背景:据报道,SARS-CoV-2可诱导细胞融合形成多核合胞体,从而促进病毒复制,传播,免疫逃避,和炎症反应。在这项研究中,我们通过电子显微镜报道了在COVID-19疾病不同阶段参与合胞体形成的细胞类型.
方法:来自轻度的支气管肺泡液(n=8,SpO2>95%,没有缺氧,在感染2-8天内),中等(n=8,室内空气中的SpO290%至≤93%,呼吸频率≥24/min,呼吸困难,在感染后9-16天内),严重(n=8,SpO2<90%,呼吸频率>30/min,外部氧气支持,感染第17天后)COVID-19患者接受PAP(细胞类型鉴定)检查,免疫荧光(病毒感染水平),扫描(SEM),和透射(TEM)电子显微镜来识别合胞体。
结果:来自每个合胞体的免疫荧光研究(S蛋白特异性抗体)表明感染水平非常高。我们在轻度感染的患者中找不到任何合胞体细胞。然而,在中度感染患者中,在TEM下观察到相同(中性粒细胞或2型肺细胞)和异型(中性粒细胞-单核细胞)质膜初始融合(表明融合开始).在嗜中性粒细胞的严重急性呼吸窘迫综合征(ARDS样)患者中发现了完全成熟的大尺寸(20-100μm)合胞细胞,单核细胞,和巨噬细胞起源在SEM下。
结论:这项对COVID-19患者合胞体细胞的超微结构研究揭示了疾病的阶段和参与合胞体形成的细胞类型。首先通过同型融合在II型肺细胞中诱导合胞体形成,然后在疾病的中度阶段(9-16天)通过异型融合与造血细胞(单核细胞和中性粒细胞)诱导合胞体形成。在疾病的晚期报道了成熟的合胞体,并形成了20至100μm的大巨细胞。
SARS-CoV-2 was reported to induce cell fusions to form multinuclear syncytia that might facilitate viral replication, dissemination, immune evasion, and inflammatory responses. In this
study, we have reported the types of cells involved in syncytia formation at different stages of COVID-19 disease through electron microscopy.
Bronchoalveolar fluids from the mild (n = 8, SpO2 > 95%, no hypoxia, within 2-8 days of infection), moderate (n = 8, SpO2 90% to ≤ 93% on room air, respiratory rate ≥ 24/min, breathlessness, within 9-16 days of infection), and severe (n = 8, SpO2 < 90%, respiratory rate > 30/min, external oxygen support, after 17th days of infection) COVID-19 patients were examined by PAP (cell type identification), immunofluorescence (for the level of viral infection), scanning (SEM), and transmission (TEM) electron microscopy to identify the syncytia.
Immunofluorescence studies (S protein-specific antibodies) from each syncytium indicate a very high infection level. We could not find any syncytial cells in mildly infected patients. However, identical (neutrophils or type 2 pneumocytes) and heterotypic (neutrophils-monocytes) plasma membrane initial fusion (indicating initiation of fusion) was observed under TEM in moderately infected patients. Fully matured large-size (20-100 μm) syncytial cells were found in severe acute respiratory distress syndrome (ARDS-like) patients of neutrophils, monocytes, and macrophage origin under SEM.
This ultrastructural
study on the syncytial cells from COVID-19 patients sheds light on the disease\'s stages and types of cells involved in the syncytia formations. Syncytia formation was first induced in type II pneumocytes by homotypic fusion and later with haematopoetic cells (monocyte and neutrophils) by heterotypic fusion in the moderate stage (9-16 days) of the disease. Matured syncytia were reported in the late phase of the disease and formed large giant cells of 20 to 100 μm.