The characteristics and evolution of pulmonary fibrosis in patients with coronavirus disease 2019 (COVID-19) have not been adequately studied. AI-assisted chest high-resolution computed tomography (HRCT) was used to investigate the proportion of COVID-19 patients with pulmonary fibrosis, the relationship between the degree of fibrosis and the clinical classification of COVID-19, the characteristics of and risk factors for pulmonary fibrosis, and the evolution of pulmonary fibrosis after discharge. The incidence of pulmonary fibrosis in patients with severe or critical COVID-19 was significantly higher than that in patients with moderate COVID-19. There were significant differences in the degree of pulmonary inflammation and the extent of the affected area among patients with mild, moderate and severe pulmonary fibrosis. The IL-6 level in the acute stage and albumin level were independent risk factors for pulmonary fibrosis. Ground-glass opacities, linear opacities, interlobular septal thickening, reticulation, honeycombing, bronchiectasis and the extent of the affected area were significantly improved 30, 60 and 90 days after discharge compared with at discharge. The more severe the clinical classification of COVID-19, the more severe the residual pulmonary fibrosis was; however, in most patients, pulmonary fibrosis was improved or even resolved within 90 days after discharge.

The current discharge criteria for COVID-19 require that patients have two consecutive negative results for RT-PCR detection. Here, we observed that recurrently positive RT-PCR test results in patients with three consecutive negative results (3xNegRPos, 5.4%) were significantly decreased compared with those in patients with two consecutive negative results (2xNegRPos, 20.6%); such patients reported positive RT-PCR test results within 1 to 12 days after meeting the discharge criteria. These results confirmed that many recovered patients could show a positive RT-PCR test result, and most of these patients could be identified by an additional RT-PCR test prior to discharge.

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Background: The Notch signaling pathway plays an important role in regulating human immune function, but the relationship between allergic rhinitis (AR) and Notch signaling remains unclear. Objective: To investigate the role of Notch signaling in the pathogenesis of AR and its regulation on Foxp3-Treg cells. Method: The sera of 100 patients with AR and 50 controls were collected to assess the differences in Notch1, Jagged1, and DLL1 (Delta-like 1) expression. Experimental mice were divided into normal control, AR, Notch inhibitor, and dexamethasone groups. Allergic symptoms, total IgE levels, and the proportion of Treg cells in the peripheral blood were detected. Notch1, Jagged1, NICD (Notch intracellular domain, also known as ICN), and Foxp3 expression and Th1/Th2/Th17-related cytokines in the spleen were detected and compared between each group of mice. Results: Compared with the control group, the expression of Notch1 and Jagged1 in patients with AR was significantly elevated (p < 0.05). The expression of Notch1 and Jagged1 in patients with severe AR was higher than that observed in the mild to moderate AR patients and positively correlated with the levels of allergen sIgE (p < 0.05). The animal experiments revealed that compared with the normal control group, the expression of Notch1, Jagged1, and NICD in the AR group was increased, Foxp3 expression was decreased, and the proportion of Treg cells was decreased (p < 0.05). Compared with the AR group, allergic symptoms and total serum IgE levels and the expression of Notch1, Jagged1, and NICD were significantly decreased in the Notch inhibited group, whereas the expression of Foxp3 and the proportion of Treg cells were increased significantly (p < 0.05). The Th2-type immune responses were also enhanced and Th1-type immune responses decreased in the AR group, but the Th1/Th2 imbalance was reversed in the Notch inhibited group. Conclusion: Notch signaling downregulates Foxp3 expression and inhibits the differentiation of Treg cells to promote the development of AR. Blocking Notch signaling may be a potential treatment for AR.

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