Tang Alan T, Buchholz David W, Szigety Katherine M, Imbhiaka Brian, Gao Siqi, Frankfurter Maxwell, Wang Min, Yang Jisheng, Hewins Peter, Mericko-Ishizuka Patricia, Adrian Leu N, Sterling Stephanie, Monreal Isaac A, Sahler Julie, August Avery, Zhu Xuming, Jurado Kellie A, Xu Mingang, Morrisey Edward E, Millar Sarah E, Aguilar Hector C, Kahn Mark L
bioRxiv. 2021 Dec 7:2021.12.04.471245. doi: 10.1101/2021.12.04.471245.
Lethal COVID-19 is associated with respiratory failure that is thought to be caused by acute respiratory distress syndrome (ARDS) secondary to pulmonary infection. To date, the cellular pathogenesis has been inferred from studies describing the expression of ACE2, a transmembrane protein required for SARS-CoV-2 infection, and detection of viral RNA or protein in infected humans, model animals, and cultured cells. To functionally test the cellular mechanisms of COVID-19, we generated animals in which human ACE2 (hACE2) is expressed from the mouse locus in a manner that permits cell-specific, Cre-mediated loss of function. animals developed lethal weight loss and hypoxemia within 7 days of exposure to SARS-CoV-2 that was associated with pulmonary infiltrates, intravascular thrombosis and patchy viral infection of lung epithelial cells. Deletion of hACE2 in lung epithelial cells prevented viral infection of the lung, but not weight loss, hypoxemia or death. Inhalation of SARS-CoV-2 by animals resulted in early infection of sustentacular cells with subsequent infection of neurons in the neighboring olfactory bulb and cerebral cortexâ€" events that did not require lung epithelial cell infection. Pharmacologic ablation of the olfactory epithelium or mediated deletion of hACE2 in olfactory epithelial cells and neurons prevented lethality and neuronal infection following SARS-CoV-2 infection. Conversely, transgenic expression of hACE2 specifically in olfactory epithelial cells and neurons in ; LSL- mice was sufficient to confer neuronal infection associated with respiratory failure and death. These studies establish mouse loss and gain of function genetic models with which to genetically dissect viral-host interactions and demonstrate that lethal disease due to respiratory failure may arise from extrapulmonary infection of the olfactory epithelium and brain. Future therapeutic efforts focused on preventing olfactory epithelial infection may be an effective means of protecting against severe COVID-19.
致死性新冠肺炎与呼吸衰竭相关，而呼吸衰竭被认为是由肺部感染继发的急性呼吸窘迫综合征（ARDS）所致。迄今为止，细胞发病机制是从描述ACE2（一种SARS-CoV-2感染所需的跨膜蛋白）表达的研究以及在受感染的人类、模型动物和培养细胞中检测病毒RNA或蛋白推断而来的。为了从功能上测试新冠肺炎的细胞机制，我们构建了一些动物，其中人类ACE2（hACE2）以允许细胞特异性、Cre介导的功能丧失的方式从小鼠基因座表达。这些动物在接触SARS-CoV-2后7天内出现致死性体重减轻和低氧血症，这与肺部浸润、血管内血栓形成以及肺上皮细胞的散在病毒感染有关。肺上皮细胞中hACE2的缺失可防止肺部的病毒感染，但不能防止体重减轻、低氧血症或死亡。这些动物吸入SARS-CoV-2导致支持细胞早期感染，随后邻近嗅球和大脑皮层中的神经元感染——这些事件并不需要肺上皮细胞感染。嗅觉上皮的药物消融或嗅上皮细胞和神经元中hACE2的Cre介导缺失可防止SARS-CoV-2感染后的致死性和神经元感染。相反，在LSL- 小鼠的嗅上皮细胞和神经元中特异性转基因表达hACE2足以导致与呼吸衰竭和死亡相关的神经元感染。这些研究建立了功能丧失和功能获得的小鼠遗传模型，用以从基因层面剖析病毒与宿主的相互作用，并证明呼吸衰竭导致的致死性疾病可能源于嗅上皮和大脑的肺外感染。未来专注于预防嗅上皮感染的治疗措施可能是预防严重新冠肺炎的有效手段。
