The capsid of human papillomavirus (HPV) consists of two capsid proteins - the major capsid protein L1 and the minor capsid protein L2. Assembled virus-like particles, which only consist of L1 proteins, are successfully applied as prophylactic vaccines against HPV infections. The capsid subunits are L1-pentamers, which are also reported to protect efficiently against HPV infections in animals.

The recombinant production of L1 has been previously shown in E. coli, yeast, insect cells, plants and mammalian cell culture. Principally, in E. coli-based expression system L1 shows high expression yields but the protein is largely insoluble. In order to overcome this problem reported strategies address fusion proteins and overexpression of bacterial chaperones. However, an insufficient cleavage of the fusion proteins and removal of co-purified chaperones can hamper subsequent down streaming.

We report a significant improvement in the production of soluble L1-pentamers by combining (I) a fusion of a N-terminal SUMO-tag to L1, (II) the heterologous co-expression of the chaperon system GroEL/ES and (III) low expression temperature. The fusion construct was purified in a 2-step protein purification including efficient removal of GroEL/ES and complete removal of the N-terminal SUMO-tag. The expression strategy was transferred to process-controlled high-cell-density fermentation with defined media according to the guidelines of good manufacturing practice. The produced L1 protein is highly pure (>95%), free of DNA (260:280 = 0.5) and pentameric. The production strategy yielded 5.73 mg of purified L1-pentamers per gram dry biomass. The optimized strategy is a suitable alternative for high yield L1-pentamer production and purification as a cheaper process for vaccine production.

人乳头瘤病毒（HPV）的衣壳由两个衣壳蛋白组成-主要衣壳蛋白L1和次要衣壳蛋白L2。仅由L1蛋白组成的装配好的病毒样颗粒已成功地用作预防HPV感染的预防性疫苗。衣壳亚基是L1戊二烯，据报道还可以有效保护动物免受HPV感染。

L1的重组生产先前已在大肠杆菌，酵母，昆虫细胞，植物和哺乳动物细胞培养物中显示。原则上，在基于大肠杆菌的表达系统中，L1显示出高表达产量，但该蛋白很大程度上不溶。为了克服这个问题，已报道的策略是解决融合蛋白和细菌伴侣蛋白的过表达。但是，融合蛋白的裂解不足和共纯化的伴侣蛋白的去除会阻碍后续的下游流动。

我们报道了通过结合（I）N端SUMO标签与L1的融合，（II）伴侣系统GroEL / ES的异源共表达，以及（III）可溶性L1-pentamers生产的显着改善。表达温度低。以两步蛋白质纯化法纯化融合构建体，包括有效去除GroEL / ES和完全去除N端SUMO标签。根据良好生产规范，将表达策略转移到具有定义培养基的过程控制的高细胞密度发酵中。产生的L1蛋白是高纯度（> 95％），不含DNA（260：280 = 0.5）和五聚体。该生产策略每克干生物质产生5.73 mg纯化的L1-戊烷。