BACKGROUND Microglia are the principal innate immune defense cells of the centeral nervous system (CNS) and the target of the human immunodeficiency virus type one (HIV-1). A complete understanding of human microglial biology and function requires the cell's presence in a brain microenvironment. Lack of relevant animal models thus far has also precluded studies of HIV-1 infection. Productive viral infection in brain occurs only in human myeloid linage microglia and perivascular macrophages and requires cells present throughout the brain. Once infected, however, microglia become immune competent serving as sources of cellular neurotoxic factors leading to disrupted brain homeostasis and neurodegeneration. METHODS Herein, we created a humanized bone-marrow chimera producing human "microglia like" cells in NOD.Cg-PrkdcscidIl2rgtm1SugTg(CMV-IL34)1/Jic mice. Newborn mice were engrafted intrahepatically with umbilical cord blood derived CD34+ hematopoietic stem progenitor cells (HSPC). After 3 months of stable engraftment, animals were infected with HIV-1ADA, a myeloid-specific tropic viral isolate. Virologic, immune and brain immunohistology were performed on blood, peripheral lymphoid tissues, and brain. RESULTS Human interleukin-34 under the control of the cytomegalovirus promoter inserted in NSG mouse strain drove brain reconstitution of HSPC derived peripheral macrophages into microglial-like cells. These human cells expressed canonical human microglial cell markers that included CD14, CD68, CD163, CD11b, ITGB2, CX3CR1, CSFR1, TREM2 and P2RY12. Prior restriction to HIV-1 infection in the rodent brain rested on an inability to reconstitute human microglia. Thus, the natural emergence of these cells from ingressed peripheral macrophages to the brain could allow, for the first time, the study of a CNS viral reservoir. To this end we monitored HIV-1 infection in a rodent brain. Viral RNA and HIV-1p24 antigens were readily observed in infected brain tissues. Deep RNA sequencing of these infected mice and differential expression analysis revealed human-specific molecular signatures representative of antiviral and neuroinflammatory responses. CONCLUSIONS This humanized microglia mouse reflected human HIV-1 infection in its known principal reservoir and showed the development of disease-specific innate immune inflammatory and neurotoxic responses mirroring what can occur in an infected human brain.

中文翻译：

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Human Interleukin-34 促进人源化小鼠的小胶质细胞样细胞分化和持续的 HIV-1 感染。

背景小胶质细胞是中枢神经系统(CNS) 的主要先天免疫防御细胞，也是人类免疫缺陷病毒1 型(HIV-1) 的目标。对人类小胶质细胞生物学和功能的完整理解需要细胞存在于大脑微环境中。迄今为止，缺乏相关的动物模型也排除了对 HIV-1 感染的研究。大脑中的生产性病毒感染仅发生在人髓系小胶质细胞和血管周围巨噬细胞中，并且需要存在于整个大脑中的细胞。然而，一旦被感染，小胶质细胞就会成为具有免疫能力的细胞神经毒性因子的来源，从而导致脑稳态和神经退化。方法在此，我们创建了一种在 NOD 中产生人类“小胶质细胞样”细胞的人源化骨髓嵌合体。Cg-PrkdcscidIl2rgtm1SugTg(CMV-IL34)1/Jic 小鼠。新生小鼠肝内移植脐带血来源的 CD34+ 造血干祖细胞 (HSPC)。稳定植入 3 个月后，动物感染 HIV-1ADA，一种骨髓特异性热带病毒分离株。对血液、外周淋巴组织和脑进行病毒学、免疫和脑免疫组织学检查。结果 在插入 NSG 小鼠品系的巨细胞病毒启动子控制下的人白细胞介素 34 促使 HSPC 衍生的外周巨噬细胞的脑重建为小胶质细胞样细胞。这些人类细胞表达典型的人类小胶质细胞标记物，包括 CD14、CD68、CD163、CD11b、ITGB2、CX3CR1、CSFR1、TREM2 和 P2RY12。之前对啮齿动物大脑中 HIV-1 感染的限制取决于无法重建人类小胶质细胞。因此，这些细胞从进入的外周巨噬细胞自然出现到大脑中，可以第一次允许对 CNS 病毒库的研究。为此，我们监测了啮齿动物大脑中的 HIV-1 感染。在受感染的脑组织中很容易观察到病毒 RNA 和 HIV-1p24 抗原。这些受感染小鼠的深度 RNA 测序和差异表达分析揭示了代表抗病毒和神经炎症反应的人类特异性分子特征。