The SARS-CoV-2 spike trimer is the primary antigen for several serology assays critical to determining the extent of SARS-CoV-2 exposure in the population. Until stable cell lines are developed to increase the titer of this secreted protein in mammalian cell culture, the low yield of spike protein produced from transient transfection of HEK293 cells will be a limiting factor for these assays. To improve the yield of spike protein and support the high demand for antigens in serology assays, we investigated several recombinant protein expression variables by altering the incubation temperature, harvest time, chromatography strategy, and final protein manipulation. Through this investigation, we developed a simplified and robust purification strategy that consistently yields 5 mg of protein per liter of expression culture for two commonly used forms of the SARS-CoV-2 spike protein. We show that these proteins form well-behaved stable trimers and are consistently functional in serology assays across multiple protein production lots.

中文翻译：

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优化用于血清学检测的 SARS-CoV-2 可溶性刺突三聚体的高产生产。

SARS-CoV-2 刺突三聚体是几种血清学检测的主要抗原，这些检测对确定人群中 SARS-CoV-2 的暴露程度至关重要。在开发出稳定的细胞系以提高哺乳动物细胞培养物中这种分泌蛋白的滴度之前，瞬时转染 HEK293 细胞产生的刺突蛋白的低产量将成为这些测定的限制因素。为了提高刺突蛋白的产量并支持血清学检测中对抗原的高需求，我们通过改变孵育温度、收获时间、层析策略和最终蛋白质操作来研究几个重组蛋白表达变量。通过本次调查，我们开发了一种简化且稳健的纯化策略，对于两种常用形式的 SARS-CoV-2 刺突蛋白，每升表达培养物始终可以产生 5 mg 的蛋白质。我们表明，这些蛋白质形成表现良好的稳定三聚体，并且在多个蛋白质生产批次的血清学分析中始终如一地发挥作用。