Infectivity and neutralizing antibody titers of flavivirus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are frequently measured using the conventional plaque assay. While the assay is useful in the determination of infectivity, conventional plaque assays generally possess lower sensitivity and are time-consuming compared to nucleic acid amplification tests. In this study, a microcrystalline cellulose (MCC), Avicel, was evaluated as an alternative to the conventional virus overlay medium, methylcellulose, for a plaque assay. The plaque assay was performed using dengue and COVID-19 clinical samples and laboratory-established flavivirus and SARS-CoV-2 strains. In virus titration of clinical samples, the plaques were significantly larger, and the virus titers were higher when Avicel MCC-containing overlay medium was used than with conventional methylcellulose overlay medium. In addition, for some clinical samples and laboratory virus strains, infectious particles were detected as plaques in the Avicel MCC-containing medium, but not in the conventional methylcellulose medium. The results suggest that the viremia titer determined using the new overlay medium containing Avicel MCC may better reflect the innate infectious and plaque-forming capabilities of clinical samples and better reflect virus infectivity.

中文翻译：

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黄病毒和 SARS-CoV-2 临床样本感染性的差异：传染性病毒脱落和病毒血症评估的改进检测

黄病毒和严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 的传染性和中和抗体滴度经常使用传统的斑块测定法进行测量。虽然该测定可用于确定感染性，但与核酸扩增测试相比，传统的噬菌斑测定通常具有较低的灵敏度且耗时。在这项研究中，微晶纤维素 (MCC) Avicel 被评估为替代常规病毒覆盖介质甲基纤维素，用于斑块测定。噬菌斑测定是使用登革热和 COVID-19 临床样本以及实验室建立的黄病毒和 SARS-CoV-2 菌株进行的。在临床样本的病毒滴定中，斑块明显较大，使用含有 Avicel MCC 的覆盖培养基比使用常规甲基纤维素覆盖培养基时病毒滴度更高。此外，对于一些临床样本和实验室病毒株，在含有 Avicel MCC 的培养基中检测到感染性颗粒作为噬菌斑，但在常规甲基纤维素培养基中没有检测到。结果表明，使用含有 Avicel MCC 的新型覆盖培养基测定的病毒滴度可以更好地反映临床样本的先天感染和斑块形成能力，更好地反映病毒感染性。