利用毕赤酵母系统的丙型肝炎病毒重组E1E2糖蛋白的表达、纯化和性质研究
发布时间：2018-09-03 07:13
【摘要】：丙型肝炎病毒(HCV)是丙型肝炎的致病原因,全球有超过3%的人口被感染。发展一个有效的HCV疫苗是控制HCV感染的关键。 由于HCV的高变异性,曾经有观点认为有效的、可以抑制不同亚型的HCV疫苗是不可能得到的。可是近来的研究结果指出,HCV包膜糖蛋白上含有保守的HCV细胞受体结合位点,可以诱导产生广泛的中和抗体,从而阻止HCV感染。以哺乳动物细胞表达产生的HCV包膜糖蛋白作为疫苗成功的在黑猩猩中证实能够保护黑猩猩免受异型的HCV感染。然而,哺乳动物细胞表达系统产生的HCV包膜糖蛋白产量很低,难以大规模应用。与细胞表达系统相比,大肠杆菌表达系统中虽然可以产生较高产量的HCV包膜蛋白,但其表达的蛋白不具备糖基化。这种缺乏糖基化的包膜蛋白在结构、性质以及免疫原性上都与天然HCV包膜糖蛋白相差巨大。因此,我们使用毕赤酵母这种经济的真核表达系统来表达HCV包膜糖蛋白。 我们在pPIC9K载体的基础上构建了真核表达质粒pPIC9K-E1E2,其编码HCV E1 187-346位氨基酸序列和E2 381-699位氨基酸序列,将其电转化进入毕赤酵母菌株SMD1168中获得重组转化子。经过甲醇利用型筛选和G418抗性筛选得到的工程菌株能够在甲醇诱导下高效表达重组HCV E1E2糖蛋白,产量可达40mg/L。经Q-S-FF柱、P-S-FF柱及G100柱对表达的包膜糖蛋白进行纯化,得到了纯度较高的重组蛋白。 得到的重组蛋白由于不同的糖基化和不同的聚集度拥有几种不同的形式：72kD、95kD、145kD和大于200kD的聚集物(Aggregation, Agg), SDS-PAGE显示其主体为72kD蛋白和Agg。糖苷酶切实验表明重组蛋白中糖基化的主要形式是甘露糖苷形成的糖基化,但是也存在着复杂形式的糖基化,而且该复杂糖基化的糖苷可以很大的影响HCV单克隆抗体A4的识别。此外,我们使用GST—pulldown实验来验证重组蛋白能否同HCV受体人CD81大胞外环(LEL)相互作用。我们构建了pET-GST-LEL质粒并在大肠杆菌BL21中转化表达GST-LEL融合蛋白,并使用Glutathione Sepharose 4B beads证实了重组E1E2糖蛋白能同GST-LEL蛋白结合,表明重组E1E2糖蛋白不仅含有HCV E2 CD81结合区的氨基酸序列,而且这结合区域形成了正确的构象。更进一步的是,重组E1E2糖蛋白能够同核心蛋白core相互作用形成病毒样粒子。将重组E1E2糖蛋白和大肠杆菌中表达的core蛋白(氨基酸序列1-137)共同复性浓缩后,得到了两种不同直径的病毒样粒子。一种粒子的直径约35nm,推测是core蛋白单独形成的粒子；另一种粒子的直径约55nm,推测该粒子是由重组E1E2蛋白与core共同作用形成的。 将得到的重组E1E2糖蛋白免疫兔子能够产生高水平的抗体应答,并能持续维持约两个月,将氢氧化铝作为佐剂加入后,抗体产生更快,峰值更高,但是持续维持的时间则较短。在小鼠中我们也得到了类似的结果。抑制实验表明,用纯化蛋白免疫获得的兔血清能阻止重组E1E2糖蛋白同CD81的相互作用,且抑制效果呈剂量依赖性,同时对照兔血清则没有影响。我们应用假病毒粒子(PP)系统和HCV细胞培养系统对血清的中和效果进行了研究,结果表明同对照血清相比,仅用重组E1E2糖蛋白免疫获得的兔血清对来源于HCV 1a亚型和HCV 1b亚型的HCV假病毒粒子,甚至对HCV 2a亚型的HCV病毒粒子都有中和作用；而用氢氧化铝作为佐剂免疫获得的兔血清仅对来源于HCV 1a亚型的HCVpp有强的中和作用,对1b亚型的HCVpp的中和作用较弱,对2a亚型的HCV病毒粒子则没有中和作用。同时,这些兔血清都对VSVpp不具中和能力,表明该中和能力是HCV特异性的。免疫获得的小鼠血清中和实验由于时间关系尚未完成,仍然在进行中。上述结果初步表明,毕赤酵母系统表达纯化的HCV E1E2糖蛋白能够诱导产生广泛的中和抗体,并且凭借其产量高的优点,有望成为一种可以大规模生产应用的HCV疫苗。
[Abstract]:Hepatitis C virus (HCV) is the cause of hepatitis C, with more than 3% of the world's population infected. The development of an effective HCV vaccine is the key to controlling HCV infection.
Because of the high variability of HCV, it was once thought that effective vaccines against different subtypes of HCV were impossible to obtain. However, recent studies have shown that HCV envelope glycoproteins contain conserved receptor binding sites for HCV cells, which can induce a wide range of neutralizing antibodies to prevent HCV infection. The production of HCV envelope glycoprotein as a vaccine has been successfully demonstrated in chimpanzees to protect chimpanzees from heterotypic HCV infection. However, the production of HCV envelope glycoprotein produced by mammalian cell expression system is very low and is difficult to be used on a large scale. This glycosylation-deficient envelope protein differs greatly from natural HCV envelope glycoproteins in structure, properties and immunogenicity. Therefore, we use Pichia pastoris as an economical eukaryotic expression system to express HCV envelope glycoproteins.
The eukaryotic expression plasmid pPIC9K-E1E2 was constructed on the basis of pPIC9K vector. It encoded the 187-346 amino acid sequence of HCV E1 and the E2 381-699 amino acid sequence of HCV E1, and was electrotransformed into Pichia pastoris strain SMD1168 to obtain the recombinant transformants. The recombinant HCV E1E2 glycoprotein was highly expressed and the yield was up to 40mg/L. The recombinant protein was purified by Q-S-FF column, P-S-FF column and G100 column.
Because of different glycosylation and different aggregation degree, the recombinant protein has several different forms: 72 kD, 95 kD, 145 kD and 200 kD aggregates (Aggregation, Agg). SDS-PAGE showed that 72 kD protein and Agg. In addition, we used GST-pulldown assay to verify whether the recombinant protein could interact with human CD81 extracellular loop (LEL) of HCV receptor. We constructed pET-GST-LEL plasmid and expressed it in E. coli BL21. Glutathione Sepharose 4B beads confirmed that recombinant E1E2 glycoprotein could bind to GST-LEL protein, indicating that the recombinant E1E2 glycoprotein contained not only the amino acid sequence of the binding region of HCV E2 CD81, but also the correct conformation of the binding region. The recombinant E1E2 glycoprotein and the core protein (amino acid sequence 1-137) expressed in E. coli were renatured and concentrated together, and two kinds of virus-like particles with different diameters were obtained. It is speculated that the particle is formed by the interaction of recombinant E1E2 protein and core.
The rabbits immunized with the recombinant E1E2 glycoprotein produced a high level of antibody response and maintained it for about two months. Adding aluminium hydroxide as an adjuvant, the antibody production was faster and the peak value was higher, but the duration was shorter. Similar results were obtained in mice. Inhibition experiments showed that the purified protein was used as an adjuvant. The immunized rabbit serum could prevent the interaction between recombinant E1E2 glycoprotein and CD81 in a dose-dependent manner, while the control rabbit serum had no effect. The serum neutralization effect was studied by using pseudovirus particle (PP) system and HCV cell culture system. The results showed that the recombinant E1E2 glycoprotein only used as control serum. Rabbit serum immunized with glycoprotein can neutralize HCV pseudovirus particles derived from HCV 1a and HCV 1b subtypes, even HCV 2A subtypes, while rabbit serum immunized with aluminium hydroxide as an adjuvant can only neutralize HCV PP derived from HCV 1A subtype and can neutralize HCV PP derived from HCV 1b subtype. At the same time, these rabbit sera did not neutralize VSVpp, suggesting that the neutralization ability was HCV-specific. The neutralization experiment of the immunized mice sera was still in progress because of the unfinished time relationship. V E1E2 glycoprotein can induce a wide range of neutralizing antibodies, and with its high yield, it is expected to become a large-scale production of HCV vaccine.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：R346
[Abstract]:Hepatitis C virus (HCV) is the cause of hepatitis C, with more than 3% of the world's population infected. The development of an effective HCV vaccine is the key to controlling HCV infection.
Because of the high variability of HCV, it was once thought that effective vaccines against different subtypes of HCV were impossible to obtain. However, recent studies have shown that HCV envelope glycoproteins contain conserved receptor binding sites for HCV cells, which can induce a wide range of neutralizing antibodies to prevent HCV infection. The production of HCV envelope glycoprotein as a vaccine has been successfully demonstrated in chimpanzees to protect chimpanzees from heterotypic HCV infection. However, the production of HCV envelope glycoprotein produced by mammalian cell expression system is very low and is difficult to be used on a large scale. This glycosylation-deficient envelope protein differs greatly from natural HCV envelope glycoproteins in structure, properties and immunogenicity. Therefore, we use Pichia pastoris as an economical eukaryotic expression system to express HCV envelope glycoproteins.
The eukaryotic expression plasmid pPIC9K-E1E2 was constructed on the basis of pPIC9K vector. It encoded the 187-346 amino acid sequence of HCV E1 and the E2 381-699 amino acid sequence of HCV E1, and was electrotransformed into Pichia pastoris strain SMD1168 to obtain the recombinant transformants. The recombinant HCV E1E2 glycoprotein was highly expressed and the yield was up to 40mg/L. The recombinant protein was purified by Q-S-FF column, P-S-FF column and G100 column.
Because of different glycosylation and different aggregation degree, the recombinant protein has several different forms: 72 kD, 95 kD, 145 kD and 200 kD aggregates (Aggregation, Agg). SDS-PAGE showed that 72 kD protein and Agg. In addition, we used GST-pulldown assay to verify whether the recombinant protein could interact with human CD81 extracellular loop (LEL) of HCV receptor. We constructed pET-GST-LEL plasmid and expressed it in E. coli BL21. Glutathione Sepharose 4B beads confirmed that recombinant E1E2 glycoprotein could bind to GST-LEL protein, indicating that the recombinant E1E2 glycoprotein contained not only the amino acid sequence of the binding region of HCV E2 CD81, but also the correct conformation of the binding region. The recombinant E1E2 glycoprotein and the core protein (amino acid sequence 1-137) expressed in E. coli were renatured and concentrated together, and two kinds of virus-like particles with different diameters were obtained. It is speculated that the particle is formed by the interaction of recombinant E1E2 protein and core.
The rabbits immunized with the recombinant E1E2 glycoprotein produced a high level of antibody response and maintained it for about two months. Adding aluminium hydroxide as an adjuvant, the antibody production was faster and the peak value was higher, but the duration was shorter. Similar results were obtained in mice. Inhibition experiments showed that the purified protein was used as an adjuvant. The immunized rabbit serum could prevent the interaction between recombinant E1E2 glycoprotein and CD81 in a dose-dependent manner, while the control rabbit serum had no effect. The serum neutralization effect was studied by using pseudovirus particle (PP) system and HCV cell culture system. The results showed that the recombinant E1E2 glycoprotein only used as control serum. Rabbit serum immunized with glycoprotein can neutralize HCV pseudovirus particles derived from HCV 1a and HCV 1b subtypes, even HCV 2A subtypes, while rabbit serum immunized with aluminium hydroxide as an adjuvant can only neutralize HCV PP derived from HCV 1A subtype and can neutralize HCV PP derived from HCV 1b subtype. At the same time, these rabbit sera did not neutralize VSVpp, suggesting that the neutralization ability was HCV-specific. The neutralization experiment of the immunized mice sera was still in progress because of the unfinished time relationship. V E1E2 glycoprotein can induce a wide range of neutralizing antibodies, and with its high yield, it is expected to become a large-scale production of HCV vaccine.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：R346
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