Identification of non-immunological signals that can induce degranulation of mast cells during RSV infection

呼吸道合胞病毒（RSV）是全球儿童呼吸道感染的主要病原体。先前，我们报道了感染RSV的A549细胞诱导肥大细胞脱颗粒，这是由RSV感染的A549细胞上表达的一些非免疫信号诱导的。因此，我们试图识别信号，但我们找不到它。然而，在他们的研究中，我们发现细胞角蛋白8和18是与RSV复制有一定关系的分子。为了阐明C8/18在RSV复制中的作用，我们用克隆的HMC-1-C8/18细胞和A549-C18KD细胞检测了病毒的复制动力学，这些细胞是通过插入C8/18从人肥大细胞系HMC-1中获得的，在A549-C18KD细胞中，用特定的shRNA表达质粒敲除C18。通过标准接种，RSV在HMC-1- c8 /18细胞中的复制效率略高于HMC-1细胞。然而，与hcc -1细胞相比，脊髓灌注后RSV RNA复制增加了10倍以上。在这种情况下，HMC-1-C8/18细胞中感染性病毒的细胞内滴度与A549细胞一致，而病毒向培养液中的释放量远低于A549细胞。此外，A549- c18kd的RSV滴度比A549低log0.5 ~ log1，不仅在细胞内如此，在上清液中也是如此。本研究表明，C8/18与RSV复制直接相关，尤其是在早期阶段。

Respiratory syncytial virus (RSV) is a major causative agent of respiratory tract infections in children worldwide. Previously, we reported that mast cell degranulation was induced by A549 cells infected with RSV and this was induced by some non-immunological signals expressed on RSV-infected A549 cells. Therefore, we had tried to identify the signals but we could not find it. However, in their instead, we found that cytokeratin 8 and 18 were the molecules that had some relation to the RSV replication. To elucidate the role of C8/18 in RSV replication, the replication kinetics of the virus were examined using cloned HMC-1-C8/18 cells, derived from the human mast cell line HMC-1 by the insertion of C8/18, and A549-C18KD cells, in which C18 was knocked down using a specific shRNA expression plasmid. By standard inoculation, the replication efficiency of RSV was slightly higher in HMC-1-C8/18 cells compared to HMC-1 cells. However, following spinoculation, RSV RNA replication was increased more than 10-fold compared with HMC-1 cells. In this situation, the intracellular titer of infectious virus in HMC-1-C8/18 cells matched that in A549 cells, while the release of virus into the culture fluid was much lower than with A549 cells. In addition, the RSV titer in A549-C18KD was log0.5 to log1 less than that in A549, not only in the cells, but also in the supernatant. This study demonstrates that C8/18 are directly associated with RSV replication, especially in the early stages.