由B.1.617.2 Delta变体引起的COVID-19肺形态病理学

 

概要

 

最近发表在《个性化医学》上的一篇论文中，研究人员对SARS-CoV-2的Delta (B. 1.617.2) 变体进行了研究。在本研究中，研究人员对2021年12月至2022年2月期间在罗马尼亚死于SARS-CoV-2感染Delta VOC的年龄在40至83岁之间的6名男性和4名女性患者进行了尸检。

病毒基因测序显示，8名患者的肺样本中存在B.1.617.2变体，2名患者中发现了Delta VOC的独特突变体。尸检还显示10名死亡患者中有7名出现了急性肺水肿现象。而在新冠患者的组织病理学检查中最常观察到的病变是急性肺水肿（70%病例），其次是DAD（即弥漫性肺泡损伤）。然而，在所有10例尸体解剖中，死者的肺部重量均有所增加，质地及触诊质地都变得更加坚硬，解剖后的肺部肝化呈红褐色（或紫色）。第4例尸检出现丛状病变，也即严重肺动脉高压的标志，其中一个肺切片还显示有支气管肺炎和脓性出血性分泌物。由于缺乏生前临床数据，研究人员无法将丛状病变与COVID-19直接相关联。最后的免疫组织化学检查显示，10名患者中有6名感染了SARS-CoV-2。

重要的是，5例肺泡细胞中的SARS-CoV-2蛋白呈阳性，其中1例在内皮细胞中。这一特殊发现表明，SARS-CoV-2还造成了血栓形成的间接损害。由于其他原因和相似的形态，COVID-19 DAD与DAD具有相似的组织病理学分期。它从渗出阶段进入组织阶段，最后进入纤维化阶段。

总体来看，研究表明肺泡细胞和内皮细胞上的SARS-CoV-2刺突蛋白结合抗体会造成血栓形成，从而导致间接损害。

 

Pulmonary morphopathology in COVID-19 caused by the B.1.617.2 Delta variant

 

In a recent study published in Personalized Medicine, researchers examined the histopathological condition of the lungs of patients who died from coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta (B.1.617.2) variant.

 

Study: Histopathological Lung Findings in COVID-19 B.1.617.2 SARS-CoV-2 Delta Variant. Image Credit: MarcinWojc/Shutterstock

 

Background

 

The Delta variant (B.1.617.2), first identified in India, was designated a variant of concern (VOC) by the World Health Organization (WHO) in May 2021. Due to its 1.4 to 1.64 times higher transmissibility than the Alpha VOC, it outpaced the rest of the variants by the spring of 2021. In addition, several studies showed that Delta was more aggressive than all the previous strains.

 

Irrespective of the causal SARS-CoV-2 VOC, data suggests that COVID-19 pneumonia alters lung perfusion, edema, atelectasis, and, therefore, recruitability. Also, SARS-CoV-2-infected patients tend to have heavy, firm, and edematous lungs. Diffuse alveolar damage (DAD) is the most commonly reported condition in COVID-19 patients, which changes lung histology.

 

About the study

 

In the present study, researchers analyzed six male and four female patients aged between 40 and 83 years who died from SARS-CoV-2 infection by the Delta VOC in Romania between December 2021 and February 2022.

 

They performed an autopsy on four of 10 patients and a postmortem lung biopsy for six patients. They retrieved two necrotic lung fragments 12 hours after the patient's death. They used one sample for SARS-CoV-2 virology analyses and the other for histopathology.

 

Results

 

Genetic sequencing during virology analysis identified B.1.617.2 in lung samples from eight patients and unique mutations of the Delta VOC in two patients. Macroscopic examination revealed acute pulmonary edema in seven of 10 deceased patients. The most frequently observed lesions in the histopathological examination were acute pulmonary edema (70% cases), followed by DAD. However, in all ten autopsied cases, the lungs had increased in weight, their consistency had become firmer, with higher consistency on palpation, and they appeared reddish–brown (or purple) from lung hepatization.

 

Case No. 4 presented a plexiform lesion, a trademark of severe pulmonary hypertension. One of the lung sections also revealed bronchopneumonia and purulent and hemorrhagic secretions. Due to a lack of antemortem clinical data, the researchers could not correlate the plexiform lesion directly with COVID-19. The immunohistochemical examination revealed that six of 10 patients were positive for SARS-CoV-2 proteins.

 

Importantly, five cases were positive for SARS-CoV-2 proteins in alveolocytes, of which one was in an endothelial cell. This particular finding suggested that SARS-CoV-2 also caused indirect damage from thrombosis. COVID-19 DAD had similar histopathological stages as DAD due to other causes and similar morphology. It entered from the exudative stage to the organizing stage, and finally, the fibrotic stage.

 

Conclusions

 

The Delta variant is one of the most aggressive strains of SARS-CoV-2. Yet, the study results did not reveal any unique pulmonary histopathological aspects for Delta compared to its predecessors. However, SARS-CoV-2 spike protein-binding antibodies on alveolocytes and endothelial cells showed the potential for indirect damage from thrombosis.

 

Source:

News-Medical

Published on February 3 2023

 

 

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