Introduction

Wild-type adult mice with intact interferon (IFN) system were neither susceptible to bluetongue virus (BTV) infection nor showed signs of morbidity/mortality. Establishment of immunologically competent wild-type adult mouse model with type I IFNs blockade is necessary to assess the pathogenesis, immune responses and testing of BTV vaccines.

Objectives

Present study aimed to establish and characterize BTV serotype 1 infection in immunocompetent adult mice with type I IFNs blockade at the time of infection by studying immune responses and sequential pathology.

Methods

Adult mice were administered with anti-mouse IFN-α/β receptor subunit-1 (IFNAR1) blocking antibody (Clone: MAR1-5A3) 24 h before and after BTV serotype 1 infection, and sacrificed at various time points. Sequential pathology, BTV localization by immunohistochemistry and quantification by qRT-PCR, immune cell kinetics and apoptosis by flow cytometry, and cytokines estimation by c-ELISA and qRT-PCR were studied.

Results

IFNAR blocked-infected mice developed clinical signs and typical lesions of BT; whereas, isotype-infected control mice did not develop any disease. The IFNAR blocked-infected mice showed enlarged, edematous, and congested lymph nodes (LNs) and spleen, and vascular (congestion and hemorrhage) and pneumonic lesions in lungs. Histopathologically, marked lymphoid depletion with “starry-sky pattern” due to lymphocytes apoptosis was noticed in the LNs and spleen. BTV antigen was detected and quantified in lymphoid organs, lungs, and other organs at various time points. Initial leukopenia (increased CD4⁺/CD8⁺ T cells ratio) followed by leukocytosis (decreased CD4⁺/CD8⁺ T cells ratio) and significantly increased biochemical values were noticed in IFNAR blocked-infected mice. Increased apoptotic cells in PBMCs and tissues coincided with viral load and levels of different cytokines in blood, spleen and draining LNs and notably varied between time points in IFNAR blocked-infected mice.

Conclusion

Present study is first to characterize BTV serotype 1 infection in immunocompetent adult mouse with type I IFNs blockade. The findings will be useful for studying pathogenesis and testing the efficacy of BTV vaccines.

中文翻译：

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I型干扰素阻断免疫活性成年小鼠蓝舌病毒血清1型感染的病理学和免疫学特征

介绍

具有完整干扰素 (IFN) 系统的野生型成年小鼠既不易受蓝舌病病毒 (BTV) 感染，也没有出现发病/死亡迹象。建立具有 I 型干扰素阻断免疫能力的野生型成年小鼠模型对于评估 BTV 疫苗的发病机制、免疫反应和测试是必要的。

目标

本研究旨在通过研究免疫反应和顺序病理学，在感染时 I 型干扰素阻断的免疫活性成年小鼠中建立和表征 BTV 血清型 1 感染。

方法

在 BTV 血清型 1 感染前后 24 小时，对成年小鼠施用抗小鼠 IFN-α/β 受体亚基-1（IFNAR1）阻断抗体（克隆：MAR1-5A3），并在不同时间点处死。研究了顺序病理学、免疫组织化学 BTV 定位和 qRT-PCR 定量、流式细胞术免疫细胞动力学和细胞凋亡，以及 c-ELISA 和 qRT-PCR 估计的细胞因子。

结果

IFNAR 阻断感染的小鼠出现临床症状和典型的 BT 病变；而同种型感染的对照小鼠没有发生任何疾病。IFNAR 阻断感染的小鼠表现出肿大、水肿和充血的淋巴结 (LN) 和脾脏，以及肺部血管（充血和出血）和肺炎病变。在组织病理学上，在淋巴结和脾脏中观察到由于淋巴细胞凋亡导致的具有“星空模式”的明显淋巴耗竭。在不同时间点检测和量化淋巴器官、肺和其他器官中的 BTV 抗原。初始白细胞减少症（CD4 ⁺ /CD8 ⁺ T 细胞比率增加），然后是白细胞增多症（CD4 ⁺ /CD8 ⁺T 细胞比率）和显着增加的生化值在 IFNAR 阻断感染的小鼠中观察到。PBMC 和组织中凋亡细胞的增加与病毒载量和血液、脾脏和引流 LN 中不同细胞因子的水平一致，并且在 IFNAR 阻断感染小鼠的时间点之间显着变化。

结论

本研究首次在具有 I 型干扰素阻断的免疫活性成年小鼠中表征 BTV 血清型 1 感染。这些发现将有助于研究发病机制和测试 BTV 疫苗的功效。