Division of Pulmonary and Critical Care Medicine, Department of Medicine, The University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA; The Center for Environmental Medicine, Asthma and Lung Biology, The University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA.
Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of North Carolina at Chapel Hill, 8033 Burnett-Womack, Chapel Hill, NC 27599-7219, USA.
Vaccine. 2014 Mar 26;32(15):1761-7. doi: 10.1016/j.vaccine.2013.12.069. Epub 2014 Jan 30.
Influenza viruses are global pathogens that infect approximately 10-20% of the world's population each year. Vaccines, including the live attenuated influenza vaccine (LAIV), are the best defense against influenza infections. The LAIV is a novel vaccine that actively replicates in the human nasal epithelium and elicits both mucosal and systemic protective immune responses. The differences in replication and innate immune responses following infection of human nasal epithelium with influenza seasonal wild type (WT) and LAIV viruses remain unknown. Using a model of primary differentiated human nasal epithelial cell (hNECs) cultures, we compared influenza WT and antigenically-matched cold adapted (CA) LAIV virus replication and the subsequent innate immune response including host cellular pattern recognition protein expression, host innate immune gene expression, secreted pro-inflammatory cytokine production, and intracellular viral RNA levels. Growth curves comparing virus replication between WT and LAIV strains revealed significantly less infectious virus production during LAIV compared with WT infection. Despite this disparity in infectious virus production the LAIV strains elicited a more robust innate immune response with increased expression of RIG-I, TLR-3, IFNβ, STAT-1, IRF-7, MxA, and IP-10. There were no differences in cytotoxicity between hNEC cultures infected with WT and LAIV strains as measured by basolateral levels of LDH. Elevated levels of intracellular viral RNA during LAIV as compared with WT virus infection of hNEC cultures at 33°C may explain the augmented innate immune response via the up-regulation of pattern recognition receptors and down-stream type I IFN expression. Taken together our results suggest that the decreased replication of LAIV strains in human nasal epithelial cells is associated with a robust innate immune response that differs from infection with seasonal influenza viruses, limits LAIV shedding and plays a role in the silent clinical phenotype seen in human LAIV inoculation.
流感病毒是全球性病原体，每年感染全球约 10-20%的人口。疫苗，包括减毒活流感疫苗（LAIV），是预防流感感染的最佳手段。LAIV 是一种新型疫苗，能在人鼻腔上皮细胞中主动复制，并引发黏膜和全身保护性免疫应答。流感季节性野生型（WT）和 LAIV 病毒感染人鼻腔上皮细胞后的复制和固有免疫应答差异尚不清楚。我们使用原代分化的人鼻腔上皮细胞（hNEC）培养模型，比较了流感 WT 和抗原匹配的冷适应（CA）LAIV 病毒复制以及随后的固有免疫应答，包括宿主细胞模式识别蛋白表达、宿主固有免疫基因表达、分泌的促炎细胞因子产生和细胞内病毒 RNA 水平。比较 WT 和 LAIV 株病毒复制的生长曲线表明，与 WT 感染相比，LAIV 产生的传染性病毒明显较少。尽管 LAIV 株产生的传染性病毒产量存在差异，但与 WT 感染相比，LAIV 株引发了更强烈的固有免疫应答，增加了 RIG-I、TLR-3、IFNβ、STAT-1、IRF-7、MxA 和 IP-10 的表达。通过测量基底外侧的 LDH 水平，hNEC 培养物感染 WT 和 LAIV 株后没有观察到细胞毒性差异。与 WT 病毒感染相比，在 33°C 时 hNEC 培养物中 LAIV 病毒感染导致细胞内病毒 RNA 水平升高，这可能通过上调模式识别受体和下游 I 型 IFN 表达来解释增强的固有免疫应答。综上所述，我们的结果表明，LAIV 株在人鼻腔上皮细胞中的复制减少与强烈的固有免疫应答有关，与季节性流感病毒感染不同，限制了 LAIV 的脱落，并在人类 LAIV 接种中观察到的无症状临床表型中发挥作用。
