Disulfide Bond Engineering of Soluble ACE2 for Thermal Stability Enhancement.

Although the primary pandemic of SARS-CoV-2 is over, there are concerns about the resurgence of the next wave of related viruses, including a wide range of variant viruses. The soluble ACE2 (sACE2) inhibits the SARS-CoV-2 spike protein ACE2 interaction and has potential as a variant-independent therapeutic against SARS-CoV-2. Here, we introduce novel disulfide bonds in the wild-type sACE2-Fc by structure-guided mutagenesis, aiming to improve its stability. The stability of each mutant was assessed by a thermal shift assay to screen mutants with increased thermal stability. As a result, we identified a mutant sACE2-Fc with a significantly increased melting temperature. X-ray crystal structure determination of the sACE2 mutant confirmed the correct formation of the designed disulfide bond, and there were no significant structural disturbances. We also proved that the thermostable sACE2-Fc preserved the spike protein binding affinity comparable to the wild-type sACE2-Fc in both molecular and cellular environments, suggesting its therapeutic potential.

An ACE2-Based Bimodular Fusion Protein Enables Reorientation of Endogenous Anti-Epstein-Barr Virus Antibodies Toward SARS-CoV-2 Spike.

The use of soluble recombinant angiotensin-converting enzyme 2 (rACE2) as a decoy capable of blocking SARS-CoV-2 entry into cells has been envisaged as a therapeutic strategy to reduce viral loads in patients with severe COVID-19. We engineered a novel form of rACE2, fused to the Epstein-Barr virus antigen P18F3 (rACE2-P18F3), to reorient a preexisting humoral response toward Epstein-Barr virus against SARS-CoV-2 particles. Recombinant ACE2-P18F3 was able to bind to the SARS-CoV-2 spike protein, neutralize viral entry into cells, and promote the phagocytosis of spheres coated with different spike variants by monocytic cells. The results position rACE2-P18F3 as a promising therapeutic candidate to universally block coronavirus cell entry and clear viral particles.

Angiotensin converting enzyme 2 level and its significance in COVID-19 and other diseases patients.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) expressions and its modulation are of great interest as being a key receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) and the protective arm of the rennin-angiotensin axis, maintaining cardiovascular homeostasis. However, ACE2 expressions and their modulation in the healthy and disease background are yet to be explored. METHOD: We performed a meta-analysis, extracting the data for ACE2 expression in human subjects with various diseases, including SARS-CoV2 infection without or with co-morbidity. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed. Out of 203 studies, 39 met the inclusion criteria with SARS-CoV2 patients without co-morbidity, SARS-CoV2 patients with co-morbidity, cardiovascular (CVD) patients, diabetes patients, kidney disorders patients, pulmonary disease patients, and other viral infections patients. RESULTS: Angiotensin-converting enzyme 2 expression was significantly increased in all diseases. There was an elevated level of ACE2, especially membrane-bound ACE2, in COVID-19 patients compared to healthy controls. A statistically significant increase in ACE2 expression was observed in CVD patients and patients with other viral diseases compared to healthy subjects. Moreover, subgroup analysis of ACE2 expression as soluble and membrane-bound ACE2 revealed a remarkable increase in membrane-bound ACE2 in CVD patients, patients with viral infection compared to soluble ACE2 and pooled standard mean difference (SMD) with the random-effects model was 0.37 and 2.23 respectively. CONCLUSION: It was observed that utilizing the ACE2 by SARS-CoV2 for its entry and its consequence leads to several complications. So there is a need to investigate the underlying mechanism along with novel therapeutic strategies.

The collectrin-like part of the SARS-CoV-1 and -2 receptor ACE2 is shed by the metalloproteinases ADAM10 and ADAM17.

The transmembrane protease angiotensin converting enzyme 2 (ACE2) is a protective regulator within the renin angiotensin system and additionally represents the cellular receptor for SARS-CoV. The release of soluble ACE2 (sACE2) from the cell surface is hence believed to be a crucial part of its (patho)physiological functions, as both, ACE2 protease activity and SARS-CoV binding ability, are transferred from the cell membrane to body fluids. Yet, the molecular sources of sACE2 are still not completely investigated. In this study, we show different sources and prerequisites for the release of sACE2 from the cell membrane. By using inhibitors as well as CRISPR/Cas9-derived cells, we demonstrated that, in addition to the metalloprotease ADAM17, also ADAM10 is an important novel shedding protease of ACE2. Moreover, we observed that ACE2 can also be released in extracellular vesicles. The degree of either ADAM10- or ADAM17-mediated ACE2 shedding is dependent on stimulatory conditions and on the expression level of the pro-inflammatory ADAM17 regulator iRhom2. Finally, by using structural analysis and in vitro verification, we determined for the first time that the susceptibility to ADAM10- and ADAM17-mediated shedding is mediated by the collectrin-like part of ACE2. Overall, our findings give novel insights into sACE2 release by several independent molecular mechanisms.

Dietary fish intake increased the concentration of soluble ACE2 in rats: can fish consumption reduce the risk of COVID-19 infection through interception of SARS-CoV-2 by soluble ACE2?

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the cells after binding to the membrane-bound receptor angiotensin-converting enzyme 2 (ACE2), but this may be prevented through interception by soluble ACE2 (sACE2) or by inhibition of the ACE2 receptor, thus obstructing cell entry and replication. The main objective of this study was to investigate if fish intake affected the concentration of sACE2 in rats. The secondary aim was to evaluate the in vitro ACE2-inhibiting activity of fish proteins. Rats were fed cod muscle as 25 % of dietary protein, and blood was collected after 4 weeks of intervention. Muscle, backbone, skin, head, stomach, stomach content, intestine and swim bladder from haddock, saithe, cod and redfish were hydrolysed with trypsin before ACE2-inhibiting activity was measured in vitro. In vivo data were compared using unpaired Student's t test, and in vitro data were compared using one-way ANOVA followed by the Tukey HSD post hoc test. The mean sACE2 concentration was 47 % higher in rats fed cod when compared with control rats (P 0·034), whereas serum concentrations of angiotensin II and TNF-α were similar between the two experimental groups. Muscle, backbone, skin and head from all four fish species inhibited ACE2 activity in vitro, whereas the remaining fractions had no effect. To conclude, our novel data demonstrate that fish intake increased the sACE2 concentration in rats and that the hydrolysed fish proteins inhibited ACE2 activity in vitro.

Potential detrimental role of soluble ACE2 in severe COVID-19 comorbid patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the host cell by binding to angiotensin-converting enzyme 2 (ACE2) receptor. Other important proteins involved in this process include disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) also known as tumour necrosis factor-α-converting enzyme and transmembrane serine protease 2. ACE2 converts angiotensin II (Ang II) to angiotensin (1-7), to balance the renin angiotensin system. Membrane-bound ACE2 ectodomain shedding is mediated by ADAM17 upon viral spike binding, Ang II overproduction and in several diseases. The shed soluble ACE2 (sACE2) retains its catalytic activity, but its precise role in viral entry is still unclear. Therapeutic sACE2 is claimed to exert dual effects; reduction of excess Ang II and blocking viral entry by masking the spike protein. Nevertheless, the paradox is why SARS-CoV-2 comorbid patients struggle to attain such benefit in viral infection despite having a high amount of sACE2. In this review, we discuss the possible detrimental role of sACE2 and speculate on a series of events where protease primed or non-primed virus-sACE2 complex might enter the host cell. As extracellular virus can bind many sACE2 molecules, sACE2 level could be reduced drastically upon endocytosis by the host cell. A consequential rapid rise in Ang II level could potentially aggravate disease severity through Ang II-angiotensin II receptor type 1 (AT1R) axis in comorbid patients. Hence, monitoring sACE2 and Ang II level in coronavirus disease 2019 comorbid patients are crucial to ensure safe and efficient intervention using therapeutic sACE2 and vaccines.

A Novel Soluble ACE2 Variant with Prolonged Duration of Action Neutralizes SARS-CoV-2 Infection in Human Kidney Organoids.

BACKGROUND: There is an urgent need for approaches to prevent and treat SARS-CoV-2 infection. Administration of soluble ACE2 protein acting as a decoy to bind to SARS-CoV-2 should limit viral uptake mediated by binding to membrane-bound full-length ACE2, and further therapeutic benefit should result from ensuring enzymatic ACE2 activity to affected organs in patients with COVID-19. METHODS: A short variant of human soluble ACE2 protein consisting of 618 amino acids (hACE2 1-618) was generated and fused with an albumin binding domain (ABD) using an artificial gene encoding ABDCon, with improved albumin binding affinity. Human kidney organoids were used for infectivity studies of SARS-CoV-2 in a BSL-3 facility to examine the neutralizing effect of these novel ACE2 variants. RESULTS: Whereas plasma ACE2 activity of the naked ACE2 1-618 and ACE2 1-740 lasted about 8 hours, the ACE2 1-618-ABD resulted in substantial activity at 96 hours, and it was still biologically active 3 days after injection. Human kidney organoids express ACE2 and TMPRSS2, and when infected with SARS-CoV-2, our modified long-acting ACE2 variant neutralized infection. CONCLUSIONS: This novel ACE2 1-618-ABD can neutralize SARS-CoV-2 infectivity in human kidney organoids, and its prolonged duration of action should ensure improved efficacy to prevent viral escape and dosing convenience.

Soluble ACE2 as a potential therapy for COVID-19.

Soluble angiotensin-converting enzyme 2 (sACE2) could be a therapeutic option to treat coronavirus disease 2019 (COVID-19) infection. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) utilizes ACE2 receptors on cell surfaces to gain intracellular entry, making them an ideal target for therapy. High-affinity variants of sACE2, engineered using high-throughput mutagenesis, are capable of neutralizing COVID-19 infection as decoy receptors. These variants compete with native ACE2 present on cells by binding with spike (S) protein of SARS-CoV-2, making native ACE2 on cell surfaces available to convert angiotensin II to angiotensin-1,7, thus alleviating the exaggerated inflammatory response associated with COVID-19 infection. This article explores the use of sACE2 as potential therapy for COVID-19 infection.

The soluble catalytic ectodomain of ACE2 a biomarker of cardiac remodelling: new insights for heart failure and COVID19.

The angiotensin-converting enzyme 2 (ACE2) is a type I integral membrane that was discovered two decades ago. The ACE2 exists as a transmembrane protein and as a soluble catalytic ectodomain of ACE2, also known as the soluble ACE2 that can be found in plasma and other body fluids. ACE2 regulates the local actions of the renin-angiotensin system in cardiovascular tissues, and the ACE2/Angiotensin 1-7 axis exerts protective actions in cardiovascular disease. Increasing soluble ACE2 has been associated with heart failure, cardiovascular disease, and cardiac remodelling. This is a review of the molecular structure and biochemical functions of the ACE2, as well we provided an updated on the evidence, clinical applications, and emerging potential therapies with the ACE2 in heart failure, cardiovascular disease, lung injury, and COVID-19 infection.

Circulating Soluble ACE2 and Upstream microRNA Expressions in Serum of Type 2 Diabetes Mellitus Patients.

The global coronavirus disease 2019 (COVID-19) pandemic was associated with multiple organ failure and comorbidities, such as type 2 diabetes mellitus (T2DM). Risk factors, such as age, gender, and obesity, were associated with COVID-19 infection. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to use several host receptors for viral entry, such as angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) in the lung and other organs. However, ACE2 could be shed from the surface to be soluble ACE2 (sACE2) in the circulation. The epigenetic factors affecting ACE2 expression include a type of small non-coding RNAs called microRNAs (miRNAs). In this study, we aimed at exploring the status of the sACE2 as well as serum levels of several upstream novel miRNAs as non-invasive biomarkers that might have a potential role in T2DM patients. Serum samples were collected from 50 T2DM patients and 50 healthy controls, and sACE2 levels were quantified using enzyme-linked immunosorbent assay (ELISA). Also, RNA was extracted, and TaqMan miRNA reverse transcription quantitative PCR (RT-qPCR) was performed to measure serum miRNA levels. Our results revealed that sACE2 is decreased in the T2DM patients and is affected by age, gender, and obesity level. Additionally, 4 miRNAs, which are revealed by in silico analysis to be potentially upstream of ACE2 were detectable in the serum. Among them, miR-421 level was found to be decreased in the serum of diabetic patients, regardless of the presence or absence of diabetic complications, as well as being differential in various body mass index (BMI) groups. The other 3 miRNAs (miR-3909, miR-212-5p, and miR-4677-3p) showed associations with multiple factors including age, gender, BMI, and serum markers, in addition to being correlated to each other. In conclusion, our study reveals a decline in the circulating serum levels of sACE2 in T2DM patients and identified 4 novel miRNAs that were associated with T2DM, which are influenced by different clinical and demographic factors.

Angiotensin-converting enzyme 2 amplification limited to the circulation does not protect mice from development of diabetic nephropathy.

Blockers of the renin-angiotensin system are effective in the treatment of experimental and clinical diabetic nephropathy. An approach different from blocking the formation or action of angiotensin II (1-8) that could also be effective involves fostering its degradation. Angiotensin-converting enzyme 2 (ACE2) is a monocarboxypeptidase that cleaves angiotensin II (1-8) to form angiotensin (1-7). Therefore, we examined the renal effects of murine recombinant ACE2 in mice with streptozotocin-induced diabetic nephropathy as well as that of amplification of circulating ACE2 using minicircle DNA delivery prior to induction of experimental diabetes. This delivery resulted in a long-term sustained and profound increase in serum ACE2 activity and enhanced ability to metabolize an acute angiotensin II (1-8) load. In mice with streptozotocin-induced diabetes pretreated with minicircle ACE2, ACE2 protein in plasma increased markedly and this was associated with a more than 100-fold increase in serum ACE2 activity. However, minicircle ACE2 did not result in changes in urinary ACE2 activity as compared to untreated diabetic mice. In both diabetic groups, glomerular filtration rate increased significantly and to the same extent as compared to non-diabetic controls. Albuminuria, glomerular mesangial expansion, glomerular cellularity, and glomerular size were all increased to a similar extent in minicircle ACE2-treated and untreated diabetic mice, as compared to non-diabetic controls. Recombinant mouse ACE2 given for 4 weeks by intraperitoneal daily injections in mice with streptozotocin-induced diabetic nephropathy also failed to improve albuminuria or kidney pathology. Thus, a profound augmentation of ACE2 confined to the circulation failed to ameliorate the glomerular lesions and hyperfiltration characteristic of early diabetic nephropathy. These findings emphasize the importance of targeting the kidney rather than the circulatory renin angiotensin system to combat diabetic nephropathy.

Identification of antibody-resistant SARS-CoV-2 mutants via N4-Hydroxycytidine mutagenesis.

Monoclonal antibodies targeting the Spike protein of SARS-CoV-2 are effective against COVID-19 and might mitigate future pandemics. However, their efficacy is challenged by the emergence of antibody-resistant virus variants. We developed a method to efficiently identify such resistant mutants based on selection from mutagenized virus pools. By inducing mutations with the active compound of Molnupiravir, N4-hydroxycytidine (NHC), and subsequently passaging the virus in the presence of antibodies, we identified specific Spike mutations linked to resistance. Validation of these mutations was conducted using pseudotypes and immunofluorescence analysis. From a Wuhan-like strain of SARS-CoV-2, we identified the following mutations conferring strong resistance towards the corresponding antibodies: Bamlanivimab - E484K, F490S and S494P; Sotrovimab - E340K; Cilgavimab - K444R/E and N450D. From the Omicron B.1.1.529 variant, the strongly selected mutations were: Bebtelovimab - V445A; Sotrovimab - E340K and K356M; Cilgavimab - K444R, V445A and N450D. We also identified escape mutations in the Wuhan-like Spike for the broadly neutralizing antibodies S2K146 - combined G485S and Q493R - and S2H97 - D428G, K462E and S514F. Structural analysis revealed that the selected mutations occurred at antibody-binding residues within the receptor-binding domains of the Spike protein. Most of the selected mutants largely maintained ACE2 binding and infectivity. Notably, many of the identified resistance-conferring mutations are prevalent in real-world SARS-CoV-2 variants, but some of them (G485S, D428G, and K462E) have not yet been observed in circulating strains. Our approach offers a strategy for predicting the therapeutic efficacy of antibodies against emerging virus variants.

Determinants of soluble angiotensin-converting enzyme 2 concentrations in adult patients with complex congenital heart disease.

BACKGROUND: Angiotensin-converting enzyme (ACE) 2 is known to be a functional receptor for SARS-CoV-2 in the current pandemic. Soluble ACE2 (sACE2) concentrations are elevated in patients with various cardiovascular disorders including heart failure. METHODS: In a total of 182 consecutive adult patients with complex congenital heart disease (CHD) and 63 healthy controls, sACE2 concentrations were measured in serum using the Human ACE2® assay by Cloud-Clone Corporation and associated with clinical, laboratory and echocardiographic parameters. RESULTS: Median sACE2 levels were increased in patients with complex CHD as compared to healthy controls (761.9 pg/ml vs 365.2 pg/ml, p < 0.001). Moreover, sACE2 concentrations were significantly elevated in patients with a higher NYHA class ≥ III (1856.2 pg/ml vs 714.5 pg/ml in patients with NYHA class I/II, p < 0.001). Using linear regression analysis, higher sACE2 levels were associated with a higher NYHA class ≥ III, more severe CHD, a morphological left systemic ventricle, higher creatinine and the use of mineralocorticoid receptor antagonists (MRA) in the univariable model. The use of ACE inhibitors or angiotensin receptor blockers (ARB) was associated with lower sACE2 levels. In the multivariable model, higher sACE2 levels were independently associated with a higher NYHA class ≥ III (p = 0.002) and lower sACE2 levels with the use of ACE inhibitors or ARB (p = 0.001). CONCLUSION: Soluble ACE2 concentrations were significantly increased in all types of complex CHD with highest levels found in patients with NYHA class ≥ III. Moreover, a higher NYHA class ≥ III was the most significant determinant that was independently associated with elevated sACE2 concentrations.

Engineered small extracellular vesicles displaying ACE2 variants on the surface protect against SARS-CoV-2 infection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry is mediated by the interaction of the viral spike (S) protein with angiotensin-converting enzyme 2 (ACE2) on the host cell surface. Although a clinical trial testing soluble ACE2 (sACE2) for COVID-19 is currently ongoing, our understanding of the delivery of sACE2 via small extracellular vesicles (sEVs) is still rudimentary. With excellent biocompatibility allowing for the effective delivery of molecular cargos, sEVs are broadly studied as nanoscale protein carriers. In order to exploit the potential of sEVs, we design truncated CD9 scaffolds to display sACE2 on the sEV surface as a decoy receptor for the S protein of SARS-CoV-2. Moreover, to enhance the sACE2-S binding interaction, we employ sACE2 variants. sACE2-loaded sEVs exhibit typical sEVs characteristics and bind to the S protein. Furthermore, engineered sEVs inhibit the entry of wild-type (WT), the globally dominant D614G variant, Beta (K417N-E484K-N501Y) variant, and Delta (L452R-T478K-D614G) variant SARS-CoV-2 pseudovirus, and protect against authentic SARS-CoV-2 and Delta variant infection. Of note, sACE2 variants harbouring sEVs show superior antiviral efficacy than WT sACE2 loaded sEVs. Therapeutic efficacy of the engineered sEVs against SARS-CoV-2 challenge was confirmed using K18-hACE2 mice. The current findings provide opportunities for the development of new sEVs-based antiviral therapeutics.

Rapid Generation of Circulating and Mucosal Decoy Human ACE2 using mRNA Nanotherapeutics for the Potential Treatment of SARS-CoV-2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause lethal pulmonary damage in humans. It contains spike proteins on its envelope that bind to human angiotensin-converting enzyme 2 (hACE2) expressed on airway cells, enabling entry of the virus, and causing infection. The soluble form of hACE2 binds SARS-CoV-2 spike protein, prevents viral entry into target cells, and ameliorates lung injury; however, its short half-life limits therapeutic utilities. Here, synthetic mRNA is engineered to encode a soluble form of hACE2 (hsACE2) to prevent viral infection. A novel lipid nanoparticle (LNP) is used for packaging and delivering mRNA to cells to produce hsACE2 proteins. Intravenously administered LNP delivers mRNA to hepatocytes, leading to the production of circulatory hsACE2 initiated within 2 h and sustained over several days. Inhaled LNP results in lung transfection and secretion of mucosal hsACE2 to lung epithelia, the primary site of entry and pathogenesis for SARS-CoV-2. Furthermore, mRNA-generated hsACE2 binds to the receptor-binding domain of the viral spike protein. Finally, hsACE2 effectively inhibits SARS-CoV-2 and its pseudoviruses from infecting host cells. The proof of principle study shows that mRNA-based nanotherapeutics can be potentially deployed to neutralize SARS-CoV-2 and open new treatment opportunities for coronavirus disease 2019 (COVID-19).

Soluble ACE2 Is Filtered into the Urine.

Background: ACE2 is a key enzyme in the renin-angiotensin system (RAS) capable of balancing the RAS by metabolizing angiotensin II (AngII). First described in cardiac tissue, abundance of ACE2 is highest in the kidney, and it is also expressed in several extrarenal tissues. Previously, we reported an association between enhanced susceptibility to hypertension and elevated renal AngII levels in global ACE2-knockout mice. Methods: To examine the effect of ACE2 expressed in the kidney, relative to extrarenal expression, on the development of hypertension, we used a kidney crosstransplantation strategy with ACE2-KO and WT mice. In this model, both native kidneys are removed and renal function is provided entirely by the transplanted kidney, such that four experimental groups with restricted ACE2 expression are generated: WT→WT (WT), KO→WT (KidneyKO), WT→KO (SystemicKO), and KO→KO (TotalKO). Additionally, we used nanoscale mass spectrometry-based proteomics to identify ACE2 fragments in early glomerular filtrate of mice. Results: Although significant differences in BP were not detected, a major finding of our study is that shed or soluble ACE2 (sACE2) was present in urine of KidneyKO mice that lack renal ACE2 expression. Detection of sACE2 in the urine of KidneyKO mice during AngII-mediated hypertension suggests that sACE2 originating from extrarenal tissues can reach the kidney and be excreted in urine. To confirm glomerular filtration of ACE2, we used micropuncture and nanoscale proteomics to detect peptides derived from ACE2 in the Bowman's space. Conclusions: Our findings suggest that both systemic and renal tissues may contribute to sACE2 in urine, identifying the kidney as a major site for ACE2 actions. Moreover, filtration of sACE2 into the lumen of the nephron may contribute to the pathophysiology of kidney diseases characterized by disruption of the glomerular filtration barrier.

Higher Soluble ACE2 Levels and Increased Risk of Infection-Related Hospitalization in Patients on Maintenance Hemodialysis.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) works as an endogenous counter-regulator of the renin-angiotensin system, which has pivotal roles in preventing both cardiovascular disease (CVD) and inflammation. In general populations, higher plasma soluble ACE2 levels were reported to be associated with increased risks of all-cause death and major CVD. Because infections are fatal in patients on maintenance hemodialysis, we aimed to explore whether soluble ACE2 levels are associated with an increased risk of infection-related hospitalization in these patients. METHODS: Using data from a prospective, multicenter, cohort study conducted in Tokyo, Japan, we performed a post-hoc analyses of 724 clinically stable patients on maintenance hemodialysis. We measured baseline serum soluble ACE2 levels and assessed potential determinants of its with infection-related hospitalization as a primary outcome as well as all-cause death and CVD as secondary outcomes using a Cox proportional hazards model. RESULTS: The soluble ACE2 level (median, 0.16 ng/ml; interquartile range, 0.07-0.57 ng/ml) showed a weak negative association with age. During a median follow-up of 39 months, 106 patients (14.6%) were hospitalized with infectious diseases. Compared with the lower half of soluble ACE2 levels, the higher half was associated with an increased risk of infection-related hospitalization (hazard ratio, 1.57; 95% confidence interval, 1.02-2.41) with adjustment by other risk factors. On the other hand, there were no significant associations between soluble ACE2 and risks of all-cause death and CVD. CONCLUSION: Higher soluble ACE2 levels may associate with an increased risk of infection-related hospitalization in patients on maintenance hemodialysis.

ACE2 is the critical in vivo receptor for SARS-CoV-2 in a novel COVID-19 mouse model with TNF- and IFNγ-driven immunopathology.

Despite tremendous progress in the understanding of COVID-19, mechanistic insight into immunological, disease-driving factors remains limited. We generated maVie16, a mouse-adapted SARS-CoV-2, by serial passaging of a human isolate. In silico modeling revealed how only three Spike mutations of maVie16 enhanced interaction with murine ACE2. maVie16 induced profound pathology in BALB/c and C57BL/6 mice, and the resulting mouse COVID-19 (mCOVID-19) replicated critical aspects of human disease, including early lymphopenia, pulmonary immune cell infiltration, pneumonia, and specific adaptive immunity. Inhibition of the proinflammatory cytokines IFNγ and TNF substantially reduced immunopathology. Importantly, genetic ACE2-deficiency completely prevented mCOVID-19 development. Finally, inhalation therapy with recombinant ACE2 fully protected mice from mCOVID-19, revealing a novel and efficient treatment. Thus, we here present maVie16 as a new tool to model COVID-19 for the discovery of new therapies and show that disease severity is determined by cytokine-driven immunopathology and critically dependent on ACE2 in vivo.

Concentrations of Soluble Angiotensin Converting Enzyme 2 (sACE2) in Children and Adults with and without COVID-19.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing the coronavirus disease 2019 (COVID-19) pandemic, leads to illness and death. Various risk factors for a severe course, such as higher age, male gender and pre-existing illnesses are known. However, pathophysiological risk factors are largely unclear. Notably, the mild course of disease in children is conspicuous. Angiotensin converting enzyme 2 (ACE2) serves as a receptor for SARS-CoV-2 and is a key enzyme in infection. Differences in the distribution of ACE2 can provide insights into different courses of COVID-19. Our aim was to elucidate the role of ACE2 as a pathophysiological risk factor by measuring soluble ACE2 (sACE2) via ELISA in blood samples (lithium-heparin-plasma or serum) of 367 individuals including children and adults with and without COVID-19. sACE2-levels were compared between the groups according to age and sex. In adults and children with COVID-19, sACE2-concentrations are significantly higher compared to healthy individuals. sACE2-levels increase with age and are lower in children compared to adults with COVID-19. Sex doesn't significantly influence sACE2-concentration. It remains unclear whether sACE2 concentrations increase because of the infection and what factors could influence this response. In conclusion, the increase of sACE2-concentration with age could indicate that ACE2 concentrations mirror increased COVID-19 severity.