Project description:The COVID-19 pandemic prompted an unprecedented effort to develop effective countermeasures against SARS-CoV-2. While efficacious vaccines and certain therapeutic monoclonal antibodies are available, here, we report the development, cryo-EM structures and functional analyses of distinct potent monoclonal antibodies (mAbs) that neutralize SARS-CoV-2 and its variant B.1.351. We established a platform for rapid identification of highly potent and specific SARS-CoV-2-neutralizing antibodies by high-throughput B cell receptor single cell sequencing of spike receptor binding domain immunized animals. We identified two highly potent and specific SARS-CoV-2 neutralizing mAb clones that have single-digit nanomolar affinity and low-picomolar avidity. We also generated a bispecific antibody of these two lead clones. The lead monospecific and bispecific antibodies showed strong neutralization ability against prototypical SARS-CoV-2 and the highly contagious South African variant B.1.351 that post a further risk of reducing the efficacy of currently available therapeutic antibodies and vaccines. The lead mAbs showed potent in vivo efficacy against authentic SARS-CoV-2 in both prophylactic and therapeutic settings. We solved five cryo-EM structures at ~3 resolution of these neutralizing antibodies in complex with the ectodomain of the prefusion spike trimer, and revealed the molecular epitopes, binding patterns and conformations between the antibodies and spike RBD, which are distinct from existing antibodies. Our recently developed antibodies expand the repertoire of the toolbox of COVID-19 countermeasures against the SARS-CoV-2 pathogen and its emerging variants.
Project description:SARS-CoV-2 has spread globally and caused the COVID-19 pandemic. Although passively delivered neutralizing antibodies against SARS-CoV-2 are in clinical trials, their mechanism of action in vivo is incompletely understood. Here, we define correlates of protection of neutralizing human monoclonal antibodies (mAbs) in SARS-CoV-2-infected mice. Whereas Fc effector functions are fully dispensable when mAbs are administered as prophylaxis, they are required for optimal protection as therapy. When given after infection, intact but not LALA-PG loss of Fc effector function variant mAbs reduce SARS-CoV-2 burden and lung disease in mice and hamsters. Fc engagement of neutralizing antibodies mitigates inflammation and improves respiratory mechanics, and transcriptional profiling suggests these phenotypes are associated with diminished innate immune signaling and enhanced tissue repair. Immune cell depletions establish that neutralizing mAbs require monocytes for therapeutic efficacy. Our study demonstrates that therapeutic neutralizing mAbs require Fc effector functions to reduce SARS-CoV-2 infection and modulate protective immune responses.
Project description:Delineating the origins and properties of antibodies elicited by SARS-CoV-2 infection and vaccination is critical for understanding their benefits and potential shortcomings. Therefore, we investigated the SARS-CoV-2 spike (S)-reactive B cell repertoire in unexposed individuals by flow cytometry and single-cell sequencing. We found that ~82% of SARS-CoV-2 S-reactive B cells show a naive phenotype, which represents an unusually high fraction of total human naive B cells (~0.1%). Approximately 10% of these naive S-reactive B cells shared an IGHV1-69/IGKV3-11 B cell receptor pairing, an enrichment of 18-fold compared to the complete naive repertoire. Following SARS-CoV-2 infection, we report an average 37-fold enrichment of IGHV1-69/IGKV3-11 B cell receptor pairing in the S-reactive memory B cells compared to the unselected memory repertoire. This class of B cells targets a previously undefined non-neutralizing epitope on the S2 subunit that becomes exposed on S proteins used in approved vaccines when they transition away from the native pre-fusion state because of instability. These findings can help guide the improvement of SARS-CoV-2 vaccines.
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:Hybrid immunity (vaccination + natural infection) to SARS-CoV-2 provides superior protection to re-infection. We performed immune profiling studies during breakthrough infections in mRNA-vaccinated hamsters to evaluate hybrid immunity induction. Vaccine was dosed to induce binding antibody titers against ancestral spike, but not efficient virus neutralization of ancestral SARS-CoV-2 or variants of concern (VoCs). Vaccination reduced morbidity and controlled lung virus titers for ancestral virus and Alpha but allowed breakthrough infections in Beta, Delta and Mu-challenged hamsters. Vaccination primed for T cell responses that were boosted by infection. Infection back-boosted neutralizing antibody responses against ancestral virus and VoCs. Hybrid immunity resulted in more cross-reactive sera, reflected by smaller antigenic cartography distances. Transcriptomics post infection reflects both vaccination status and disease course, and suggests a role for interstitial macrophages in vaccine-mediated protection. Therefore, protection by vaccination, even in the absence of neutralizing antibodies, correlates with recall of broadly reactive B- and T-cell responses.
Project description:RNA vaccines are efficient preventive measures to combat the SARS-CoV-2 pandemic. High levels of neutralizing SARS-CoV-2-antibodies are an important component of vaccine-induced immunity. Shortly after the initial two mRNA vaccine doses, the IgG response mainly consists of the pro-inflammatory subclasses IgG1 and IgG3. Here, we report that several months after the second vaccination, SARS-CoV-2-specific antibodies were increasingly composed of non-inflammatory IgG4, which were further boosted by a third mRNA vaccination and/or SARS-CoV-2 variant breakthrough infections. IgG4 antibodies among all spike-specific IgG antibodies rose on average from 0.04% shortly after the second vaccination to 19.27% late after the third vaccination. This induction of IgG4 antibodies was not observed after homologous or heterologous SARS-CoV-2 vaccination with adenoviral vectors. Single-cell sequencing and flow cytometry revealed substantial frequencies of IgG4-switched B cells within the spike-binding memory B-cell population (median 14.4%; interquartile range (ICR) 6.7-18.1%) compared to the overall memory B-cell repertoire (median 1.3%; ICR 0.9-2.2%) after three immunizations. Importantly, this class switch was associated with a reduced capacity of the spike-specific antibodies to mediate antibody-dependent cellular phagocytosis and complement deposition. Since Fc-mediated effector functions are critical for antiviral immunity, these findings may have consequences for the choice and timing of vaccination regimens using mRNA vaccines, including future booster immunizations against SARS-CoV-2.
Project description:RNA vaccines are efficient preventive measures to combat the SARS-CoV-2 pandemic. High levels of neutralizing SARS-CoV-2-antibodies are an important component of vaccine-induced immunity. Shortly after the initial two mRNA vaccine doses, the IgG response mainly consists of the pro-inflammatory subclasses IgG1 and IgG3. Here, we report that several months after the second vaccination, SARS-CoV-2-specific antibodies were increasingly composed of non-inflammatory IgG4, which were further boosted by a third mRNA vaccination and/or SARS-CoV-2 variant breakthrough infections. IgG4 antibodies among all spike-specific IgG antibodies rose on average from 0.04% shortly after the second vaccination to 19.27% late after the third vaccination. This induction of IgG4 antibodies was not observed after homologous or heterologous SARS-CoV-2 vaccination with adenoviral vectors. Single-cell sequencing and flow cytometry revealed substantial frequencies of IgG4-switched B cells within the spike-binding memory B-cell population (median 14.4%; interquartile range (ICR) 6.7-18.1%) compared to the overall memory B-cell repertoire (median 1.3%; ICR 0.9-2.2%) after three immunizations. Importantly, this class switch was associated with a reduced capacity of the spike-specific antibodies to mediate antibody-dependent cellular phagocytosis and complement deposition. Since Fc-mediated effector functions are critical for antiviral immunity, these findings may have consequences for the choice and timing of vaccination regimens using mRNA vaccines, including future booster immunizations against SARS-CoV-2.
Project description:Peptides derived from SARS-CoV-2 spike protein-reactive antibodies isolated from convalescent plasma from subjects recovering from COVID-19.
Project description:Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the global COVID-19 pandemic and the lack of therapeutics hinders pandemic control. Although lung disease is the primary clinical outcome in COVID-19 patients, how SARS-CoV-2 induces tissue pathology in the lung remains elusive. Here we describe a high-throughput-based platform to generate tens of thousands of self-organizing, nearly identical, and genetically matched human lung buds derived from human pluripotent stem cells (hPSCs) cultured on confined geometries on micropattern chips. Strikingly, in vitro-derived human lung buds resemble fetal human lung tissue and display in vivo-like proximo-distal coordination of alveolar and airway tissue differentiation whose 3D epithelial self-organization is directed by the levels of KGF. Single-cell transcriptomics unveiled the cell identities and ontogeny of airway and alveolar tissue and the specification of WNThi cycling alveolar stem cells from alveolar progenitors. These synthetic human lung buds are susceptible to SARS-CoV-2 infection and can be used to track cell type-dependent susceptibilities to infection, intercellular transmission and cytopathology in airway and alveolar tissue in individual synthetic lung buds. We detected an increased susceptibility to infection in alveolar cells and identified cycling alveolar stem cells as targets of SARS-CoV-2. We used this platform to test neutralizing antibodies isolated from convalescent plasma that efficiently blocked SARS-CoV-2 infection and intercellular transmission. Our platform offers unlimited, rapid and scalable access to disease-relevant lung tissue that recapitulate human lung development and can be used to track SARS-CoV-2 infection and identify pre-clinical candidate therapeutics for COVID-19.