宿主限制因子 SAMHD1 通过 PA 介导的宿主转录因子 IRF3 的去磷酸化抑制来损害流感 A 病毒的复制。

BACKGROUND: Influenza A virus (IAV) can cause severe and life-threatening illness in humans and animals. Therefore, it is important to search for host antiviral proteins and elucidate their antiviral mechanisms for the development of potential treatments. As a part of human innate immunity, host restriction factors can inhibit the replication of viruses, among which SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1 (SAMHD1) can restrict the replication of viruses, such as HIV and enterovirus EV71. Viruses also developed countermeasures in the arms race with their hosts. There are few reports about whether SAMHD1 has a restriction effect on IAV. METHODS: To investigate the impact of IAV infection on SAMHD1 expression in A549 cells, we infected A549 cells with a varying multiplicity of infection (MOI) of IAV and collected cell samples at different time points for WB and RT-qPCR analysis to detect viral protein and SAMHD1 levels. The virus replication level in the cell culture supernatant was determined using TCID50 assay. Luciferase assay was used to reveal that H5N1 virus polymerase acidic protein (PA) affected the activity of the SAMHD1 promoter. To assess the antiviral capacity of SAMHD1, we generated a knockdown and overexpressed cell line for detecting H5N1 replication. RESULTS: In this study, we observed that SAMHD1 can restrict the intracellular replication of H5N1 and that the H5N1 viral protein PA can downregulate the expression of SAMHD1 by affecting SAMHD1 transcriptional promoter activity. We also found that SAMHD1's ability to restrict H5N1 is related to phosphorylation at 592-tyrosine. CONCLUSIONS: In conclusion, we found that SAMHD1 may affect the replication of IAVs as a host restriction factor and be countered by PA. Furthermore, SAMHD1 may be a potential target for developing antiviral drugs.

背景：甲型流感病毒（IAV）可导致人类和动物发生严重且危及生命的疾病。因此，寻找宿主抗病毒蛋白并阐明其抗病毒机制对于开发潜在治疗方法非常重要。作为人体先天免疫的一部分，宿主限制因子可以抑制病毒的复制，其中 SAM 和 HD 结构域包含的脱氧核苷三磷酸三磷酸水解酶 1（SAMHD1）可以限制 HIV 和肠道病毒 EV71 等病毒的复制。病毒也在与宿主的军备竞赛中开发了对策。关于 SAMHD1 是否对 IAV 具有限制作用的报道很少。

方法：为了研究 IAV 感染对 A549 细胞中 SAMHD1 表达的影响，我们用不同感染复数（MOI）的 IAV 感染 A549 细胞，并在不同时间点收集细胞样本进行 WB 和 RT-qPCR 分析，以检测病毒蛋白和 SAMHD1 水平。用 TCID50 测定法测定细胞培养上清液中的病毒复制水平。荧光素酶测定法用于揭示 H5N1 病毒聚合酶酸性蛋白（PA）影响 SAMHD1 启动子活性。为了评估 SAMHD1 的抗病毒能力，我们生成了一个用于检测 H5N1 复制的 SAMHD1 敲低和过表达细胞系。

结果：在这项研究中，我们观察到 SAMHD1 可以限制 H5N1 的细胞内复制，并且 H5N1 病毒蛋白 PA 通过影响 SAMHD1 转录启动子活性来下调 SAMHD1 的表达。我们还发现，SAMHD1 限制 H5N1 的能力与 592 位酪氨酸的磷酸化有关。

结论：总之，我们发现 SAMHD1 作为宿主限制因子可能影响 IAV 的复制，并被 PA 拮抗。此外，SAMHD1 可能是开发抗病毒药物的潜在靶点。