The trimeric SARS-CoV-2 Spike protein mediates viral attachment facilitating cell entry. Most COVID-19 vaccines direct mammalian cells to express the Spike protein or deliver it directly via inoculation to engender a protective immune response. The trafficking and cellular tropism of the Spike protein in vivo and its impact on immune cells remains incompletely elucidated. In this study, we inoculated mice intranasally, intravenously, and subcutaneously with fluorescently labeled recombinant SARS-CoV-2 Spike protein. Using flow cytometry and imaging techniques, we analyzed its localization, immune cell tropism, and acute functional impact. Intranasal administration led to rapid lung alveolar macrophage uptake, pulmonary vascular leakage, and neutrophil recruitment and damage. When injected near the inguinal lymph node medullary, but not subcapsular macrophages, captured the protein, while scrotal injection recruited and fragmented neutrophils. Widespread endothelial and liver Kupffer cell uptake followed intravenous administration. Human peripheral blood cells B cells, neutrophils, monocytes, and myeloid dendritic cells all efficiently bound Spike protein. Exposure to the Spike protein enhanced neutrophil NETosis and augmented human macrophage TNF-α (tumor necrosis factor-α) and IL-6 production. Human and murine immune cells employed C-type lectin receptors and Siglecs to help capture the Spike protein. This study highlights the potential toxicity of the SARS-CoV-2 Spike protein for mammalian cells and illustrates the central role for alveolar macrophage in pathogenic protein uptake.

中文翻译：

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鼻内施用的 SARS-CoV-2 刺突蛋白引起小鼠肺泡巨噬细胞快速积累，导致中性粒细胞募集和损伤

三聚体 SARS-CoV-2 刺突蛋白介导病毒附着，促进细胞进入。大多数 COVID-19 疫苗指导哺乳动物细胞表达 Spike 蛋白或通过接种直接递送它以产生保护性免疫反应。刺突蛋白在体内的运输和细胞向性及其对免疫细胞的影响仍未完全阐明。在这项研究中，我们通过鼻内、静脉内和皮下给小鼠接种荧光标记的重组 SARS-CoV-2 Spike 蛋白。使用流式细胞术和成像技术，我们分析了其定位、免疫细胞向性和急性功能影响。鼻内给药导致肺泡巨噬细胞快速摄取、肺血管渗漏以及中性粒细胞募集和损伤。当注射到腹股沟淋巴结髓质附近时，而不是包膜下巨噬细胞捕获蛋白质，而阴囊注射则募集并破碎中性粒细胞。静脉内给药后，内皮和肝脏库普弗细胞广泛摄取。人外周血细胞B细胞、中性粒细胞、单核细胞和骨髓树突状细胞均能有效结合Spike蛋白。暴露于 Spike 蛋白可增强中性粒细胞 NETosis 并增强人巨噬细胞 TNF-α（肿瘤坏死因子-α）和 IL-6 的产生。人类和小鼠免疫细胞利用 C 型凝集素受体和 Siglecs 来帮助捕获 Spike 蛋白。这项研究强调了 SARS-CoV-2 刺突蛋白对哺乳动物细胞的潜在毒性，并说明了肺泡巨噬细胞在致病蛋白摄取中的核心作用。