SARS-CoV-2 and the brain: A review of the current knowledge on neuropathology in COVID-19

Prevalence, risk factors, and long-term outcomes of cerebral ischemia in hospitalized COVID-19 patients – study rationale and protocol of the CORONIS study: A multicentre prospective cohort study

Background:

COVID-19 is often complicated by thrombo-embolic events including ischemic stroke. The underlying mechanisms of COVID-19-associated ischemic stroke, the incidence and risk factors of silent cerebral ischemia, and the long-term functional outcome in these patients are currently unknown.

Patients and methods:

CORONavirus and Ischemic Stroke (CORONIS) is a multicentre prospective cohort study investigating the prevalence, risk factors and long-term incidence of (silent) cerebral ischemia, and the long-term functional outcome among patients with COVID-19. We aim to include 200 adult patients hospitalized with COVID-19 without symptomatic ischemic stroke to investigate the prevalence of silent cerebral ischemia compared with 60 (matched) controls with MRI. In addition, we will identify potential risk factors and/or causes of cerebral ischemia in COVID-19 patients with (n = 70) or without symptomatic stroke (n = 200) by means of blood sampling, cardiac workup and brain MRI. We will measure functional outcome and cognitive function after 3 and 12 months with standardized questionnaires in all patients with COVID-19. Finally, the long-term incidence of (new) silent cerebral ischemia in patients with COVID-19 will be assessed with follow up MRI (n = 120).

Summary:

The CORONIS study is designed to add further insight into the prevalence, long-term incidence and risk factors of cerebral ischemia, and the long-term functional outcome in hospitalized adult patients with COVID-19.

Does SARS-CoV-2 affect neurodegenerative disorders? TLR2, a potential receptor for SARS-CoV-2 in the CNS

The coronavirus (COVID-19) pandemic, caused by severe acute respiratory system coronavirus 2 (SARS-CoV-2), has created significant challenges for scientists seeking to understand the pathogenic mechanisms of SARS-CoV-2 infection and to identify the best therapies for infected patients. Although ACE2 is a known receptor for the virus and has been shown to mediate viral entry into the lungs, accumulating reports highlight the presence of neurological symptoms resulting from infection. As ACE2 expression is low in the central nervous system (CNS), these neurological symptoms are unlikely to be caused by ACE2-virus binding. In this review, we will discuss a proposed interaction between SARS-CoV-2 and Toll-like receptor 2 (TLR2) in the CNS. TLR2 is an innate immune receptor that recognizes exogenous microbial components but has also been shown to interact with multiple viral components, including the envelope (E) protein of SARS-CoV-2. In addition, TLR2 plays an important role in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Based on these observations, we hypothesize that TLR2 may play a critical role in the response to SARS-CoV-2 infiltration in the CNS, thereby resulting in the induction or acceleration of AD and PD pathologies in patients.

Awaiting a cure for COVID-19: therapeutic approach in patients with different severity levels of COVID-19

COVID-19 is an unpredictable infectious disease caused by SARS-CoV-2. The development of effective anti-COVID-19 vaccines has enormously minimized the risk of severe illness in most immunocompetent patients. However, unvaccinated patients and non-responders to the COVID-19 vaccine are at risk of shortand long-term consequences. In these patients, the outcome of COVID-19 relies on an interplay of multiple factors including age, immunocompetence, comorbidities, inflammatory response triggered by the virus as well as the virulence of SARS-CoV-2 variants. Generally, COVID-19 is asymptomatic or mildly symptomatic in young people, but it may manifest with respiratory insufficiency requiring mechanical ventilation in certain susceptible groups of patients. Furthermore, severe SARS-CoV-2 infection induces multiorgan failure syndrome by affecting liver, kidney heart and nervous system. Since December 2019, multiple drugs have been tested to treat COVID-19, but only a few have been proven effective to mitigate the course of the disease that continues to cause death and comorbidity worldwide. Current treatment of COVID-19 patients is essentially based on the administration of supportive oxygen therapy and the use of specific drugs such as steroids, anticoagulants, antivirals, anti-SARS-CoV-2 antibodies and immunomodulators. However, the rapid spread of new variants and the release of new data coming from the numerous ongoing clinical trials have created the conditions for maintaining a continuous updating of the therapeutic management of COVID-19 patients. Furthermore, we believe that a well-established therapeutic strategy along with the continuum of medical care for all patients with COVID-19 is pivotal to improving disease outcomes and restoring healthcare care fragmentation caused by the pandemic. This narrative review, focusing on the therapeutic management of COVID-19 patients, aimed to provide an overview of current therapies for (i) asymptomatic or mildly/moderate symptomatic patients, (ii) hospitalized patients requiring low-flow oxygen, (iii) high-flow oxygen and (iv) mechanical ventilation.

SARS-CoV-2 Morbidity in the CNS and the Aged Brain Specific Vulnerability

The infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be the cause of a fatal disease known as coronavirus disease 2019 (COVID-19) affecting the lungs and other organs. Particular attention has been given to the effects of the infection on the brain due to recurring neurological symptoms associated with COVID-19, such as ischemic or hemorrhagic stroke, encephalitis and myelitis, which are far more severe in the elderly compared to younger patients. The specific vulnerability of the aged brain could derive from the impaired immune defenses, from any of the altered homeostatic mechanisms that contribute to the aging phenotype, and from particular changes in the aged brain involving neurons and glia. While neuronal modifications could contribute indirectly to the damage induced by SARS-CoV-2, glia alterations could play a more direct role, as they are involved in the immune response to viral infections. In aged patients, changes regarding glia include the accumulation of dystrophic forms, reduction of waste removal, activation of microglia and astrocytes, and immunosenescence. It is plausible to hypothesize that SARS-CoV-2 infection in the elderly may determine severe brain damage because of the frail phenotype concerning glial cells.

Death after the Administration of COVID-19 Vaccines Approved by EMA: Has a Causal Relationship Been Demonstrated?

More than eight billion doses of COVID-19 vaccines have been administered globally so far and 44.29% of people are fully vaccinated. Pre-authorization clinical trials were carried out and the safety of vaccines is still continuously monitored through post-commercialization surveillance. However, some people are afraid of vaccine side effects, claiming they could lead to death, and hesitate to get vaccinated. Herein, a literature review of COVID-19-vaccine-related deaths has been carried out according to the PRISMA standards to understand if there is a causal relationship between vaccination and death and to highlight the real extent of such events. There have been 55 cases of death after COVID-19 vaccination reported and a causal relationship has been excluded in 17 cases. In the remaining cases, the causal link between the vaccine and the death was not specified (8) or considered possible (15), probable (1), or very probable/demonstrated (14). The causes of deaths among these cases were: vaccine-induced immune thrombotic thrombocytopenia (VITT) (32), myocarditis (3), ADEM (1), myocardial infarction (1), and rhabdomyolysis (1). In such cases, the demonstration of a causal relationship is not obvious, and more studies, especially with post-mortem investigations, are needed to deepen understanding of the possible pathophysiological mechanisms of fatal vaccine side effects. In any event, given the scarcity of fatal cases, the benefits of vaccination outweigh the risks and the scientific community needs to be cohesive in asserting that vaccination is fundamental to containing the spread of SARS-CoV-2.

Cytokine Storm in COVID-19: Immunopathogenesis and Therapy

A cytokine storm is a hyperinflammatory state secondary to the excessive production of cytokines by a deregulated immune system. It manifests clinically as an influenza-like syndrome, which can be complicated by multi-organ failure and coagulopathy, leading, in the most severe cases, even to death. The term cytokine storm was first used in 1993 to describe the graft-versus-host disease following allogeneic hematopoietic stem cell transplantation. It was then reused to define the adverse syndromes secondary to the administration of immunostimulating agents, such as anti-CD28 antibodies or bioengineered immune cells, i.e., CAR T-cell therapy. Currently, the concept of cytokine storm has been better elucidated and extended to the pathogenesis of many other conditions, such as sepsis, autoinflammatory disease, primary and secondary hemophagocytic lymphohistiocytosis, and multicentric Castleman disease. Moreover, cytokine storm has recently emerged as a key aspect in the novel Coronavirus disease 2019, as affected patients show high levels of several key pro-inflammatory cytokines, such as IL-1, IL-2, IL-6, TNF-α, IFN-γ, IP-10, GM-CSF, MCP-1, and IL-10, some of which also correlate with disease severity. Therefore, since the onset of the pandemic, numerous agents have been tested in the effort to mitigate the cytokine storm in COVID-19 patients, some of which are effective in reducing mortality, especially in critically ill patients, and are now becoming standards of care, such as glucocorticoids or some cytokine inhibitors. However, the challenge is still far from being met, and other therapeutic strategies are being tested in the hope that we can eventually overcome the disease.

The Effects of the SARS-CoV-2 Virus on the Cardiovascular System and Coagulation State Leading to Cardiovascular Diseases: A Narrative Review

The novel coronavirus pandemic has led to morbidity and mortality throughout the world. Until now, it is a highly virulent contagion attacking the respiratory system in humans, especially people with chronic diseases and the elderly who are most vulnerable. A majority of afflicted are those suffering from cardiovascular and coronary diseases. In this review article, an attempt has been made to discuss and thoroughly review the mode of therapies that alleviate cardiac complications and complications due to hypercoagulation in patients infected with the SARS-CoV-2 virus. Presently a host of thrombolytic drugs are in use like Prourokinase, Retelapse, RhTNK-tPA and Urokinase. However, thrombolytic therapy, especially if given intravenously, is associated with a serious risk of intracranial haemorrhage, systemic haemorrhage, immunologic complications, hypotension and myocardial rupture. The effects of the SARS-CoV-2 virus upon the cardiovascular system and coagulation state of the body are being closely studied. In connection to the same, clinical prognosis and complications of thrombolytic therapy are being scrutinized. It is noteworthy to mention that myocardial oxygen supply/demand mismatch, direct myocardial cells injury and acute plaque rupture are the multiple mechanisms responsible for acute coronary syndrome and cardiac complications in Covid-19 infection. However, this review has limitations as data available in this context is limited, scattered and heterogenous that questions the reliability of the same. So, more multi-centric studies involving representative populations, carried out meticulously, could further assist in responding better to cardiac complications among Covid-19 patients.

APOE ε4 associates with increased risk of severe COVID-19, cerebral microhaemorrhages and post-COVID mental fatigue: a Finnish biobank, autopsy and clinical study

Apolipoprotein E ε4 allele (APOE4) has been shown to associate with increased susceptibility to SARS-CoV-2 infection and COVID-19 mortality in some previous genetic studies, but information on the role of APOE4 on the underlying pathology and parallel clinical manifestations is scarce. Here we studied the genetic association between APOE and COVID-19 in Finnish biobank, autopsy and prospective clinical cohort datasets. In line with previous work, our data on 2611 cases showed that APOE4 carriership associates with severe COVID-19 in intensive care patients compared with non-infected population controls after matching for age, sex and cardiovascular disease status. Histopathological examination of brain autopsy material of 21 COVID-19 cases provided evidence that perivascular microhaemorrhages are more prevalent in APOE4 carriers. Finally, our analysis of post-COVID fatigue in a prospective clinical cohort of 156 subjects revealed that APOE4 carriership independently associates with higher mental fatigue compared to non-carriers at six months after initial illness. In conclusion, the present data on Finns suggests that APOE4 is a risk factor for severe COVID-19 and post-COVID mental fatigue and provides the first indication that some of this effect could be mediated via increased cerebrovascular damage. Further studies in larger cohorts and animal models are warranted.

Delirium and Cognitive Impairment as Predisposing Factors of COVID-19 Infection in Neuropsychiatric Patients: A Narrative Review

SARS-CoV-2 neuroinvasive and neurotropic abilities may underlie delirium onset and neuropsychiatric outcomes. Only a limited number of studies have addressed the potential effect of SARS-CoV-2 infection on mental health so far. Most studies mainly reported the acute onset of mixed neuropsychiatric conditions in patients infected with SARS-CoV-2, characterized by agitated behavior, altered level of consciousness, and disorganized thinking, regardless of psychological or socioeconomic triggering factors. The present narrative review aims to analyze and discuss the mechanisms underlying the neuroinvasive/neurotropic properties of SARS-CoV-2 and the subsequent mental complications. Delirium appeared as a clinical manifestation of SARS-CoV-2 brain infection in some patients, without systemic or multiple organ failure symptoms. A small number of studies demonstrated that neuropsychiatric symptoms associated with COVID-19, initially presenting as a confused state, may subsequently evolve in a way that is consistent with the patients' neuropsychiatric history. A literature analysis on this topic prevalently showed case reports and case series of patients presenting delirium or delirium-like symptoms as the main outburst of COVID-19, plus a cognitive impairment, from mild to severe, which pre-existed or was demonstrated during the acute phase or after infection. Dementia appeared as one of the most frequent predisposing factors to SARS-CoV-2 infection complicated with delirium. Instead, contrasting data emerged on the potential link between COVID-19 and delirium in patients with cognitive impairment and without a neuropsychiatric history. Therefore, clinicians should contemplate the possibility that COVID-19 appears as delirium followed by a psychiatric exacerbation, even without other systemic symptoms. In addition, cognitive impairment might act as a predisposing factor for COVID-19 in patients with delirium.

SARS-CoV-2 causes lung infection without severe disease in human ACE2 knock-in mice

The development of mouse models for coronavirus disease 2019 (COVID-19) has enabled testing of vaccines and therapeutics and defining aspects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis. SARS-CoV-2 disease is severe in K18 transgenic mice (K18-hACE2 Tg) expressing human angiotensin-converting enzyme 2 (hACE2), the SARS-CoV-2 receptor, under an ectopic cytokeratin promoter, with high levels of infection measured in the lung and brain. Here, we evaluated SARS-CoV-2 infection in hACE2 knock-in (KI) mice that express hACE2 under an endogenous promoter in place of murine ACE2 (mACE2). Intranasal inoculation of hACE2 KI mice with SARS-CoV-2 WA1/2020 resulted in substantial viral replication within the upper and lower respiratory tracts with limited spread to extrapulmonary organs. However, SARS-CoV-2-infected hACE2 KI mice did not lose weight and developed limited pathology. Moreover, no significant differences in viral burden were observed in hACE2 KI mice infected with B.1.1.7 or B.1.351 variants compared to the WA1/2020 strain. Because the entry mechanisms of SARS-CoV-2 in mice remain uncertain, we evaluated the impact of the naturally occurring, mouse-adapting N501Y mutation by comparing infection of hACE2 KI, K18-hACE2 Tg, ACE2-deficient, and wild-type C57BL/6 mice. The N501Y mutation minimally affected SARS-CoV-2 infection in hACE2 KI mice but was required for viral replication in wild-type C57BL/6 mice in a mACE2-dependent manner and augmented pathogenesis in the K18-hACE2 Tg mice. Thus, the N501Y mutation likely enhances interactions with mACE2 or hACE2 in vivo. Overall, our study highlights the hACE2 KI mice as a model of mild SARS-CoV-2 infection and disease and clarifies the requirement of the N501Y mutation in mice.

IMPORTANCE Mouse models of SARS-CoV-2 pathogenesis have facilitated the rapid evaluation of countermeasures. While the first generation of models developed pneumonia and severe disease after SARS-CoV-2 infection, they relied on ectopic expression of supraphysiological levels of human ACE2 (hACE2). This has raised issues with their relevance to humans, as the hACE2 receptor shows a more restricted expression pattern in the respiratory tract. Here, we evaluated SARS-CoV-2 infection and disease with viruses containing or lacking a key mouse-adapting mutation in the spike gene in hACE2 KI mice, which express hACE2 under an endogenous promoter in place of murine ACE2. While infection of hACE2 KI mice with multiple strains of SARS-CoV-2 including variants of concern resulted in viral replication within the upper and lower respiratory tracts, the animals did not sustain severe lung injury. Thus, hACE2 KI mice serve as a model of mild infection with both ancestral and emerging SARS-CoV-2 variant strains.

Myocardial Pathology in COVID-19-Associated Cardiac Injury: A Systematic Review

Coronavirus disease 2019 (COVID-19) can potentially affect all organs owing to the ubiquitous diffusion of the angiotensin-converting enzyme II (ACE2) receptor-binding protein. Indeed, the SARS-CoV-2 virus is capable of causing heart disease. This systematic review can offer a new perspective on the potential consequences of COVID-19 through an analysis of the current literature on cardiac involvement. This systematic review, conducted from March 2020 to July 2021, searched the current literature for postmortem findings in patients who were positive for SARS-CoV-2 by combining and meshing the terms “COVID-19”, “postmortem”, “autopsy”, and “heart” in titles, abstracts, and keywords. The PubMed database was searched following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Sixteen papers met the inclusion criteria (case reports and series, original research, only English-written). A total of 209 patients were found (mean age (interquartile range (IQR)), 60.17 years (IQR, 54.75–70.75 years); 122 men (58.37%, ratio of men to women of 1:0.7%)). Each patient tested positive for SARS-CoV-2. Death was mainly the result of respiratory failure. The second most common cause of death was acute heart failure. Few patients specifically died of myocarditis. Variables such as pathological findings, immunohistochemical data, and previous clinical assessments were analyzed. Main cardiac pathological findings were cardiac dilatation, necrosis, lymphocytic infiltration of the myocardium, and small coronary vessel microthrombosis. Immunohistochemical analyses revealed an inflammatory state dominated by the constant presence of CD3+ and CD8+ cytotoxic lymphocytes and CD68+ macrophages. COVID-19 leads to a systemic inflammatory response and a constant prothrombotic state. The results of our systematic review suggest that SARS-CoV-2 was able to cause irreversible changes in several organs, including the heart; this is reflected by the increased cardiac risk in patients who survive COVID-19. Postmortem analysis (including autopsy, histologic, and immunohistochemical examination) is an indispensable tool to better understand pathological changes caused by emerging diseases such as COVID-19. Our results may provide more information on the involvement of the heart in COVID-19 patients.

Cytokine storm and histopathological findings in 60 cases of COVID-19-related death: from viral load research to immunohistochemical quantification of major players IL-1β, IL-6, IL-15 and TNF-α

This study involves the histological analysis of samples taken during autopsies in cases of COVID-19 related death to evaluate the inflammatory cytokine response and the tissue localization of the virus in various organs. In all the selected cases, SARS-CoV-2 RT-PCR on swabs collected from the upper (nasopharynx and oropharynx) and/or the lower respiratory (trachea and primary bronchi) tracts were positive. Tissue localization of SARS-CoV-2 was detected using antibodies against the nucleoprotein and the spike protein. Overall, we tested the hypothesis that the overexpression of proinflammatory cytokines plays an important role in the development of COVID-19-associated pneumonia by estimating the expression of multiple cytokines (IL-1β, IL-6, IL-10, IL-15, TNF-α, and MCP-1), inflammatory cells (CD4, CD8, CD20, and CD45), and fibrinogen. Immunohistochemical staining showed that endothelial cells expressed IL-1β in lung samples obtained from the COVID-19 group (p < 0.001). Similarly, alveolar capillary endothelial cells showed strong and diffuse immunoreactivity for IL-6 and IL-15 in the COVID-19 group (p < 0.001). TNF-α showed a higher immunoreactivity in the COVID-19 group than in the control group (p < 0.001). CD8 + T cells where more numerous in the lung samples obtained from the COVID-19 group (p < 0.001). Current evidence suggests that a cytokine storm is the major cause of acute respiratory distress syndrome (ARDS) and multiple organ failure and is consistently linked with fatal outcomes.

SARS-CoV-2 and the brain: A review of the current knowledge on neuropathology in COVID-19

SARS‐CoV‐2 (severe acute respiratory syndrome coronavirus 2), the new coronavirus responsible for the pandemic disease in the last year, is able to affect the central nervous system (CNS). Compared with its well‐known pulmonary tropism and respiratory complications, little has been studied about SARS‐CoV‐2 neurotropism and pathogenesis of its neurological manifestations, but also about postmortem histopathological findings in the CNS of patients who died from COVID‐19 (coronavirus disease 2019). We present a systematic review, carried out according to the Preferred Reporting Items for Systematic Review standards, of the neuropathological features of COVID‐19. We found 21 scientific papers, the majority of which refer to postmortem examinations; the total amount of cases is 197. Hypoxic changes are the most frequently reported alteration of brain tissue, followed by ischemic and hemorrhagic lesions and reactive astrogliosis and microgliosis. These findings do not seem to be specific to SARS‐CoV‐2 infection, they are more likely because of systemic inflammation and coagulopathy caused by COVID‐19. More studies are needed to confirm this hypothesis and to detect other possible alterations of neural tissue. Brain examination of patients dead from COVID‐19 should be included in a protocol of standardized criteria to perform autopsies on these subjects.