Interferons and viruses induce a novel primate-specific isoform dACE2 and not the SARS-CoV-2 receptor ACE2

The systemic renin-angiotensin system in COVID-19

SARS-CoV-2 gains cell entry via angiotensin-converting enzyme (ACE) 2, a membrane-bound enzyme of the "alternative" (alt) renin-angiotensin system (RAS). ACE2 counteracts angiotensin II by converting it to potentially protective angiotensin 1-7. Using mass spectrometry, we assessed key metabolites of the classical RAS (angiotensins I-II) and alt-RAS (angiotensins 1-7 and 1-5) pathways as well as ACE and ACE2 concentrations in 159 patients hospitalized with COVID-19, stratified by disease severity (severe, n = 76; non-severe: n = 83). Plasma renin activity (PRA-S) was calculated as the sum of RAS metabolites. We estimated ACE activity using the angiotensin II:I ratio (ACE-S) and estimated systemic alt-RAS activation using the ratio of alt-RAS axis metabolites to PRA-S (ALT-S). We applied mixed linear models to assess how PRA-S and ACE/ACE2 concentrations affected ALT-S, ACE-S, and angiotensins II and 1-7. Median angiotensin I and II levels were higher with severe versus non-severe COVID-19 (angiotensin I: 86 versus 30 pmol/L, p < 0.01; angiotensin II: 114 versus 58 pmol/L, p < 0.05), demonstrating activation of classical RAS. The difference disappeared with analysis limited to patients not taking a RAS inhibitor (angiotensin I: 40 versus 31 pmol/L, p = 0.251; angiotensin II: 76 versus 99 pmol/L, p = 0.833). ALT-S in severe COVID-19 increased with time (days 1-6: 0.12; days 11-16: 0.22) and correlated with ACE2 concentration (r = 0.831). ACE-S was lower in severe versus non-severe COVID-19 (1.6 versus 2.6; p < 0.001), but ACE concentrations were similar between groups and correlated weakly with ACE-S (r = 0.232). ACE2 and ACE-S trajectories in severe COVID-19, however, did not differ between survivors and non-survivors. Overall RAS alteration in severe COVID-19 resembled severity of disease-matched patients with influenza. In mixed linear models, renin activity most strongly predicted angiotensin II and 1-7 levels. ACE2 also predicted angiotensin 1-7 levels and ALT-S. No single factor or the combined model, however, could fully explain ACE-S. ACE2 and ACE-S trajectories in severe COVID-19 did not differ between survivors and non-survivors. In conclusion, angiotensin II was elevated in severe COVID-19 but was markedly influenced by RAS inhibitors and driven by overall RAS activation. ACE-S was significantly lower with severe COVID-19 and did not correlate with ACE concentrations. A shift to the alt-RAS axis because of increased ACE2 could partially explain the relative reduction in angiotensin II levels.

Interferon-Lambda Intranasal Protection and Differential Sex Pathology in a Murine Model of SARS-CoV-2 Infection

Outbreaks of emerging viral pathogens like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are a major medical challenge. There is a pressing need for antivirals that can be rapidly deployed to curb infection and dissemination. We determined the efficacy of interferon lambda-1 (IFN-λ) as a broad-spectrum antiviral agent to inhibit SARS-CoV-2 infection and reduce pathology in a mouse model of disease. IFN-λ significantly limited SARS-CoV-2 production in primary human bronchial epithelial cells in culture. Pretreatment of human lung cells with IFN-λ completely blocked infectious virus production, and treatment with IFN-λ at the time of infection inhibited virus production more than 10-fold. To interrogate the protective effects of IFN-λ in response to SARS-CoV-2 infection, transgenic mice expressing the human angiotensin-converting enzyme 2 (ACE-2) were tested. One dose of IFN-λ administered intranasally was found to reduce animal morbidity and mortality. Our study with SARS-CoV-2 also revealed a sex differential in disease outcome. Male mice had higher mortality, reflecting the more severe symptoms and mortality found in male patients infected with SARS-CoV-2. The results indicate that IFN-λ potentially can treat early stages of SARS-CoV-2 infection and decrease pathology, and this murine model can be used to investigate the sex differential documented in COVID-19. IMPORTANCE The COVID-19 pandemic has claimed millions of lives worldwide. In this report, we used a preclinical mouse model to investigate the prophylactic and therapeutic value of intranasal IFN-λ for this acute respiratory disease. Specific vaccines have been responsible for curbing the transmission of SARS-CoV-2 in developed nations. However, vaccines require time to generate and keep pace with antigenic variants. There is a need for broad-spectrum prophylactic and therapeutic agents to combat new emerging viral pathogens. Our mouse model suggests IFN-λ has clinical utility, and it reflects the well-documented finding that male COVID-19 patients manifest more severe symptoms and mortality. Understanding this sex bias is critical for considering therapeutic approaches to COVID-19.

Effective Prophylaxis of COVID-19 in Rhesus Macaques Using a Combination of Two Parenterally-Administered SARS-CoV-2 Neutralizing Antibodies

SARS-CoV-2 is a respiratory borne pathogenic beta coronavirus that is the source of a worldwide pandemic and the cause of multiple pathologies in man. The rhesus macaque model of COVID-19 was utilized to test the added benefit of combinatory parenteral administration of two high-affinity anti-SARS-CoV-2 monoclonal antibodies (mAbs; C144-LS and C135-LS) expressly developed to neutralize the virus and modified to extend their pharmacokinetics. After completion of kinetics study of mAbs in the primate, combination treatment was administered prophylactically to mucosal viral challenge. Results showed near complete virus neutralization evidenced by no measurable titer in mucosal tissue swabs, muting of cytokine/chemokine response, and lack of any discernable pathologic sequalae. Blocking infection was a dose-related effect, cohorts receiving lower doses (6, 2 mg/kg) resulted in low grade viral infection in various mucosal sites compared to that of a fully protective dose (20 mg/kg). A subset of animals within this cohort whose infectious challenge was delayed 75 days later after mAb administration were still protected from disease. Results indicate this combination mAb effectively blocks development of COVID-19 in the rhesus disease model and accelerates the prospect of clinical studies with this effective antibody combination.

Expression of the SARS-CoV-2 receptorACE2 in human heart is associated with uncontrolled diabetes, obesity, and activation of the renin angiotensin system

Background

Diabetic and obese patients are at higher risk of severe disease and cardiac injury in corona virus 2 (SARS-CoV-2) infections. Cellular entry of SARS-CoV-2 is mainly via the angiotensin-converting enzyme 2 (ACE2) receptor, which is highly expressed in normal hearts. There is a disagreement regarding the effect of factors such as obesity and diabetes on ACE2 expression in the human heart and whether treatment with renin–angiotensin system inhibitors or anti-diabetic medications increases ACE2 expression and subsequently the susceptibility to infection. We designed this study to elucidate factors that control ACE2 expression in human serum, human heart biopsies, and mice.

Methods

Right atrial appendage biopsies were collected from 79 patients that underwent coronary artery bypass graft (CABG) surgery. We investigated the alteration in ACE2 mRNA and protein expression in heart tissue and serum. ACE2 expression was compared with clinical risk factors: diabetes, obesity and different anti-hypertensive or anti-diabetic therapies. WT or db/db mice were infused with Angiotensin II (ATII), treated with different anti-diabetic drugs (Metformin, GLP1A and SGLT2i) were also tested.

Results

ACE2 gene expression was increased in diabetic hearts compared to non-diabetic hearts and was positively correlated with glycosylated hemoglobin (HbA1c), body mass index (BMI), and activation of the renin angiotensin system (RAS), and negatively correlated with ejection fraction. ACE2 was not differentially expressed in patients who were on angiotensin converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) prior to the operation. We found no correlation between plasma free ACE2 and cardiac tissue ACE2 expression. Transmembrane serine protease 2 (TMPRSS2), metalloprotease ADAM10 and ADAM17 that facilitate viral-ACE2 complex entry and degradation were increased in diabetic hearts. ACE2 expression in mice was increased with ATII infusion and attenuated following anti-diabetic drugs treatment.

Conclusion

Patients with uncontrolled diabetes or obesity with RAS activation have higher ACE2 expressions therefore are at higher risk for severe infection. Since ACEi or ARBs show no effect on ACE2 expression in the heart further support their safety.

Immune response to SARS-CoV-2 in the nasal mucosa in children and adults

RATIONALE

Despite similar viral load and infectivity rates between children and adults infected with SARS-CoV-2, children rarely develop severe illness. Differences in the host response to the virus at the primary infection site are among the proposed mechanisms.

OBJECTIVES

To investigate the host response to SARS-CoV-2, respiratory syncytial virus (RSV), and influenza virus (IV) in the nasal mucosa in children and adults.

METHODS

Clinical outcomes and gene expression in the nasal mucosa were analyzed in 36 children hospitalized with SARS-CoV-2 infection, 24 children with RSV infection, 9 children with IV infection, 16 adults with mild to moderate SARS-CoV-2 infection, and 7 healthy pediatric and 13 healthy adult controls.

RESULTS

In both children and adults, infection with SARS-CoV-2 leads to an interferon response in the nasal mucosa. The magnitude of the interferon response correlated with the abundance of viral reads and was comparable between symptomatic children and adults infected with SARS-CoV-2 and symptomatic children infected with RSV and IV. Cell type deconvolution identified an increased abundance of immune cells in the samples from children and adults with a viral infection. Expression of ACE2 and TMPRSS2 - key entry factors for SARS-CoV-2 - did not correlate with age or presence or absence of viral infection.

CONCLUSIONS

Our findings support the hypothesis that differences in the immune response to SARS-CoV-2 determine disease severity, independent of viral load and interferon response at the primary infection primary site.

Nucleic Acid-Sensing Pathways During SARS-CoV-2 Infection: Expectations versus Reality

The coronavirus disease 2019 (COVID-19) pandemic has affected millions of people and crippled economies worldwide. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for this pandemic has triggered avid research on its pathobiology to better understand the pathophysiology of COVID-19. In the absence of approved antiviral therapeutic strategies or vaccine platforms capable of effectively targeting this global threat, the hunt for effective therapeutics has led to many candidates being actively evaluated for their efficacy in controlling or preventing COVID-19. In this review, we gathered current evidence on the innate nucleic acid-sensing pathways expected to be elicited by SARS-CoV-2 and the immune evasion mechanisms they have developed to promote viral replication and infection. Within the nucleic acid-sensing pathways, SARS-CoV-2 infection and evasion mechanisms trigger the activation of NOD-signaling and NLRP3 pathways leading to the production of inflammatory cytokines, IL-1β and IL-6, while muting or blocking cGAS-STING and interferon type I and III pathways, resulting in decreased production of antiviral interferons and delayed innate response. Therefore, blocking the inflammatory arm and boosting the interferon production arm of nucleic acid-sensing pathways could facilitate early control of viral replication and dissemination, prevent disease progression, and cytokine storm development. We also discuss the rationale behind therapeutic modalities targeting these sensing pathways and their implications in the treatment of COVID-19.

Genetic Dissection of the Regulatory Mechanisms of Ace2 in the Infected Mouse Lung

Acute lung injury (ALI) is an important cause of morbidity and mortality after viral infections, including influenza A virus H1N1, SARS-CoV, MERS-CoV, and SARS-CoV-2. The angiotensin I converting enzyme 2 (ACE2) is a key host membrane-bound protein that modulates ALI induced by viral infection, pulmonary acid aspiration, and sepsis. However, the contributions of ACE2 sequence variants to individual differences in disease risk and severity after viral infection are not understood. In this study, we quantified H1N1 influenza-infected lung transcriptomes across a family of 41 BXD recombinant inbred strains of mice and both parents—C57BL/6J and DBA/2J. In response to infection Ace2 mRNA levels decreased significantly for both parental strains and the expression levels was associated with disease severity (body weight loss) and viral load (expression levels of viral NA segment) across the BXD family members. Pulmonary RNA-seq for 43 lines was analyzed using weighted gene co-expression network analysis (WGCNA) and Bayesian network approaches. Ace2 not only participated in virus-induced ALI by interacting with TNF, MAPK, and NOTCH signaling pathways, but was also linked with high confidence to gene products that have important functions in the pulmonary epithelium, including Rnf128, Muc5b, and Tmprss2. Comparable sets of transcripts were also highlighted in parallel studies of human SARS-CoV-infected primary human airway epithelial cells. Using conventional mapping methods, we determined that weight loss at two and three days after viral infection maps to chromosome X—the location of Ace2. This finding motivated the hierarchical Bayesian network analysis, which defined molecular endophenotypes of lung infection linked to Ace2 expression and to a key disease outcome. Core members of this Bayesian network include Ace2, Atf4, Csf2, Cxcl2, Lif, Maml3, Muc5b, Reg3g, Ripk3, and Traf3. Collectively, these findings define a causally-rooted Ace2 modulatory network relevant to host response to viral infection and identify potential therapeutic targets for virus-induced respiratory diseases, including those caused by influenza and coronaviruses.

STAT2 signaling restricts viral dissemination but drives severe pneumonia in SARS-CoV-2 infected hamsters

Emergence of SARS-CoV-2 causing COVID-19 has resulted in hundreds of thousands of deaths. In search for key targets of effective therapeutics, robust animal models mimicking COVID-19 in humans are urgently needed. Here, we show that Syrian hamsters, in contrast to mice, are highly permissive to SARS-CoV-2 and develop bronchopneumonia and strong inflammatory responses in the lungs with neutrophil infiltration and edema, further confirmed as consolidations visualized by micro-CT alike in clinical practice. Moreover, we identify an exuberant innate immune response as key player in pathogenesis, in which STAT2 signaling plays a dual role, driving severe lung injury on the one hand, yet restricting systemic virus dissemination on the other. Our results reveal the importance of STAT2-dependent interferon responses in the pathogenesis and virus control during SARS-CoV-2 infection and may help rationalizing new strategies for the treatment of COVID-19 patients.

Discovery and characterization of ACE2 - a 20-year journey of surprises from vasopeptidase to COVID-19

Angiotensin-converting enzyme (ACE) is a zinc membrane metallopeptidase that plays a key role in regulating vasoactive peptide levels and hence cardiovascular activity through its conversion of angiotensin I (Ang I) to Ang II and its metabolism of bradykinin. The discovery of its homologue, ACE2, 20 years ago has led to intensive comparisons of these two enzymes revealing surprising structural, catalytic and functional distinctions between them. ACE2 plays multiple roles not only as a vasopeptidase but also as a regulator of amino acid transport and serendipitously as a viral receptor, mediating the cellular entry of the coronaviruses causing severe acute respiratory syndrome (SARS) and, very recently, COVID-19. Catalytically, ACE2 functions as a monocarboxypeptidase principally converting the vasoconstrictor angiotensin II to the vasodilatory peptide Ang-(1-7) thereby counterbalancing the action of ACE on the renin-angiotensin system (RAS) and providing a cardioprotective role. Unlike ACE, ACE2 does not metabolise bradykinin nor is it inhibited by classical ACE inhibitors. However, it does convert a number of other regulatory peptides in vitro and in vivo. Interest in ACE2 biology and its potential as a possible therapeutic target has surged in recent months as the COVID-19 pandemic rages worldwide. This review highlights the surprising discoveries of ACE2 biology during the last 20 years, its distinctions from classical ACE and the therapeutic opportunities arising from its multiple biological roles.

Expression of SARS-CoV-2 entry receptors in the respiratory tract of healthy individuals, smokers and asthmatics

SARS-CoV-2 is causing a pandemic with currently > 29 million confirmed cases and > 900,000 deaths worldwide. The locations and mechanisms of virus entry into the human respiratory tract are incompletely characterized. We analyzed publicly available RNA microarray datasets for SARS-CoV-2 entry receptors and cofactors ACE2, TMPRSS2, BSG (CD147) and FURIN. We found that ACE2 and TMPRSS2 are upregulated in the airways of smokers. In asthmatics, ACE2 tended to be downregulated in nasal epithelium, and TMPRSS2 was upregulated in the bronchi. Furthermore, respiratory epithelia were negative for ACE-2 and TMPRSS2 protein expression while positive for BSG and furin, suggesting a possible alternative entry route for SARS-CoV-2.