Omicron harbours 15 mutations in the RBD including almost all the sites of the existing VOCs

Omicron harbours 15 mutations in the RBD including almost all the sites of the existing VOCs. Gamma, and Delta variants. JS026 and the cocktail reduced virus titers in the infected lungs of hACE2 transgenic mice and relieved pathological changes. These findings would benefit antibody-based therapeutic countermeasures in the treatment of NSC-207895 (XI-006) COVID-19. KEYWORDS: SARS-CoV-2, etesevimab, JS026, antibody cocktail, variants of concern Main text The power of monoclonal antibody (mAb) treatment for the deadly virus has been widely acknowledged [1,2]. Since the initial outbreak of coronavirus disease 2019 (COVID-19) in late 2019, mAbs-based approaches hold enormous promise for the treatment of COVID-19. The phase 3 BLAZE-1 clinical trial shows that early administration bamlanivimab and etesevimab (also named CB6, JS016, or LY-CoV016) accelerated the decline in the SARS-CoV-2 viral load and led to a lower incidence of COVID-19-related hospitalization by 70% and mortality by 100% [3]. Emergency use authorizations (EUA) were authorized for bamlanivimab and etesevimab NSC-207895 (XI-006) administered together to treat individuals of mild to moderate symptoms at high risk for progression to severe COVID-19 and post-exposure prophylaxis of COVID-19 [4]. In recent months, the neutralizing activity of bamlanivimab has been NSC-207895 (XI-006) markedly diminished due to the emergence of SARS-CoV-2 variants of concern (VOCs), beta, gamma, and delta strains, which has become the predominant strain in this pandemic [5]. Identifying a new neutralizing antibody (NAb) that could replace bamlanivimab to combat these VOCs has become an urgent matter. It has been shown that NAbs that do not compete for binding to the RBD exhibit exceptionally potent neutralization activities to SARS-CoV-2 and VOCs [6]. Discovering such a new NAb to combine with etesevimab may be a good strategy to develop broadly effective therapies to limit morbidity and mortality of the devastating COVID-19 VOCs currently ongoing. In this study, we sorted SARS-CoV-2-RBD-specific memory B cells from peripheral blood mononuclear cells (PBMCs) of COVID-19 convalescents and amplified the variable region coding sequences of IgG antibodies as previously reported method [7]. To investigate the blocking breadth and potency of isolated human mAbs, soluble RBDs of currently circulating SARS-CoV-2 VOCs and HEK293T-hACE2 cells were used to perform flow cytometry (FACS) based assays. Strikingly, a potent mAb, JS026, showed broadly blocking all five RBDs binding to ACE2 receptor with a median half-maximal inhibitory concentration (IC50) value of 0.6-3.2 g/mL (Figure 1(a)). Bio-Layer Interferometry (BLI) assays demonstrated that JS026 bound to the wild-type (WT) RBD protein with a KD of 2.04 nM, to VOCs RBD antigens with similar affinities (Supplementary Table 1). The majority of SARS-CoV-2-neutralizing mAbs authorized or in development are clustered to class 1C4 as structural comparisons revealed these molecules flexibly direct to different epitopes on the RBD [8]. The competition-binding assay indicated JS026 locates between epitopes for class 2 (P2B-2F6) and class 3 (S309) mAbs as opposed to that of class 1 (etesevimab) antibodies (Supplementary Figure 1). To gain insights into the structural basis of the blocking, we solved the crystal structures of JS026-Fab/RBD at a resolution of 2.5 ? (Supplementary Table 2). Structural analyses revealed that JS026 blocks SARS-CoV-2-RBD binding to hACE2 mainly through the steric clash and the mAb inclines to share overlapping sites of class 3 antibodies instead of etesevimab (Figure 1(b) and Supplementary Figure 2). According to the pseudovirus neutralization assay, JS026 exhibited very low 50% Rabbit polyclonal to DARPP-32.DARPP-32 a member of the protein phosphatase inhibitor 1 family.A dopamine-and cyclic AMP-regulated neuronal phosphoprotein.Both dopaminergic and glutamatergic (NMDA) receptor stimulation regulate the extent of DARPP32 phosphorylation, but in opposite directions.Dopamine D1 receptor stimulation enhances cAMP formation, resulting in the phosphorylation of DARPP32 neutralization dose (ND50) values of 5.6-10.8?ng/mL for main circulating SARS-CoV-2 VOCs. Importantly, a cocktail of etesevimab and JS026 exhibit exceptionally potent neutralization activities against both WT and SARS-CoV-2 VOCs pseudovirus including the recent emergence of delta variant characterized by increased transmission fitness and decreased sensitivity to preventive measures [9] (Figure 1(c)). Omicron harbours 15 mutations in the RBD including almost all the sites of the existing VOCs. To investigate the breadth of etesevimab, JS026, and cocktail neutralizing activity to pseudotyped Omicron, neutralization assays were conducted in vitro. For etesevimab, the K417N mutation fully decreased its binding ability to the RBD [10]. The structure revealed that N440 forms 29 contacts.