Project description:This experiment aims to profile polyclonal antibody binding profiles in serum from vaccinated animals relative to antibody function in a virus neutralization assay. Rabbits received three vaccinations with a DNA vaccine encoding the spike protein of the SARS-CoV-2 index strain. Serum samples were selected based on a three-tier (low, intermediate, and high) capacity to cross-neutralize SARS-CoV-2 strains with known neutralization resistance. Following normalization of total anti-spike IgG levels, serum of each animal (n=3) were evaluated for antibody binding to 10mer cyclic constrained peptides spanning the entire spike protein and regions with known SARS-CoV-2 variant of concern spike mutations.
Project description:We here identified that the trimeric spike protein of SARS-CoV-2 could bind to TLR4 directly and robustly activate downstream signaling in monocytes and neutrophils. Moreover, specific TLR4 or NFKB inhibitor, or knockout of MyD88 could significantly block IL-1B induction by spike protein. We thus reveal that spike protein of SARS-CoV-2 functions as a potent stimulus causing TLR4 activation and sepsis related abnormal responses.
Project description:The field of structural biology is increasingly focusing on studying proteins in situ, i.e. in a larger biological context. Crosslinking mass spectrometry is contributing to this effort, typically through the use of MS-cleavable crosslinkers. Here, we apply the popular non-cleavable crosslinker disuccinimidyl suberate to mitochondria and identify 5,518 distance restraints between protein residues. Each distance restraint within or between proteins provides structural information on proteins and their processes within mitochondria. Comparing these restraints to high-throughput comparative models and PDB deposited structures reveals novel protein conformations. Our data suggest substrates and flexibility of mitochondrial heat shock proteins. Crosslinking mass spectrometry is progressing towards large-scale in situ structural biology that reveals protein dynamics in addition to protein-protein interaction topologies.
Project description:Human cardiac pericytes express the receptors for SARS-CoV-2 and contribute to microvascular dysfunction in COVID-19 patients. The SARS-CoV-2 capsid Spike protein seems to play a direct role in COVID-19 microangiopathy, but it is not known yet whether the Spike protein alone, without the infectious virus, can induce transcriptional alterations in pericytes. This study investigated the signalling pathways activated by the Spike protein in cultured human cardiac pericytes. We found that 309 RNA transcripts were significantly modulated in pericytes exposed to the Spike protein, with the upregulation of pathways linked to inflammation and viral infection.
Project description:mRNA vaccination of individuals with prior SARS-CoV-2 infection provides superior protection against breakthrough infections with variants of concern compared to vaccination in the absence of prior infection. However, the immune mechanisms by which this ‘hybrid immunity’ is generated and maintained are unknown. While genetic variation in spike glycoprotein effectively subverts neutralizing antibodies, spike-specific T cells are generally maintained against SARS-CoV-2 variants. Thus, we comprehensively profiled T cell responses against the S1 and S2 domains of spike glycoprotein in a cohort of SARS-CoV-2-naive or convalescent individuals who received two-dose mRNA vaccine series and were matched by age, sex, and vaccine type. Using flow cytometry, we observed that the overall functional breadth of CD4 T cells as well as polyfunctional Th1 responses were similar between the two groups. However, polyfunctional cytotoxic CD4 T cell responses against both S1 and S2 domains trended higher among convalescent subjects. Multi-modal single-cell RNA sequencing revealed diverse functional programs in spike-specific CD4 and CD8 T cells in both groups. However, convalescent individuals displayed enhanced cytotoxic and antiviral CD8 T cell responses to both S1 and S2 in the absence of cytokine production. Taken together, our data suggest that cytotoxic CD4 and CD8 T cells targeting spike glycoprotein may partially account for hybrid immunity and protection against breakthrough infections with SARS-CoV-2.
Project description:Cross-linking mass spectrometry (XL-MS) has progressed from studying purified protein assemblies in-vitro towards investigating the same assemblies in intact cells, tissues, and even whole organisms (so called “in situ XL-MS”). In situ XL-MS offers the great advantage of reporting on the architectures of protein complexes as they occur inside cells and tissues. Here we developed a complete workflow of in-situ XL-MS followed by purification, and employ it to investigate SARS-CoV2 protein inside the host cell. We focused on three Sars-Cov-2 proteins for which the structural information is either missing or incomplete: NSP1, NSP2, and the Nucleocapsid protein (N protein). Relatively little is known about the structures of these specific proteins, which was our motivation for choosing them. We were able to identify considerable cross-link sets, of in-situ origin. Integration of the cross-links with additional structural information allowed us to build almost complete models for NSP2 and the N protein.
Project description:SARS-CoV-2 is a respiratory virus spreading via aerosol particles. Aerosol particles can exhibit extreme environmental conditions affecting contained viruses, including acidic pH. Here, we study how harsh pH conditions, such as pH 2, can affect the structure of Spike, which is the main protein mediating viral entry into host cells. By performing limited proteolysis with the unspecific protease K coupled to mass spectrometry, we identified 4 semi-tryptic peptides in the S2 subdomain of spike. These results indicate structural changes in the S2 subdomain induced by treatment at pH 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.