Department of Immunology, University of Colorado, Aurora, Colorado, USA.
Department of Microbiology, University of Colorado, Aurora, Colorado, USA.
J Virol. 2023 Mar 30;97(3):e0180522. doi: 10.1128/jvi.01805-22. Epub 2023 Feb 21.
West Nile virus (WNV) is the leading cause of epidemic arboviral encephalitis in the United States. As there are currently no proven antiviral therapies or licensed human vaccines, understanding the neuropathogenesis of WNV is critical for rational therapeutic design. In WNV-infected mice, the depletion of microglia leads to enhanced viral replication, increased central nervous system (CNS) tissue injury, and increased mortality, suggesting that microglia play a critical role in protection against WNV neuroinvasive disease. To determine if augmenting microglial activation would provide a potential therapeutic strategy, we administered granulocyte-macrophage colony-stimulating factor (GM-CSF) to WNV-infected mice. Recombinant human GM-CSF (rHuGMCSF) (sargramostim [Leukine]) is an FDA-approved drug used to increase white blood cells following leukopenia-inducing chemotherapy or bone marrow transplantation. Daily treatment of both uninfected and WNV-infected mice with subcutaneous injections of GM-CSF resulted in microglial proliferation and activation as indicated by the enhanced expression of the microglia activation marker ionized calcium binding adaptor molecule 1 (Iba1) and several microglia-associated inflammatory cytokines, including CCL2 (C-C motif chemokine ligand 2), interleukin 6 (IL-6), and IL-10. In addition, more microglia adopted an activated morphology as demonstrated by increased sizes and more pronounced processes. GM-CSF-induced microglial activation in WNV-infected mice was associated with reduced viral titers and apoptotic activity (caspase 3) in the brains of WNV-infected mice and significantly increased survival. WNV-infected brain slice cultures (BSCs) treated with GM-CSF also showed reduced viral titers and caspase 3 apoptotic cell death, indicating that GM-CSF specifically targets the CNS and that its actions are not dependent on peripheral immune activity. Our studies suggest that stimulation of microglial activation may be a viable therapeutic approach for the treatment of WNV neuroinvasive disease. Although rare, WNV encephalitis poses a devastating health concern, with few treatment options and frequent long-term neurological sequelae. Currently, there are no human vaccines or specific antivirals against WNV infections, so further research into potential new therapeutic agents is critical. This study presents a novel treatment option for WNV infections using GM-CSF and lays the foundation for further studies into the use of GM-CSF as a treatment for WNV encephalitis as well as a potential treatment for other viral infections.
西尼罗河病毒（WNV）是美国流行的虫媒脑炎的主要原因。由于目前尚无经过验证的抗病毒疗法或获得许可的人类疫苗，因此了解 WNV 的神经发病机制对于合理的治疗设计至关重要。在感染 WNV 的小鼠中，小胶质细胞的耗竭会导致病毒复制增加、中枢神经系统（CNS）组织损伤增加和死亡率增加，这表明小胶质细胞在保护免受 WNV 神经侵袭性疾病方面起着关键作用。为了确定增强小胶质细胞激活是否会提供一种潜在的治疗策略，我们向感染 WNV 的小鼠中给予粒细胞-巨噬细胞集落刺激因子（GM-CSF）。重组人 GM-CSF（rHuGMCSF）（沙格司亭[Leukine]）是一种获得 FDA 批准的药物，用于在引起白细胞减少症的化疗或骨髓移植后增加白细胞。每日向未感染和感染 WNV 的小鼠皮下注射 GM-CSF 治疗会导致小胶质细胞增殖和激活，这表现为小胶质细胞激活标志物离子钙结合接头分子 1（Iba1）和几种小胶质细胞相关炎症细胞因子的表达增强，包括 CCL2（C 型趋化因子配体 2）、白细胞介素 6（IL-6）和白细胞介素 10（IL-10）。此外，更多的小胶质细胞呈现出激活的形态，这表现为体积增大和更明显的突起。GM-CSF 诱导的感染 WNV 的小鼠中的小胶质细胞激活与感染 WNV 的小鼠大脑中的病毒滴度降低和凋亡活性（半胱天冬酶 3）以及显著增加的存活率相关。用 GM-CSF 处理的感染 WNV 的脑切片培养物（BSC）也显示出降低的病毒滴度和半胱天冬酶 3 凋亡细胞死亡，这表明 GM-CSF 特异性靶向 CNS，并且其作用不依赖于外周免疫活性。我们的研究表明，刺激小胶质细胞激活可能是治疗 WNV 神经侵袭性疾病的可行治疗方法。尽管罕见，但 WNV 脑炎会带来毁灭性的健康问题，治疗选择很少，且经常伴有长期的神经后遗症。目前，尚无针对 WNV 感染的人类疫苗或特定抗病毒药物，因此进一步研究潜在的新治疗药物至关重要。本研究提出了使用 GM-CSF 治疗 WNV 感染的新治疗选择，并为进一步研究 GM-CSF 作为 WNV 脑炎的治疗方法以及其他病毒感染的潜在治疗方法奠定了基础。
