The Astrocyte Type I Interferon Response Is Essential for Protection against Herpes Simplex Encephalitis
The Astrocyte Type I Interferon Response Is Essential for Protection against Herpes Simplex Encephalitis
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DOI：
10.1128/jvi.01783-21
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发表时间：
2022-02-01
影响因子：
5.4
通讯作者：
Longnecker, Richard
中科院分区：
文献类型：
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作者：
Hayes, Cooper K.;Giraldo, Daniel;Longnecker, Richard
中枢神经系统(CNS)驻留细胞的天然免疫激活是控制单纯疱疹病毒1型(HSV-1)复制的关键。特别是，在单纯疱疹病毒性脑炎(HSE)的小鼠模型中，I型干扰素(干扰素)的反应已被证明可以限制早期复制并降低死亡率(1，2)。然而，在HSE期间，不同的中枢神经系统细胞群在激发完整的I型干扰素反应中的相对重要性仍未得到很大程度的研究。众所周知，小胶质细胞在对嗜神经性病原体的先天反应中起着重要作用，但我们实验室和其他实验室最近的工作表明，小胶质细胞和星形胶质细胞之间的串扰在HSV-1(3，4)的免疫反应中也发挥着重要作用。星形胶质细胞特异性的I型干扰素的产生在HSV-1感染的眼部模型中也被证明是有保护作用的(5)。为了评估星形胶质细胞中的I型干扰素信号在HSE发病机制中的作用，我们通过将由胶质纤维酸性蛋白(GFAP)启动子驱动的表达Cre重组酶的小鼠系(IFNARf1/fl)(6，7)与小鼠系(IFNARfl/fl)(6，7)杂交，产生了星形胶质细胞特异性的干扰素-a受体(IFNAR)基因敲除(KO)小鼠。Cre在星形胶质细胞中表达的特异性已被证实(8)。在我们实验室以前使用的HSE模型中，当GFAP-Cre+/IFNARfl/fl小鼠在(Ic)脑内感染低毒株Kos时，其存活率明显低于同窝对照组(图1a)(9)。重要的是，HSV-1在所有死于感染的GFAP-Cre+/IFNARfl/fl小鼠的大脑中复制到高水平，表明星形胶质细胞中的I型干扰素信号对于清除HSE中的病毒复制是重要的(图1B)。定量聚合酶链式反应(QPCR)显示，GFAP-Cre+/IFNARfl/fl小鼠在感染后24小时(HPI)的脑内干扰素-b的表达水平显著低于IFNARf1/fl对照小鼠(图1C)。在任一时间点，GFAP-Cre+/IFNARfl/f1小鼠和产仔对照小鼠之间的IL-6水平没有显著差异(图1D)，IL-6是一种独立于I型干扰素信号转导产生的促炎细胞因子。为了评估小胶质细胞在感染过程中对星形胶质细胞I型干扰素反应的贡献，我们分离了小鼠的小胶质细胞和星形胶质细胞，并在感染复数(MOI)为0.1的情况下感染HSV-1。通过qPCR检测，小胶质细胞在24HPI时强劲上调干扰素-b(图2a)，而星形胶质细胞则不能很好地产生干扰素-b，在任何时间点都没有显著上调(图2b)。这些结果表明，在这些细胞类型中，小胶质细胞而不是星形胶质细胞是感染期间干扰素-b表达的主要驱动因素。接下来，我们收集了紫外线灭活的小胶质细胞条件培养液。
Innate immune activation by central nervous system (CNS)-resident cells is critical for controlling herpes simplex virus 1 (HSV-1) replication. In particular, the type I interferon (IFN) response has been shown to limit early replication and reduce mortality in mouse models of herpes simplex encephalitis (HSE)(1, 2). However, the relative importance of different CNS cell populations in eliciting a complete type I IFN response during HSE remains largely understudied. Microglia are well known to have an important role in the innate response to neurotropic pathogens, but recent work in our laboratory and others demonstrated that cross talk between microglia and astrocytes also plays an important role in the immune response to HSV-1 (3, 4). Astrocyte-specific production of type I IFNs has also been shown to be protective in an ocular model of HSV-1 infection (5).To assess the effect that type I IFN signaling in astrocytes has on HSE pathogenesis, we generated astrocyte-specific IFN-a receptor (IFNAR) knockout (KO) mice by crossing a mouse line expressing Cre recombinase driven by the glial fibrillary acidic protein (GFAP) promoter with a mouse line containing floxed IFNAR1 loci (IFNARfl/fl)(6, 7). The specificity of Cre expression in astrocytes has previously been demonstrated (8). GFAP-Cre+/IFNARfl/fl mice had significantly worse survival than littermate controls when intracranially (ic) infected with the low-virulence strain KOS in a model of HSE previously used in our laboratory (Fig. 1A)(9). Importantly, HSV-1 replicated to high levels in the brains of all GFAP-Cre+/IFNARfl/fl mice that succumbed to infection, indicating that type I IFN signaling in astrocytes is important for the clearance of viral replication in HSE (Fig. 1B). GFAP-Cre+/IFNARfl/fl mice had significantly lower expression levels of IFN-b in their brains at 24 h postinfection (hpi) than IFNARfl/fl littermate controls as measured by quantitative PCR (qPCR)(Fig. 1C). Levels of interleukin-6 (IL-6), a proinflammatory cytokine produced independently of type I IFN signaling, did not significantly differ between GFAP-Cre+/IFNARfl/fl mice and littermate controls at either time point (Fig. 1D). To assess the contribution of microglia to the astrocyte type I IFN response during infection, primary microglia and astrocytes were isolated from mice and infected with HSV-1 at a multiplicity of infection (MOI) of 0.1 as previously reported (4). Microglia robustly upregulated IFN-b at 24 hpi as measured by qPCR (Fig. 2A), whereas astrocytes were poor producers of IFN-b, with no significant upregulation at any time point (Fig. 2B). These results suggest that microglia, not astrocytes, are the primary drivers of IFN-b expression during infection among these cell types. We next collected UV-inactivated microglia-conditioned medium