RESUMO
SARS-CoV-2 cell entry starts with membrane attachment and ends with spike-protein (S) catalyzed membrane fusion depending on two cleavage steps, one usually by furin in producing cells and the second by TMPRSS2 on target cells. Endosomal cathepsins can carry out both. Using real-time 3D single virion tracking, we show fusion and genome penetration requires virion exposure to an acidic milieu of pH 6.2-6.8, even when furin and TMPRSS2 cleavages have occurred. We detect the sequential steps of S1-fragment dissociation, fusion, and content release from the cell surface in TMPRRS2 overexpressing cells only when exposed to acidic pH. We define a key role of an acidic environment for successful infection, found in endosomal compartments and at the surface of TMPRSS2 expressing cells in the acidic milieu of the nasal cavity. Significance StatementInfection by SARS-CoV-2 depends upon the S large spike protein decorating the virions and is responsible for receptor engagement and subsequent fusion of viral and cellular membranes allowing release of virion contents into the cell. Using new single particle imaging tools, to visualize and track the successive steps from virion attachment to fusion, combined with chemical and genetic perturbations of the cells, we provide the first direct evidence for the cellular uptake routes of productive infection in multiple cell types and their dependence on proteolysis of S by cell surface or endosomal proteases. We show that fusion and content release always require the acidic environment from endosomes, preceded by liberation of the S1 fragment which depends on ACE2 receptor engagement. One sentence summaryDetailed molecular snapshots of the productive infectious entry pathway of SARS-CoV-2 into cells
RESUMO
Introduction: NSAID-exacerbated respiratory disease (N-ERD) is mainly treated with topical and oral corticosteroids, as well as acetylsalicylic acid (ASA) treatment after desensitization (ATAD). During desensitization and ATAD, it is common to experience an exacerbation of respiratory symptoms and other side effects, which may lead to cessation of treatment. Objectives: The aim of this retrospective follow-up study was to evaluate the effect of ATAD on lung functions and respiratory symptoms, and to clarify the occurrence of adverse events. Methods: We analysed the patient data of 67 patients treated with ASA desensitization between 2006 and 2016 in three hospitals, concerning adverse events, respiratory symptoms, lung function tests, and reasons for discontinuation. Results: 26 patients discontinued AD or ATAD. The most common reasons for discontinuation were lack of response (9%) and side effects (18%). ATAD did not affect lung function values in the follow-up of up to 5 years. Upper respiratory symptoms improved in 31 (52%) and lower respiratory symptoms (LRS) in 7 (10%) cases. Side effects occurred in 42 (63%) cases, the most common being dyspepsia and lower respiratory symptoms. Conclusion: Our study suggests that ATAD has little effect on lower airway functions. Side effects were common, and discontinuation rates high.
