Han Young Woo, Choi Jin Young, Uyangaa Erdenebelig, Kim Seong Bum, Kim Jin Hyoung, Kim Bum Seok, Kim Koanhoi, Eo Seong Kug
College of Veterinary Medicine and Bio-Safety Research Institute, College of Natural Science, Chonbuk National University, Jeonju, Republic of Korea.
Department of Biology, College of Natural Science, Chonbuk National University, Jeonju, Republic of Korea.
PLoS Pathog. 2014 Sep 4;10(9):e1004319. doi: 10.1371/journal.ppat.1004319. eCollection 2014 Sep.
Japanese encephalitis (JE) is major emerging neurologic disease caused by JE virus. To date, the impact of TLR molecules on JE progression has not been addressed. Here, we determined whether each TLR modulates JE, using several TLR-deficient mouse strains (TLR2, TLR3, TLR4, TLR7, TLR9). Surprisingly, among the tested TLR-deficient mice there were contrasting results in TLR3(-/-) and TLR4(-/-) mice, i.e. TLR3(-/-) mice were highly susceptible to JE, whereas TLR4(-/-) mice showed enhanced resistance to JE. TLR3 ablation induced severe CNS inflammation characterized by early infiltration of inflammatory CD11b(+)Ly-6Chigh monocytes along with profoundly increased viral burden, proinflammatory cytokine/chemokine expression as well as BBB permeability. In contrast, TLR4(-/-) mice showed mild CNS inflammation manifested by reduced viral burden, leukocyte infiltration and proinflammatory cytokine expression. Interestingly, TLR4 ablation provided potent in vivo systemic type I IFN innate response, as well as ex vivo type I IFN production associated with strong induction of antiviral PRRs (RIG-I, MDA5), transcription factors (IRF-3, IRF-7), and IFN-dependent (PKR, Oas1, Mx) and independent ISGs (ISG49, ISG54, ISG56) by alternative activation of IRF3 and NF-κB in myeloid-derived DCs and macrophages, as compared to TLR3(-/-) myeloid-derived cells which were more permissive to viral replication through impaired type I IFN innate response. TLR4 ablation also appeared to mount an enhanced type I IFN innate and humoral, CD4(+) and CD8(+) T cell responses, which were mediated by altered immune cell populations (increased number of plasmacytoid DCs and NK cells, reduced CD11b(+)Ly-6C(high) monocytes) and CD4(+)Foxp3(+) Treg number in lymphoid tissue. Thus, potent type I IFN innate and adaptive immune responses in the absence of TLR4 were closely coupled with reduced JE lethality. Collectively, these results suggest that a balanced triggering of TLR signal array by viral components during JE progression could be responsible for determining disease outcome through regulating negative and positive factors.
日本脑炎（JE）是由日本脑炎病毒引起的主要新发神经疾病。迄今为止，TLR分子对JE病程的影响尚未得到研究。在此，我们使用几种TLR缺陷小鼠品系（TLR2、TLR3、TLR4、TLR7、TLR9）来确定每种TLR是否调节JE。令人惊讶的是，在测试的TLR缺陷小鼠中，TLR3（-/-）和TLR4（-/-）小鼠出现了相反的结果，即TLR3（-/-）小鼠对JE高度易感，而TLR4（-/-）小鼠对JE表现出增强的抵抗力。TLR3缺失诱导了严重的中枢神经系统炎症，其特征为炎症性CD11b（+）Ly-6Chigh单核细胞早期浸润，同时病毒载量、促炎细胞因子/趋化因子表达以及血脑屏障通透性显著增加。相比之下，TLR4（-/-）小鼠表现出轻度的中枢神经系统炎症，表现为病毒载量降低、白细胞浸润和促炎细胞因子表达减少。有趣的是，TLR4缺失在体内提供了强大的全身性I型干扰素固有反应，以及与抗病毒PRR（RIG-I、MDA5）、转录因子（IRF-3、IRF-7）以及I型干扰素依赖性（PKR、Oas1、Mx）和非依赖性ISG（ISG49、ISG54、ISG56）的强烈诱导相关的体外I型干扰素产生，这是通过髓样来源的DC和巨噬细胞中IRF3和NF-κB的交替激活实现的，而TLR3（-/-）髓样来源的细胞由于I型干扰素固有反应受损而对病毒复制更具易感性。TLR4缺失似乎还引发了增强的I型干扰素固有和体液、CD4（+）和CD8（+）T细胞反应，这是由免疫细胞群体的改变（浆细胞样DC和NK细胞数量增加，CD11b（+）Ly-6C（高）单核细胞减少）以及淋巴组织中CD4（+）Foxp3（+）调节性T细胞数量介导的。因此，在没有TLR4的情况下，强大的I型干扰素固有和适应性免疫反应与JE致死率降低密切相关。总体而言，这些结果表明，JE病程中病毒成分对TLR信号阵列的平衡触发可能通过调节正负因素来决定疾病结局。
