Engineered immunogens to elicit antibodies against conserved coronavirus epitopes.

Immune responses to SARS-CoV-2 primarily target the receptor binding domain of the spike protein, which continually mutates to escape acquired immunity. Other regions in the spike S2 subunit, such as the stem helix and the segment encompassing residues 815-823 adjacent to the fusion peptide, are highly conserved across sarbecoviruses and are recognized by broadly reactive antibodies, providing hope that vaccines targeting these epitopes could offer protection against both current and emergent viruses. Here we employ computational modeling to design scaffolded immunogens that display the spike 815-823 peptide and the stem helix epitopes without the distracting and immunodominant receptor binding domain. These engineered proteins bind with high affinity and specificity to the mature and germline versions of previously identified broadly protective human antibodies. Epitope scaffolds interact with both sera and isolated monoclonal antibodies with broadly reactivity from individuals with pre-existing SARS-CoV-2 immunity. When used as immunogens, epitope scaffolds elicit sera with broad betacoronavirus reactivity and protect as "boosts" against live virus challenge in mice, illustrating their potential as components of a future pancoronavirus vaccine.

Engineered Immunogens to Elicit Antibodies Against Conserved Coronavirus Epitopes.

Immune responses to SARS-CoV-2 primarily target the receptor binding domain of the spike protein, which continually mutates to escape acquired immunity. Other regions in the spike S2 subunit, such as the stem helix and the segment encompassing residues 815-823 adjacent to the fusion peptide, are highly conserved across sarbecoviruses and are recognized by broadly reactive antibodies, providing hope that vaccines targeting these epitopes could offer protection against both current and emergent viruses. Here we employed computational modeling to design scaffolded immunogens that display the spike 815-823 peptide and the stem helix epitopes without the distracting and immunodominant RBD. These engineered proteins bound with high affinity and specificity to the mature and germline versions of previously identified broadly protective human antibodies. Epitope scaffolds interacted with both sera and isolated monoclonal antibodies with broadly reactivity from individuals with pre-existing SARS-CoV-2 immunity. When used as immunogens, epitope scaffolds elicited sera with broad betacoronavirus reactivity and protected as "boosts" against live virus challenge in mice, illustrating their potential as components of a future pancoronavirus vaccine.

Cryo-EM structures of SARS-CoV-2 Omicron BA.2 spike

The BA.2 sub-lineage of the SARS-CoV-2 Omicron variant has gained in proportion relative to BA.1. As differences in spike (S) proteins may underlie differences in their pathobiology, here we determine cryo-EM structures of a BA.2 S ectodomain and compare 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 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 variant, and reveal differences in key functional regions in the BA.1 and BA.2 S proteins.

Clinical features and surgical treatment of abdominal unicentric Castleman's disease / 中华普通外科杂志

Objective:To summarize the clinical manifestations, diagnosis and surgical treatment of abdominal unicentric Castleman's disease.Methods:The clinical data of abdominal unicentric Castleman's disease cases admitted to the General Surgery Department of the First Affiliated Hospital,Nanjing Medical University from Jan 2009 to Dec 2019 was retrospectively analyzed.Results:A total of 18 patients were included with definite pathological diagnosis. The main complaint was abdominal pain and discomfort (50%, 6/12), dizziness and fatigue (25%, 3/12), multiple rash with oral ulcer (16.7%, 2/12) and weight loss (8.3%, 1/12). All patients received surgical resection. Postoperative pathology showed clear vascular type in 15 patients and plasma cell type in 3 patients. There were no major complications nor mortality.Conclusion:Abdominal unicentric Castleman's disease has diverse clinical manifestations, which was difficult for preoperative diagnosis, postoperative prognosis is satisfactory.

A broadly neutralizing antibody protects against SARS-CoV, pre-emergent bat CoVs, and SARS-CoV-2 variants in mice

SARS-CoV in 2003, SARS-CoV-2 in 2019, and SARS-CoV-2 variants of concern (VOC) can cause deadly infections, underlining the importance of developing broadly effective countermeasures against Group 2B Sarbecoviruses, which could be key in the rapid prevention and mitigation of future zoonotic events. Here, we demonstrate the neutralization of SARS-CoV, bat CoVs WIV-1 and RsSHC014, and SARS-CoV-2 variants D614G, B.1.1.7, B.1.429, B1.351 by a receptor-binding domain (RBD)-specific antibody DH1047. Prophylactic and therapeutic treatment with DH1047 demonstrated protection against SARS-CoV, WIV-1, RsSHC014, and SARS-CoV-2 B1.351infection in mice. Binding and structural analysis showed high affinity binding of DH1047 to an epitope that is highly conserved among Sarbecoviruses. We conclude that DH1047 is a broadly neutralizing and protective antibody that can prevent infection and mitigate outbreaks caused by SARS-like strains and SARS-CoV-2 variants. Our results argue that the RBD conserved epitope bound by DH1047 is a rational target for pan Group 2B coronavirus vaccines.

The functions of SARS-CoV-2 neutralizing and infection-enhancing antibodies in vitro and in mice and nonhuman primates

SARS-CoV-2 neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) and the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV-1 infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-{gamma} (Fc{gamma}R)-mediated enhancement of virus infection in vitro, while five non-neutralizing NTD antibodies mediated Fc{gamma}R-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Nonetheless, three of 31 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo, increased lung inflammation can occur in SARS-CoV-2 antibody-infused macaques.

Cold sensitivity of the SARS-CoV-2 spike ectodomain

The SARS-CoV-2 spike (S) protein, a primary target for COVID-19 vaccine development, presents its Receptor Binding Domain in two conformations: receptor-accessible "up" or receptor-inaccessible "down" conformations. Here, we report that the commonly used stabilized S ectodomain construct "2P" is sensitive to cold temperature, and that this cold sensitivity is resolved in a "down" state stabilized spike. Our results will impact structural, functional and vaccine studies that use the SARS-CoV-2 S ectodomain.