S19W, T27W, and N330Y mutations in ACE2 enhance SARS-CoV-2 S-RBD binding toward both wild-type and antibody-resistant viruses and its molecular basis

SARS-CoV-2 recognizes, via its spike receptor-binding domain (S-RBD), human angiotensin-converting enzyme 2 (ACE2) to initiate infection. Ecto-domain protein of ACE2 can therefore function as a decoy. Here we show that mutations of S19W, T27W, and N330Y in ACE2 could individually enhance SARS-CoV-2 S-RBD binding. Y330 could be synergistically combined with either W19 or W27, whereas W19 and W27 are mutually unbeneficial. The structures of SARS-CoV-2 S-RBD bound to the ACE2 mutants reveal that the enhanced binding is mainly contributed by the van der Waals interactions mediated by the aromatic side-chains from W19, W27, and Y330. While Y330 and W19/W27 are distantly located and devoid of any steric interference, W19 and W27 are shown to orient their side-chains toward each other and to cause steric conflicts, explaining their incompatibility. Finally, using pseudotyped SARS-CoV-2 viruses, we demonstrate that these residue substitutions are associated with dramatically improved entry-inhibition efficacy toward both wild-type and antibody-resistant viruses. Taken together, our biochemical and structural data have delineated the basis for the elevated S-RBD binding associated with S19W, T27W, and N330Y mutations in ACE2, paving the way for potential application of these mutants in clinical treatment of COVID-19.

Heparan Sulfate Binding Cationic Peptides Restrict SARS-CoV-2 Entry

A novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic. While the world is striving for a treatment modality against SARS-CoV-2, our understanding about the virus entry mechanisms may help to design entry inhibitors, which may help to limit the virus spreading. Owing to the importance of cellular ACE2 and heparan sulfate in SARS-CoV-2 entry, we aimed to evaluate the efficacy of cationic G1 and G2 peptides in virus entry inhibition. In silico binding affinity studies revealed possible binding sites of G1 and G2 peptides on HS and ACE2, which are required for the spike–HS and spike–ACE2 interactions. Prophylactic treatment of G1 and G2 peptide was also proved to decrease the cell surface HS, an essential virus entry receptor. With these two mechanisms we confirm the possible use of cationic peptides to inhibit the entry of SARS-CoV-2.

Synthesis and In Vitro Anti-HCV and Antitumor Evaluation of Schisan-dronic acid derivatives

Background: Schisandronic acid (SA), a triterpenoid from fruits of Schisandra sphenanthera, inhibited pan-genotypic HCV entry into human hepatocytes by interfering with virion-cell membrane fusion. It was a promising lead compound for development of novel HCV entry inhibition agents. Objective: To search for compounds with more potent anti-HCV and antitumor activities and explore SARs, a series of nov-el derivatives of SA were designed and synthesized and evaluated for in vitro their anti-HCV and antitumor activities. Methods: SA derivatives were synthesized by reduction, condensation, esterification or amidation. The anti-HCV activity of title compounds was tested by inhibition on HCVcc infection of Huh7 cells, and preliminary MOA study was conducted by determining inhibition on HCVpp entry into Huh7 cells. The antitumor activity in vitro was determined by MTT methods. Results: Totally 24 novel derivatives were synthesized. Most of the compounds inhibited HCVcc infection. Compounds 5hand 6 showed most potent anti-HCVcc activities and inhibition of HCVpp entry into Huh7 cells without obvious cytotoxici-ty. Most of title compounds showed potent in vitro antitumor activities against Bel7404 and SMMC7721 tumor cell lines. Compounds 5j and 6 exhibited more potent antitumor activity than positive controlSA and DOX. Conclusion: Structural modification of SA could lead to the discovery of potent anti-HCV or antitumor agents. Compounds 5h, 5j and 6 werepromising lead compounds development of novel HCV entry inhibition or antitumor agents.

Molecular mechanism of SARS-CoV-2 cell entry inhibition via TMPRSS2 by Camostat and Nafamostat mesylate

The entry of the coronavirus SARS-CoV-2 into human cells can be inhibited by the approved drugs camostat and nafamostat. Here we elucidate the molecular mechanism of these drugs by combining experiments and simulations. In vitro assays confirm the hypothesis that both drugs act by inhibiting the human protein TMPRSS2. As no experimental structure is available, we provide a model of the TMPRSS2 equilibrium structure and its fluctuations by relaxing an initial homology structure with extensive 280 microseconds of all-atom molecular dynamics (MD) and Markov modeling. We describe the binding mode of both drugs with TMPRSS2 in a Michaelis complex (MC) state preceding the formation of a long-lived covalent inhibitory state. We find that nafamostat to has a higher MC population, which in turn leads to the more frequent formation of the covalent complex and thus higher inhibition efficacy, as confirmed in vitro and consistent with previous virus cell entry assays. Our TMPRSS2-drug structures are made public to guide the design of more potent and specific inhibitors.

Current Concepts on Immunopathology of COVID-19 and Emerging Therapies

Context: This scoping review tries to synthesize early findings on the immunopathogenicity of SARS-CoV-2 to assess the emerging therapies and vaccines by evaluating their impact based on the mechanism of pathogenicity. Methods: The three databases of PubMed, Scopus, and Google Scholar were searched from January 1, 2020, to March 15, 2020. To extract the results from the studies, the content, thematic analysis method was used. In this method, the topics studied were coded in the articles, and then major topics related to the articles were determined. After identifying major issues, the contents of the articles were reviewed. Results: A total of 2,250 articles were retrieved after deleting duplications, and after reviewing the thematic relevance, 45 of them were selected for the final analysis. Topics studied in the articles were classified into four main areas, including “virus entry inhibition and immune response”, “vaccine and treatment targets”, “genome structure similarity to other coronaviruses,” and “pathogensis”. Conclusions: Results of this review showed that we have a long way to develop an effective and safe vaccine due to the structural and behavioral complexities of this virus. In the meantime, the scientific community should use results of megatrials, but until their accomplishing them, we have to use results of systematic reviews of randomized controlled trials.

The Serine/Threonine Kinase AP2-Associated Kinase 1 Plays an Important Role in Rabies Virus Entry

Rabies virus (RABV) invades the central nervous system and nearly always causes fatal disease in humans. RABV enters cells via clathrin-mediated endocytosis upon receptor binding. The detailed mechanism of this process and how it is regulated are not fully understood. Here, we carried out a high-through-put RNAi analysis and identified AP2-associated kinase 1 (AAK1), a serine/threonine kinase, as an important cellular component in regulating the entry of RABV. AAK1 knock-down greatly inhibits RABV infection of cells, and AAK1-induced phosphorylation of threonine 156 of the μ subunit of adaptor protein 2 (AP2M1) is found to be required for RABV entry. Inhibition of AAK1 kinase activity by sunitinib blocked AP2M1 phosphorylation, significantly inhibiting RABV infection and preventing RABV from entering early endosomes. In vivo studies revealed that sunitinib prolongs the survival of mice challenged with RABV street virus. Our findings indicate that AAK1 is a potential drug target for postexposure prophylaxis against rabies.