Inflammation Immunobiology Section, Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Weill Cornell Medical College, New York, NY 10021, USA.
Viruses. 2020 Dec 22;13(1):2. doi: 10.3390/v13010002.
Virus-induced inflammation plays a critical role in determining the clinical outcome of an acute respiratory virus infection. We have shown previously that the administration of immunobiotic (Lp) directly to the respiratory tract prevents lethal inflammatory responses to subsequent infection with a mouse respiratory virus pathogen. While Lp-mediated protective responses involve non-redundant contributions of both Toll-like receptor 2 (TLR2) and NOD2, the cellular basis of these findings remains unclear. Here, we address the impact of Lp and its capacity to suppress inflammation in virus-infected respiratory epithelial cells in two cell culture models. We found that both MLE-12 cells and polarized mouse tracheal epithelial cells (mTECs) were susceptible to infection with Influenza A and released proinflammatory cytokines, including CCL2, CCL5, CXCL1, and CXCL10, in response to replicating virus. MLE-12 cells express NOD2 (81 ± 6.3%) and TLR2 (19 ± 4%), respond to Lp, and are TLR2-specific, but not NOD2-specific, biochemical agonists. By contrast, we found that mTECs express NOD2 (81 ± 17%) but minimal TLR2 (0.93 ± 0.58%); nonetheless, mTECs respond to Lp and the TLR2 agonist, Pam2CSK4, but not NOD2 agonists or the bifunctional TLR2-NOD2 agonist, CL-429. Although MLE-12 cells and mTECS were both activated by Lp, little to no cytokine suppression was observed in response to Lp followed by virus infection via a protocol that replicated experimental conditions that were effective in vivo. Further study and a more complex approach may be required to reveal critical factors that suppress virus-induced inflammatory responses.
病毒引起的炎症在决定急性呼吸道病毒感染的临床结果中起着关键作用。我们之前已经表明，直接将免疫生物制剂（Lp）施用于呼吸道可防止随后感染小鼠呼吸道病毒病原体时发生致命的炎症反应。虽然 Lp 介导的保护反应涉及 Toll 样受体 2（TLR2）和 NOD2 的非冗余贡献，但这些发现的细胞基础仍不清楚。在这里，我们在两种细胞培养模型中研究了 Lp 及其抑制病毒感染呼吸道上皮细胞中炎症的能力的影响。我们发现，MLE-12 细胞和极化的小鼠气管上皮细胞（mTECs）均易感染流感病毒，并对复制的病毒产生炎症细胞因子，包括 CCL2、CCL5、CXCL1 和 CXCL10。MLE-12 细胞表达 NOD2（81±6.3%）和 TLR2（19±4%），对 Lp 作出反应，并且是 TLR2 特异性而非 NOD2 特异性的生化激动剂。相比之下，我们发现 mTECs 表达 NOD2（81±17%）但表达极少的 TLR2（0.93±0.58%）；尽管如此，mTECs 对 Lp 和 TLR2 激动剂 Pam2CSK4 作出反应，但对 NOD2 激动剂或双功能 TLR2-NOD2 激动剂 CL-429 没有反应。尽管 MLE-12 细胞和 mTECs 均被 Lp 激活，但在遵循病毒感染的方案中，对 Lp 进行反应几乎没有或没有观察到细胞因子抑制，该方案复制了体内有效的实验条件。可能需要进一步的研究和更复杂的方法来揭示抑制病毒诱导的炎症反应的关键因素。
