Viral vectors derived from vesicular stomatitis virus (VSV) are important vectors for the development of vaccines and for the treatment of cancer. The efficiency of therapy based on VSV is dependent on the dose of virus used. Therefore it is essential to measure accurately and reproducibly the amount of functional vectors in the samples to be tested. Two common methods used to measure the titer of VSV are TCID50% and plaque assay. In the current study, we compared these two titration methods by using a recombinant VSV expressing the green fluorescent protein (VSV-GFP) as a model virus. Some culture media developed for suspension mammalian cells contain dextran sulfate. We observed that plaque assay, but not TCID50%, can underestimate the virus titer up to 10 fold when VSV-GFP was produced in culture media containing dextran sulfate. Dextran sulfate is commonly used in serum-free culture media to reduce cell aggregation in suspension culture. The inhibitory effect of dextran sulfate on the titration of VSV-GFP was confirmed by supplementing the culture medium with this compound during virus production. Our results also demonstrated that extending the incubation time during plaque assay and TCID50% increases virus titer.

中文翻译：

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培养基中硫酸右旋糖酐对水泡性口炎病毒滴定的影响。

源自水泡性口炎病毒（VSV）的病毒载体是开发疫苗和治疗癌症的重要载体。基于VSV的治疗效率取决于所用病毒的剂量。因此，必须准确，可重复地测量待测样品中功能载体的量。用于测量VSV滴度的两种常见方法是TCID50％和噬斑测定。在当前的研究中，我们通过使用表达绿色荧光蛋白（VSV-GFP）的重组VSV作为模型病毒比较了这两种滴定方法。开发用于悬浮哺乳动物细胞的某些培养基含有硫酸葡聚糖。我们观察到，当在含有硫酸葡聚糖的培养基中生产VSV-GFP时，噬菌斑测定法（而不是TCID50％）可以低估病毒效价高达10倍。硫酸葡聚糖常用于无血清培养基中，以减少悬浮培养中的细胞聚集。硫酸葡聚糖对VSV-GFP滴定的抑制作用是通过在病毒生产过程中向培养基中补充该化合物来证实的。我们的结果还表明，延长噬菌斑测定期间的孵育时间和TCID50％会增加病毒滴度。