Project description:Here, we have used a SARS-naïve, bovine ultralong CDRH3 library to isolate a bovine paratope that engages the SARS-CoV and SARS-CoV-2 receptor-binding domain (RBD). This scFv (B9-scFv) neutralises viruses pseudo-typed with SARS-CoV Spike protein. Using differential hydrogen-deuterium exchange mass spectrometry and site-directed mutagenesis, we demonstrate that this CDRH3 recognises a conserved, cryptic epitope.
Project description:Germinal centers (GC) are key sites for antibody diversification and affinity maturation. SARS-CoV-2 mRNA vaccines elicit robust GC B cell responses in humans, but how these influence the breadth of immunity against viral variants remains unclear. We analyzed GC B cell responses in nine healthy adults following mRNA booster immunization. We show that 77.8% of the B cell clones in the GC expressed representative monoclonal antibodies (mAbs) recognizing the spike protein, with 37.8% of these targeting the receptor-binding domain (RBD). One RBD-targeting mAb, mAb-52, neutralized all tested SARS-CoV-2 strains, including the recent XEC variant. mAb-52 utilized the IGHV3-66 public clonotype, protected hamsters challenged against the EG.5.1 variant, and targeted the class I/II RBD epitope, closely mimicking the binding footprint of ACE2. Its broad reactivity was driven by extensive somatic hypermutation, underscoring the critical role of GC reactions in shaping cross-variant B cell immunity following SARS-CoV-2 booster vaccination.
Project description:Universal vaccines cross-protecting against sarbecoviruses including SARS-CoV-2 are in great need under continuous emergence of SARS-CoV-2 variants and potential novel coronavirus. Nanoparicle vaccines displaying mosaic receptor-binding domains (RBDs) or spike (S) proteins from SARS-CoV-2 and other sarbecoviruses were used for preparedness to emergent zoonotic outbreak. Here, we describe a self-assembling nanoparticle using lumazine synthase (LuS) as the scaffold to display RBDs from different sarbecoviruses. The mosaic LuS-RBD vaccines induced cross-reactive binding and neutralizing antibody responses to sarbecoviruses. Single B cell sequencing revealed that mosaic LuS-RBD elicited B-cell receptor (BCR) repertoire using an immunodominant germline gene pair of IGHV14-3: IGKV14-111 in mice. Most of the tested IGHV14-3: IGKV14-111 monoclonal antibodies (mAbs) are broadly cross-reactive to the clade 1a, 1b and 3 sarbecoviruses. By antibody binning and cryo-electron microscopy, we determined a reprensentative IGHV14-3: IGKV14-111 mAb, M2-7, bound to an conserved epitope on RBD largely overlapping with a pan-sarbecovirus mAb S2H97, which suggested that mosaic nanoparticles expended B cells recognizing the common epitopes shared by different clades of sarbecoviruses. These results provide immunological insights into the cross-reactive responses elicited by mosaic nanoparticle against emerging sarbecoviruses.
Project description:The COVID-19 pandemic is an infectious disease caused by SARS-CoV-2. The first step of SARS-CoV-2 infection is the recognition of angiotensin-converting enzyme 2 (hACE2) receptors by the receptor-binding domain (RBD) of the viral spike (S) glycoprotein. Although the molecular and structural bases of the SARS-CoV-2-RBD/hACE2 interaction have been thoroughly investigated in vitro, the relationship between hACE2 expression and in vivo infection is less understood. Here, we developed an efficient SARS-CoV-2-RBD binding assay suitable for super resolution microscopy and simultaneous hACE2 immunodetection and mapped the correlation between hACE2 receptor abundance and SARS-CoV-2-RBD binding, both in vitro and in human lung biopsies. Next, we explored the specific proteome of SARS-CoV-2-RBD/hACE2 through a comparative mass spectrometry approach. We found that only a minority of hACE2 positive spots are actually SARS-CoV-2-RBD binding sites, and that the relationship between SARS-CoV-2-RBD binding and hACE2 presence is variable, suggesting the existence of additional factors. Indeed, we found several interactors that are involved in receptor localization and viral entry and characterized one of them: SLC1A5, an amino acid transporter. High-resolution receptor-binding studies showed that co-expression of membrane-bound SLC1A5 with hACE2 predicted SARS-CoV-2 binding and entry better than hACE2 expression alone. Accordingly, SLC1A5 depletion reduces SARS-CoV-2 binding and entry. Notably, the Omicron variant is more efficient in binding hACE2 sites, but equally sensitive to SLC1A5 downregulation. We propose a method for mapping functional SARS-CoV-2 receptors in vivo. We confirm the existence of hACE2 co-factors that may contribute to differential sensitivity of cells to infection.
2023-01-09 | PXD038005 | Pride
Project description:Deep mutational scanning for epitope mapping of antibodies targeting SARS-CoV-2.
Project description:The continuous evolution of SARS-CoV-2 poses global health challenges. A safe, rapid, and versatile method for assessing functions of Spike protein mutations in ACE2 receptor binding and immune evasion would be highly valuable. To address this, we engineered a transcription- and replication-competent virus-like particle (trVLP) derived from the Sindbis virus, pseudotyped with the SARS-CoV-2 receptor binding domain (RBD). This trVLP exclusively propagates in BHK-21 cell engineered to express both RNA replicase and human ACE2, providing a controllable, safe model of SARS-CoV-2 RBD-ACE2 interaction mediated virus entry. The system enables characterization of RBD interactions with ACE2 from various mammalian hosts, demonstrating its utility for studying host-virus interactions. By leveraging the evolutionary capability of trVLP mediated by error-prone RNA replication, we screened for RBD variants that evade the antibody-mediated inhibition of cell entry. Together, these findings underscore the utility of the trVLP as a safe, rapid, and flexible platform for dissecting SARS-CoV-2 RBD evolution and identifying key adaptive mutations with implications for surveillance and countermeasure development.
Project description:The continuous evolution of SARS-CoV-2 poses global health challenges. A safe, rapid, and versatile method for assessing functions of Spike protein mutations in ACE2 receptor binding and immune evasion would be highly valuable. To address this, we engineered a transcription- and replication-competent virus-like particle (trVLP) derived from the Sindbis virus, pseudotyped with the SARS-CoV-2 receptor binding domain (RBD). This trVLP exclusively propagates in BHK-21 cell engineered to express both RNA replicase and human ACE2, providing a controllable, safe model of SARS-CoV-2 RBD-ACE2 interaction mediated virus entry. The system enables characterization of RBD interactions with ACE2 from various mammalian hosts, demonstrating its utility for studying host-virus interactions. By leveraging the evolutionary capability of trVLP mediated by error-prone RNA replication, we screened for RBD variants that evade the antibody-mediated inhibition of cell entry. Together, these findings underscore the utility of the trVLP as a safe, rapid, and flexible platform for dissecting SARS-CoV-2 RBD evolution and identifying key adaptive mutations with implications for surveillance and countermeasure development.
Project description:The continuous evolution of SARS-CoV-2 poses global health challenges. A safe, rapid, and versatile method for assessing functions of Spike protein mutations in ACE2 receptor binding and immune evasion would be highly valuable. To address this, we engineered a transcription- and replication-competent virus-like particle (trVLP) derived from the Sindbis virus, pseudotyped with the SARS-CoV-2 receptor binding domain (RBD). This trVLP exclusively propagates in BHK-21 cell engineered to express both RNA replicase and human ACE2, providing a controllable, safe model of SARS-CoV-2 RBD-ACE2 interaction mediated virus entry. The system enables characterization of RBD interactions with ACE2 from various mammalian hosts, demonstrating its utility for studying host-virus interactions. By leveraging the evolutionary capability of trVLP mediated by error-prone RNA replication, we screened for RBD variants that evade the antibody-mediated inhibition of cell entry. Together, these findings underscore the utility of the trVLP as a safe, rapid, and flexible platform for dissecting SARS-CoV-2 RBD evolution and identifying key adaptive mutations with implications for surveillance and countermeasure development.
Project description:The spike S of SARS-CoV-2 recognizes ACE2 on the host cell membrane to initiate entry. Soluble decoy receptors, in which the ACE2 ectodomain is engineered to block S with high affinity, potently neutralize infection and, due to close similarity with the natural receptor, hold out the promise of being broadly active against virus variants without opportunity for escape. Here, we directly test this hypothesis. Using deep mutagenesis, we find that the ACE2-binding surface of the SARS-CoV-2 spike tolerates high mutational diversity, which may act as a source for resistance to therapeutics. However, saturation mutagenesis of the receptor-binding domain (RBD) followed by in vitro selection, with wild type ACE2 and the engineered decoy competing for binding sites, failed to find S mutants that discriminate in favor of the wild type receptor. We conclude that resistance to engineered decoys will be rare.