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

Update on the measurement of "soluble angiotensin converting enzyme 2" in plasma and its emerging significance as a novel biomarker of cardiovascular and kidney diseases: A concise commentary

Angiotensin Converting Enzyme 2 has emerged as a major cell-surface enzyme receptor for controlling the Renin-Angiotensin-Aldosterone-System. The SARS-Cov-2 pandemics has focused a major interest on that cell-surface receptor. It is the virus entry door for cell infection, and when inside it can replicate and lead to cell destruction. In some physio-pathological conditions, ADAM 17 and TMPSSR2 enzymes can cleave ACE2 on the cell surface and release its extra-cellular domain into the blood circulation. Measurement of this soluble protein then becomes possible, preferentially in plasma, but also in serum. Clinical studies have shown that Soluble ACE2 is an emerging biomarker for cardiovascular and kidney diseases and it could be of prognostic value for heart failure and kidney dysfunctions. In Covid-19 its diagnostic value is controversial, and the various studies lead to different conclusions. Many laboratory assays have been reported for the measurement of this biomarker. They concern enzymatic assays, aptamer methods, or immunoassays, either chemiluminescent or ELISA. Normal and pathological plasma concentrations reported with the various assays yet lack standardization and are very heterogenous. Recently introduced immunoassays tend to yield more compliant results despite variations due to the assay design and calibration, or the antibody targeted epitopes and reactivity. This article reports an ELISA designed with affinity purified rabbit polyclonal antibodies, obtained with recombinant ACE2 and calibrated with the recombinant protein in plasma. This assay has a global reactivity with the various ACE2 protein epitopes. Assay performance characteristics, and values measured in normal populations are presented. Availability of optimized ELISAs can contribute to a better harmonization of sACE2 measurements in plasma, and confirm its clinical significance as biomarker.

Targeting SARS-CoV-2 and host cell receptor interactions

Despite the availability of vaccines and therapeutics, continual genetic alterations render the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) a persistent threat, particularly for the immunocompromised and elderly. Through interactions of its spike (S) protein with different receptors and coreceptors on host cell surfaces, the virus enters the cell either via fusion with the plasma membrane or through endocytosis. Angiotensin-converting enzyme 2 (ACE2) has been identified as a key receptor utilized by SARS-CoV-2 and related human coronaviruses to mediate cell entry in the lung airways. Auxiliary SARS-CoV-2 entry receptors such as ASGPR1, Kremen protein 1, integrins have also been reported. In this review, therapeutic approaches to block SARS-CoV-2 and host cell receptor interactions are discussed.

S Protein, ACE2 and Host Cell Proteases in SARS-CoV-2 Cell Entry and Infectivity; Is Soluble ACE2 a Two Blade Sword? A Narrative Review

Since the spread of the deadly virus SARS-CoV-2 in late 2019, researchers have restlessly sought to unravel how the virus enters the host cells. Some proteins on each side of the interaction between the virus and the host cells are involved as the major contributors to this process: (1) the nano-machine spike protein on behalf of the virus, (2) angiotensin converting enzyme II, the mono-carboxypeptidase and the key component of renin angiotensin system on behalf of the host cell, (3) some host proteases and proteins exploited by SARS-CoV-2. In this review, the complex process of SARS-CoV-2 entrance into the host cells with the contribution of the involved host proteins as well as the sequential conformational changes in the spike protein tending to increase the probability of complexification of the latter with angiotensin converting enzyme II, the receptor of the virus on the host cells, are discussed. Moreover, the release of the catalytic ectodomain of angiotensin converting enzyme II as its soluble form in the extracellular space and its positive or negative impact on the infectivity of the virus are considered.

Rational design of AAVrh10-vectored ACE2 functional domain to broadly block the cell entry of SARS-CoV-2 variants

The frequently emerging SARS-CoV-2 variants have weakened the effectiveness of existing COVID-19 vaccines and neutralizing antibody therapy. Nevertheless, the infections of SARS-CoV-2 variants still depend on angiotensin-converting enzyme 2 (ACE2) receptor-mediated cell entry, and thus the soluble human ACE2 (shACE2) is a potential decoy for broadly blocking SARS-CoV-2 variants. In this study, we firstly generated the recombinant AAVrh10-vectored shACE2 constructs, a kind of adeno-associated virus (AAV) serotype with pulmonary tissue tropism, and then validated its inhibition capacity against SARS-CoV-2 infection. To further optimize the minimized ACE2 functional domain candidates, a comprehensive analysis was performed to clarify the interactions between the ACE2 orthologs from various species and the receptor binding domain (RBD) of SARS-CoV-2 spike (S) protein. Based on the key interface amino acids, we designed a series of truncated ACE2 orthologs, and then assessed their potential affinity to bind to SARS-CoV-2 variants RBD in silico. Of note, we found that the 24-83aa fragment of dog ACE2 (dACE2_24-83) had a higher affinity to the RBD of SARS-CoV-2 variants than that of human ACE2. Importantly, AAVrh10-vectored shACE2 or dACE2_24-83 constructs exhibited a broadly blockage breadth against SARS-CoV-2 prototype and variants in vitro and ex vivo. Collectively, these data highlighted a promising therapeutic strategy against SARS-CoV-2 variants.

COVID-19 therapies: do we see substantial progress?

The appearance of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its spread all over the world is the cause of the coronavirus disease 2019 (COVID-19) pandemic, which has recently resulted in almost 400 million confirmed cases and 6 million deaths, not to mention unknown long-term or persistent side effects in convalescent individuals. In this short review, we discuss approaches to treat COVID-19 that are based on current knowledge of the mechanisms of viral cell receptor recognition, virus-host membrane fusion, and inhibition of viral RNA and viral assembly. Despite enormous progress in antiviral therapy and prevention, new effective therapies are still in great demand.