Biology subjects

Vidarsson, G.

Publications and source records attributed to Vidarsson, G..

25 records · Page 2Linked to original sources

bioRxiv2021

C1q binding to surface-bound IgG is stabilized by C1r2s2 proteases

Complement is an important effector mechanism for antibody-mediated clearance of infections and tumor cells. Upon binding to target cells, the antibodys constant (Fc) domain recruits complement component C1 to initiate a proteolytic cascade that generates lytic pores and stimulates phagocytosis. The C1 complex (C1qr2s2) consists of the large recognition protein C1q and a heterotetramer of proteases C1r and C1s (C1r2s2). While interactions between C1 and IgG-Fcs are believed to be mediated by the globular heads of C1q, we here find that C1r2s2 proteases affect the capacity of C1q to form an avid complex with surface-bound IgG molecules (on various DNP-coated surfaces and pathogenic Staphylococcus aureus). The extent to which C1r2s2 contribute to C1q-IgG stability strongly differs between human IgG subclasses. Using antibody engineering of monoclonal IgG we reveal that hexamer-enhancing mutations improve C1q-IgG stability, both in absence and presence of C1r2s2. In addition, hexamer-enhanced IgGs targeting S. aureus mediate improved complement-dependent phagocytosis by human neutrophils. Altogether, these molecular insights into complement binding to surface-bound IgGs could be important for optimal design of antibody therapies.

immunology↗

bioRxiv2020

Anti-SARS-CoV-2 IgG from severely ill COVID-19 patients promotes macrophage hyper-inflammatory responses

For yet unknown reasons, severely ill COVID-19 patients often become critically ill around the time of activation of adaptive immunity. Here, we show that anti-Spike IgG from serum of severely ill COVID-19 patients induces a hyper-inflammatory response by human macrophages, which subsequently breaks pulmonary endothelial barrier integrity and induces microvascular thrombosis. The excessive inflammatory capacity of this anti-Spike IgG is related to glycosylation changes in the IgG Fc tail. Moreover, the hyper-inflammatory response induced by anti-Spike IgG can be specifically counteracted in vitro by use of the active component of fostamatinib, an FDA- and EMA-approved therapeutic small molecule inhibitor of Syk. One sentence summaryAnti-Spike IgG promotes hyper-inflammation.

immunology↗

bioRxiv2020

Afucosylated immunoglobulin G responses are a hallmark of enveloped virus infections and show an exacerbated phenotype in COVID-19

IgG antibodies are crucial for protection against invading pathogens. A highly conserved N-linked glycan within the IgG-Fc-tail, essential for IgG function, shows variable composition in humans. Afucosylated IgG variants are already used in anti-cancer therapeutic antibodies for their elevated binding and killing activity through Fc receptors (Fc{gamma}RIIIa). Here, we report that afucosylated IgG which are of minor abundance in humans ([~]6% of total IgG) are specifically formed against surface epitopes of enveloped viruses after natural infections or immunization with attenuated viruses, while protein subunit immunization does not elicit this low fucose response. This can give beneficial strong responses, but can also go awry, resulting in a cytokine-storm and immune-mediated pathologies. In the case of COVID-19, the critically ill show aggravated afucosylated-IgG responses against the viral spike protein. In contrast, those clearing the infection unaided show higher fucosylation levels of the anti-spike protein IgG. Our findings indicate antibody glycosylation as a potential factor in inflammation and protection in enveloped virus infections including COVID-19.

immunology↗

bioRxiv2020

Potent neutralizing antibodies from COVID-19 patients define multiple targets of vulnerability

The rapid spread of SARS-CoV-2 has a significant impact on global health, travel and economy. Therefore, preventative and therapeutic measures are urgently needed. Here, we isolated neutralizing antibodies from convalescent COVID-19 patients using a SARS-CoV-2 stabilized prefusion spike protein. Several of these antibodies were able to potently inhibit live SARS-CoV-2 infection at concentrations as low as 0.007 {micro}g/mL, making them the most potent human SARS-CoV-2 antibodies described to date. Mapping studies revealed that the SARS-CoV-2 spike protein contained multiple distinct antigenic sites, including several receptor-binding domain (RBD) epitopes as well as previously undefined non-RBD epitopes. In addition to providing guidance for vaccine design, these mAbs are promising candidates for treatment and prevention of COVID-19.

microbiology↗

bioRxiv2020

Site-specific glycosylation mapping of Fc gamma receptor IIIb from neutrophils of health donors

Fc gamma receptors (Fc{gamma}R) translate antigen-recognition by immunoglobulin G (IgG) into various immune responses. A better understanding of this key element of immunity promises novel insights into mechanisms of (auto-/allo-)immune diseases and more rationally designed antibody-based drugs. Glycosylation on both IgG and Fc{gamma}R impacts their interaction dramatically. In this study, we developed a straightforward and comprehensive analytical methodology to map Fc{gamma}RIIIb glycosylation from primary human material. In contrast to recently published alternatives, we assessed all glycosylation sites in a single LC-MS/MS run and simultaneously determined the donor allotype. Studying Fc{gamma}RIIIb derived from healthy donor neutrophils, we observed profound differences as compared to the soluble variant and the homologous Fc{gamma}RIIIa on natural killer cells. This method will allow assessment of Fc{gamma}RIII glycosylation differences between individuals, cell types, subcellular locations and pathophysiological conditions.

immunology↗

bioRxiv2019

NK cell activation by RSV-specific antibodies is decreased in infants with severe respiratory infections and correlates with Fc-glycosylation

BackgroundRespiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infections in infants and there is no vaccine available. In early life, the most important contributors to protection against infectious diseases are the innate immune system and maternal antibodies. However, the mechanisms by which antibodies can protect against RSV disease are incompletely understood, as both antibody levels and neutralization capacity correlate poorly with protection. We therefore asked whether antibody-mediated natural killer (NK) cell activation correlates with RSV disease.\n\nMethodsWe performed an observational case-control study including infants hospitalized for RSV infection (n=43, cases), hernia surgery (n=16, controls), or RSV-negative viral respiratory tract infections (n=18, controls). First, we determined RSV antigen-specific antibody levels in infant plasma using a multiplex immunoassay. Subsequently, we measured the capacity of these antibodies to activate NK cells. Finally, we assessed Fc-glycosylation of the RSV-specific antibodies by mass spectrometry.\n\nResultsWe found that RSV-specific maternal antibodies potently activate NK cells in vitro. While the concentrations of RSV-specific antibodies did not differ between cases and controls, antibodies from infants hospitalized for severe lower respiratory tract infections (RSV and/or other) induced significantly less NK cell interferon gamma production than those from uninfected controls. Furthermore, NK cell activation correlated with Fc-fucosylation of RSV-specific antibodies, but their glycosylation status did not significantly differ between cases and controls.\n\nConclusionsOur results suggest that Fc-dependent antibody function and quality, exemplified by NK cell activation and glycosylation, contribute to protection against severe RSV disease and warrant further studies to evaluate the potential of harnessing these activities to develop an effective vaccine.

immunology↗

bioRxiv2019

Functional diversification of hybridoma produced antibodies by CRISPR/HDR genomic engineering

Hybridoma technology is instrumental for the development of novel antibody therapeutics and diagnostics. Recent preclinical and clinical studies highlight the importance of antibody isotype for therapeutic efficacy. However, since the sequence encoding the constant domains is fixed, tuning antibody function in hybridomas has been restricted. Here, we demonstrate a versatile CRISPR/HDR platform to rapidly engineer the constant immunoglobulin domains to obtain recombinant hybridomas which secrete antibodies in the preferred format, species and isotype. Using this platform, we obtained recombinant hybridomas secreting Fab fragments, isotype switched chimeric antibodies, and Fc-silent mutants. These antibody products are stable, retain their antigen specificity, and display their intrinsic Fc-effector functions in vitro and in vivo. Furthermore, we can site-specifically attach cargo to these antibody products via chemo-enzymatic modification. We believe this versatile platform facilitates antibody engineering for the entire scientific community, empowering preclinical antibody research. One Sentence SummaryWe demonstrate a universal CRISPR/HDR based platform for rapid genetic engineering of hybridomas to obtain functionally diverse antibody isotype panels in the species and format of choice.

bioengineering↗