Is COVID-19 associated thrombosis caused by overactivation of the complement cascade? A literature review

Feature Paper in Oral Physiology and Pathology

In the realm of life sciences, the journal 'Life' has consistently served as a beacon for groundbreaking research and scientific discovery [...].

In Silico Analyses Indicate a Lower Potency for Dimerization of TLR4/MD-2 as the Reason for the Lower Pathogenicity of Omicron Compared to Wild-Type Virus and Earlier SARS-CoV-2 Variants

The SARS-CoV-2 Omicron variants have replaced all earlier variants, due to increased infectivity and effective evasion from infection- and vaccination-induced neutralizing antibodies. Compared to earlier variants of concern (VoCs), the Omicron variants show high TMPRSS2-independent replication in the upper airway organs, but lower replication in the lungs and lower mortality rates. The shift in cellular tropism and towards lower pathogenicity of Omicron was hypothesized to correlate with a lower toll-like receptor (TLR) activation, although the underlying molecular mechanisms remained undefined. In silico analyses presented here indicate that the Omicron spike protein has a lower potency to induce dimerization of TLR4/MD-2 compared to wild type virus despite a comparable binding activity to TLR4. A model illustrating the molecular consequences of the different potencies of the Omicron spike protein vs. wild-type spike protein for TLR4 activation is presented. Further analyses indicate a clear tendency for decreasing TLR4 dimerization potential during SARS-CoV-2 evolution via Alpha to Gamma to Delta to Omicron variants.

Impact of mRNA-based vaccines in the prevention of adverse outcomes of COVID-19 infection in pregnancy: a single-center cohort study

Several data have suggested that pregnant women have an increased risk of severe COVID-19 compared to those who are not pregnant. Moreover, different studies have showed that severe COVID-19 is limited mostly to unvaccinated women. The aim of the present study was to ascertain the different maternal and fetal outcomes in pregnant women with COVID-19 according to their vaccination status. A retrospective cohort study was carried out including all women admitted to the high-risk pregnancy unit of our center with COVID-19 between December 2021 and February 2022. Among the 163 women included in the study, 60 were vaccinated with an mRNA vaccine and 103 were unvaccinated. Pregnancy outcome and obstetrical and neonatal complications were encountered. Vaccinated women showed higher educational levels and lower prevalence of cases, with BMI >25 compared to unvaccinated women. Moreover, vaccinated women were admitted mostly for obstetrical indications rather than for COVID-related symptoms. In addition, the risk of developing COVID-19 pneumonia was significantly higher in unvaccinated women (p = 0.01) compared with vaccinated ones. Furthermore, pregnancy and neonatal outcomes showed some differences in the two cohorts. In unvaccinated women, the rate of C-section was higher (p = 0.03), and the mean birthweight percentile in their infants was impaired by COVID-19 infection (p = 0.01) when compared to those born to vaccinated women. Based on these results, we suggest that women who received a full course of vaccination were protected from the severity of the disease, having milder symptoms of SARS-Cov2 infection, while also presenting a more favorable pregnancy outcome.

Association of Serum Complement C3 Levels with Severity and Mortality in COVID 19

The severe acute respiratory distress syndrome-associated coronavirus-2 infection can activate innate and adaptive immune responses which may lead to harmful tissue damage, both locally and systemically. C3, a member of complement system of serum proteins, is a major component of innate immune and inflammatory responses. This study is aimed to assess serum C3 as a marker of COVID-19 severity and a predictor of disease progression. A total of 150 COVID-19 patients, confirmed by RT-PCR, and 50 healthy controls were recruited. Serum C3 levels were determined by using direct colorimetric method. Median levels of serum C3 in total cases and controls were 157.8 and 165.7 mg/dL respectively. Serum C3 although not significantly decreased, they were lower in cases when compared to controls. Similarly, significant differences were found between the groups, with severe group (140.6 mg/dL) having low levels of serum C3 protein when compared to mild (161.0 mg/dL) and moderate group (167.1 mg/dL). Interestingly, during hospitalization, significant difference between baseline (admission) and follow-up (discharge) was observed only in patients with moderate disease. Based on our results, lower levels of C3, with an increase in IL-6 and d-dimer levels, are associated with higher odds of mortality. Therefore, we would like to emphasize that measuring serum C3 levels along with other inflammatory markers might give an added advantage in early identification of patients who are prone to having a severe disease course and can help in a more effective follow-up of disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-023-01148-x.

Modelling and analysis of the complement system signalling pathways: roles of C3, C5a and pro-inflammatory cytokines in SARS-CoV-2 infection

The complement system is an essential part of innate immunity. It is activated by invading pathogens causing inflammation, opsonization, and lysis via complement anaphylatoxins, complement opsonin's and membrane attack complex (MAC), respectively. However, in SARS-CoV-2 infection overactivation of complement system is causing cytokine storm leading to multiple organs damage. In this study, the René Thomas kinetic logic approach was used for the development of biological regulatory network (BRN) to model SARS-CoV-2 mediated complement system signalling pathways. Betweenness centrality analysis in cytoscape was adopted for the selection of the most biologically plausible states in state graph. Among the model results, in strongly connected components (SCCs) pro-inflammatory cytokines (PICyts) oscillatory behaviour between recurrent generation and downregulation was found as the main feature of SARS-CoV-2 infection. Diversion of trajectories from the SCCs leading toward hyper-inflammatory response was found in agreement with in vivo studies that overactive innate immunity response caused PICyts storm during SARS-CoV-2 infection. The complex of negative regulators FI, CR1 and DAF in the inhibition of complement peptide (C5a) and PICyts was found desirable to increase immune responses. In modelling role of MAC and PICyts in lowering of SARS-CoV-2 titre was found coherent with experimental studies. Intervention in upregulation of C5a and PICyts by C3 was found helpful in back-and-forth variation of signalling pattern linked with the levels of PICyts. Moreover, intervention in upregulation of PICyts by C5a was found productive in downregulation of all activating factors in the normal SCCs. However, the computational model predictions require experimental studies to be validated by exploring the activation role of C3 and C5a which could change levels of PICyts at various phases of SARS-CoV-2 infection.

Rare variants in complement system genes associate with endothelial damage after pediatric allogeneic hematopoietic stem cell transplantation

Introduction

Complement system has a postulated role in endothelial problems after hematopoietic stem cell transplantation (HSCT). In this retrospective, singlecenter study we studied genetic complement system variants in patients with documented endotheliopathy. In our previous study among pediatric patients with an allogeneic HSCT (2001-2013) at the Helsinki University Children´s Hospital, Finland, we identified a total of 19/122 (15.6%) patients with vascular complications, fulfilling the criteria of capillary leak syndrome (CLS), venoocclusive disease/sinusoidal obstruction syndrome (VOD/SOS) or thrombotic microangiopathy (TMA).

Methods

We performed whole exome sequencing (WES) on 109 patients having an adequate pre-transplantation DNA for the analysis to define possible variations and mutations potentially predisposing to functional abnormalities of the complement system. In our data analysis, we focused on 41 genes coding for complement components.

Results

50 patients (45.9%) had one or several, nonsynonymous, rare germline variants in complement genes. 21/66 (31.8%) of the variants were in the terminal pathway. Patients with endotheliopathy had variants in different complement genes: in the terminal pathway (C6 and C9), lectin pathway (MASP1) and receptor ITGAM (CD11b, part of CR3). Four had the same rare missense variant (rs183125896; Thr279Ala) in the C9 gene. Two of these patients were diagnosed with endotheliopathy and one with capillary leak syndrome-like problems. The C9 variant Thr279Ala has no previously known disease associations and is classified by the ACMG guidelines as a variant of uncertain significance (VUS). We conducted a gene burden test with gnomAD Finnish (fin) as the reference population. Complement gene variants seen in our patient population were investigated and Total Frequency Testing (TFT) was used for execution of burden tests. The gene variants seen in our patients with endotheliopathy were all significantly (FDR < 0.05) enriched compared to gnomAD. Overall, 14/25 genes coding for components of the complement system had an increased burden of missense variants among the patients when compared to the gnomAD Finnish population (N=10 816).

Discussion

Injury to the vascular endothelium is relatively common after HSCT with different phenotypic appearances suggesting yet unidentified underlying mechanisms. Variants in complement components may be related to endotheliopathy and poor prognosis in these patients.

The Hemostatic System in Newborns and the Risk of Neonatal Thrombosis

Newborns are the most vulnerable patients for thrombosis development among all children, with critically ill and premature infants being in the highest risk group. The upward trend in the rate of neonatal thrombosis could be attributed to progress in the treatment of severe neonatal conditions and the increased survival in premature babies. There are physiological differences in the hemostatic system between neonates and adults. Neonates differ in concentrations and rate of synthesis of most coagulation factors, turnover rates, the ability to regulate thrombin and plasmin, and in greater variability compared to adults. Natural inhibitors of coagulation (protein C, protein S, antithrombin, heparin cofactor II) and vitamin K-dependent coagulation factors (factors II, VII, IX, X) are low, but factor VIII and von Willebrand factor are elevated. Newborns have decreased fibrinolytic activity. In the healthy neonate, the balance is maintained but appears more easily converted into thrombosis. Neonatal hemostasis has less buffer capacity, and almost 95% of thrombosis is provoked. Different triggering risk factors are responsible for thrombosis in neonates, but the most important risk factors for thrombosis are central catheters, fluid fluctuations, liver dysfunction, and septic and inflammatory conditions. Low-molecular-weight heparins are the agents of choice for anticoagulation.

Correlation between Hepatocyte Growth Factor (HGF) with D-Dimer and Interleukin-6 as Prognostic Markers of Coagulation and Inflammation in Long COVID-19 Survivors

In general, an individual who experiences the symptoms of Severe Acute Respiratory Syndrome Coronavirus 2 or SARS-CoV-2 infection is declared as recovered after 2 weeks. However, approximately 10-20% of these survivors have been reported to encounter long-term health problems, defined as 'long COVID-19', e.g., blood coagulation which leads to stroke with an estimated incidence of 3%, and pulmonary embolism with 5% incidence. At the time of infection, the immune response produces pro-inflammatory cytokines that stimulate stromal cells to produce pro-hepatocyte growth factor (pro-HGF) and eventually is activated into hepatocyte growth factor (HGF), which helps the coagulation process in endothelial and epithelial cells. HGF is a marker that appears as an inflammatory response that leads to coagulation. Currently, there is no information on the effect of SARS-CoV-2 infection on serum HGF concentrations as a marker of the prognosis of coagulation in long COVID-19 survivors. This review discusses the pathophysiology between COVID-19 and HGF, IL-6, and D-dimer.

Sepsis - it is all about the platelets

Sepsis is accompanied by thrombocytopenia and the severity of the thrombocytopenia is associated with mortality. This thrombocytopenia is characteristic of disseminated intravascular coagulation (DIC), the sepsis-associated coagulopathy. Many of the pathogens, both bacterial and viral, that cause sepsis also directly activate platelets, which suggests that pathogen-induced platelet activation leads to systemic thrombosis and drives the multi-organ failure of DIC. In this paper we review the mechanisms of platelet activation by pathogens and the evidence for a role for anti-platelet agents in the management of sepsis.

Coagulopathy and thromboembolic events a pathogenic mechanism of COVID-19 associated with mortality: An updated review

During 2019, the SARS-CoV-2 emerged from China, and during months, COVID-19 spread in many countries around the world. The expanding data about pathogenesis of this virus could elucidate the exact mechanism by which COVID-19 caused death in humans. One of the pathogenic mechanisms of this disease is coagulation. Coagulation disorders that affect both venous and arterial systems occur in patients with COVID-19. The possible mechanism involved in the coagulation could be excessive inflammation induced by SARS-CoV-2. However, it is not yet clear well how SARS-CoV-2 promotes coagulopathy. However, some factors, such as pulmonary endothelial cell damage and some anticoagulant system disorders, are assumed to have an important role. In this study, we assessed conducted studies about COVID-19-induced coagulopathy to obtain clearer vision of the wide range of manifestations and possible pathogenesis mechanisms.

Unraveling the Underlying Molecular Mechanism of 'Silent Hypoxia' in COVID-19 Patients Suggests a Central Role for Angiotensin II Modulation of the AT1R-Hypoxia-Inducible Factor Signaling Pathway

A few days after being infected with SARS-CoV-2, a fraction of people remain asymptomatic but suffer from a decrease in arterial oxygen saturation in the absence of apparent dyspnea. In light of our clinical investigation on the modulation of molecules belonging to the renin angiotensin system (RAS) in COVID-19 patients, we propose a model that explains 'silent hypoxia'. The RAS imbalance caused by SARS-CoV-2 results in an accumulation of angiotensin 2 (Ang II), which activates the angiotensin 2 type 1 receptor (AT1R) and triggers a harmful cascade of intracellular signals leading to the nuclear translocation of the hypoxia-inducible factor (HIF)-1α. HIF-1α transactivates many genes including the angiotensin-converting enzyme 1 (ACE1), while at the same time, ACE2 is downregulated. A growing number of cells is maintained in a hypoxic condition that is self-sustained by the presence of the virus and the ACE1/ACE2 ratio imbalance. This is associated with a progressive worsening of the patient's biological parameters including decreased oxygen saturation, without further clinical manifestations. When too many cells activate the Ang II-AT1R-HIF-1α axis, there is a 'hypoxic spillover', which marks the tipping point between 'silent' and symptomatic hypoxia in the patient. Immediate ventilation is required to prevent the 'hypoxic spillover'.

Alternative pathway dysregulation in tissues drives sustained complement activation and predicts outcome across the disease course in COVID-19

Complement, a critical defence against pathogens, has been implicated as a driver of pathology in COVID-19. Complement activation products are detected in plasma and tissues and complement blockade is considered for therapy. To delineate roles of complement in immunopathogenesis, we undertook the largest comprehensive study of complement in COVID-19 to date, comprehensive profiling of 16 complement biomarkers, including key components, regulators and activation products, in 966 plasma samples from 682 hospitalized COVID-19 patients collected across the hospitalization period as part of the UK ISARIC4C (International Acute Respiratory and Emerging Infection Consortium) study. Unsupervised clustering of complement biomarkers mapped to disease severity and supervised machine learning identified marker sets in early samples that predicted peak severity. Compared to healthy controls, complement proteins and activation products (Ba, iC3b, terminal complement complex) were significantly altered in COVID-19 admission samples in all severity groups. Elevated alternative pathway activation markers (Ba and iC3b) and decreased alternative pathway regulator (properdin) in admission samples were associated with more severe disease and risk of death. Levels of most complement biomarkers were reduced in severe disease, consistent with consumption and tissue deposition. Latent class mixed modelling and cumulative incidence analysis identified the trajectory of increase of Ba to be a strong predictor of peak COVID-19 disease severity and death. The data demonstrate that early-onset, uncontrolled activation of complement, driven by sustained and progressive amplification through the alternative pathway amplification loop is a ubiquitous feature of COVID-19, further exacerbated in severe disease. These findings provide novel insights into COVID-19 immunopathogenesis and inform strategies for therapeutic intervention.

Sagittal sinus thrombosis with subarachnoid haemorrhage in a patient with COVID-19 infection

A man in his late 50s was admitted with a 10-day history of right frontotemporal headache, left arm and leg weakness, and a sudden decline in visual acuity in the right eye. The patient had recent exposure to COVID-19 infection and tested positive for the same on admission. A CT scan of the head done on arrival demonstrated a subarachnoid haemorrhage in the right central sulcus with an underlying superior sagittal sinus thrombosis. No other known risk factors for central venous sinus thrombosis could be identified. The patient had a normal level of consciousness on admission clinically; however, he was in severe pain. A collective decision was made to administer anticoagulants to the patient with heparin after carefully deliberating the risk-to-benefit ratio of a superior sagittal thrombus with an associated subarachnoid haemorrhage. Our patient recovered and was discharged after 2 weeks on warfarin. We present this case to highlight the potential risks of hypercoagulable and neurotropic complications of COVID-19 infections, with special emphasis on cerebral venous thrombosis.

Neutrophil activation and neutrophil extracellular traps (NETs) in COVID-19 ARDS and immunothrombosis

Acute respiratory distress syndrome (ARDS) is an acute inflammatory condition with a dramatic increase in incidence since the beginning of the coronavirus disease 19 (COVID-19) pandemic. Neutrophils play a vital role in the immunopathology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by triggering the formation of neutrophil extracellular traps (NETs), producing cytokines including interleukin-8 (CXCL8), and mediating the recruitment of other immune cells to regulate processes such as acute and chronic inflammation, which can lead to ARDS. CXCL8 is involved in the recruitment, activation, and degranulation of neutrophils, and therefore contributes to inflammation amplification and severity of disease. Furthermore, activation of neutrophils also supports a prothrombotic phenotype, which may explain the development of immunothrombosis observed in COVID-19 ARDS. This review aims to describe hyperinflammatory ARDS due to SARS-CoV-2 infection. In addition, we address the critical role of polymorphonuclear neutrophils, inflammatory cytokines, and the potential targeting of CXCL8 in treating the hyperinflammatory ARDS population.

An update on angiotensin-converting enzyme 2 structure/functions, polymorphism, and duplicitous nature in the pathophysiology of coronavirus disease 2019: Implications for vascular and coagulation disease associated with severe acute respiratory syndrome coronavirus infection

It has been known for many years that the angiotensin-converting enzyme 2 (ACE2) is a cell surface enzyme involved in the regulation of blood pressure. More recently, it was proven that the severe acute respiratory syndrome coronavirus (SARS-CoV-2) interacts with ACE2 to enter susceptible human cells. This functional duality of ACE2 tends to explain why this molecule plays such an important role in the clinical manifestations of coronavirus disease 2019 (COVID-19). At the very start of the pandemic, a publication from our Institute (entitled "ACE2 receptor polymorphism: susceptibility to SARS-CoV-2, hypertension, multi-organ failure, and COVID-19 disease outcome"), was one of the first reviews linking COVID-19 to the duplicitous nature of ACE2. However, even given that COVID-19 pathophysiology may be driven by an imbalance in the renin-angiotensin system (RAS), we were still far from understanding the complexity of the mechanisms which are controlled by ACE2 in different cell types. To gain insight into the physiopathology of SARS-CoV-2 infection, it is essential to consider the polymorphism and expression levels of the ACE2 gene (including its alternative isoforms). Over the past 2 years, an impressive amount of new results have come to shed light on the role of ACE2 in the pathophysiology of COVID-19, requiring us to update our analysis. Genetic linkage studies have been reported that highlight a relationship between ACE2 genetic variants and the risk of developing hypertension. Currently, many research efforts are being undertaken to understand the links between ACE2 polymorphism and the severity of COVID-19. In this review, we update the state of knowledge on the polymorphism of ACE2 and its consequences on the susceptibility of individuals to SARS-CoV-2. We also discuss the link between the increase of angiotensin II levels among SARS-CoV-2-infected patients and the development of a cytokine storm associated microvascular injury and obstructive thrombo-inflammatory syndrome, which represent the primary causes of severe forms of COVID-19 and lethality. Finally, we summarize the therapeutic strategies aimed at preventing the severe forms of COVID-19 that target ACE2. Changing paradigms may help improve patients' therapy.

Targeting the Complement-Sphingolipid System in COVID-19 and Gaucher Diseases: Evidence for a New Treatment Strategy

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2)-induced disease (COVID-19) and Gaucher disease (GD) exhibit upregulation of complement 5a (C5a) and its C5aR1 receptor, and excess synthesis of glycosphingolipids that lead to increased infiltration and activation of innate and adaptive immune cells, resulting in massive generation of pro-inflammatory cytokines, chemokines and growth factors. This C5a-C5aR1-glycosphingolipid pathway- induced pro-inflammatory environment causes the tissue damage in COVID-19 and GD. Strikingly, pharmaceutically targeting the C5a-C5aR1 axis or the glycosphingolipid synthesis pathway led to a reduction in glycosphingolipid synthesis and innate and adaptive immune inflammation, and protection from the tissue destruction in both COVID-19 and GD. These results reveal a common involvement of the complement and glycosphingolipid systems driving immune inflammation and tissue damage in COVID-19 and GD, respectively. It is therefore expected that combined targeting of the complement and sphingolipid pathways could ameliorate the tissue destruction, organ failure, and death in patients at high-risk of developing severe cases of COVID-19.

Associations between serum levels of C3, C4, and total classical complement activity in COVID-19 patients at the time of admission and clinical outcome

In the present study, we investigated the association between complement system status at the time of admission and clinical outcomes in COVID-19 patients. This single-center study was carried out with sixty-one adult patients with COVID-19 who were hospitalized at Imam Hassan Hospital of North Khorasan University of Medical Sciences (Bojnurd, Iran) with less than three days passage since onset of COVID-19 symptoms. Twenty-three healthy volunteers with demographic features similar to the patient group (matched by age and gender) were included in the study as a control group. Patient information including demographic information, demographic data, clinical characteristics, and clinical outcomes were obtained from electronic medical records. Of 61 hospitalized patients with COVID-19, 28 (47.54%) were female, and the average age was 48.78.8 years. The healthy control group included 23 cases (11 (47.8%) female, 12 (52.1%) males, mean age 46.44.4 years). Twenty-one of the 61 patients (34.4%) were admitted to the ICU, and sixteen of them (26.2%) died. Thirty-three (54.10%) patients with COVID-19 were hospitalized for less than 7 days, and 28 (45.90%) of them were hospitalized for 7 days. Our results show that length of hospital stay in the no-ICU group was significantly lower than the ICU admission or death groups (6.490.24 vs. 8.851.59 and 10.531.80, p = 0.0002). The levels of C3, C4, and CH50 were determined through the immunoturbidimetric method and single-radial-haemolysis plates, respectively, on serum samples obtained from patients at the time of admission or those in the control group. Our results indicate that C3, C4 and CH50 levels were markedly lower in COVID-19 patients than in the control group. We also found that complement parameter levels in COVID-19 patients who died or were admitted to ICU were significantly lower than in non-ICU COVID-19 patients. In general, it seems that serum level of C3, C4, and CH50 at admission may predict disease progression or adverse clinical outcome in COVID-19 patients.

Complement and endothelial cell activation in COVID-19 patients compared to controls with suspected SARS-CoV-2 infection: A prospective cohort study

Background

Thromboinflammation may influence disease outcome in COVID-19. We aimed to evaluate complement and endothelial cell activation in patients with confirmed COVID-19 compared to controls with clinically suspected but excluded SARS-CoV-2 infection.

Methods

In a prospective, observational, single-center study, patients presenting with clinically suspected COVID-19 were recruited in the emergency department. Blood samples on presentation were obtained for analysis of C5a, sC5b-9, E-selectin, Galectin-3, ICAM-1 and VCAM-1.

Results

153 cases and 166 controls (suffering mainly from non-SARS-CoV-2 respiratory viral infections, non-infectious inflammatory conditions and bacterial pneumonia) were included. Hospital admission occurred in 62% and 45% of cases and controls, respectively. C5a and VCAM-1 concentrations were significantly elevated and E-selectin concentrations decreased in COVID-19 out- and inpatients compared to the respective controls. However, relative differences in outpatients vs. inpatients in most biomarkers were comparable between cases and controls. Elevated concentrations of C5a, Galectin-3, ICAM-1 and VCAM-1 on presentation were associated with the composite outcome of ICU- admission or 30-day mortality in COVID-19 and controls, yet more pronounced in COVID-19. C5a and sC5b-9 concentrations were significantly higher in COVID-19 males vs. females, which was not observed in the control group.

Conclusions

Our data indicate an activation of the complement cascade and endothelium in COVID-19 beyond a nonspecific inflammatory trigger as observed in controls (i.e., “over”-activation).

Highly pathogenic coronavirus N protein aggravates inflammation by MASP-2-mediated lectin complement pathway overactivation

Excessive inflammatory responses contribute to the pathogenesis and lethality of highly pathogenic human coronaviruses, but the underlying mechanism remains unclear. In this study, the N proteins of highly pathogenic human coronaviruses, including severe acute respiratory syndrome coronavirus (SARS-CoV), middle east respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), were found to bind MASP-2, a key serine protease in the lectin pathway of complement activation, resulting in excessive complement activation by potentiating MBL-dependent MASP-2 activation, and the deposition of MASP-2, C4b, activated C3 and C5b-9. Aggravated inflammatory lung injury was observed in mice infected with adenovirus expressing the N protein. Complement hyperactivation was also observed in SARS-CoV-2-infected patients. Either blocking the N protein:MASP-2 interaction, MASP-2 depletion or suppressing complement activation can significantly alleviate N protein-induced complement hyperactivation and lung injury in vitro and in vivo. Altogether, these data suggested that complement suppression may represent a novel therapeutic approach for pneumonia induced by these highly pathogenic coronaviruses.

Coagulopathy in COVID-19 and anticoagulation clinical trials

Severe acute respiratory disease coronavirus 2 (SARS-COV-2) first emerged in Wuhan, China, in December 2019 and has caused a global pandemic of a scale unprecedented in the modern era. People infected with SARS-CoV-2 can be asymptomatic, moderate symptomatic or develop severe COVID-19. Other than the typical acute respiratory distress syndrome (ARDS), patients with moderate or severe COVID-19 also develop a distinctive systemic coagulopathy, known as COVID-19-associated coagulopathy (CAC), which is different from sepsis-related forms of disseminated intravascular coagulation (DIC). Endotheliopathy or endotheliitis are other unique features of CAC. The endothelial cell perturbation can further increase the risk of thrombotic events in COVID-19 patients. In this review, we will summarize the current knowledge on COVID-19 coagulopathy and the possible mechanisms for the condition. We also discuss the results of clinical trials testing methods for mitigating thrombosis events in COVID-19 patients.

Dysregulated miRNAs network in the critical COVID-19: An important clue for uncontrolled immunothrombosis/thromboinflammation

Known as a pivotal immunohemostatic response, immunothrombosis is activated to restrict the diffusion of pathogens. This beneficial intravascular defensive mechanism represents the close interaction between the immune and coagulation systems. However, its uncontrolled form can be life-threatening to patients with the critical coronavirus disease 2019 (COVID-19). Hyperinflammation and ensuing cytokine storm underlie the activation of the coagulation system, something which results in the provocation of more immune-inflammatory responses by the thrombotic mediators. This vicious cycle causes grave clinical complications and higher risks of mortality. Classified as an evolutionarily conserved family of the small non-coding RNAs, microRNAs (miRNAs) serve as the fine-tuners of genes expression and play a key role in balancing the pro/anticoagulant and pro-/anti-inflammatory factors maintaining homeostasis. Therefore, any deviation from their optimal expression levels or efficient functions can lead to severe complications. Despite their extensive effects on the molecules and processes involved in uncontrolled immunothrombosis, some genetic agents and uncontrolled immunothrombosis-induced interfering factors (e.g., miRNA-single nucleotide polymorphysms (miR-SNPs), the complement system components, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, and reactive oxygen species (ROS)) have apparently disrupted their expressions/functions. This review study aims to give an overview of the role of miRNAs in the context of uncontrolled immunothrombosis/thromboinflammation accompanied by some presumptive interfering factors affecting their expressions/functions in the critical COVID-19. Detecting, monitoring, and resolving these interfering agents mafy facilitate the design and development of the novel miRNAs-based therapeutic approaches to the reduction of complications incidence and mortality in patients with the critical COVID-19.

Prognostic significance of complement factors in severely ill patients with COVID-19

Coagulopathy, cytokine release, platelet hyperactivity and endothelial activation are regarded as potential major contributors to COVID-19 morbidity. Complement activation might provide a bridge linking these factors in severe COVID-19 illness. In this study, we investigated the prognostic significance of selected complement factors in hospitalized patients with severe COVID-19 infection. The study included 300 hospitalized adults with severe COVID-19 infection. Complement factors (C3, C3a, C4, sC5b-9) were assessed by commercial ELISA kits. Outcome parameters included mortality, intensive care unit admission and duration of hospital stay. It was found that survivors had significantly higher serum C3 (median (IQR): 128.5 (116.3-141.0) mg/dL vs 98.0 (70.0-112.8) mg/dL, p<0.001) and C4 (median (IQR): 36.0 (30.0-42.0) mg/dL vs 31.0 (26.0-35.0) mg/dL, p<0.001) levels when compared with non-survivors. On the other hand, it was shown that survivors had significantly lower C3a (median (IQR): 203.0 (170.3-244.0) ng/mL vs 385.0 (293.0-424.8) ng/mL, p<0.001) and sC5b-9 (median (IQR): 294.0 (242.0-318.8) ng/mL vs 393.0 (342.0-436.5) ng/mL, p<0.001) levels when compared with non-survivors. Multivariate logistic regression analysis identified C3a (OR: 0.97 (95% CI 0.96 to 0.99), p<0.001) and C4 (OR: 0.92 (95% CI 0.86 to 0.98), p=0.011) levels as significant predictors of mortality. In conclusion, serum levels of complement factors are related to mortality in severely ill patients with COVID-19.

A structural homology approach to identify potential cross-reactive antibody responses following SARS-CoV-2 infection

The emergence of the novel SARS-CoV-2 virus is the most important public-health issue of our time. Understanding the diverse clinical presentations of the ensuing disease, COVID-19, remains a critical unmet need. Here we present a comprehensive listing of the diverse clinical indications associated with COVID-19. We explore the theory that anti-SARS-CoV-2 antibodies could cross-react with endogenous human proteins driving some of the pathologies associated with COVID-19. We describe a novel computational approach to estimate structural homology between SARS-CoV-2 proteins and human proteins. Antibodies are more likely to interrogate 3D-structural epitopes than continuous linear epitopes. This computational workflow identified 346 human proteins containing a domain with high structural homology to a SARS-CoV-2 Wuhan strain protein. Of these, 102 proteins exhibit functions that could contribute to COVID-19 clinical pathologies. We present a testable hypothesis to delineate unexplained clinical observations vis-à-vis COVID-19 and a tool to evaluate the safety-risk profile of potential COVID-19 therapies.

Could a Lower Toll-like Receptor (TLR) and NF-κB Activation Due to a Changed Charge Distribution in the Spike Protein Be the Reason for the Lower Pathogenicity of Omicron?

The novel SARS-CoV-2 Omicron variant B.1.1.529, which emerged in late 2021, is currently active worldwide, replacing other variants, including the Delta variant, due to an enormously increased infectivity. Multiple substitutions and deletions in the N-terminal domain (NTD) and the receptor binding domain (RBD) in the spike protein collaborate with the observed increased infectivity and evasion from therapeutic monoclonal antibodies and vaccine-induced neutralizing antibodies after primary/secondary immunization. In contrast, although three mutations near the S1/S2 furin cleavage site were predicted to favor cleavage, observed cleavage efficacy is substantially lower than in the Delta variant and also lower compared to the wild-type virus correlating with significantly lower TMPRSS2-dependent replication in the lungs, and lower cellular syncytium formation. In contrast, the Omicron variant shows high TMPRSS2-independent replication in the upper airway organs, but lower pathogenicity in animal studies and clinics. Based on recent data, we present here a hypothesis proposing that the changed charge distribution in the Omicron’s spike protein could lead to lower activation of Toll-like receptors (TLRs) in innate immune cells, resulting in lower NF-κB activation, furin expression, and viral replication in the lungs, and lower immune hyper-activation.

A novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) artificial lung membrane for enhanced gas transport and excellent hemo-compatibility

Extracorporeal membrane oxygenation is a technique that provides short-term supports to the heart and lungs. It removes CO₂ from the blood and provides enough oxygen, which is a huge help in the fight against COVID-19. As the key component, the artificial lung membranes have evolved in three generations including silicon, polypropylene and poly (4-methyl-1-pentene). Herein, we for the first time design and fabricate a novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) membrane with the anticoagulant coating composed of poly (sodium 4-styrenesulfonate) and cross-linked poly (vinyl alcohol). Poly (sodium 4-styrenesulfonate) provides sulfonic acid groups to inhibit the coagulant factors (FVIII and FXII), and cross-linked poly (vinyl alcohol) increase the stability of the anticoagulant coating and further improve the hydrophilicity via abundant hydroxyl groups to depress the protein adsorption. Long-term anticoagulant property was demonstrated by whole human blood for 28 days. Blood compatibility was evaluated by hemolysis rate, anticoagulation activity (APTT, TT and PT), complement activation, platelet activation and contact activation. Pure CO₂, O₂ and N₂ permeation rates were determined to evaluate the mass transfer properties of PMP/PP TFC membranes. Gas permeation results revealed that gas permeation flux increased in the TFC membranes because of the decrease of crystallinity. Overall, the so prepared PMP/PP membrane shows good CO₂/O₂ selectivity and blood compatibility as novel TFC artificial lung membrane.

Anticoagulation in Patients With COVID-19: JACC Review Topic of the Week

Clinical, laboratory, and autopsy findings support an association between coronavirus disease-2019 (COVID-19) and thromboembolic disease. Acute COVID-19 infection is characterized by mononuclear cell reactivity and pan-endothelialitis, contributing to a high incidence of thrombosis in large and small blood vessels, both arterial and venous. Observational studies and randomized trials have investigated whether full-dose anticoagulation may improve outcomes compared with prophylactic dose heparin. Although no benefit for therapeutic heparin has been found in patients who are critically ill hospitalized with COVID-19, some studies support a possible role for therapeutic anticoagulation in patients not yet requiring intensive care unit support. We summarize the pathology, rationale, and current evidence for use of anticoagulation in patients with COVID-19 and describe the main design elements of the ongoing FREEDOM COVID-19 Anticoagulation trial, in which 3,600 hospitalized patients with COVID-19 not requiring intensive care unit level of care are being randomized to prophylactic-dose enoxaparin vs therapeutic-dose enoxaparin vs therapeutic-dose apixaban. (FREEDOM COVID-19 Anticoagulation Strategy [FREEDOM COVID]; NCT04512079)

Covid-19: pharmacotherapeutic insights on various curative approaches in terms of vulnerability, comorbidities, and vaccination

A novel coronavirus disease (COVID-19), caused by a severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), was discovered in Wuhan, China, in December 2019, and the world has suffered from a pandemic. As of 22nd March 2020, at least 185 countries worldwide had been affected by COVID-19. SARS-CoV-2, leading to COVID-19 pneumonia, infects cells through ACE-2 receptors. The disease has different clinical signs and symptoms, including chills, high fever, dyspnea, and cough. Other symptoms including haemoptysis, myalgia, diarrhoea, expectoration, and fatigue may also occur. The rapid rise in confirmation cases is severe in preventing and controlling COVID-19. In this review, the article will explore and evaluate the insights into how COVID influences patients with other comorbid conditions such as cardiovascular disease, diabetes, Parkinson's, and how conditions Urolithiasis, anosmia, and anuria may develop after infection. The virus mutates and the variants are now prevalent in the present scenario where the world stands in eradicating the pandemic by looking into the development of vaccines by several countries and how the vaccination can temporarily help prevent COVID spread.

Typical and Atypical Clinical Presentation of COVID-19 Infection in Children in The Top of Pandemic in EL-Minia Governorate (Two Center Experience)

BACKGROUND

A novel coronavirus that is identified as the cause of pandemic situation inFebruary2020 and affects adults and children with variable presentation and outcome.

OBJECTIVE

We studied the typical and atypical clinical and laboratory presentation of COVID-19 during the peak of the first wave in two main referral hospitals, upper Egypt EL-Minia governorate.

METHODS

Among 88 children with suspected cases tested for COVID-19, only 22 proved to be positive. Studied patients were classified into three groups based on age. The first group was 2-5years, the second was 5-10years, and the third included those aged more than 10 years. All patients met diagnostic guidelines established by the Egyptian Ministry of Health.

RESULTS

out of the positive 22 (25%) patients, 13(59.1%) of them were male, while 9 (40.9%) were females. All enrolled patients have a history of near contact exposure (100%). Thrombocytopenia was the highest presenting symptom in all enrolled patients18 (81.8%), while other hematological findings were anemia in 11 (50%), thrombotic symptoms in 2 (9.1%), pancytopenia in 2(9.1%) while bleeding was found in 1 patient (4.5%). Fever, present in 16 (72.7%), the most common constitutional symptom in COVID-19, was not reported in all enrolled patients, while sore throat was reported in only 2 patients (9.1%). The respiratory presentation was only dominant in positive chest C.T. finding, 17(72.3%), rather than clinical symptoms; GUT symptoms were the dominant presenting features as vomiting was found in 15 (68.2%), diarrhea in 10 (45.5%), abdominal pain in 11 (50%), jaundice in 9 (40.9%) and dehydration in 6 (27.3%). Neurological symptoms were convulsions in 4 (18.2%), while encephalopathy was 2 (9.1%). Nephritis was the only renal presentation in the enrolled patients, 3 (13.6%). Cardiac presentations were only cyanosis 8 (36.4%) and arrhythmias 6 (27.3%).

CONCLUSION

COVID-19 has many clinical classic presentations in children; however other non-typical presentations like hematological, CNS, and renal presentations have been reported.

COVID-19 associated symmetrical peripheral gangrene: A case series

BACKGROUND AND AIMS

The novel coronavirus disease (COVID-19) caused by SARS-CoV-2 has turned the world topsy-turvy since its onset in 2019. The thromboinflammatory complications of this disease are common in critically ill patients and associated with poor prognosis. Symmetrical peripheral gangrene (SPG) is characterized by symmetrical distal gangrene in absence of any large vessel occlusion or vasculitis and it is usually associated with critical illness. Our aim was to report the clinical profile and outcome of patients diagnosed with SPG associated with COVID-19. To the best of our knowledge, no such similar cases have been reported till date.

METHODS

In this case series, we have discussed the clinical presentation, laboratory parameters and outcome in a series of two patients of SPG associated with COVID-19 and also compared those findings. Due to paucity of data, we also reviewed the literature on this under-diagnosed and rarely reported condition and association.

RESULTS

Two consecutive patients (both males, age range: 37-42 years, mean: 39.5 years) were admitted with the diagnosis of COVID-19 associated SPG. Both patients had clinical and laboratory evidence of disseminated intravascular coagulation (DIC). Leucopenia was noted in both patients. Despite vigorous therapy, both patients succumbed to their illness within a fortnight of admission.

CONCLUSION

SPG in the background of COVID-19 portends a fatal outcome. Physicians should be aware of its grim prognosis.

Role of neutrophils, platelets, and extracellular vesicles and their interactions in COVID-19-associated thrombopathy

The COVID-19 pandemic extended all around the world causing millions of deaths. In addition to acute respiratory distress syndrome, many patients with severe COVID-19 develop thromboembolic complications associated to multiorgan failure and death. Here, we review evidence for the contribution of neutrophils, platelets, and extracellular vesicles (EVs) to the thromboinflammatory process in COVID-19. We discuss how the immune system, influenced by pro-inflammatory molecules, EVs, and neutrophil extracellular traps (NETs), can be caught out in patients with severe outcomes. We highlight how the deficient regulation of the innate immune system favors platelet activation and induces a vicious cycle amplifying an immunothrombogenic environment associated with platelet/NET interactions. In light of these considerations, we discuss potential therapeutic strategies underlining the modulation of purinergic signaling as an interesting target.

Thromboinflammation as a Driver of Venous Thromboembolism

Thrombus formation has been identified as an integral part in innate immunity, termed immunothrombosis. Activation of host defense systems is known to result in a procoagulant environment. In this system, cellular players as well as soluble mediators interact with each other and their dysregulation can lead to the pathological process of thromboinflammation. These mechanisms have been under intensified investigation during the COVID-19 pandemic. In this review, we focus on the underlying mechanisms leading to thromboinflammation as one trigger of venous thromboembolism.

Severe COVID-19 Complicated by Cerebral Venous Thrombosis in a Newborn Successfully Treated with Remdesivir, Glucocorticoids, and Hyperimmune Plasma

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) pandemic, affecting all age groups with a wide spectrum of clinical presentation ranging from asymptomatic to severe interstitial pneumonia, hyperinflammation, and death. Children and infants generally show a mild course of the disease, although infants have been observed to have a higher risk of hospitalization and severe outcomes. Here, we report the case of a preterm infant with a severe form of SARS-CoV-2 infection complicated by cerebral venous thrombosis successfully treated with steroids, hyperimmune plasma, and remdesivir.

COVID-19 and Venous Thromboembolism: From Pathological Mechanisms to Clinical Management

Coronavirus disease 2019 (COVID-19), which is becoming a global pandemic, is caused by SARS-CoV-2 infection. In COVID-19, thrombotic events occur frequently, mainly venous thromboembolism (VTE), which is closely related to disease severity and clinical prognosis. Compared with historical controls, the occurrence of VTE in hospitalized and critical COVID-19 patients is incredibly high. However, the pathophysiology of thrombosis and the best strategies for thrombosis prevention in COVID-19 remain unclear, thus needing further exploration. Virchow’s triad elements have been proposed as important risk factors for thrombotic diseases. Therefore, the three factors outlined by Virchow can also be applied to the formation of venous thrombosis in the COVID-19 setting. A thorough understanding of the complex interactions in these processes is important in the search for effective treatments for COVID-19. In this work, we focus on the pathological mechanisms of VTE in COVID-19 from the aspects of endothelial dysfunction, hypercoagulability, abnormal blood flow. We also discuss the treatment of VTE as well as the ongoing clinical trials of heparin anticoagulant therapy. In addition, according to the pathophysiological mechanism of COVID-19-associated thrombosis, we extended the range of antithrombotic drugs including antiplatelet drugs, antifibrinolytic drugs, and anti-inflammatory drugs, hoping to find effective drug therapy and improve the prognosis of VTE in COVID-19 patients.

Patients with Covid 19 have significantly reduced CH50 activity

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), is a new virus that emerged in China and immediately spread around the world. Evidence has been documented that the immune system is impressively involved in the pathogenesis of this disease, especially in causing inflammation. One of the important components of the immune system is the complement system whose increased activity has been shown in inflammatory diseases and consequently damage caused by the activity of its components. In the present study, serum levels of C3 and C4 factors as well as the activity level of complement system in the classical pathway were measured by CH50 test in patients with SARS-CoV-2. Participants in the study consisted of 53 hospitalized patients whose real-time PCR test was positive for SARS-CoV-2. The mean age of these patients was 42.06 ± 18.7 years, including 40% women and 60% men. The most common symptoms in these patients were cough (70%), fever (59%), dyspnea (53%) and chills (53%), respectively. Analysis of biochemical and hematological test results revealed that 26 (49%) patients had lymphopenia, 34 (64%) patients were positive for C-reactive protein (CRP) and 26 (49%) patients had ESR and LDH levels significantly higher than normal. In addition, 27 patients (51%) had vitamin D deficiency. The mean CH50 activity level in COVID-19 patients was significantly reduced compared to healthy individuals (84.9 versus 169.9 U/ml, p = < 0.0001). Comparison of the mean CH50 activity levels between different subgroups of patients indicated that COVID-19 patients with decreased peripheral blood lymphocyte count and positive CRP had a significant increase in activity compared to the other groups (p = 0.0002). The serum levels of C3 and C4 factors had no significant change between patients and healthy individuals. Conclusion: The activity level of complement system in the classical pathway decreases in COVID-19 patients compared to healthy individuals, due to increased activity of complement system factors in these patients.

COVID-19 and renal infarct: To be or not to be on anticoagulation

We present a unique case of a male veteran with a history of Castleman disease, presenting with multiple arterial and venous vascular thromboses in the setting of recent Coronavirus (COVID-19)-disease diagnosis. We explore this patient’s morbidity related to thrombotic complications of his COVID-19 diagnosis that were potentially avoidable with a comprehensive outpatient evaluation of his risk for thrombosis, as well as the initiation of anticoagulation and/or antiplatelet therapy given his high risk. Our case highlights the need for a standardized clinical workup of patients in the outpatient setting for risk assessment of vascular thrombosis associated with COVID-19 infection to direct medical management, in order to minimize adverse outcomes, complications requiring inpatient admission, and the need for additional yet limited medical resources and interventions. We propose a minimum of low-dose aspirin 81 mg daily as a reasonable approach for outpatient clinicians to consider, based on their best clinical judgement, when managing mild COVID-19, while other options, such as novel oral anticoagulants, are undergoing further investigation.

Acute Mesenteric Ischemia in a COVID-19 Patient: Delay in Referral and Recommendation for Surgery

Coronavirus (COVID-19) is more common with symptoms such as fever, dry cough, and shortness of breath. However, it may be associated with COVID-19-induced gastrointestinal (GI) symptoms including acute mesenteric ischemia (AMI). These conditions make the diagnosis of AMI challenging. Timely referral with correct diagnosis and attention to the uncommon symptoms of COVID-19 can play an important role in the management and treatment of AMI in COVID-19 patients. We present a patient with AMI due to thrombotic complications of COVID-19, who referred to the hospital too late and ignored the recommendation for abdominal surgery.

High levels of Von Willebrand factor markers in COVID-19: a systematic review and meta-analysis

The SARS-CoV-2 virus has spread to all corners of the world. Thrombosis is the cause of organ failure and subsequent death in COVID-19. The pathophysiology of thrombosis in COVID-19 needs to be further explored to shed light on its downside. For this reason, this meta-analysis of Von Willebrand Factor profile (VWF: Ag, VWF: activity, VWF: RCo), ADAMTS-13, and factor VIII levels in COVID-19 was performed. To obtain data on the status of the aforementioned hemostatic factors, a systematic literature review and meta-analysis were performed on COVID-19. After reviewing the evaluation of 348 papers, 28 papers included in the meta-analysis, which was performed using STATA. The analysis showed an increase in VWF: Ag levels in COVID‐19 patients. VWF: Ac was higher in all COVID-19 patients, while it was lower in the COVID‐19 ICU patients. The pooled mean of VWF: RCO in all patients with COVID-19 was 307.94%. In subgroup analysis, VWF: RCO was significantly higher in ICU patients than in all COVID-19 patients. The pooled mean of ADAMTS-13 activity was 62.47%, and 58.42% in ICU patients. The pooled mean of factor VIII level was 275.8%, which was significantly higher in ICU patients with COVID-19 than all patients with COVID-19. Levels of VWF: Ag, VWF: activity, VWF: ristocetin, and factor VIII are increased in patients with COVID-19. The elevated levels in ICU patients with COVID-19 suggest that these markers may have prognostic value in determining the severity of COVID-19. New therapeutic programs can be developed as a result.

COVID19 infection in a patient undergoing treatment for Paroxysmal Nocturnal Hemoglobinuria (PNH) with Ravulizumab

BACKGROUND

In the recent COVID19 pandemic, patients with hematological disorders were considered at high risk for severe disease. Limited data is available regarding the course of COVID19 infection in this subgroup.

CASE PRESENTATION

We describe a case of a 32-year-old man with paroxysmal nocturnal hemoglobinuria (PNH) undergoing treatment with ravulizumab (Ultomiris) who presented with COVID19 infection. He experienced only mild symptoms and had a rapid recovery from COVID19 infection.

CONCLUSION

This case may demonstrate the beneficial effects of ravulizumab on complement mediated inflammatory damage linked with COVID19 infection especially in PNH patients.

When Immunity Kills: The Lessons of SARS-CoV-2 Outbreak

Since its emergence at the end of 2019, SARS-CoV-2 has spread worldwide at a very rapid pace. While most infected individuals have an asymptomatic or mild disease, a minority, mainly the elderly, develop a severe disease that may lead to a fatal acute respiratory distress syndrome (ARDS). ARDS results from a highly inflammatory immunopathology process that includes systemic manifestations and massive alveolar damages that impair gas exchange. The present review summarizes our current knowledge in the rapidly evolving field of SARS-CoV-2 immunopathology, emphasizing the role of specific T cell responses. Indeed, accumulating evidence suggest that while T-cell response directed against SARS-CoV-2 likely plays a crucial role in virus clearance, it may also participate in the immunopathology process that leads to ARDS.

Coagulopathies after Vaccination against SARS-CoV-2 May Be Derived from a Combined Effect of SARS-CoV-2 Spike Protein and Adenovirus Vector-Triggered Signaling Pathways

Novel coronavirus SARS-CoV-2 has resulted in a global pandemic with worldwide 6-digit infection rates and thousands of death tolls daily. Enormous efforts are undertaken to achieve high coverage of immunization to reach herd immunity in order to stop the spread of SARS-CoV-2 infection. Several SARS-CoV-2 vaccines based on mRNA, viral vectors, or inactivated SARS-CoV-2 virus have been approved and are being applied worldwide. However, the recent increased numbers of normally very rare types of thromboses associated with thrombocytopenia have been reported, particularly in the context of the adenoviral vector vaccine ChAdOx1 nCoV-19 from Astra Zeneca. The statistical prevalence of these side effects seems to correlate with this particular vaccine type, i.e., adenoviral vector-based vaccines, but the exact molecular mechanisms are still not clear. The present review summarizes current data and hypotheses for molecular and cellular mechanisms into one integrated hypothesis indicating that coagulopathies, including thromboses, thrombocytopenia, and other related side effects, are correlated to an interplay of the two components in the vaccine, i.e., the spike antigen and the adenoviral vector, with the innate and immune systems, which under certain circumstances can imitate the picture of a limited COVID-19 pathological picture.

PHYSICAL MEDICINE AND REHABILITATION APPROACHES IN THROMBOSIS ASSOCIATED WITH COVID-19

An increasing number of publications have supported the determination of thrombosis associated with coronavirus disease 2019 (COVID-19). Despite prophylactic drug applications, post-COVID-19 thrombosis cannot be completely prevented. Thrombosis becomes a complex problem that is difficult to avoid, particularly in intensive care patients. It is also possible to see cases of thromboembolism secondary to quarantine and home isolation. In addition to the classical pathophysiological mechanisms in Virchow’s triad, more complex processes specific to COVID-19 may also trigger thrombosis. The aims of this review were to describe physical medicine and rehabilitation practices that can be applied in addition to medical recommendations for thrombosis in COVID-19 patients, and to explain the specific features and mechanism of action of these methods. This process, which starts with education sessions, should continue to reduce immobility as much as possible. Personalized exercise programs should be recommended after evaluating the individual’s condition, exercise history, risk of falling, and comorbid diseases. In parallel with technological progress, more innovative devices have been developed and thus mechanical compression methods and neuromuscular electrical stimulation have become available for this purpose. The most important features of physical medicine and rehabilitation practices are the relatively low cost and the low incidence of complications.

SARS-CoV-2 and Plasma Hypercoagulability

Hypercoagulability has emerged as a prominent consequence of COVID-19. This presents challenges not only in the clinic, but also in thrombosis research. Health and safety considerations, the status of the blood and plasma supply, the infection status of individual donors, and the mechanisms by which SARS-CoV-2 activates coagulation are all of concern. In this review, we discuss these topics from the basic research perspective. As in other respiratory illnesses, blood and plasma from COVID-19 positive patients carries minimal to no risk of infection to practitioners or researchers. There are currently no special regulatory mandates directing individual donors (for research purposes), blood centers/services or vendors (for blood products for research) to test blood/plasma for SARS-CoV-2 or antibodies. We discuss current theories about how SARS-CoV-2 leads to hyper-coagulant state in severe cases of COVID-19. Our current understanding of the mechanisms behind COVID-19 associated thromboembolic events have centered around three different pathways: (1) direct activation of platelets, enhancing coagulation; (2) direct infection and indirect activation (e.g. cytokine storm) of endothelial cells by SARS-CoV-2, shifting endothelium from an anti-thrombotic to a pro-thrombotic state; and (3) direct activation of complement pathways, promoting thrombin generation. Further investigation on how SARS-CoV-2 affects thrombosis in COVID-19 patients may bring novel anti-thrombotic therapies to combat the disease.

Hypercoagulability Due to COVID-19 Leading to Impending Phlegmasia Cerulea Dolens and Sub-Massive Bilateral Pulmonary Embolism

This is a case report of a 47-year-old male with a history of hypertension and pre-diabetes who presented to the emergency department with dyspnea, progressive unilateral leg swelling and pain. The patient tested positive for coronavirus disease 2019 (COVID-19) infection about a week earlier. The patient was found to have an extensive clot burden of his lower extremity veins, both deep and superficial, which extended to his inferior vena cava (IVC). Based on the patient’s clinical exam and ultrasound findings, the patient was diagnosed with impending phlegmasia cerulea dolens. Due to his renal failure, the patient was taken for a ventilation/perfusion (V/Q) scan which found widespread V/Q mismatch highly suggestive of pulmonary embolism. Interventional radiology took the patient for lower extremity venogram, catheter-directed alteplase administration, and IVC filter placement. The patient was admitted to the intensive care unit (ICU) for further management and had a stable recovery.

Self-sustaining IL-8 loops drive a prothrombotic neutrophil phenotype in severe COVID-19

Neutrophils provide a critical line of defense in immune responses to various pathogens, inflicting self-damage upon transition to a hyperactivated, procoagulant state. Recent work has highlighted proinflammatory neutrophil phenotypes contributing to lung injury and acute respiratory distress syndrome (ARDS) in patients with coronavirus disease 2019 (COVID-19). Here, we use state-of-the art mass spectrometry-based proteomics and transcriptomic and correlative analyses as well as functional in vitro and in vivo studies to dissect how neutrophils contribute to the progression to severe COVID-19. We identify a reinforcing loop of both systemic and neutrophil intrinsic IL-8 (CXCL8/IL-8) dysregulation, which initiates and perpetuates neutrophil-driven immunopathology. This positive feedback loop of systemic and neutrophil autocrine IL-8 production leads to an activated, prothrombotic neutrophil phenotype characterized by degranulation and neutrophil extracellular trap (NET) formation. In severe COVID-19, neutrophils directly initiate the coagulation and complement cascade, highlighting a link to the immunothrombotic state observed in these patients. Targeting the IL-8-CXCR-1/-2 axis interferes with this vicious cycle and attenuates neutrophil activation, degranulation, NETosis, and IL-8 release. Finally, we show that blocking IL-8-like signaling reduces severe acute respiratory distress syndrome of coronavirus 2 (SARS-CoV-2) spike protein-induced, human ACE2-dependent pulmonary microthrombosis in mice. In summary, our data provide comprehensive insights into the activation mechanisms of neutrophils in COVID-19 and uncover a self-sustaining neutrophil-IL-8 axis as a promising therapeutic target in severe SARS-CoV-2 infection.

COVID-19: Mechanistic Model of the African Paradox Supports the Central Role of the NF-κB Pathway

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has expanded into a global pandemic, with more than 220 million affected persons and almost 4.6 million deaths by 8 September 2021. In particular, Europe and the Americas have been heavily affected by high infection and death rates. In contrast, much lower infection rates and mortality have been reported generally in Africa, particularly in the sub-Saharan region (with the exception of the Southern Africa region). There are different hypotheses for this African paradox, including less testing, the young age of the population, genetic disposition, and behavioral and epidemiological factors. In the present review, we address different immunological factors and their correlation with genetic factors, pre-existing immune status, and differences in cytokine induction patterns. We also focus on epidemiological factors, such as specific medication coverage, helminth distribution, and malaria endemics in the sub-Saharan region. An analysis combining different factors is presented that highlights the central role of the NF-κB signaling pathway in the African paradox. Importantly, insights into the interplay of different factors with the underlying immune pathological mechanisms for COVID-19 can provide a better understanding of the disease and the development of new targets for more efficient treatment strategies.

Age-Associated Increase in Thrombogenicity and Its Correlation with von Willebrand Factor

Endothelial cells that cover the lumen of all blood vessels have the inherent capacity to express both pro and anticoagulant molecules. However, under normal physiological condition, they generally function to maintain a non-thrombogenic surface for unobstructed blood flow. In response to injury, certain stimuli, or as a result of dysfunction, endothelial cells release a highly adhesive procoagulant protein, von Willebrand factor (VWF), which plays a central role in formation of platelet aggregates and thrombus generation. Since VWF expression is highly restricted to endothelial cells, regulation of its levels is among the most important functions of endothelial cells for maintaining hemostasis. However, with aging, there is a significant increase in VWF levels, which is concomitant with a significant rise in thrombotic events. It is not yet clear why and how aging results in increased VWF levels. In this review, we have aimed to discuss the age-related increase in VWF, its potential mechanisms, and associated coagulopathies as probable consequences.

Thrombotic and Hypercoagulability Complications of COVID-19: An Update

The current COVID-19 pandemic emerged in December 2019, in China, affecting millions of people worldwide. COVID-19 is mainly a disease of the respiratory system, yet systematic complications have also been reported among SARS-CoV-2 infected patients. Thrombotic complications are one of the severe clinical outcomes of COVID-19, especially among critically ill patients, and are associated with poor prognosis. To date, many studies have concluded that COVID-19 increases the incidence of thrombotic events and coagulopathies; however, the exact mechanism behind such a disease outcome is not well known. Various pathophysiological mechanisms for thrombotic events in COVID-19 have been proposed, these include virus-induced endothelial cell damage, inflammation, and excess production of pro-inflammatory cytokines. As a result, most critically diseased COVID-19 patients are managed with prophylactic anticoagulant, yet some still develop thrombotic episodes. Therefore, better understanding of the mechanisms behind the thrombotic complications is needed to develop treatments that specifically target such pathways, which may aid in better disease management and improve the prognosis.

Bioactive Molecules Derived from Snake Venoms with Therapeutic Potential for the Treatment of Thrombo-Cardiovascular Disorders Associated with COVID-19

As expected, several new variants of Severe Acute Respiratory Syndrome-CoronaVirus-2 (SARS-CoV-2) emerged and have been detected around the world throughout this Coronavirus Disease of 2019 (COVID-19) pandemic. Currently, there is no specific developed drug against COVID-19 and the challenge of developing effective antiviral strategies based on natural agents with different mechanisms of action becomes an urgent need and requires identification of genetic differences among variants. Such data is used to improve therapeutics to combat SARS-CoV-2 variants. Nature is known to offer many biotherapeutics from animal venoms, algae and plant that have been historically used in traditional medicine. Among these bioresources, snake venom displays many bioactivities of interest such as antiviral, antiplatelet, antithrombotic, anti-inflammatory, antimicrobial and antitumoral. COVID-19 is a viral respiratory sickness due to SARS-CoV-2 which induces thrombotic disorders due to cytokine storm, platelet hyperactivation and endothelial dysfunction. This review aims to: (1) present an overview on the infection, the developed thrombo-inflammatory responses and mechanisms of induced thrombosis of COVID-19 compared to other similar pathogenesis; (2) underline the role of natural compounds such as anticoagulant, antiplatelet and thrombolytic agents; (3) investigate the management of coagulopathy related to COVID-19 and provide insight on therapeutic such as venom compounds. We also summarize the updated advances on antiviral proteins and peptides derived from snake venoms that could weaken coagulopathy characterizing COVID-19.

Complement and the prothrombotic state

In 2007 and 2009 the regulatory approval of the first-in-class complement inhibitor Eculizumab has revolutionized the clinical management of two rare, life-threatening clinical conditions: paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). While being completely distinct diseases affecting blood cells and the glomerulus, PNH and aHUS remarkably share several features in their etiology and clinical presentation. An imbalance between complement activation and regulation at host surfaces underlies both diseases precipitating in severe thrombotic events that are largely resistant to anti-coagulant and/or anti-platelet therapies. Inhibition of the common terminal complement pathway by Eculizumab prevents the frequently occurring thrombotic events responsible for the high mortality and morbidity observed in patients not treated with anti-complement therapy. While many in vitro and ex vivo studies elaborate numerous different molecular interactions between complement activation products and hemostasis, this review focuses on the clinical evidence that links these two fields in humans. Several non-infectious conditions with known complement involvement are scrutinized for common patterns concerning a prothrombotic statues and the occurrence of certain complement activation levels. Next to PNH and aHUS, germline encoded CD59 or CD55 deficiency (the latter causing the disease Complement Hyperactivation, Angiopathic thrombosis, and Protein-Losing Enteropathy; CHAPLE), autoimmune hemolytic anemia (AIHA), (catastrophic) anti-phospholipid syndrome (APS, CAPS) and C3 glomerulopathy are considered. Parallels and distinct features among these conditions are discussed against the background of thrombosis, complement activation, and potential complement diagnostic and therapeutic avenues.