Search

Nevertheless, although Nafamostat-mediated inhibition of -1PRF did not translate into reduced SARS-CoV-2 replication in our study, interference with SARS-CoV-2 -1PRF by more potent compounds could still represent a promising antiviral strategy. Nafamostat-Mediated Inhibition of SARS-CoV-2 Ribosomal Frameshifting Is Insufficient to Impair Viral Replication in Vero Cells. Importantly, the same Nafamostat concentration that inhibited -1PRF in Vero 76 cells did not block SARS-CoV-2 infection of these cells, although it reduced infection of a control cell line, Calu-3, by more than a thousand-fold. Vero 76 and Calu-3 cells were incubated with the indicated 10-fold serial dilutions of Nafamostat for 1 h prior to infection with SARS-CoV-2, Pango lineage B.1.513, at a multiplicity of infection of 0.01 for 1 h. [Extracted from the article]

WHICH ANTIVIRAL TREATMENT OPTIONS ARE SUITABLE FOR THERAPY OF PATIENTS INFECTED WITH THE OMIC... Treatment with recombinant monoclonal antibodies (mAbs) that neutralize SARS-CoV-2 can reduce the risk for severe disease. In contrast, neutralization of the Omicron variant is dramatically reduced,1 indicating that immunity following infection by previously circulating SARS-CoV-2 variants provides little to no protection against the Omicron variant. Keywords: antibody; omicron; SARS-CoV-2; spike EN antibody omicron SARS-CoV-2 spike 1 3 3 05/31/22 20220501 NES 220501 The severe acute respiratory syndrome coronavirus 2 Omicron variant (B.1.1.529) swept the globe with breathtaking speed, rapidly displacing the Delta variant and causing record numbers of new infections. [Extracted from the article]

Recent emergence of SARS-CoV-1 variants demonstrates the potential of this virus for targeted evolution, despite its overall genomic stability. Here we show the dynamics and the mechanisms behind the rapid adaptation of SARS-CoV-2 to growth in Vero E6 cells. The selective advantage for growth in Vero E6 cells is due to increased cleavage efficiency by cathepsins at the mutated S1/S2 site. S1/S2 site also constitutes a heparan sulfate (HS) binding motif that influenced virus growth in Vero E6 cells, but HS antagonist did not inhibit virus adaptation in these cells. The entry of Vero E6-adapted virus into human cells is defective because the mutated spike variants are poorly processed by furin or TMPRSS2. Minor subpopulation that lack the furin cleavage motif in the spike protein rapidly become dominant upon passaging through Vero E6 cells, but wild type sequences are maintained at low percentage in the virus swarm and mediate a rapid reverse adaptation if the virus is passaged again on TMPRSS21 human cells. Our data show that the spike protein of SARSCoV- 2 can rapidly adapt itself to available proteases and argue for deep sequence surveillance to identify the emergence of novel variants. IMPORTANCE Recently emerging SARS-CoV-2 variants B.1.1.7 (alpha variant), B.1.617.2 (delta variant), and B.1.1.529 (omicron variant) harbor spike mutations and have been linked to increased virus pathogenesis. The emergence of these novel variants highlights coronavirus adaptation and evolution potential, despite the stable consensus genotype of clinical isolates. We show that subdominant variants maintained in the virus population enable the virus to rapidly adapt to selection pressure. Although these adaptations lead to genotype change, the change is not absolute and genomes with original genotype are maintained in the virus swarm. Thus, our results imply that the relative stability of SARS-CoV-2 in numerous independent clinical isolates belies its potential for rapid adaptation to new conditions. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic remains a global health threat and novel antiviral strategies are urgently needed. SARS-CoV-2 employs the cellular serine protease TMPRSS2 for entry into lung cells, and TMPRSS2 inhibitors are being developed for COVID-19 therapy. However, the SARS-CoV-2 Omicron variant, which currently dominates the pandemic, prefers the endo/lysosomal cysteine protease cathepsin L over TMPRSS2 for cell entry, raising doubts as to whether TMPRSS2 inhibitors would be suitable for the treatment of patients infected with the Omicron variant. Nevertheless, the contribution of TMPRSS2 to the spread of SARS-CoV-2 in the infected host is largely unclear. In this study, we show that the loss of TMPRSS2 strongly reduced the replication of the Beta variant in the nose, trachea and lung of C57BL/6 mice, and protected the animals from weight loss and disease. The infection of mice with the Omicron variant did not cause disease, as expected, but again, TMPRSS2 was essential for efficient viral spread in the upper and lower respiratory tract. These results identify the key role of TMPRSS2 in SARS-CoV-2 Beta and Omicron infection, and highlight TMPRSS2 as an attractive target for antiviral intervention. [ABSTRACT FROM AUTHOR]

Recently, a recombinant SARS-CoV-2 lineage, XD, emerged that harbors a spike gene that is largely derived from the Omicron variant BA.1 in the genetic background of the Delta variant. This finding raised concerns that the recombinant virus might exhibit altered biological properties as compared to the parental viruses and might pose an elevated threat to human health. Here, using pseudotyped particles, we show that ACE2 binding and cell tropism of XD mimics that of BA.1. Further, XD and BA.1 displayed comparable sensitivity to neutralization by antibodies induced upon vaccination with BNT162b2/Comirnaty (BNT) or BNT vaccination followed by breakthrough infection. Our findings reveal important biological commonalities between XD and Omicron BA.1 host cell entry and its inhibition by antibodies. [ABSTRACT FROM AUTHOR]

The transmembrane serine protease 2 (TMPRSS2) primes the SARS-CoV-2 Spike (S) protein for host cell entry and represents a promising target for COVID-19 therapy. Here we describe the in silico development and in vitro characterization of peptidomimetic TMPRSS2 inhibitors. Molecular docking studies identified peptidomimetic binders of the TMPRSS2 catalytic site, which were synthesized and coupled to an electrophilic serine trap. The compounds inhibit TMPRSS2 while demonstrating good off-target selectivity against selected coagulation proteases. Lead candidates are stable in blood serum and plasma for at least ten days. Finally, we show that selected peptidomimetics inhibit SARS-CoV-2 Spike-driven pseudovirus entry and authentic SARS-CoV-2 infection with comparable efficacy as camostat mesylate. The peptidomimetic TMPRSS2 inhibitors also prevent entry of recent SARS-CoV-2 variants of concern Delta and Omicron BA.1. In sum, our study reports antivirally active and stable TMPRSS2 inhibitors with prospects for further preclinical and clinical development as antiviral agents against SARS-CoV-2 and other TMPRSS2-dependent viruses. This study describes the development and characterization of peptidomimetic inhibitors of TMPRSS2, which primes the Spike protein of SARS-CoV-2. The inhibitors are shown to prevent SARS-CoV-2 infection in cells as efficiently as camostat mesylate. [ABSTRACT FROM AUTHOR]

Several SARS-CoV-2 variants emerged that harbor mutations in the surface unit of the viral spike (S) protein that enhance infectivity and transmissibility. Here, we analyzed whether ten naturally-occurring mutations found within the extended loop harboring the S1/S2 cleavage site of the S protein, a determinant of SARS-CoV-2 cell tropism and pathogenicity, impact S protein processing and function. None of the mutations increased but several decreased S protein cleavage at the S1/S2 site, including S686G and P681H, the latter of which is found in variants of concern B.1.1.7 (Alpha variant) and B.1.1.529 (Omicron variant). None of the mutations reduced ACE2 binding and cell-cell fusion although several modulated the efficiency of host cell entry. The effects of mutation S686G on viral entry were cell-type dependent and could be linked to the availability of cathepsin L for S protein activation. These results show that polymorphisms at the S1/S2 site can modulate S protein processing and host cell entry. [ABSTRACT FROM AUTHOR]

The devastating impact of COVID-19 on global health shows the need to increase our pandemic preparedness. Recombinant therapeutic antibodies were successfully used to treat and protect at-risk patients from COVID-19. However, the currently circulating Omicron subvariants of SARS-CoV-2 are largely resistant to therapeutic antibodies, and novel approaches to generate broadly neutralizing antibodies are urgently needed. Here, we describe a tetravalent bispecific antibody, A7A9 TVB, which actively neutralized many SARS-CoV-2 variants of concern, including early Omicron subvariants. Interestingly, A7A9 TVB neutralized more variants at lower concentration as compared to the combination of its parental monoclonal antibodies, A7K and A9L. A7A9 also reduced the viral load of authentic Omicron BA.1 virus in infected pseudostratified primary human nasal epithelial cells. Overall, A7A9 displayed the characteristics of a potent broadly neutralizing antibody, which may be suitable for prophylactic and therapeutic applications in the clinics, thus highlighting the usefulness of an effective antibody-designing approach. • Efficient modular antibody-designing and delivery with gene therapy tools. • Retrovirus-based pseudoparticles of 12 SAR-CoV-2 variants of concern tested. • Tetravalent bispecific neutralizing antibody overcomes viral evasion. • Tetravalent design outperforms the combination of monoclonal antibodies. • Early neutralizing antibody clones benefit with new design. [ABSTRACT FROM AUTHOR]