呼吸道合胞病毒(respiratory syncytial virus，RSV)是导致婴幼儿严重下呼吸道感染的最重要病原体，但该病毒的灭活疫苗可引起RSV疫苗增强性疾病(RSV vaccine-enhanced disease，RVED)，因此至今仍未研制出安全、有效的疫苗。RVED的发生机制目前仍不清楚。使用能有效模拟RVED的动物模型是探索RVED发生机制的主要手段，而本研究的目的就是建立能稳定模拟RVED表现的小鼠模型。将BALB/c小鼠分成3组，即甲醛灭活RSV疫苗接种组(FV组)、活RSV接种组(VV组)和对照组(BV组)，并模拟自然感染对其攻毒。通过小鼠体重监测、肺组织苏木精-伊红染色、荧光定量聚合酶链反应(polymerase chain reaction，PCR)、流式细胞术等，观察FV组小鼠感染RSV后的病毒载量、肺部炎症和T细胞免疫状态。结果显示，与VV组和BV组相比，FV组小鼠RSV攻毒后的体重占初始体重百分比显著降低，肺部炎症最明显，且仅FV组出现支气管和毛细血管周围有大量淋巴细胞浸润及嗜酸性粒细胞浸润。荧光定量PCR显示，FV组小鼠的肺部RSV载量最低。流式细胞术显示，攻毒4 d后FV组CD4^＋ T细胞数与其他两组相比显著增加，且CD4^＋ T细胞分泌的白细胞介素4(interleukin 4，IL-4)及IL-4/γ干扰素(interferon γ，IFN-γ)比值显著高于其他两组，而CD8^＋ T细胞分泌的肿瘤坏死因子α(tumor necrosis factor α，TNF-α)和IFN-γ低于VV组。结果提示，RVED小鼠呈现出Th2优势型免疫应答及CD8^＋ T细胞功能不足，模型初步建立成功，为RVED发生机制的探索和RSV疫苗的研发奠定了良好基础。

Respiratory syncytial virus (RSV) is the most important pathogen responsible for children’s severe lower respiratory tract infection worldwide. As inactivated RSV vaccine could lead to RSV vaccine-enhanced disease (RVED)，no safe RSV vaccine has been permitted in clinical use yet, and the mechanism of RVED is still unclear. The aim of the present study is to establish a murine model that can steadily mimic the performance of RVED. A total of 30 BALB/c mice were divided into three groups and vaccinated with formalin-inactivated RSV (FV group), live RSV (VV group) or sterilized phosphate buffered saline (PBS) (BV group), respectively. Four weeks later, all the mice were challenged with live RSV intranasally. The bodyweight of the tested animals was measured on the day of viral challenge and the following 3 days. T cell immune response, lung RSV load and pulmonary pathology were detected by flow cytometry, quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) and lung hematoxylin-eosin (HE) staining respectively. Compared with the VV group and the BV group, the bodyweight of the mice in the FV group showed the largest weight loss after challenge. Severe pneumonia with extensive lymphocytic and eosinophilic infiltration could be seen in the FV group only. Lung RSV load in the FV group was the lowest. The number of CD4^＋ T cells in the FV group was higher than those in the other two groups, while the number of CD8^＋ T cells showed no significant difference among the three groups. The secretion of interleukin 4 (IL-4) in CD4^＋ T cells and IL-4/interferon γ (IFN-γ) ratio in the FV group were much higher than those in the other two groups, while the secretions of tumor necrosis factor α (TNF-α) and IFN-γ in the FV group were much lower than those in the VV group. In conclusion, a murine model of RVED has been established successfully, showing an unbalanced Th2-biased immune response and impaired CD8^＋ T cell function. The model could be used to help the study of RVED and development of protective and safe RSV vaccines.