE)和ELISA证明这2个基因在毕赤酵母中能有效表达。且表达产物均具有生物活性。结论：从实验结果发现乙肝表面抗原决定簇以外的少数氨基酸变化不影响其活性。因此可以利用这2个基因对乙肝表面抗原进行表达。     

Expression, purification and characterization of the Hepatitis B virus entire envelope large protein in Pichia pastoris

The current HBsAg vaccine has performed a vital role in preventing the transmission of HBV during the past 20 years. However, a number of individuals still show no response or a low response to the vaccine. In the present study, the HBV envelope large protein gene was cloned into the eukaryotic expression vector pPIC9k and was subsequently expressed in the yeast Pichia pastoris. The HBV large protein (L protein) was produced and secreted into the medium, where some of the L protein formed particles. The soluble L protein and particles were purified by column chromatography and sucrose density gradient centrifugation. Western blot analysis demonstrated that the particle was composed of both HBV L and S protein. To compare the antigenicity of the L protein and HBsAg, rabbits were immunized with the soluble L protein and the commercially available HBV vaccine and the increasing level of antibodies was determined by ELISA. The results showed that the anti-HBsAg antibody, from rabbits injected with the L protein at a dose of 2 and 10microg, was detected on day 14, whereas rabbits vaccinated with 10 and 2microg HBsAg did not develop antibodies until day 21 and 28, respectively. The antibody level in groups inoculated with the L protein was approximately 50% higher than in the group injected with HBsAg using the same dose. Furthermore, 2microg L protein induced a significant and rapid anti-HBsAg antibody response than 10microg HBsAg. Therefore, we suggest that the L protein is an ideal candidate for a new generation HB vaccine to protect people from HBV infection.     

戊型肝炎病毒ORF2编码多肽抗原的表达及其特性研究

迄今所发现的唯一的戊型肝炎病毒（HEV）中和表位定位于开放读码框架2（ORF2）编码蛋白的第578和第607氨基酸（aa）之间的区域。将对应此区域的基因片段通过一段柔性的甘氨酸铰链与乙型肝炎病毒（HBV）表面抗原（HBsAg）基因的3′端相连,构建成HBV/HEV融合基因。该融合基因在毕赤酵母细胞内的表达产物物为分子量约29kDa的融合蛋白,具有组装成嵌合病毒样颗粒（VLP）的能力。此嵌合VLP具有与HBsAgVLP相似的特性且保留了天然HBV/HEV双重抗原性。对此嵌合VLP特性的初步研究提示其可能具有HBV/HEV双价重组疫苗的潜在应用前景。     

HBscFv–IFNγ在毕赤酵母X33中的表达、纯化及鉴定

为了有效治疗乙肝病而研究了将抗乙肝病毒表面抗原单链抗体(single-chain Fv against HBV surface antigen, HBscFv)与临床治疗乙肝常用的γ-干扰素(γ-interferon, IFNγ)连接的融合蛋白(HBscFv-IFNγ)。采用重叠PCR法将基因hbscfv与ifnγ连接成hbscfv-ifnγ, 再构建成多拷贝重组质粒pPICZαA/(hbscfv-ifnγ)1,2,4, 然后转入巴斯德毕赤酵母X33。从中筛选出的工程菌株X4能够分泌表达目的蛋白HBscFv-IFNγ, 并用SDS-PAGE、Western blotting和ELISA方法进行了初步鉴定, 结果表明组成HBscFv-IFNγ的HBscFv和IFNγ仍具有生物学活性。用14F7亲合层析纯化X4的发酵液可获得纯度达95%~98%的HBscFv-IFNγ。它可中和HBV转基因小鼠血清中27.9%的乙肝病毒表面抗原(HBV surface antigen, HbsAg), 这表明HBscFv-IFNγ上的抗体能够与生物体内的HBV有效结合。可见, HBscFv-IFNγ将是一种防治乙肝病而有开发前景的靶向新药。     

Expression of hepatitis B virus S gene in Pichia pastoris and application of the product for detection of anti-HBs antibody

Antibody to hepatitis B surface antigen (HBsAb) is the important serological marker of the hepatitis B virus (HBV) infection. Conventionally, the hepatitis B surface antigen (HBsAg) obtained from the plasma of HBV carriers is used as the diagnostic antigen for detection of HBsAb. This blood-origin antigen has some disadvantages involved in high cost, over-elaborate preparation, risk of infection, et al. In an attempt to explore the suitable recombinant HBsAg for the diagnostic purpose, the HBV S gene was expressed in Pichia pastoris and the product was applied for detection of HBsAb. Hepatitis B virus S gene was inserted into the yeast vector and the expressed product was analyzed by sodium dodecyl sulphate polyacrolamide gel electrophoresis (SDS-PAGE), immunoblot, electronic microscope and enzyme linked immunosorbent assay (ELISA). The preparations of synthesized S protein were applied to detect HBsAb by sandwich ELISA. The S gene encoding the 226 amino acid of HBsAg carrying a hexa-histidine tag at C terminus was successfully expressed in Pichia pastoris. The His-Tagged S protein in this strain was expressed at a level of about 14.5 % of total cell protein. Immunoblot showed the recombinant HBsAg recognized by monoclonal HBsAb and there was no cross reaction between all proteins from the host and normal sera. HBsAb detection indicated that the sensitivity reached 10 mIu (micro international unit)/ml and the specificity was 100 % with HBsAb standard of National Center for Clinical Laboratories. A total of 293 random sera were assayed using recombinant S protein and a commercial HBsAb ELISA kit (produced by blood-origin HBsAg), 35 HBsAb positive sera and 258 HBsAb negative sera were examined. The same results were obtained with two different reagents and there was no significant difference in the value of S/CO between the two reagents. The recombinant HBV S protein with good immunoreactivity and specificity was successfully expressed in Pichia pastoris. The reagent for HBsAb detection prepared by Pichia pastoris-derived S protein showed high sensitivity and specificity for detection of HBsAb standard. And a good correlation was obtained between the reagent produced by recombinant S protein and commercial kit produced by blood-origin HBsAg in random samples.     

Expression of GST-fused kinase domain of human Csk homologous kinase from Pichia pastoris facilitates easy purification

Human Csk Homologous Kinase (CHK), a protein of 527 amino acid residues, is involved in suppression of breast tumors. The kinase domain of CHK (amino acid residues 228 to 485) expressed with C-terminal 6HIS fusion in Pichia pastoris is heavily glycosylated. Expression of the C-terminal 6HIS fused kinase domain of CHK, with an N-terminal glutathione S-transferase fusion, in Pichia pastoris alleviated the hyperglycosylation. The expressed protein was purified by affinity chromatography to 1 mg l(-1) culture and remained active. A simple plate assay to identify colonies of P. pastoris expressing the recombinant protein is also presented.     

超抗原SEA增强小鼠对HBV DNA 疫苗的免疫反应

观察超抗原SEA(D227A)的真核表达载体(pmSEA),对HBVDNA疫苗诱导Balbc小鼠(H2d)免疫应答的调节作用。肌内注射空载体pcDNA3、HBVDNA疫苗加pmSEA佐剂(pHBVS2S+pmSEA)或不加佐剂(pHBVS2S);ELISA法测定血清抗HBs;ELISPOT检测分泌IFNγ的脾淋巴细胞;4h51Cr释放法检测小鼠脾细胞CTL活性。HBVDNA佐剂组免疫小鼠抗HBsAg抗体滴度明显高于不加佐剂组,其IgG1IgG2a的比例不同于多肽免疫组,二者分别为0.282与10。HBVDNA佐剂组均能增强IgG1和IgG2a的产生,是不加佐剂组的1.36、1.73倍。佐剂组小鼠脾淋巴细胞IFNγ的分泌量是不加佐剂组2～3倍。CTL细胞杀伤活性(E:T=100)佐剂组与不加佐剂组分别为:69.77%±7.5%、42.81%±7.7%,差异显著(P<0.05)。HBVDNA疫苗具有较强的免疫原性,能够诱导机体产生特异性的抗体及CTL反应;pmSEA佐剂能够提高小鼠对DNA疫苗的免疫应答,有望成为DNA疫苗的免疫佐剂。