Characterization of a suspension Vero cell line for viral vaccine production

Vero cells, as approved by the World Health Organization, have been the most commonly used continuous cell line for viral vaccine production over the last 25 years, but their adherent phenotype continues to limit productivity. Adapting to a suspension culture would overcome this restriction and reduce production costs. First, a Vero suspension isolate was obtained and metabolically characterized. Second, RNA sequencing analysis was used to identify differentially expressed genes between adherent and suspension cells, which revealed complete downregulation of adhesion and matrix-associated genes. Additionally, signaling pathways involving Wnt and other tyrosine kinase receptors were identified as potential leads for growth optimization. In particular, supplementation with fibroblast growth factor 2 allowed for a 20% increase in cell density. Finally, a comparative viral productivity assay revealed a 30% increase in poliovirus production in suspension Vero cells compared to adherent cells depending on the serotype, as well as a 140% increase in respiratory syncytial virus production and a 150% increase in yellow fever virus production.This work establishes the potential of the suspension Vero cell line as a new cell platform for viral vaccine production. Overall design: We established a Vero cell line that can grow in suspension. To understand the mechanism of adaptation to this new method of culture, we performed a gene expression profiling analysis of the parental adherent cell line and the new suspension isolate at three timepoints. We then determined differentially expressed genes between the two cell lines.

经世界卫生组织（World Health Organization）批准的Vero细胞（Vero cells）是近25年来病毒疫苗生产中最常用的连续细胞系（continuous cell line），但其黏附表型（adherent phenotype）仍会限制生产效能。采用悬浮培养（suspension culture）可克服这一限制并降低生产成本。首先，本研究成功获得Vero悬浮分离株并完成代谢特性表征。其次，通过RNA测序（RNA sequencing）分析鉴定黏附细胞与悬浮细胞间的差异表达基因（differentially expressed genes），结果显示黏附相关及基质相关基因均被完全下调。此外，涉及Wnt信号通路及其他酪氨酸激酶受体（tyrosine kinase receptors）的信号通路被鉴定为细胞生长优化的潜在靶点。具体而言，添加成纤维细胞生长因子2（fibroblast growth factor 2）可使细胞密度提升20%。最后，对比病毒生产力测定结果显示，依血清型不同，悬浮培养Vero细胞的脊髓灰质炎病毒（poliovirus）产量较黏附细胞提升30%；呼吸道合胞病毒（respiratory syncytial virus）产量提升140%，黄热病毒（yellow fever virus）产量提升150%。本研究证实了悬浮培养Vero细胞系作为新型病毒疫苗生产细胞平台的应用潜力。研究整体设计：我们构建了可在悬浮状态下生长的Vero细胞系。为解析适应新型培养方式的分子机制，我们分别在三个时间点对亲本黏附细胞系与新型悬浮分离株进行基因表达谱分析，并鉴定二者间的差异表达基因。