Carossino Mariano, Kenney Devin, O'Connell Aoife K, Montanaro Paige, Tseng Anna E, Gertje Hans P, Grosz Kyle A, Ericsson Maria, Huber Bertrand R, Kurnick Susanna A, Subramaniam Saravanan, Kirkland Thomas A, Walker Joel R, Francis Kevin P, Klose Alexander D, Paragas Neal, Bosmann Markus, Saeed Mohsan, Balasuriya Udeni B R, Douam Florian, Crossland Nicholas A
Louisiana Animal Disease Diagnostic Laboratory (LADDL), Louisiana State University, Baton Rouge, LA 61329, USA.
Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 61329, USA.
Viruses. 2022 Mar 5;14(3):535. doi: 10.3390/v14030535.
Animal models recapitulating COVID-19 are critical to enhance our understanding of SARS-CoV-2 pathogenesis. Intranasally inoculated transgenic mice expressing human angiotensin-converting enzyme 2 under the cytokeratin 18 promoter (K18-hACE2) represent a lethal model of SARS-CoV-2 infection. We evaluated the clinical and virological dynamics of SARS-CoV-2 using two intranasal doses (10 and 10 PFUs), with a detailed spatiotemporal pathologic analysis of the 10 dose cohort. Despite generally mild-to-moderate pneumonia, clinical decline resulting in euthanasia or death was commonly associated with hypothermia and viral neurodissemination independent of inoculation dose. Neuroinvasion was first observed at 4 days post-infection, initially restricted to the olfactory bulb suggesting axonal transport via the olfactory neuroepithelium as the earliest portal of entry. Absence of viremia suggests neuroinvasion occurs independently of transport across the blood-brain barrier. SARS-CoV-2 tropism was neither restricted to ACE2-expressing cells (e.g., AT1 pneumocytes), nor inclusive of some ACE2-positive cell lineages (e.g., bronchiolar epithelium and brain vasculature). Absence of detectable ACE2 protein expression in neurons but overexpression in neuroepithelium suggest this as the most likely portal of neuroinvasion, with subsequent ACE2 independent lethal neurodissemination. A paucity of epidemiological data and contradicting evidence for neuroinvasion and neurodissemination in humans call into question the translational relevance of this model.
能够重现新型冠状病毒肺炎（COVID-19）的动物模型对于增进我们对严重急性呼吸综合征冠状病毒2（SARS-CoV-2）发病机制的理解至关重要。在细胞角蛋白18启动子（K18-hACE2）控制下经鼻内接种表达人血管紧张素转换酶2的转基因小鼠代表了一种SARS-CoV-2感染的致死模型。我们使用两种经鼻内接种剂量（10⁴和10⁵菌斑形成单位[PFU]）评估了SARS-CoV-2的临床和病毒学动态，并对10⁴剂量组进行了详细的时空病理学分析。尽管通常为轻度至中度肺炎，但导致安乐死或死亡的临床病情恶化通常与体温过低和病毒神经播散有关，且与接种剂量无关。感染后4天首次观察到神经侵袭，最初局限于嗅球，提示通过嗅神经上皮的轴突运输是最早的进入途径。无病毒血症表明神经侵袭独立于穿过血脑屏障的运输而发生。SARS-CoV-2嗜性既不限于表达ACE2的细胞（如1型肺泡上皮细胞），也不包括一些ACE2阳性细胞谱系（如细支气管上皮和脑血管系统）。神经元中未检测到ACE2蛋白表达，但神经上皮中过表达，提示这是最可能的神经侵袭途径，随后发生独立于ACE2的致死性神经播散。人类中关于神经侵袭和神经播散的流行病学数据匮乏且证据相互矛盾，这使得该模型的转化相关性受到质疑。
