High affinity binding of SARS-CoV-2 spike protein enhances ACE2 carboxypeptidase activity

Exploring non-coding genetic variability in ACE2: Functional annotation and in vitro validation of regulatory variants

The surge in human whole-genome sequencing data has facilitated the study of non-coding region variations, yet understanding their biological significance remains a challenge. We used a computational workflow to assess the regulatory potential of non-coding variants, with a particular focus on the Angiotensin Converting Enzyme 2 (ACE2) gene. This gene is crucial in physiological processes and serves as the entry point for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 19 (COVID-19). In our analysis, using data from the gnomAD population database and functional annotation, we identified 17 significant Single Nucleotide Variants (SNVs) in ACE2, particularly in its enhancers, promoters, and 3' untranslated regions (UTRs). We found preliminary evidence supporting the regulatory impact of some of these variants on ACE2 expression. Our detailed examination of two SNVs, rs147718775 and rs140394675, in the ACE2 promoter revealed that these co-occurring SNVs, when mutated, significantly enhance promoter activity, suggesting a possible increase in specific ACE2 isoform expression. This method proves effective in identifying and interpreting impactful non-coding variants, aiding in further studies and enhancing understanding of molecular bases of monogenic and complex traits.

Angiotensin I and II Stimulate Cell Invasion of SARS-CoV-2: Potential Mechanism via Inhibition of ACE2 Arm of RAS

Angiotensin-converting enzyme 2 (ACE2), one of the key enzymes of the renin-angiotensin system (RAS), plays an important role in SARS-CoV-2 infection by functioning as a virus receptor. Angiotensin peptides Ang I and Ang II, the substrates of ACE2, can modulate the binding of SARS-CoV-2 Spike protein to the ACE2 receptor. In the present work, we found that co incubation of HEK-ACE2 and Vero E6 cells with the SARS-CoV-2 Spike pseudovirus (PVP) resulted in stimulation of the virus entry at low and high micromolar concentrations of Ang I and Ang II, respectively. The potency of Ang I and Ang II stimulation of virus entry corresponds to their binding affinity to ACE2 catalytic pocket with 10 times higher efficiency of Ang II. The Ang II induced mild increase of PVP infectivity at 20 microM; while at 100 microM the increase (129.74+/-3.99 %) was highly significant (p<0.001). Since the angiotensin peptides act in HEK ACE2 cells without the involvement of angiotensin type I receptors, we hypothesize that there is a steric interaction between the catalytic pocket of the ACE2 enzyme and the SARS-CoV-2 S1 binding domain. Oversaturation of the ACE2 with their angiotensin substrate might result in increased binding and entry of the SARS-CoV-2. In addition, the analysis of angiotensin peptides metabolism showed decreased ACE2 and increased ACE activity upon SARS-CoV-2 action. These effects should be taken into consideration in COVID-19 patients suffering from comorbidities such as the over-activated renin-angiotensin system as a mechanism potentially influencing the SARS-CoV-2 invasion into recipient cells.

Neurovascular coupling impairment as a mechanism for cognitive deficits in COVID-19

Components that comprise our brain parenchymal and cerebrovascular structures provide a homeostatic environment for proper neuronal function to ensure normal cognition. Cerebral insults (e.g. ischaemia, microbleeds and infection) alter cellular structures and physiologic processes within the neurovascular unit and contribute to cognitive dysfunction. COVID-19 has posed significant complications during acute and convalescent stages in multiple organ systems, including the brain. Cognitive impairment is a prevalent complication in COVID-19 patients, irrespective of severity of acute SARS-CoV-2 infection. Moreover, overwhelming evidence from in vitro, preclinical and clinical studies has reported SARS-CoV-2-induced pathologies in components of the neurovascular unit that are associated with cognitive impairment. Neurovascular unit disruption alters the neurovascular coupling response, a critical mechanism that regulates cerebromicrovascular blood flow to meet the energetic demands of locally active neurons. Normal cognitive processing is achieved through the neurovascular coupling response and involves the coordinated action of brain parenchymal cells (i.e. neurons and glia) and cerebrovascular cell types (i.e. endothelia, smooth muscle cells and pericytes). However, current work on COVID-19-induced cognitive impairment has yet to investigate disruption of neurovascular coupling as a causal factor. Hence, in this review, we aim to describe SARS-CoV-2's effects on the neurovascular unit and how they can impact neurovascular coupling and contribute to cognitive decline in acute and convalescent stages of the disease. Additionally, we explore potential therapeutic interventions to mitigate COVID-19-induced cognitive impairment. Given the great impact of cognitive impairment associated with COVID-19 on both individuals and public health, the necessity for a coordinated effort from fundamental scientific research to clinical application becomes imperative. This integrated endeavour is crucial for mitigating the cognitive deficits induced by COVID-19 and its subsequent burden in this especially vulnerable population.

Effects of spike proteins on angiotensin converting enzyme 2 (ACE2)

The Coronavirus Disease 2019 (COVID-19) pandemic was caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), which enters host cells through interactions of its spike protein to Angiotensin-Converting Enzyme 2 (ACE2). ACE2 is a peptidase that cleaves Angiotensin II, a critical pathological mediator. This study investigated if the spike protein binding to ACE2 compromises its peptidase activity. Spike/ACE2 Binding Assays suggested that spike proteins of SARS-CoV-2, SARS-CoV and MERS-CoV, but not HKU1, bind to ACE2. S1 and receptor-binding domain (RBD), but not S2, extracellular domain (ECD) or CendR domain, bind to ACE2. While glycosylated spike proteins prepared in HEK293 cells bind to ACE2, non-glycosylated proteins produced in E. coli do not. Cysteine residues of the spike protein expressed in HEK293 cells are fully oxidized, while those of the protein expressed in E. coli are reduced. The deglycosylation of HEK cell-produced protein attenuates the ACE2 binding, while the oxidation of the E. coli protein does not promote the binding. The S1 protein of SARS-CoV-2 enhances the ACE2 peptidase activity, while SARS-CoV, MERS-CoV or HKU1 does not. The ACE2 activity is enhanced by RBD, but not ECD or CendR. In contrast to distinct ACE2 binding capacities of proteins expressed in HEK293 cells and in E. coli, spike proteins expressed in both systems enhance the ACE2 activity. Thus, the spike protein of SARS-CoV-2, but not other coronaviruses, enhances the ACE2 peptidase activity through its RBD in a glycosylation-independent manner.

Riding the Wave: Unveiling the Conformational Waves from RBD of SARS-CoV-2 Spike Protein to ACE2

The binding affinity between angiotensin-converting enzyme 2 (ACE2) and the receptor-binding domain (RBD) plays a crucial role in the transmission and reinfection of SARS-CoV2. Here, microsecond molecular dynamics simulations revealed that point mutations in the RBD domain induced conformational transitions that determined the binding affinity between ACE2 and RBD. These structural changes propagated through the RBD domain, altering the orientation of both ACE2 and RBD residues at the binding site. ACE2 receptor shows significant structural heterogeneity, whereas its binding to the RBD domain indicates a much greater degree of structural homogeneity. The receptor was more flexible in its unbound state with the binding of RBD domains inducing structural transitions. The structural heterogeneity observed in the ACE2 unbound form plays a role in the promiscuity of viral entry, as it may allow the receptor to interact with various related and unrelated ligands. Furthermore, rigidity may be important for stabilizing the complex and ensuring the proper orientation of the RBD-binding interface with ACE2. The greater structural homogeneity observed in the ACE2-RBD complex revealed the effectiveness of neutralizing antibodies and vaccines that are primarily directed toward the RBD-binding interface. The binding of the B38 monoclonal antibody revealed restricted conformational transitions in the RBD and ACE2 receptors, attributed to its potent binding interaction.

Immunomodulatory approaches in managing lung inflammation in COVID-19: A double-edge sword

INTRODUCTION

The novel coronavirus infectious disease 2019 (COVID-19) which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a gigantic problem. The lung is the major target organ of SARS-CoV-2 and some of its variants like Delta and Omicron variant adapted in such a way that these variants can significantly damage this vital organ of the body. These variants raised a few eyebrows as the outbreaks have been seen in the vaccinated population. Patients develop severe respiratory illnesses which eventually prove fatal unless treated early.

MAIN BODY

Studies have shown that SARS-CoV-2 causes the release of pro-inflammatory cytokines such as interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α which are mediators of lung inflammation, lung damage, fever, and fibrosis. Additionally, various chemokines have been found to play an important role in the disease progression. A plethora of pro-inflammatory cytokines "cytokine storm" has been observed in severe cases of SARS-CoV-2 infection leading to acute respiratory distress syndrome (ARDS) and pneumonia that may prove fatal. To counteract cytokine storm-inducing lung inflammation, several promising immunomodulatory approaches are being investigated in numerous clinical trials. However, the benefits of using these strategies should outweigh the risks involved as the use of certain immunosuppressive approaches might lead the host susceptible to secondary bacterial infections.

CONCLUSION

The present review discusses promising immunomodulatory approaches to manage lung inflammation in COVID-19 cases which may serve as potential therapeutic options in the future and may prove lifesaving.

Biosensor Based on Graphene Directly Grown by MW-PECVD for Detection of COVID-19 Spike (S) Protein and Its Entry Receptor ACE2

Biosensors based on graphene field-effect transistors (G-FET) for detecting COVID-19 spike S protein and its receptor ACE2 were reported. The graphene, directly synthesized on SiO2/Si substrate by microwave plasma-enhanced chemical vapor deposition (MW-PECVD), was used for FET biosensor fabrication. The commercial graphene, CVD-grown on a copper substrate and subsequently transferred onto a glass substrate, was applied for comparison purposes. The graphene structure and surface morphology were studied by Raman scattering spectroscopy and atomic force microscope. Graphene surfaces were functionalized by an aromatic molecule PBASE (1-pyrenebutanoic acid succinimidyl ester), and subsequent immobilization of the receptor angiotensin-converting enzyme 2 (ACE2) was performed. A microfluidic system was developed, and transfer curves of liquid-gated FET were measured after each graphene surface modification procedure to investigate ACE2 immobilization by varying its concentration and subsequent spike S protein detection. The directly synthesized graphene FET sensitivity to the receptor ACE2, evaluated in terms of the Dirac voltage shift, exceeded the sensitivity of the transferred commercial graphene-based FET. The concentration of the spike S protein was detected in the range of 10 ag/mL up to 10 μg/mL by using a developed microfluidic system and measuring the transfer characteristics of the liquid-gated G-FETs. It was found that the shift of the Dirac voltage depends on the spike S concentration and was 27 mV with saturation at 10 pg/mL for directly synthesized G-FET biosensor, while for transferred G-FET, the maximal shift of 70 mV was obtained at 10 μg/mL with a tendency of saturation at 10 ng/mL. The detection limit as low as 10 ag/mL was achieved for both G-FETs. The sensitivity of the biosensors at spike S concentration of 10 pg/mL measured as relative current change at a constant gate voltage corresponding to the highest transconductance of the G-FETs was found at 5.6% and 8.8% for directly synthesized and transferred graphene biosensors, respectively. Thus, MW-PECVD-synthesized graphene-based biosensor demonstrating high sensitivity and low detection limit has excellent potential for applications in COVID-19 diagnostics.

Circulating ACE2 level and zinc/albumin ratio as potential biomarkers for a precision medicine approach to COVID-19

Highly mutable influenza is successfully countered based on individual susceptibility and similar precision-like medicine approach should be effective against SARS-COV-2. Among predictive markers to bring precision medicine to COVID-19, circulating ACE2 has potential features being upregulated in both severe COVID-19 and predisposing comorbidities. Spike SARS-CoVs were shown to induce ADAM17-mediated shedding of enzymatic active ACE2, thus accounting for its increased activity that has also been suggested to induce positive feedback loops leading to COVID-19-like manifestations. For this reason, pre-existing ACE2 activity and inhibition of ACE2/ADAM17 zinc-metalloproteases through zinc chelating agents have been proposed to predict COVID-19 outcome before infection and to protect from COVID-19, respectively. Since most diagnostic laboratories are not equipped for enzymatic activity determination, other potential predictive markers of disease progression exploitable by diagnostic laboratories were explored. Concentrations of circulating albumin, zinc, ACE2 protein and its activity were investigated in healthy, diabetic (COVID-19-susceptible) and SARS-CoV-2-negative COVID-19 individuals. ACE2 both protein levels and activity significantly increased in COVID-19 and diabetic patients. Abnormal high levels of ACE2 characterised a subgroup (16-19%) of diabetics, while COVID-19 patients were characterised by significantly higher zinc/albumin ratios, pointing to a relative increase of albumin-unbound zinc species, such as free zinc ones. Data on circulating ACE2 levels are in line with the hypothesis that they can drive susceptibility to COVID-19 and elevated zinc/albumin ratios support the therapeutic use of zinc chelating inhibitors of ACE2/ADAM17 zinc-metalloproteases in a targeted therapy for COVID-19.

Protein nanopore reveals the renin-angiotensin system crosstalk with single-amino-acid resolution

The discovery of crosstalk effects on the renin-angiotensin system (RAS) is limited by the lack of approaches to quantitatively monitor, in real time, multiple components with subtle differences and short half-lives. Here we report a nanopore framework to quantitatively determine the effect of the hidden crosstalk between angiotensin-converting enzyme (ACE) and angiotensin-converting enzyme 2 (ACE2) on RAS. By developing an engineered aerolysin nanopore capable of single-amino-acid resolution, we show that the ACE can be selectively inhibited by ACE2 to prevent cleavage of angiotensin I, even when the concentration of ACE is more than 30-fold higher than that of ACE2. We also show that the activity of ACE2 for cleaving angiotensin peptides is clearly suppressed by the spike protein of SARS-CoV-2. This leads to the relaxation of ACE and the increased probability of accumulation of the principal effector angiotensin II. The spike protein of the SARS-CoV-2 Delta variant is demonstrated to have a much greater impact on the crosstalk than the wild type.

SARS-CoV-2 triggers pericyte-mediated cerebral capillary constriction

The SARS-CoV-2 receptor, ACE2, is found on pericytes, contractile cells enwrapping capillaries that regulate brain, heart and kidney blood flow. ACE2 converts vasoconstricting angiotensin II into vasodilating angiotensin-(1-7). In brain slices from hamster, which has an ACE2 sequence similar to human ACE2, angiotensin II evoked a small pericyte-mediated capillary constriction via AT1 receptors, but evoked a large constriction when the SARS-CoV-2 receptor binding domain (RBD, original Wuhan variant) was present. A mutated non-binding RBD did not potentiate constriction. A similar RBD-potentiated capillary constriction occurred in human cortical slices, and was evoked in hamster brain slices by pseudotyped virions expressing SARS-CoV-2 spike protein. This constriction reflects an RBD-induced decrease in the conversion of angiotensin II to angiotensin-(1-7) mediated by removal of ACE2 from the cell surface membrane and was mimicked by blocking ACE2. The clinically used drug losartan inhibited the RBD-potentiated constriction. Thus, AT1 receptor blockers could be protective in COVID-19 by preventing pericyte-mediated blood flow reductions in the brain, and perhaps the heart and kidney.

O-GalNAc glycosylation affects the immunogenicity of the receptor-binding domain (RBD) of SARS-CoV-2 spike protein

The spike protein of SARS-CoV-2 has been widely used as an effective vaccine immunogen, although some limitations still remain. Herein, O-GalNAc glycosylated RBD (Tn-RBD) was synthesized as an antigen via in vitro glycosylation reactions. The inhibition ability against hACE2 binding of antibodies induced with Tn-RBD was 30-40% increased compared to that induced with RBD. This result implies that Tn-glycosylation might play important roles in the immunogenicity of the RBD protein, which should be considered in the design of novel vaccines to fight against COVID-19.

Immune Response and Molecular Mechanisms of Cardiovascular Adverse Effects of Spike Proteins from SARS-CoV-2 and mRNA Vaccines

The SARS-CoV-2 (severe acute respiratory syndrome coronavirus responsible for the COVID-19 disease) uses the Spike proteins of its envelope for infecting target cells expressing on the membrane the angiotensin converting enzyme 2 (ACE2) enzyme that acts as a receptor. To control the pandemic, genetically engineered vaccines have been designed for inducing neutralizing antibodies against the Spike proteins. These vaccines do not act like traditional protein-based vaccines, as they deliver the message in the form of mRNA or DNA to host cells that then produce and expose the Spike protein on the membrane (from which it can be shed in soluble form) to alert the immune system. Mass vaccination has brought to light various adverse effects associated with these genetically based vaccines, mainly affecting the circulatory and cardiovascular system. ACE2 is present as membrane-bound on several cell types, including the mucosa of the upper respiratory and of the gastrointestinal tracts, the endothelium, the platelets, and in soluble form in the plasma. The ACE2 enzyme converts the vasoconstrictor angiotensin II into peptides with vasodilator properties. Here we review the pathways for immunization and the molecular mechanisms through which the Spike protein, either from SARS-CoV-2 or encoded by the mRNA-based vaccines, interferes with the Renin-Angiotensin-System governed by ACE2, thus altering the homeostasis of the circulation and of the cardiovascular system. Understanding the molecular interactions of the Spike protein with ACE2 and the consequent impact on cardiovascular system homeostasis will direct the diagnosis and therapy of the vaccine-related adverse effects and provide information for development of a personalized vaccination that considers pathophysiological conditions predisposing to such adverse events.

Angiotensin-Converting Enzyme 2-Based Biosensing Modalities and Devices for Coronavirus Detection

Rapid and cost-effective diagnostic tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are a critical and valuable weapon for the coronavirus disease 2019 (COVID-19) pandemic response. SARS-CoV-2 invasion is primarily mediated by human angiotensin-converting enzyme 2 (hACE2). Recent developments in ACE2-based SARS-CoV-2 detection modalities accentuate the potential of this natural host-virus interaction for developing point-of-care (POC) COVID-19 diagnostic systems. Although research on harnessing ACE2 for SARS-CoV-2 detection is in its infancy, some interesting biosensing devices have been developed, showing the commercial viability of this intriguing new approach. The exquisite performance of the reported ACE2-based COVID-19 biosensors provides opportunities for researchers to develop rapid detection tools suitable for virus detection at points of entry, workplaces, or congregate scenarios in order to effectively implement pandemic control and management plans. However, to be considered as an emerging approach, the rationale for ACE2-based biosensing needs to be critically and comprehensively surveyed and discussed. Herein, we review the recent status of ACE2-based detection methods, the signal transduction principles in ACE2 biosensors and the development trend in the future. We discuss the challenges to development of ACE2-biosensors and delineate prospects for their use, along with recommended solutions and suggestions.

Differential effects of age, sex and dexamethasone therapy on ACE2/TMPRSS2 expression and susceptibility to SARS-CoV-2 infection

ACE2 and TMPRSS2 are crucial for SARS-CoV-2 entry into the cell. Although ACE2 facilitates viral entry, its loss leads to promoting the devastating clinical symptoms of COVID-19 disease. Thus, enhanced ACE2/TMPRSS2 expression is likely to increase predisposition of target cells to SARS-CoV-2 infection. However, little evidence existed about the biological kinetics of these two enzymes and whether dexamethasone treatment modulates their expression. Here, we show that the expression of ACE2 at the protein and mRNA levels was significantly higher in the lung and heart tissues of neonatal compared to adult mice. However, the expression of TMPRSS2 was developmentally regulated. Our results may introduce a novel concept for the reduced susceptibility of the young to SARS-CoV-2 infection. Moreover, ACE2 expression but not TMPRSS2 was upregulated in adult female lungs compared to their male counterparts. Interestingly, the ACE2 and TMPRSS2 expressions were upregulated by dexamethasone treatment in the lung and heart tissues in both neonatal and adult mice. Furthermore, our findings provide a novel mechanism for the observed differential therapeutic effects of dexamethasone in COVID-19 patients. As such, dexamethasone exhibits different therapeutic effects depending on the disease stage. This was supported by increased ACE2/TMPRSS2 expression and subsequently enhanced infection of normal human bronchial epithelial cells (NHBE) and Vero E6 cells with SARS-CoV-2 once pre-treated with dexamethasone. Therefore, our results suggest that individuals who take dexamethasone for other clinical conditions may become more prone to SARS-CoV-2 infection.

Is Diminazene an Angiotensin-Converting Enzyme 2 (ACE2) Activator? Experimental Evidence and Implications

Antiprotozoal veterinary drug diminazene aceturate (DIZE) has been proposed to be an angiotensin-converting enzyme 2 (ACE2) activator. Since then, DIZE was used in dozens of experimental studies, but its mechanism of action attributed to ACE2 activation and enhanced formation of angiontensin-(1-7) [Ang-(1-7)] from Ang II was not carefully verified. The aim of this study was to confirm the effect of DIZE on catalytic activity of ACE2 and extend it to other peptidases involved in formation and degradation of Ang-(1-7). Concentration-dependent effect of DIZE on the initial rate of a fluorogenic substrate hydrolysis by human and mouse recombinant ACE2 was measured at assay conditions imitating that of the original report, but no activation of ACE2 was documented. Similar results were obtained with a more physiologically relevant assay buffer. In addition, DIZE did not affect activity of recombinant neprilysin, neurolysin, thimet oligopeptidase, and ACE. Efficiency of the fluorogenic substrate hydrolysis (Vmax/Km value) by ACE2 in response to different concentrations of DIZE was also measured, but no substantial effects were documented. Likewise, DIZE failed to enhance the hydrolysis of ACE2 endogenous substrate Ang II. Identity of the commercial recombinant ACE2 variants used in these experiments was confirmed by inhibition with two well characterized inhibitors (DX600 and MLN4760), activation by NaCl, and Western Blotting using validated antibodies. These observations challenge the widely accepted notion about the molecular mechanism of DIZE action and call for not ascribing this molecule as an ACE2 activator. SIGNIFICANCE STATEMENT: DIZE has been proposed and widely used in experimental studies as an ACE2 activator. The detailed in vitro pharmacological studies failed to confirm that DIZE is an ACE2 activator. In addition, DIZE did not substantially affect the activity of other peptidases involved in formation and degradation of angiotensin-(1-7). Researchers should refrain from calling DIZE an ACE2 activator. Other mechanisms are responsible for the therapeutic benefits attributed to DIZE.

An ACE2-Based Decoy Inhibitor Effectively Neutralizes SARS-CoV-2 Omicron BA.5 Variant

The recently circulating SARS-CoV-2 Omicron BA.5 is rampaging the world with elevated transmissibility compared to the original SARS-CoV-2 strain. Immune escape of BA.5 was observed after treatment with many monoclonal antibodies, calling for broad-spectrum, immune-escape-evading therapeutics. In retrospect, we previously reported Kansetin as an ACE2 mimetic and a protein antagonist against SARS-CoV-2, which proved potent neutralization bioactivity on the Reference, Alpha, Beta, Delta, and Omicron strains of SARS-CoV-2. Since BA.5 is expected to rely on the interaction of the Spike complex with human ACE2 for cell entry, we reasonably assumed the lasting efficacy of the ACE2-mimicking Kansetin for neutralizing the new SARS-CoV-2 variant. The investigation was accordingly performed on in vitro Kansetin-Spike binding affinity by SPR and cell infection inhibition ability with pseudovirus and live virus assays. As a result, Kansetin showed dissociation constant K_D and half inhibition concentration IC₅₀ at the nanomolar to picomolar level, featuring a competent inhibition effect against the BA.5 sublineage. Conclusively, Kansetin is expected to be a promising therapeutic option against BA.5 and future SARS-CoV-2 sublineages.

As the virus evolves, so too must we: a drug developer's perspective : We need a new paradigm in searching for next-generation countermeasures

The SARS-CoV-2 virus has been raging globally for over 2 years with no end in sight. It has become clear that this virus possesses enormous genetic plasticity, and it will not be eradicated. Under increasing selective pressure from population immunity, the evolution of SARS-CoV-2 has driven it towards greater infectivity, and evasion of humoral and cellular immunity. Omicron and its expanding army of subvariants and recombinants have impaired vaccine protection and made most antibody drugs obsolete. Antiviral drugs, though presently effective, may select for more resistant strains over time. It may be inevitable, then, that future SARS-CoV-2 variants will be immune to our current virus-directed countermeasures. Thus, to gain control over the virus, we need to adopt a new paradigm in searching for next-generation countermeasures and develop host-directed therapeutics (HDTx) and host-directed antivirals (HDA). Different from the virus-directed countermeasures, HDTx and HDA may offer variant agnostic treatment to reduce the risk and severity of infections. In addition, they may exert more uniform effects against the genetically diverse SARS-CoV-2 quasispecies, thereby diminishing the risk of selecting resistant variants. Some promising HDTx and HDA approaches are summarized here.

Intranasal application of adeno-associated viruses: a systematic review

Adeno-associated viruses (AAVs) represent some of the most commonly employed vectors for targeted gene delivery and their extensive study has resulted in the approval of multiple gene therapies to treat human diseases. The intranasal route of vector application in gene therapy offers several advantages over traditional ways of administration. In addition to targeting local tissue like the olfactory epithelium, it provides minimally invasive access to various organ systems, including the central nervous system and the respiratory tract. Through a systematic literature review, a total of 53 articles that investigated the intranasal application of AAVs were identified, included, and summarized in this manuscript. Within these studies, AAV-based gene therapy was mainly investigated for its application in various infectious, pulmonary, or neurologic and/or psychiatric diseases. This review gives a comprehensive overview of the current technological state of the art regarding the intranasal application of AAVs for gene transfer and discusses remaining hurdles, which still have to be resolved before this approach can effectively be implemented in the routine clinical setting.

Evolutionary progression of collective mutations in Omicron sub-lineages towards efficient RBD-hACE2: Allosteric communications between and within viral and human proteins

The interaction between the Spike (S) protein of SARS-CoV-2 and the human angiotensin converting enzyme 2 (hACE2) is essential for infection, and is a target for neutralizing antibodies. Consequently, selection of mutations in the S protein is expected to be driven by the impact on the interaction with hACE2 and antibody escape. Here, for the first time, we systematically characterized the collective effects of mutations in each of the Omicron sub-lineages (BA.1, BA.2, BA.3 and BA.4) on both the viral S protein receptor binding domain (RBD) and the hACE2 protein using post molecular dynamics studies and dynamic residue network (DRN) analysis. Our analysis suggested that Omicron sub-lineage mutations result in altered physicochemical properties that change conformational flexibility compared to the reference structure, and may contribute to antibody escape. We also observed changes in the hACE2 substrate binding groove in some sub-lineages. Notably, we identified unique allosteric communication paths in the reference protein complex formed by the DRN metrics betweenness centrality and eigencentrality hubs, originating from the RBD core traversing the receptor binding motif of the S protein and the N-terminal domain of the hACE2 to the active site. We showed allosteric changes in residue network paths in both the RBD and hACE2 proteins due to Omicron sub-lineage mutations. Taken together, these data suggest progressive evolution of the Omicron S protein RBD in sub-lineages towards a more efficient interaction with the hACE2 receptor which may account for the increased transmissibility of Omicron variants.

Detection of COVID-19-related biomarkers by electrochemical biosensors and potential for diagnosis, prognosis, and prediction of the course of the disease in the context of personalized medicine

As a more efficient and effective way to address disease diagnosis and intervention, cutting-edge technologies, devices, therapeutic approaches, and practices have emerged within the personalized medicine concept depending on the particular patient's biology and the molecular basis of the disease. Personalized medicine is expected to play a pivotal role in assessing disease risk or predicting response to treatment, understanding a person's health status, and, therefore, health care decision-making. This work discusses electrochemical biosensors for monitoring multiparametric biomarkers at different molecular levels and their potential to elucidate the health status of an individual in a personalized manner. In particular, and as an illustration, we discuss several aspects of the infection produced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as a current health care concern worldwide. This includes SARS-CoV-2 structure, mechanism of infection, biomarkers, and electrochemical biosensors most commonly explored for diagnostics, prognostics, and potentially assessing the risk of complications in patients in the context of personalized medicine. Finally, some concluding remarks and perspectives hint at the use of electrochemical biosensors in the frame of other cutting-edge converging/emerging technologies toward the inauguration of a new paradigm of personalized medicine.

High-sensitivity and point-of-care detection of SARS-CoV-2 from nasal and throat swabs by magnetic SERS biosensor

The outbreak of COVID-19 caused by SARS-CoV-2 urges the development of rapidly and accurately diagnostic methods. Here, one high-sensitivity and point-of-care detection method based on magnetic SERS biosensor composed of Fe₃O₄-Au nanocomposite and Au nanoneedles array was developed to detect SARS-CoV-2 directly. Among, the magnetic Fe₃O₄-Au nanocomposite is applied to capture and separate virus from nasal and throat swabs and enhance the Raman signals of SARS-CoV-2. The magnetic SERS biosensor possessed high sensitivity by optimizing the Fe₃O₄-Au nanocomposite. More significantly, the on-site detection of inactivated SARS-CoV-2 virus was achieved based on the magnetic SERS biosensor with ultra-low limit of detection of 100 copies/mL during 15 mins. Furthermore, the contaminated nasal and throat swabs samples were identified by support vector machine, and the diagnostic accuracy of 100% was obtained. The magnetic SERS biosensor combined with support vector machine provides giant potential as the point-of-care detection tool for SARS-CoV-2.

SARS-CoV-2 couples evasion of inflammatory response to activated nucleotide synthesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused the global COVID-19 pandemic. Although ongoing vaccination drastically reduces SARS-CoV-2 infection, mutant viruses are emerging under the pressure of neutralizing antibodies, calling for new antiviral strategies. Here, we report that SARS-CoV-2 couples evasion of inflammatory response to activated nucleotide synthesis. Inhibition of a key metabolic enzyme not only depletes the nucleotide pool but also restores host inflammatory defense, thereby effectively impeding SARS-CoV-2 replication. Targeting cellular enzymes offers an avenue to combat rapidly evolving SARS-CoV-2 variants.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolves rapidly under the pressure of host immunity, as evidenced by waves of emerging variants despite effective vaccinations, highlighting the need for complementing antivirals. We report that targeting a pyrimidine synthesis enzyme restores inflammatory response and depletes the nucleotide pool to impede SARS-CoV-2 infection. SARS-CoV-2 deploys Nsp9 to activate carbamoyl-phosphate synthetase, aspartate transcarbamoylase, and dihydroorotase (CAD) that catalyzes the rate-limiting steps of the de novo pyrimidine synthesis. Activated CAD not only fuels de novo nucleotide synthesis but also deamidates RelA. While RelA deamidation shuts down NF-κB activation and subsequent inflammatory response, it up-regulates key glycolytic enzymes to promote aerobic glycolysis that provides metabolites for de novo nucleotide synthesis. A newly synthesized small-molecule inhibitor of CAD restores antiviral inflammatory response and depletes the pyrimidine pool, thus effectively impeding SARS-CoV-2 replication. Targeting an essential cellular metabolic enzyme thus offers an antiviral strategy that would be more refractory to SARS-CoV-2 genetic changes.

Identification of SARS-CoV-2 Variants of Concern Using Amplicon Next-Generation Sequencing

COVID-19 is caused by SARS-CoV-2, several virulent variants of which have emerged since 2019. More than 529 million people have been infected, and at least 6 million have died. Our aim was to develop a fast, accurate, low-cost method for detecting and identifying newly emerging variants of concern (VOCs) that could pose a global threat. The 341-bp DNA sequence of a specific region of the SARS-CoV-2’s spike protein was amplified by a one-step PCR on RNA samples from 46 patients. The product was sequenced using next-generation sequencing (NGS). DNA sequences from seven genomes, the original Wuhan isolate and six different representative variants obtained from the GISAID website, were used as references. Complete whole-genome sequences from local isolates were also obtained from the GISAID website, and their RNA was used for comparison. We used an amplicon-based NGS method (termed VOC-NGS) for genotyping and successfully identified all 46 samples. Fifteen (32.6%) were like the original isolate. Twenty-seven were VOCs: nine (19.5%) Alpha, eight (19%) Delta, six (14%) Beta, and four (8.7%) Omicron. Two were variants of interest (VOI): one (2%) Kappa and one (2%) Zeta. Two samples were mixtures of two variants, one of Alpha and Beta and one of Alpha and Delta. The Spearman correlation between whole-genome sequencing (WGS) and VOC-NGS was significant (P < 0.001) with perfect agreement (Kappa = 0.916) for 36/38 (94.7%) samples with VOC-NGS detecting all the known VOCs. Genotyping by VOC-NGS enables rapid screening of high-throughput clinical samples that includes the identification of VOCs and mixtures of variants, at lower cost than WGS.

IMPORTANCE The manuscript described SARS-Cov-2 genotyping by VOC-NGS, which presents an ideal balance of accuracy, rapidity, and cost for detecting and globally tracking VOCs and some VOI of SARS-CoV-2. A large number of clinical samples can be tested together. Rapid introduction of new mutations at a specific site of the spike protein necessitates efficient strain detection and identification to enable choice of treatment and the application of vaccination, as well as planning public health policy.

Mast Cell Activation Syndrome in COVID-19 and Female Reproductive Function: Theoretical Background vs. Accumulating Clinical Evidence

Coronavirus disease 2019 (COVID-19), a pandemic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, can affect almost all systems and organs of the human body, including those responsible for reproductive function in women. The multisystem inflammatory response in COVID-19 shows many analogies with mast cell activation syndrome (MCAS), and MCAS may be an important component in the course of COVID-19. Of note, the female sex hormones estradiol (E2) and progesterone (P4) significantly influence mast cell (MC) behavior. This review presents the importance of MCs and the mediators from their granules in the female reproductive system, including pregnancy, and discusses the mechanism of potential disorders related to MCAS. Then, the available data on COVID-19 in the context of hormonal disorders, the course of endometriosis, female fertility, and the course of pregnancy were compiled to verify intuitively predicted threats. Surprisingly, although COVID-19 hyperinflammation and post-COVID-19 illness may be rooted in MCAS, the available clinical data do not provide grounds for treating this mechanism as significantly increasing the risk of abnormal female reproductive function, including pregnancy. Further studies in the context of post COVID-19 condition (long COVID), where inflammation and a procoagulative state resemble many aspects of MCAS, are needed.

COVID-19 Diagnosis: A Comprehensive Review of the RT-qPCR Method for Detection of SARS-CoV-2

The world is grappling with the coronavirus disease 2019 (COVID-19) pandemic, the causative agent of which is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 symptoms are similar to the common cold, including fever, sore throat, cough, muscle and chest pain, brain fog, dyspnoea, anosmia, ageusia, and headache. The manifestation of the disease can vary from being asymptomatic to severe life-threatening conditions warranting hospitalization and ventilation support. Furthermore, the emergence of mutecated variants of concern (VOCs) is paramount to the devastating effect of the pandemic. This highly contagious virus and its emergent variants challenge the available advanced viral diagnostic methods for high-accuracy testing with faster result yields. This review is to shed light on the natural history, pathology, molecular biology, and efficient diagnostic methods of COVID-19, detecting SARS-CoV-2 in collected samples. We reviewed the gold standard RT-qPCR method for COVID-19 diagnosis to confer a better understanding and application to combat the COVID-19 pandemic. This comprehensive review may further develop awareness about the management of the COVID-19 pandemic.

Insertion-and-Deletion Mutations between the Genomes of SARS-CoV, SARS-CoV-2, and Bat Coronavirus RaTG13

The evolutional process of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) development remains inconclusive. This study compared the genome sequences of severe acute respiratory syndrome coronavirus (SARS-CoV), bat coronavirus RaTG13, and SARS-CoV-2. In total, the genomes of SARS-CoV-2 and RaTG13 were 77.9% and 77.7% identical to the genome of SARS-CoV, respectively. A total of 3.6% (1,068 bases) of the SARS-CoV-2 genome was derived from insertion and/or deletion (indel) mutations, and 18.6% (5,548 bases) was from point mutations from the genome of SARS-CoV. At least 35 indel sites were confirmed in the genome of SARS-CoV-2, in which 17 were with ≥10 consecutive bases long. Ten of these relatively long indels were located in the spike (S) gene, five in nonstructural protein 3 (Nsp3) gene of open reading frame (ORF) 1a, and one in ORF8 and noncoding region. Seventeen (48.6%) of the 35 indels were based on insertion-and-deletion mutations with exchanged gene sequences of 7–325 consecutive bases. Almost the complete ORF8 gene was replaced by a single 325 consecutive base-long indel. The distribution of these indels was roughly in accordance with the distribution of the rate of point mutation rate around the indels. The genome sequence of SARS-CoV-2 was 96.0% identical to that of RaTG13. There was no long insertion-and-deletion mutation between the genomes of RaTG13 and SARS-CoV-2. The findings of the uneven distribution of multiple indels and the presence of multiple long insertion-and-deletion mutations with exchanged consecutive base sequences in the viral genome may provide insights into SARS-CoV-2 development.

IMPORTANCE The developmental mechanism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains inconclusive. This study compared the base sequence one-by-one between severe acute respiratory syndrome coronavirus (SARS-CoV) or bat coronavirus RaTG13 and SARS-CoV-2. The genomes of SARS-CoV-2 and RaTG13 were 77.9% and 77.7% identical to the genome of SARS-CoV, respectively. Seventeen of the 35 sites with insertion and/or deletion mutations between SARS-CoV-2 and SARS-CoV were based on insertion-and-deletion mutations with the replacement of 7–325 consecutive bases. Most of these long insertion-and-deletion sites were concentrated in the nonstructural protein 3 (Nsp3) gene of open reading frame (ORF) 1a, S1 domain of the spike protein, and ORF8 genes. Such long insertion-and-deletion mutations were not observed between the genomes of RaTG13 and SARS-CoV-2. The presence of multiple long insertion-and-deletion mutations in the genome of SARS-CoV-2 and their uneven distributions may provide further insights into the development of the virus.

SARS-CoV-2 electrochemical immunosensor based on the spike-ACE2 complex

Rapid, straightforward, and massive diagnosis of coronavirus disease 2019 (COVID-19) is one of the more important measures to mitigate the current pandemics. This work reports on an immunosensor to rapidly detect the spike protein from the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The immunosensing device entraps the spike protein linked to angiotensin-converting enzyme host receptor (ACE2) protein in a sandwich between carboxylated magnetic beads functionalized with an anti-spike antibody and an anti-ACE2 antibody, further labeled with streptavidin (poly)horseradish peroxidase (HRP) reporter enzyme. The particles were confined at the surface of screen-printed gold electrodes, whose signal resulting from the interaction of the enzyme with a mediator was recorded in a portable potentiostat. The immunosensor showed a sensitivity of 0.83 μA∗mL/μg and a limit of detection of 22.5 ng/mL of spike protein, with high reproducibility. As a proof-of-concept, it detected commercial spike protein-supplemented buffer solutions, pseudovirions, isolated viral particles and ten nasopharyngeal swab samples from infected patients compared to samples from three healthy individuals paving the way to detect the virus closer to the patient.

Elucidating Design Principles for Engineering Cell-Derived Vesicles to Inhibit SARS-CoV-2 Infection

The ability of pathogens to develop drug resistance is a global health challenge. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents an urgent need wherein several variants of concern resist neutralization by monoclonal antibody (mAb) therapies and vaccine-induced sera. Decoy nanoparticles-cell-mimicking particles that bind and inhibit virions-are an emerging class of therapeutics that may overcome such drug resistance challenges. To date, quantitative understanding as to how design features impact performance of these therapeutics is lacking. To address this gap, this study presents a systematic, comparative evaluation of various biologically derived nanoscale vesicles, which may be particularly well suited to sustained or repeated administration in the clinic due to low toxicity, and investigates their potential to inhibit multiple classes of model SARS-CoV-2 virions. A key finding is that such particles exhibit potent antiviral efficacy across multiple manufacturing methods, vesicle subclasses, and virus-decoy binding affinities. In addition, these cell-mimicking vesicles effectively inhibit model SARS-CoV-2 variants that evade mAbs and recombinant protein-based decoy inhibitors. This study provides a foundation of knowledge that may guide the design of decoy nanoparticle inhibitors for SARS-CoV-2 and other viral infections.

Possibility of blood test parameters usage in the evaluation of COVID-19 patients’ inflammatory status

Background: C-reactive protein (CRP) is a key laboratory biomarker for anti-inflammatory treatment initiation. Unfortunately, biochemical blood analyzers are not always easily accessible in medical institutions located far from major regional health facilities. Aim: To develop an approach for inflammatory status estimation based on blood test results in patients with COVID-19 in cases with limited laboratory equipment availability. Methods: The present retrospective study included 423 patients (male 54.6%; female 45.4%; mean age 59.1 years) receiving hospital treatment due to COVID-19 in Medical Research and Educational Center of Lomonosov Moscow State University from April 21st to June 13th 2020. All patients donated blood for full biochemistry and hematology testing and underwent chest computer tomography (CT). Results: CRP levels (60 mg/L) qualitative estimation model was developed based on hematologic test results. It included erythrocyte sedimentation rate and neutrophils to lymphocytes ratio. According to the results of Receiver Operating Characteristic (ROC) analysis present model was characterized by sensitivity of 70.2%, specificity of 74.6%, and area under the ROC-curve of 0.781. Comparison of key clinical parameters reflecting COVID-19 severity, such as length of hospitalization, lung damage at CT (hospital admission and discharge), revealed statistically significant difference between groups with routinely measured CRP levels 60 mg/L and 60 mg/L for all the above-mentioned parameters (p 0.05). These differences remained significant when measured CRP levels were substituted with estimated CRP values, indicating interchangeability of these approaches to CRP levels determination, regarding clinically important parameters. Conclusions: Presented model for inflammatory status estimation based on hematologic test results might be used to overcome clinical challenges in cases with limited laboratory equipment availability.

Functional ACE2 deficiency leading to angiotensin imbalance in the pathophysiology of COVID-19

SARS-CoV-2, the virus responsible for COVID-19, uses angiotensin converting enzyme 2 (ACE2) as its primary cell-surface receptor. ACE2 is a key enzyme in the counter-regulatory pathway of the broader renin-angiotensin system (RAS) that has been implicated in a broad array of human pathology. The RAS is composed of two competing pathways that work in opposition to each other: the "conventional" arm involving angiotensin converting enzyme (ACE) generating angiotensin-2 and the more recently identified ACE2 pathway that generates angiotensin (1-7). Following the original SARS pandemic, additional studies suggested that coronaviral binding to ACE2 resulted in downregulation of the membrane-bound enzyme. Given the similarities between the two viruses, many have posited a similar process with SARS-CoV-2. Proponents of this ACE2 deficiency model argue that downregulation of ACE2 limits its enzymatic function, thereby skewing the delicate balance between the two competing arms of the RAS. In this review we critically examine this model. The available data remain incomplete but are consistent with the possibility that the broad multisystem dysfunction of COVID-19 is due in large part to functional ACE2 deficiency leading to angiotensin imbalance with consequent immune dysregulation and endothelial cell dysfunction.

COVID-19-Associated Myocarditis: An Evolving Concern in Cardiology and Beyond

Simple Summary

Coronavirus disease-2019 (COVID-19) affects many organs in the body, including the heart. One complication of particular concern is inflammation of the heart muscle, called myocarditis. This paper presents updated research data on COVID-19-associated myocarditis. Specifically, we review the incidence, potential mechanisms, blood and imaging tests that can be used to detect the disease. We emphasize that, in contrast with early reports, recent data suggest that myocarditis in the setting of COVID-19 is relatively uncommon, yet infected individuals are at a substantially increased risk for poor outcomes. It is important to continue research in this area.

Abstract

The direct and indirect adverse effects of SARS-CoV-2 infection on the cardiovascular system, including myocarditis, are of paramount importance. These not only affect the disease course but also determine clinical outcomes and recovery. In this review, the authors aimed at providing an update on the incidence of Coronavirus disease-2019 (COVID-19)-associated myocarditis. Our knowledge and experience relevant to this area continues to evolve rapidly since the beginning of the pandemic. It is crucial for the scientific and medical community to stay abreast of current information. Contrasting early reports, recent data suggest that the overall incidence of SARS-CoV-2-associated myocarditis is relatively low, yet infected individuals are at a substantially increased risk. Therefore, understanding the pathophysiology and diagnostic evaluation, including the use of serum biomarkers and imaging modalities, remain important. This review aims to summarize the most recent data in these areas as they relate to COVID-19-associated myocarditis. Given its increasing relevance, a brief update is included on the proposed mechanisms of myocarditis in COVID-19 vaccine recipients.

Missense variants in human ACE2 strongly affect binding to SARS-CoV-2 Spike providing a mechanism for ACE2 mediated genetic risk in Covid-19: A case study in affinity predictions of interface variants

SARS-CoV-2 Spike (Spike) binds to human angiotensin-converting enzyme 2 (ACE2) and the strength of this interaction could influence parameters relating to virulence. To explore whether population variants in ACE2 influence Spike binding and hence infection, we selected 10 ACE2 variants based on affinity predictions and prevalence in gnomAD and measured their affinities and kinetics for Spike receptor binding domain through surface plasmon resonance (SPR) at 37°C. We discovered variants that reduce and enhance binding, including three ACE2 variants that strongly inhibited (p.Glu37Lys, ΔΔG = –1.33 ± 0.15 kcal mol^-1 and p.Gly352Val, predicted ΔΔG = –1.17 kcal mol^-1) or abolished (p.Asp355Asn) binding. We also identified two variants with distinct population distributions that enhanced affinity for Spike. ACE2 p.Ser19Pro (ΔΔG = 0.59 ± 0.08 kcal mol^-1) is predominant in the gnomAD African cohort (AF = 0.003) whilst p.Lys26Arg (ΔΔG = 0.26 ± 0.09 kcal mol^-1) is predominant in the Ashkenazi Jewish (AF = 0.01) and European non-Finnish (AF = 0.006) cohorts. We compared ACE2 variant affinities to published SARS-CoV-2 pseudotype infectivity data and confirmed that ACE2 variants with reduced affinity for Spike can protect cells from infection. The effect of variants with enhanced Spike affinity remains unclear, but we propose a mechanism whereby these alleles could cause greater viral spreading across tissues and cell types, as is consistent with emerging understanding regarding the interplay between receptor affinity and cell-surface abundance. Finally, we compared mCSM-PPI2 ΔΔG predictions against our SPR data to assess the utility of predictions in this system. We found that predictions of decreased binding were well-correlated with experiment and could be improved by calibration, but disappointingly, predictions of highly enhanced binding were unreliable. Recalibrated predictions for all possible ACE2 missense variants at the Spike interface were calculated and used to estimate the overall burden of ACE2 variants on Covid-19.

One of the first things the SARS-CoV-2 virus does to invade human cells is bind to a cell surface receptor called angiotensin-converting enzyme 2 (ACE2). The virus attaches to this receptor through its Spike protein and knowledge from other viruses tells us that the strength of this interaction influences how infectious and or virulent it is. We hypothesised that the Spike-ACE2 affinity might vary in people who have different amino acids in the part of ACE2 where Spike binds and consequently might be protected–or more at risk–from the virus. To test this idea, we measured the affinity of several ACE2 mutants, representing different versions found in humans, for the Spike protein and we found that some strengthened the interactions alongside others that weakened it. Most of these variants are rare, but two are present in over 1 in 1,000 individuals in certain populations and so might be important for the epidemiology of COVID-19. We then used computational methods to predict the affinity of even more ACE2 mutants than we could test in the lab and again found many that might alter this interaction. These data may help identify people who are at higher or lower risk from COVID-19.

COVID-19 diagnosis by SARS-CoV-2 Spike protein detection in saliva using an ultrasensitive magneto-assay based on disposable electrochemical sensor

The outbreak of the COVID-19 pandemic, caused by Severe Acute Respiratory Syndrome of Coronavirus 2 (SARS-CoV-2), has fueled the search for diagnostic tests aiming at the control and reduction of the viral transmission. The main technique used for diagnosing the Coronavirus disease (COVID-19) is the reverse transcription-polymerase chain reaction (RT-PCR) technique. However, considering the high number of cases and the underlying limitations of the RT-PCR technique, especially with regard to accessibility and cost of the test, one does not need to overemphasize the need to develop new and less expensive testing techniques that can aid the early diagnosis of the disease. With that in mind, we developed an ultrasensitive magneto-assay using magnetic beads and gold nanoparticles conjugated to human angiotensin-converting enzyme 2 (ACE2) peptide (Gln²⁴-Gln⁴²) for the capturing and detection of SARS-CoV-2 Spike protein in human saliva. The technique applied involved the use of a disposable electrochemical device containing eight screen-printed carbon electrodes which allow the simultaneous analysis of eight samples. The magneto-assay exhibited an ultralow limit of detection of 0.35 ag mL^-1 for the detection of SARS-CoV-2 Spike protein in saliva. The magneto-assay was tested in saliva samples from healthy and SARS-CoV-2-infected individuals. In terms of efficiency, the proposed technique - which presented a sensitivity of 100.0% and specificity of 93.7% for SARS-CoV-2 Spike protein-exhibited great similarity with the RT-PCR technique. The results obtained point to the application potential of this simple, low-cost magneto-assay for saliva-based point-of-care COVID-19 diagnosis.

COVID-19 diagnosis by SARS-CoV-2 Spike protein detection in saliva using an ultrasensitive magneto-assay based on disposable electrochemical sensor

The outbreak of the COVID-19 pandemic, caused by Severe Acute Respiratory Syndrome of Coronavirus 2 (SARS-CoV-2), has fueled the search for diagnostic tests aiming at the control and reduction of the viral transmission. The main technique used for diagnosing the Coronavirus disease (COVID-19) is the reverse transcription-polymerase chain reaction (RT-PCR) technique. However, considering the high number of cases and the underlying limitations of the RT-PCR technique, especially with regard to accessibility and cost of the test, one does not need to overemphasize the need to develop new and less expensive testing techniques that can aid the early diagnosis of the disease. With that in mind, we developed an ultrasensitive magneto-assay using magnetic beads and gold nanoparticles conjugated to human angiotensin-converting enzyme 2 (ACE2) peptide (Gln²⁴-Gln⁴²) for the capturing and detection of SARS-CoV-2 Spike protein in human saliva. The technique applied involved the use of a disposable electrochemical device containing eight screen-printed carbon electrodes which allow the simultaneous analysis of eight samples. The magneto-assay exhibited an ultralow limit of detection of 0.35 ag mL^-1 for the detection of SARS-CoV-2 Spike protein in saliva. The magneto-assay was tested in saliva samples from healthy and SARS-CoV-2-infected individuals. In terms of efficiency, the proposed technique - which presented a sensitivity of 100.0% and specificity of 93.7% for SARS-CoV-2 Spike protein-exhibited great similarity with the RT-PCR technique. The results obtained point to the application potential of this simple, low-cost magneto-assay for saliva-based point-of-care COVID-19 diagnosis.

Role of artificial intelligence in fast-track drug discovery and vaccine development for COVID-19

COVID-19 is a global pandemic spread across more than 200 countries and several measures are being taken to control it. Researchers in pharmaceutical academia/industry are incessantly targeting this disease through vaccine and drug development protocols. Artificial intelligence is being extensively explored for surveillance, diagnostics, contact tracing, and for clinical management of COVID-19. The most common application has been for repurposing of existing drugs through various AI tools. Successful training of artificial neural networks based on identification of specific patterns in binding of known antiviral drugs with protein sequences from diverse virus species have generated models giving good predictions for molecules against SARS-CoV-2 virus, in sync with clinical studies. ML tools have also been used to investigate immunogenic components of the virus to be exploited as vaccine candidates. In this chapter, the utilization of artificial intelligence to accelerate drug-design and vaccine design research for COVID-19 has been reviewed.

Bioengineered angiotensin-converting-enzyme-2: a potential therapeutic option against SARS-CoV-2 infection

The recombinant soluble human angiotensin-converting enzyme 2 (rshACE2) is a promising therapy against SARS-CoV-2 infection, but it has some drawbacks that reduce the success of its clinical applications. The bioengineered ACE2 (Tag-sACE2 and probiotic-ACE2) as a way may overcome its therapeutic limitations against ongoing current pandemic.

Anti-SARS-CoV-2 immunoglobulin profile in patients with celiac disease living in a high incidence area

BACKGROUND AND AIM

How symptoms and antibodies related to SARS-CoV-2 infection develop in patients with celiac disease (CD) is unclear. We aimed to investigate the impact of SARS-CoV-2 infection in CD patients.

METHODS

CD patients were interviewed about the development of COVID-19 symptoms, compliance with anti-virus measures and adherence to a gluten-free diet (GFD). The presence of anti-SARS-CoV-2 IgG and IgA (anti-RBD and N proteins) was compared to that in non-CD subjects. Expression of the duodenal ACE2 receptor was investigated. When available, data on duodenal histology, anti-tissue transglutaminase IgA (tTGA), comorbidities and GFD adherence were analyzed.

RESULTS

Of 362 CD patients, 42 (12%) reported COVID-19 symptoms and 21% of these symptomatic patients presented anti-SARS-CoV-2 Ig. Overall, 18% of CD patients showed anti-SARS-CoV-2 Ig versus 25% of controls (p = 0.18). CD patients had significantly lower levels of anti-N IgA. tTGA, duodenal atrophy, GFD adherence or other comorbidities did not influence symptoms and/or antibodies. The ACE2 receptor was detected in the non-atrophic duodenal mucosa of patients; atrophy was associated with lower expression of the ACE2 receptor.

CONCLUSION

CD patients have an anti-SARS-CoV-2 Ig profile similar to non-celiac controls, except for anti-N IgA. No risk factors were identified among CD parameters and GFD adherence.

Development of targeted nanoparticles loaded with antiviral drugs for SARS-CoV-2 inhibition

Recently, a novel coronavirus, known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has raised global concerns, being the etiological agent of the current pandemic infectious coronavirus disease 2019 (COVID-19). Specific prophylactic treatments like vaccines, have been authorized for use by regulatory bodies in multiple countries, however there is an urgent need to identify new, safe, and targeted therapeutics as post-exposure therapy for COVID-19. Among a plethora of potential pharmacological targets, the angiotensin-converting enzyme 2 (ACE2) membrane receptor, which plays a crucial role in viral entry, is representing an attractive intervention opportunity for SARS-CoV-2 antiviral discovery process.

In this scenario, we envisioned that binding to ACE2 by multivalent attachment of ligands to nanocarriers incorporating antiviral therapeutics, it would increase receptor avidity and impart specificity to these nanovectors for host cells, particularly in the pulmonary tract, which is the primary entry route for SARS-CoV-2.

Herein, we report the design and development of novel polymeric nanoparticles (NP), densely grafted with various ligands to selectively bind to ACE2, as innovative nanovectors for targeted drug delivery. We first evaluated the impact of these biocompatible targeted NP (TNP) on ligand binding toward ACE2 and measured their competition ability vs a model of spike protein (Lipo-S1). Next, we tested the effectiveness of the most performing nanoprotopype, TNP-1, loaded with a model anti-SARS-CoV-2 drug such as remdesivir (RDV), on antiviral activity against SARS-CoV-2 infected Vero E6 cells. The RDV-TNP-1 exhibited a significantly improved antiviral effect compared to RDV at the same concentration. Interestingly, unloaded TNP (TNP-1E) also exhibited a basal antiviral activity, potentially due to a direct competitive mechanism with viral particles for the ACE2 binding site. We also measured the anti-exopeptidase activity of TNP-1E against ACE2 protein. Collectively, these insights warrant in-depth preclinical development for our nanoprototypes, for example as potential inhalable drug carriers, with the perspective of a clinical translation.

Foe and friend in the COVID-19-associated acute kidney injury: an insight on intrarenal renin-angiotensin system

Since the first reported case in December of 2019, the coronavirus disease 2019 (COVID-19) has became an international public health emergency. So far, there are more than 228,206,384 confirmed cases including 4,687,066 deaths. Kidney with high expression of angiotensin-converting enzyme 2 (ACE2) is one of the extrapulmonary target organs affected in patients with COVID-19. Acute kidney injury (AKI) is one of the independent risk factors for the death of COVID-19 patients. The imbalance between ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R axis in the kidney may contribute to COVID-19-associated AKI. Although series of research have shown the inconsistent effects of multiple common RAS inhibitors on ACE2 expression and enzyme activity, most of the retrospective cohort studies indicated the safety and protective effects of ACEI/ARB in COVID-19 patients. This review article highlights the current knowledge on the possible involvement of intrarenal RAS in COVID-19-associated AKI with a primary focus on the opposing effects of ACE2-Ang(1-7)-MasR and ACE-Ang II-AT1R signaling in the kidney. Human recombinant soluble ACE2 or ACE2 variants with preserved ACE2-enzymatic activity may be the best options to improve COVID-19-associated AKI.

SARS-CoV-2 Spike Protein Destabilizes Microvascular Homeostasis

SARS-CoV-2 infection can cause compromised respiratory function and thrombotic events. SARS-CoV-2 binds to and mediates downregulation of angiotensin converting enzyme 2 (ACE2) on cells that it infects. Theoretically, diminished enzymatic activity of ACE2 may result in increased concentrations of pro-inflammatory molecules, angiotensin II, and Bradykinin, contributing to SARS-CoV-2 pathology. Using immunofluorescence microscopy of lung tissues from uninfected, and SARS-CoV-2 infected individuals, we find evidence that ACE2 is highly expressed in human pulmonary alveolar epithelial cells and significantly reduced along the alveolar lining of SARS-CoV-2 infected lungs. Ex vivo analyses of primary human cells, indicated that ACE2 is readily detected in pulmonary alveolar epithelial and aortic endothelial cells. Exposure of these cells to spike protein of SARS-CoV-2 was sufficient to reduce ACE2 expression. Moreover, exposure of endothelial cells to spike protein-induced dysfunction, caspase activation, and apoptosis. Exposure of endothelial cells to bradykinin caused calcium signaling and endothelial dysfunction (increased expression of von Willibrand Factor and decreased expression of Krüppel-like Factor 2) but did not adversely affect viability in primary human aortic endothelial cells. Computer-assisted analyses of molecules with potential to bind bradykinin receptor B2 (BKRB2), suggested a potential role for aspirin as a BK antagonist. When tested in our in vitro model, we found evidence that aspirin can blunt cell signaling and endothelial dysfunction caused by bradykinin in these cells. Interference with interactions of spike protein or bradykinin with endothelial cells may serve as an important strategy to stabilize microvascular homeostasis in COVID-19 disease.

IMPORTANCE SARS-CoV-2 causes complex effects on microvascular homeostasis that potentially contribute to organ dysfunction and coagulopathies. SARS-CoV-2 binds to, and causes downregulation of angiotensin converting enzyme 2 (ACE2) on cells that it infects. It is thought that reduced ACE2 enzymatic activity can contribute to inflammation and pathology in the lung. Our studies add to this understanding by providing evidence that spike protein alone can mediate adverse effects on vascular cells. Understanding these mechanisms of pathogenesis may provide rationale for interventions that could limit microvascular events associated with SARS-CoV-2 infection.

Pannexin-1 channel opening is critical for COVID-19 pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly rampaged worldwide, causing a pandemic of coronavirus disease (COVID -19), but the biology of SARS-CoV-2 remains under investigation. We demonstrate that both SARS-CoV-2 spike protein and human coronavirus 229E (hCoV-229E) or its purified S protein, one of the main viruses responsible for the common cold, induce the transient opening of Pannexin-1 (Panx-1) channels in human lung epithelial cells. However, the Panx-1 channel opening induced by SARS-CoV-2 is greater and more prolonged than hCoV-229E/S protein, resulting in an enhanced ATP, PGE₂, and IL-1β release. Analysis of lung lavages and tissues indicate that Panx-1 mRNA expression is associated with increased ATP, PGE₂, and IL-1β levels. Panx-1 channel opening induced by SARS-CoV-2 spike protein is angiotensin-converting enzyme 2 (ACE-2), endocytosis, and furin dependent. Overall, we demonstrated that Panx-1 channel is a critical contributor to SARS-CoV-2 infection and should be considered as an alternative therapy.

Elucidating design principles for engineering cell-derived vesicles to inhibit SARS-CoV-2 infection

The ability of pathogens to develop drug resistance is a global health challenge. The SARS-CoV-2 virus presents an urgent need wherein several variants of concern resist neutralization by monoclonal antibody therapies and vaccine-induced sera. Decoy nanoparticles-cell-mimicking particles that bind and inhibit virions-are an emerging class of therapeutics that may overcome such drug resistance challenges. To date, we lack quantitative understanding as to how design features impact performance of these therapeutics. To address this gap, here we perform a systematic, comparative evaluation of various biologically-derived nanoscale vesicles, which may be particularly well-suited to sustained or repeated administration in the clinic due to low toxicity, and investigate their potential to inhibit multiple classes of model SARS-CoV-2 virions. A key finding is that such particles exhibit potent antiviral efficacy across multiple manufacturing methods, vesicle subclasses, and virus-decoy binding affinities. In addition, these cell-mimicking vesicles effectively inhibit model SARS-CoV-2 variants that evade monoclonal antibodies and recombinant protein-based decoy inhibitors. This study provides a foundation of knowledge that may guide the design of decoy nanoparticle inhibitors for SARS-CoV-2 and other viral infections.

Root Causes of Fungal Coinfections in COVID-19 Infected Patients

COVID-19 is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has infected over 200 million people, causing over 4 million deaths. COVID-19 infection has been shown to lead to hypoxia, immunosuppression, host iron depletion, hyperglycemia secondary to diabetes mellitus, as well as prolonged hospitalizations. These clinical manifestations provide favorable conditions for opportunistic fungal pathogens to infect hosts with COVID-19. Interventions such as treatment with corticosteroids and mechanical ventilation may further predispose COVID-19 patients to acquiring fungal coinfections. Our literature review found that fungal coinfections in COVID-19 infected patients were most commonly caused by Aspergillus, Candida species, Cryptococcus neoformans, and fungi of the Mucorales order. The distribution of these infections, particularly Mucormycosis, was found to be markedly skewed towards low- and middle-income countries. The purpose of this review is to identify possible explanations for the increase in fungal coinfections seen in COVID-19 infected patients so that physicians and healthcare providers can be conscious of factors that may predispose these patients to fungal coinfections in order to provide more favorable patient outcomes. After identifying risk factors for coinfections, measures should be taken to minimize the dosage and duration of drugs such as corticosteroids, immunosuppressants, and antibiotics.

SARS-CoV-2 receptor binding domain fusion protein efficiently neutralizes virus infection

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the COVID-19 pandemic. Currently, as dangerous mutations emerge, there is an increased demand for specific treatments for SARS-CoV-2 infected patients. The spike glycoprotein on the virus envelope binds to the angiotensin converting enzyme 2 (ACE2) on host cells through its receptor binding domain (RBD) to mediate virus entry. Thus, blocking this interaction may inhibit viral entry and consequently stop infection. Here, we generated fusion proteins composed of the extracellular portions of ACE2 and RBD fused to the Fc portion of human IgG1 (ACE2-Ig and RBD-Ig, respectively). We demonstrate that ACE2-Ig is enzymatically active and that it can be recognized by the SARS-CoV-2 RBD, independently of its enzymatic activity. We further show that RBD-Ig efficiently inhibits in-vivo SARS-CoV-2 infection better than ACE2-Ig. Mechanistically, we show that anti-spike antibody generation, ACE2 enzymatic activity, and ACE2 surface expression were not affected by RBD-Ig. Finally, we show that RBD-Ig is more efficient than ACE2-Ig at neutralizing high virus titers. We thus propose that RBD-Ig physically blocks virus infection by binding to ACE2 and that RBD-Ig should be used for the treatment of SARS-CoV-2-infected patients.

Evolutionary pathways to SARS-CoV-2 resistance are opened and closed by epistasis acting on ACE2

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infects a broader range of mammalian species than previously predicted, binding a diversity of angiotensin converting enzyme 2 (ACE2) orthologs despite extensive sequence divergence. Within this sequence degeneracy, we identify a rare sequence combination capable of conferring SARS-CoV-2 resistance. We demonstrate that this sequence was likely unattainable during human evolution due to deleterious effects on ACE2 carboxypeptidase activity, which has vasodilatory and cardioprotective functions in vivo. Across the 25 ACE2 sites implicated in viral binding, we identify 6 amino acid substitutions unique to mouse-one of the only known mammalian species resistant to SARS-CoV-2. Substituting human variants at these positions is sufficient to confer binding of the SARS-CoV-2 S protein to mouse ACE2, facilitating cellular infection. Conversely, substituting mouse variants into either human or dog ACE2 abolishes viral binding, diminishing cellular infection. However, these same substitutions decrease human ACE2 activity by 50% and are predicted as pathogenic, consistent with the extreme rarity of human polymorphisms at these sites. This trade-off can be avoided, however, depending on genetic background; if substituted simultaneously, these same mutations have no deleterious effect on dog ACE2 nor that of the rodent ancestor estimated to exist 70 million years ago. This genetic contingency (epistasis) may have therefore opened the road to resistance for some species, while making humans susceptible to viruses that use these ACE2 surfaces for binding, as does SARS-CoV-2.

Association between angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and angiotensin-II receptor 1 (AGTR1) polymorphisms and COVID-19 infection in the southeast of Iran: a preliminary case-control study

BACKGROUND

The COVID-19 pandemic remains an emerging public health crisis with serious adverse effects. The disease is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV--2) infection, targeting angiotensin-converting enzyme-2 (ACE2) receptor for cell entry. However, changes in the renin-angiotensin system (RAS) balance alter an individual's susceptibility to COVID-19 infection. We aimed to evaluate the association between AGT rs699 C > T, ACE rs4646994 I/D, and AGTR1 rs5186 C > A variants and the risk of COVID-19 infection and the severity in a sample of the southeast Iranian population.

METHODS

A total of 504 subjects, including 258 COVID-19 positives, and 246 healthy controls, were recruited. Genotyping of the ACE gene rs4646994, and AGT rs699, and AGTR1 rs5186 polymorphisms was performed by polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP), respectively.

RESULTS

Our results showed that the II genotype of ACE rs4646994 and the I allele decreased the risk of COVID-19 infection. Moreover, we found that the TC genotype and C allele of AGT rs699 increased the risk of COVID-19 infection. The AGTR1 rs5186 was not associated with COVID-19 infection. Also, we did not find any association between these polymorphisms and the severity of the disease. However, we found a significantly higher age and prevalence of diabetes and hypertension in patients with severe disease than a non-severe disease.

CONCLUSIONS

These findings suggest that ACE rs4646994 and AGT rs699 polymorphisms increase the risk of COVID-19 infection in a southeast Iranian population.

Common cardiac medications potently inhibit ACE2 binding to the SARS-CoV-2 Spike, and block virus penetration and infectivity in human lung cells

To initiate SARS-CoV-2 infection, the Receptor Binding Domain (RBD) on the viral spike protein must first bind to the host receptor ACE2 protein on pulmonary and other ACE2-expressing cells. We hypothesized that cardiac glycoside drugs might block the binding reaction between ACE2 and the Spike (S) protein, and thus block viral penetration into target cells. To test this hypothesis we developed a biochemical assay for ACE2:Spike binding, and tested cardiac glycosides as inhibitors of binding. Here we report that ouabain, digitoxin, and digoxin, as well as sugar-free derivatives digitoxigenin and digoxigenin, are high-affinity competitive inhibitors of ACE2 binding to the Original [D614] S1 and the α/β/γ [D614G] S1 proteins. These drugs also inhibit ACE2 binding to the Original RBD, as well as to RBD proteins containing the β [E484K], Mink [Y453F] and α/β/γ [N501Y] mutations. As hypothesized, we also found that ouabain, digitoxin and digoxin blocked penetration by SARS-CoV-2 Spike-pseudotyped virus into human lung cells, and infectivity by native SARS-CoV-2. These data indicate that cardiac glycosides may block viral penetration into the target cell by first inhibiting ACE2:RBD binding. Clinical concentrations of ouabain and digitoxin are relatively safe for short term use for subjects with normal hearts. It has therefore not escaped our attention that these common cardiac medications could be deployed worldwide as inexpensive repurposed drugs for anti-COVID-19 therapy.

Killing Two Birds with One Stone by Administration of Soluble ACE2: A Promising Strategy to Treat Both Cardiovascular Diseases and SARS-CoV-2 Infection

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters host cells mainly by the angiotensin converting enzyme 2 (ACE2) receptor, which can recognize the spike (S) protein by its extracellular domain. Previously, recombinant soluble ACE2 (sACE2) has been clinically used as a therapeutic treatment for cardiovascular diseases. Recent data demonstrated that sACE2 can also be exploited as a decoy to effectively inhibit the cell entry of SARS-CoV-2, through blocking SARS-CoV-2 binding to membrane-anchored ACE2. In this study, we summarized the current findings on the optimized sACE2-based strategies as a therapeutic agent, including Fc fusion to prolong the half-life of sACE2, deep mutagenesis to create high-affinity decoys for SARS-CoV-2, or designing the truncated functional fragments to enhance its safety, among others. Considering that COVID-19 patients are often accompanied by manifestations of cardiovascular complications, we think that administration of sACE2 in COVID-19 patients may be a promising therapeutic strategy to simultaneously treat both cardiovascular diseases and SARS-CoV-2 infection. This review would provide insights for the development of novel therapeutic agents against the COVID-19 pandemic.

Analysis of the Role of N-Linked Glycosylation in Cell Surface Expression, Function, and Binding Properties of SARS-CoV-2 Receptor ACE2

Human angiotensin I-converting enzyme 2 (hACE2) is a type I transmembrane glycoprotein that serves as the major cell entry receptor for SARS-CoV and SARS-CoV-2. The viral spike (S) protein is required for the attachment to ACE2 and subsequent virus-host cell membrane fusion. Previous work has demonstrated the presence of N-linked glycans in ACE2. N-glycosylation is implicated in many biological activities, including protein folding, protein activity, and cell surface expression of biomolecules. However, the contribution of N-glycosylation to ACE2 function is poorly understood. Here, we examined the role of N-glycosylation in the activity and localization of two species with different susceptibility to SARS-CoV-2 infection, porcine ACE2 (pACE2) and hACE2. The elimination of N-glycosylation by tunicamycin (TM) treatment, or mutagenesis, showed that N-glycosylation is critical for the proper cell surface expression of ACE2 but not for its carboxiprotease activity. Furthermore, nonglycosylable ACE2 was localized predominantly in the endoplasmic reticulum (ER) and not at the cell surface. Our data also revealed that binding of SARS-CoV or SARS-CoV-2 S protein to porcine or human ACE2 was not affected by deglycosylation of ACE2 or S proteins, suggesting that N-glycosylation does not play a role in the interaction between SARS coronaviruses and the ACE2 receptor. Impairment of hACE2 N-glycosylation decreased cell-to-cell fusion mediated by SARS-CoV S protein but not that mediated by SARS-CoV-2 S protein. Finally, we found that hACE2 N-glycosylation is required for an efficient viral entry of SARS-CoV/SARS-CoV-2 S pseudotyped viruses, which may be the result of low cell surface expression of the deglycosylated ACE2 receptor. IMPORTANCE Understanding the role of glycosylation in the virus-receptor interaction is important for developing approaches that disrupt infection. In this study, we showed that deglycosylation of both ACE2 and S had a minimal effect on the spike-ACE2 interaction. In addition, we found that the removal of N-glycans of ACE2 impaired its ability to support an efficient transduction of SARS-CoV and SARS-CoV-2 S pseudotyped viruses. Our data suggest that the role of deglycosylation of ACE2 on reducing infection is likely due to a reduced expression of the viral receptor on the cell surface. These findings offer insight into the glycan structure and function of ACE2 and potentially suggest that future antiviral therapies against coronaviruses and other coronavirus-related illnesses involving inhibition of ACE2 recruitment to the cell membrane could be developed.

Quantifying Renin-Angiotensin-System Alterations in COVID-19

The renin-angiotensin system (RAS) plays a pivotal role in a wide series of physiological processes, among which inflammation and blood pressure regulation. One of its key components, the angiotensin-converting enzyme 2, has been identified as the entry point of the SARS-CoV-2 virus into the host cells, and therefore a lot of research has been devoted to study RAS dysregulation in COVID-19. Here we discuss the alterations of the regulatory RAS axes due to SARS-CoV-2 infection on the basis of a series of recent clinical investigations and experimental analyzes quantifying, e.g., the levels and activity of RAS components. We performed a comprehensive meta-analysis of these data in view of disentangling the links between the impaired RAS functioning and the pathophysiological characteristics of COVID-19. We also review the effects of several RAS-targeting drugs and how they could potentially help restore the normal RAS functionality and minimize the COVID-19 severity. Finally, we discuss the conflicting evidence found in the literature and the open questions on RAS dysregulation in SARS-CoV-2 infection whose resolution would improve our understanding of COVID-19.