Coronavirus disease 2019 (COVID‐19), caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), continues to spread globally despite the worldwide implementation of preventive measures to combat the disease. Although most COVID‐19 cases are characterised by a mild, self‐limiting disease course, a considerable subset of patients develop a more severe condition, varying from pneumonia and acute respiratory distress syndrome (ARDS) to multi‐organ failure (MOF). Progression of COVID‐19 is thought to occur as a result of a complex interplay between multiple pathophysiological mechanisms, all of which may orchestrate SARS‐CoV‐2 infection and contribute to organ‐specific tissue damage. In this respect, dissecting currently available knowledge of COVID‐19 immunopathogenesis is crucially important, not only to improve our understanding of its pathophysiology but also to fuel the rationale of both novel and repurposed treatment modalities. Various immune‐mediated pathways during SARS‐CoV‐2 infection are relevant in this context, which relate to innate immunity, adaptive immunity, and autoimmunity. Pathological findings in tissue specimens of patients with COVID‐19 provide valuable information with regard to our understanding of pathophysiology as well as the development of evidence‐based treatment regimens. This review provides an updated overview of the main pathological changes observed in COVID‐19 within the most commonly affected organ systems, with special emphasis on immunopathology. Current management strategies for COVID‐19 include supportive care and the use of repurposed or symptomatic drugs, such as dexamethasone, remdesivir, and anticoagulants. Ultimately, prevention is key to combat COVID‐19, and this requires appropriate measures to attenuate its spread and, above all, the development and implementation of effective vaccines. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

The SARS-CoV-2 pandemic is a healthcare crisis caused by insufficient knowledge applicable to effectively combat the virus. Therefore, different scientific discovery strategies need to be connected, to generate a rational treatment which can be made available as rapidly as possible. This relies on a solid theoretical understanding of the mechanisms of SARS-CoV-2 infection and host responses, which is coupled to the practical experience of clinicians that are treating patients. Because SARS-CoV-2 enters the cell by binding to angiotensin-converting enzyme 2 (ACE2), targeting ACE2 to prevent such binding seems an obvious strategy to combat infection. However, ACE2 performs its functions outside the cell and was found to enter the cell only by angiotensin II type 1 receptor (AT1R)-induced endocytosis, after which ACE2 is destroyed. This means that preventing uptake of ACE2 into the cell by blocking AT1R would be a more logical approach to limit entry of SARS-CoV-2 into the cell. Since ACE2 plays an important protective role in maintaining key biological processes, treatments should not disrupt the functional capacity of ACE2, to counterbalance the negative effects of the infection. Based on known mechanisms and knowledge of the characteristics of SARS-CoV we propose the hypothesis that the immune system facilitates SARS-CoV-2 replication which disrupts immune regulatory mechanisms. The proposed mechanism by which SARS-CoV-2 causes disease immediately suggests a possible treatment, since the AT1R is a key player in this whole process. AT1R antagonists appear to be the ideal candidate for the treatment of SARS-CoV-2 infection. AT1R antagonists counterbalance the negative consequences of angiotesnin II and, in addition, they might even be involved in preventing the cellular uptake of the virus without interfering with ACE2 function. AT1R antagonists are widely available, cheap, and safe. Therefore, we propose to consider using AT1R antagonists in the treatment of SARS-CoV-2.

RAASi (renin-angiotensin-aldosterone system inhibitors) are suggested as possible treatment option in the early phase of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection. A meta-analysis investigating the possible detrimental effects of RAASi on the severity of (SARS-CoV-2) infection showed that ambulatory use of RAASi, by hospitalized patients, has a neutral effect. It is, however, conceivable that this observation is biased by the fact that antihypertensive medications, are often discontinued at or during admission in hospitalized patients with SARS-CoV-2. We, therefore, investigated the effect of discontinuation of antihypertensive medications, in hospitalized patients with SARS-CoV-2. We performed a retrospective observational study on 1584 hospitalized patients with SARS-CoV-2 from 10 participating hospitals in the Netherlands. Differences in the outcome (severity of disease or death) between the groups in which medications were either continued or discontinued during the course of hospitalization were assessed using logistic regression models. Discontinuation of angiotensin receptor blockers, ACE (angiotensin-converting enzyme) inhibitors and β-blockers, even when corrected for sex, age, and severity of symptoms during admission, resulted in a 2 to 4× higher risk of dying from SARS-CoV-2 infection (odds ratio [95% CI]); angiotensin receptor blockers 2.65 [1.17–6.04], ACE inhibitor (2.28 [1.15–4.54]), and β-blocker (3.60 [1.10–10.27]). In conclusion, discontinuation of at-home ACE inhibitor, angiotensin receptor blockers, or β-blocker in patients hospitalized for a SARS-CoV-2 infection was associated with an increased risk of dying, whereas discontinuation of calcium channel blockers and diuretics was not.

During the current COVID-19 pandemic caused by SARS-CoV-2, clinicians and scientists are working assiduously to unravel its pathophysiology and find effective treatments. An impressive number of papers has been published on SARS-CoV-2, exposing the complexity of the disease, the tendency of scientists to form hypotheses within their area of expertise, and the lack of orchestration of research. Hypotheses and research findings mainly complement each other, though sometimes controversies can be discerned among various theories and study results. Our overview aims to portray the ‘big picture’ of COVID-19, visualising the interwovenness of different pathophysiological pathways, with a focus on cytokine-induced pathology, the sequelae of ACE2 downregulation, and thrombosis associated with microvascular injury. It aids in overseeing the effects of repurposed drugs on intended targets, but also alerts to the (adverse) effects on interacting pathways. The overview shows how comorbidities probably increase susceptibility to (severe) COVID-19 and provides the possible pathophysiological origin of signs, symptoms, and biochemical abnormalities.