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1.
Cell Rep ; 39(13): 111009, 2022 06 28.
Article in English | MEDLINE | ID: covidwho-1944463

ABSTRACT

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron BA.2 sub-lineage has gained in proportion relative to BA.1. Because spike (S) protein variations may underlie differences in their pathobiology, here we determine cryoelectron microscopy (cryo-EM) structures of the BA.2 S ectodomain and compare these with previously determined BA.1 S structures. BA.2 receptor-binding domain (RBD) mutations induce remodeling of the RBD structure, resulting in tighter packing and improved thermostability. Interprotomer RBD interactions are enhanced in the closed (or 3-RBD-down) BA.2 S, while the fusion peptide is less accessible to antibodies than in BA.1. Binding and pseudovirus neutralization assays reveal extensive immune evasion while defining epitopes of two outer RBD face-binding antibodies, DH1044 and DH1193, that neutralize both BA.1 and BA.2. Taken together, our results indicate that stabilization of the closed state through interprotomer RBD-RBD packing is a hallmark of the Omicron variant and show differences in key functional regions in the BA.1 and BA.2 S proteins.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Cryoelectron Microscopy , Humans , Receptors, Virus/metabolism , Spike Glycoprotein, Coronavirus
2.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-333084

ABSTRACT

Summary The BA.2 lineage of the SARS-CoV-2 Omicron variant has gained in proportion relative to BA.1. As differences in their spike (S) proteins may underlie differences in their pathobiology, here we determined cryo-EM structures of a BA.2 S protein ectodomain and compared these to previously determined BA.1 S structures. BA.2 Receptor Binding Domain (RBD) mutations induced remodeling of the internal RBD structure resulting in its improved thermostability and tighter packing within the 3-RBD-down spike. In the S2 subunit, the fusion peptide in the BA.2 was less accessible to antibodies than in BA.1. Pseudovirus neutralization and spike binding assays revealed extensive immune evasion while defining epitopes of two RBD-directed antibodies, DH1044 and DH1193, that bound the outer RBD face to neutralize both BA.1 and BA.2. Taken together, our results indicate that stabilization of the 3-RBD-down state through interprotomer RBD-RBD packing is a hallmark of the Omicron lineages, and reveal differences in key functional regions in the BA.1 and BA.2 S proteins.

3.
J Biol Chem ; 296: 100630, 2021.
Article in English | MEDLINE | ID: covidwho-1333548

ABSTRACT

Unchecked inflammation can result in severe diseases with high mortality, such as macrophage activation syndrome (MAS). MAS and associated cytokine storms have been observed in COVID-19 patients exhibiting systemic hyperinflammation. Interleukin-18 (IL-18), a proinflammatory cytokine belonging to the IL-1 family, is elevated in both MAS and COVID-19 patients, and its level is known to correlate with the severity of COVID-19 symptoms. IL-18 binds its specific receptor IL-1 receptor 5 (IL-1R5, also known as IL-18 receptor alpha chain), leading to the recruitment of the coreceptor, IL-1 receptor 7 (IL-1R7, also known as IL-18 receptor beta chain). This heterotrimeric complex then initiates downstream signaling, resulting in systemic and local inflammation. Here, we developed a novel humanized monoclonal anti-IL-1R7 antibody to specifically block the activity of IL-18 and its inflammatory signaling. We characterized the function of this antibody in human cell lines, in freshly obtained peripheral blood mononuclear cells (PBMCs) and in human whole blood cultures. We found that the anti-IL-1R7 antibody significantly suppressed IL-18-mediated NFκB activation, reduced IL-18-stimulated IFNγ and IL-6 production in human cell lines, and reduced IL-18-induced IFNγ, IL-6, and TNFα production in PBMCs. Moreover, the anti-IL-1R7 antibody significantly inhibited LPS- and Candida albicans-induced IFNγ production in PBMCs, as well as LPS-induced IFNγ production in whole blood cultures. Our data suggest that blocking IL-1R7 could represent a potential therapeutic strategy to specifically modulate IL-18 signaling and may warrant further investigation into its clinical potential for treating IL-18-mediated diseases, including MAS and COVID-19.


Subject(s)
Anti-Inflammatory Agents/pharmacology , Antibodies, Monoclonal/pharmacology , Antibodies, Neutralizing/pharmacology , Immunologic Factors/pharmacology , Interleukin-18/genetics , Receptors, Interleukin-18/genetics , Anti-Inflammatory Agents/metabolism , Antibodies, Monoclonal/biosynthesis , Antibodies, Neutralizing/biosynthesis , COVID-19/drug therapy , Candida albicans/growth & development , Candida albicans/pathogenicity , Gene Expression Regulation , HEK293 Cells , Humans , Immunologic Factors/biosynthesis , Inflammation , Interferon-gamma/genetics , Interferon-gamma/immunology , Interleukin-18/immunology , Interleukin-6/genetics , Interleukin-6/immunology , Leukocytes, Mononuclear/drug effects , Leukocytes, Mononuclear/immunology , Leukocytes, Mononuclear/microbiology , Lipopolysaccharides/antagonists & inhibitors , Lipopolysaccharides/pharmacology , Macrophage Activation Syndrome/drug therapy , NF-kappa B/genetics , NF-kappa B/immunology , Primary Cell Culture , Receptors, Interleukin-18/antagonists & inhibitors , Receptors, Interleukin-18/immunology , SARS-CoV-2/immunology , SARS-CoV-2/pathogenicity , Signal Transduction/drug effects , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/immunology
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