COVID-19 pandemic has been a global health emergency due to its association with severe pneumonia and high rate of mortality. In the current study, we reported the direct evidence for the variable level of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus infection on several types of oral epithelial cells isolated from the aspirated oropharyngeal and bronchoalveolar secretions of severely infected and intubated patients using cytology, confocal based immunofluorescence imaging (IF), scanning electron microscope (SEM) and transmission electron microscopic (TEM) studies. Cytological analysis showed the presence of keratinised and non-keratinised oral epithelial cells with viral inclusion bodies in stratum granulosum and intermedium cells. IF imaging using SARS-CoV-2 spike protein specific antibody confirmed the presence of virus inside the stratum spinosum/granulosum (keratinised) and stratum intermedium/superficial cells (non-keratinised). No SARS-CoV-2 viruses were seen in stratum corneum cells. SEM analysis also confirms the absence of virus like structure on stratum corneum surface while viruses like structure were seen on the stratum spinosum/granulosum/stratum/intermedium and stratum superficial cells. This advanced microscopic study confirms directly that the virus tends to infect and multiply in the metabolically active or sub-basal cells of oral epithelium and absent in the inactive keratinised stratum corneum from shedding zones of oral mucosa.

中文翻译：

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COVID-19 阳性插管患者支气管肺泡液的显微成像揭示了口腔鳞状上皮细胞上不同水平的 SARS-CoV-2 感染

由于 COVID-19 大流行与严重肺炎和高死亡率有关，因此它已成为全球卫生紧急情况。在目前的研究中，我们报告了严重急性呼吸系统综合症冠状病毒 2 (SARS-CoV-2) 病毒在从严重感染和插管的吸入口咽和支气管肺泡分泌物中分离的几种口腔上皮细胞的不同水平的直接证据。使用细胞学、基于共聚焦的免疫荧光成像 (IF)、扫描电子显微镜 (SEM) 和透射电子显微镜 (TEM) 研究的患者。细胞学分析显示在颗粒层和中间细胞中存在带有病毒包涵体的角化和非角化口腔上皮细胞。使用 SARS-CoV-2 刺突蛋白特异性抗体的 IF 成像证实了在棘层/颗粒层（角化）和中层/表层细胞（非角化）中存在病毒。在角质层细胞中未观察到 SARS-CoV-2 病毒。SEM分析还证实角质层表面不存在病毒样结构，而在棘层/颗粒层/中层/中层和表层细胞上看到病毒样结构。这项先进的显微镜研究直接证实，该病毒倾向于在口腔上皮的代谢活跃或亚基底细胞中感染和繁殖，而在口腔黏膜脱落区的非活性角化角质层中不存在。在角质层细胞中未观察到 SARS-CoV-2 病毒。SEM分析还证实角质层表面不存在病毒样结构，而在棘层/颗粒层/中层/中层和表层细胞上观察到病毒样结构。这项先进的显微镜研究直接证实，该病毒倾向于在口腔上皮的代谢活跃或亚基底细胞中感染和繁殖，而在口腔黏膜脱落区的非活性角化角质层中不存在。在角质层细胞中未观察到 SARS-CoV-2 病毒。SEM分析还证实角质层表面不存在病毒样结构，而在棘层/颗粒层/中层/中层和表层细胞上观察到病毒样结构。这项先进的显微镜研究直接证实，该病毒倾向于在口腔上皮的代谢活跃或亚基底细胞中感染和繁殖，而在口腔黏膜脱落区的非活性角化角质层中不存在。