Reovirus serotype 3 Dearing (T3D) replicates preferentially in transformed cells and is in clinical trials as a cancer therapy. Laboratory strains of T3D, however, exhibit differences in plaque size on cancer cells and differences in oncolytic activity in vivo This study aimed to determine why the most oncolytic T3D reovirus lab strain, the Patrick Lee laboratory strain (T3DPL), replicates more efficiently in cancer cells than other commonly used laboratory strains, the Kevin Coombs laboratory strain (T3DKC) and Terence Dermody laboratory (T3DTD) strain. In single-step growth curves, T3DPL titers increased at higher rates and produced ∼9-fold higher burst size. Furthermore, the number of reovirus antigen-positive cells increased more rapidly for T3DPL than for T3DTD In conclusion, the most oncolytic T3DPL possesses replication advantages in a single round of infection. Two specific mechanisms for enhanced infection by T3DPL were identified. First, T3DPL exhibited higher cell attachment, which was attributed to a higher proportion of virus particles with insufficient (≤3) σ1 cell attachment proteins. Second, T3DPL transcribed RNA at rates superior to those of the less oncolytic T3D strains, which is attributed to polymorphisms in M1-encoding μ2 protein, as confirmed in an in vitro transcription assay, and which thus demonstrates that T3DPL has an inherent transcription advantage that is cell type independent. Accordingly, T3DPL established rapid onset of viral RNA and protein synthesis, leading to more rapid kinetics of progeny virus production, larger virus burst size, and higher levels of cell death. Together, these results emphasize the importance of paying close attention to genomic divergence between virus laboratory strains and, mechanistically, reveal the importance of the rapid onset of infection for reovirus oncolysis.IMPORTANCE Reovirus serotype 3 Dearing (T3D) is in clinical trials for cancer therapy. Recently, it was discovered that highly related laboratory strains of T3D exhibit large differences in their abilities to replicate in cancer cells in vitro, which correlates with oncolytic activity in a murine model of melanoma. The current study reveals two mechanisms for the enhanced efficiency of T3DPL in cancer cells. Due to polymorphisms in two viral genes, within the first round of reovirus infection, T3DPL binds to cells more efficiency and more rapidly produces viral RNAs; this increased rate of infection relative to that of the less oncolytic strains gives T3DPL a strong inherent advantage that culminates in higher virus production, more cell death, and higher virus spread.

中文翻译：

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大多数溶瘤呼肠孤病毒株中的多态性可增强细胞附着，转录和单步复制动力学。

呼肠孤病毒血清型3 Dearing（T3D）在复制的细胞中优先复制，目前正在作为癌症疗法进行临床试验。然而，T3D实验室菌株在癌细胞上的噬菌斑大小和体内溶瘤活性存在差异。这项研究旨在确定为什么最溶瘤的T3D呼肠孤病毒实验室菌株Patrick Lee实验室菌株（T3DPL）在癌症中更有效地复制细胞比其他常用的实验室菌株，Kevin Coombs实验室菌株（T3DKC）和Terence Dermody实验室（T3DTD）菌株高。在单步生长曲线中，T3DPL滴度以较高的速率增加，并产生约9倍的猝发量。此外，T3DPL的呼肠孤病毒抗原阳性细胞数量比T3DTD的增长更快。大多数溶瘤性T3DPL在单轮感染中具有复制优势。确定了两种增强T3DPL感染的机制。首先，T3DPL表现出更高的细胞附着力，这归因于病毒颗粒中比例更高的σ1细胞附着蛋白不足（≤3）。其次，T3DPL转录RNA的速率优于溶瘤性较低的T3D菌株，其归因于编码M1的μ2蛋白的多态性，如体外转录测定法所证实的那样，因此证明T3DPL具有固有的转录优势：与单元格类型无关。因此，T3DPL建立了病毒RNA和蛋白质合成的快速发作，从而导致子代病毒产生的动力学更快，病毒爆发量更大，细胞死亡水平更高。一起，这些结果强调了密切注意病毒实验室毒株之间的基因组差异的重要性，并且从机理上揭示了感染的快速发作对于呼肠孤病毒溶瘤的重要性。重要提示呼肠孤病毒血清型3 Dearing（T3D）正在癌症治疗的临床试验中。最近，发现高度相关的实验室T3D菌株在体外在癌细胞中复制的能力表现出很大差异，这与黑色素瘤小鼠模型的溶瘤活性有关。当前的研究揭示了提高癌细胞中T3DPL效率的两种机制。由于在呼肠孤病毒感染的第一轮中，两个病毒基因具有多态性，因此T3DPL与细胞结合的效率更高，并且可以更快地产生病毒RNA。