Immunoglobulin G Binding Research Articles

Cold plasma-induced covalent binding with epigallo-catechin 3-gallate: A strategy for antigenicity reduction and antioxidant improvement of β-lactoglobulin

The application of cold plasma (CP) treatment was investigated for its effectiveness in promoting the covalent grafting of β-lactoglobulin (β-LG) and epigallo-catechin 3 -gallate (EGCG), as well as improving the antioxidant capacity of β-LG and eliminating its antigenicity. The results indicated that CP treatment significantly enhanced the covalent grafting of β-LG and EGCG. The maximum EGCG content in β-LG-EGCG complexes reached 47.08 ± 0.58 mg/g (with 45 s treatment), as confirmed by SDS-PAGE analysis and FTIR spectroscopy. Additionally, LC-MS/MS identifies two binding sites (T76 and K77) of EGCG in the β-LG-EGCG conjugates. After 60 s treatments, there was a significant reduction in the IgG binding capacity of β-LG-EGCG conjugates (29.97 ± 0.05%). Further analysis suggested that the change in the conformational epitopes of β-LG, due to the conjugating with EGCG, was likely the main factor responsible for the reduced binding Immunoglobulin G (IgG) capacity. The maximum antioxidant activities of β-LG-EGCG conjugates were found to be 974.14 ± 1.94 μmol TE g−1 for ABTS and 748.48 ± 9.66 μmol TE g−1 for DPPH). These values represent an eightfold increase in DPPH activity and a twofold increase in ABTS compared to the control sample. This study demonstrated that the CP treatment is highly effective technology for facilitating the covalent grafting of polyphenols to proteins, thereby enhancing their antioxidant properties and eliminate their antigenicity.

Structure Derivatization of IgG-Binding Peptides and Analysis of Their Secondary Structure by Circular Dichroism Spectroscopy.

Mid-sized cyclic peptides are a promising modality for modern drug discovery. Their larger interaction area coupled with an appropriate secondary structure is more suitable than small molecules for binding to the target protein. In this study, we conducted a structure derivatization of an immunoglobulin G (IgG)-binding peptide (15-IgBP), a β-hairpin-like cyclic peptide with a twisted β-strand and assessed the effect of the secondary structure on IgG-binding activity using circular dichroism (CD) spectra analysis. As a result, derivatization at the Ala5 and Gly9 positions affected the secondary structure of 15-IgBP, in particular the appearance of a small positive peak in the 220-240 nm region characteristic of 15-IgBP in the CD spectrum. Maintaining this peak at a moderate level may be important for the expression of IgG binding activity. We found the small methyl group at Ala5 to be crucial for retaining the preferred secondary structure; we also found Gly9 could be replaced by D-amino acids. By integrating these findings with previous results of the structure-activity relationship, we obtained four potent affinity peptides for IgG binding (Kd = 4.24-5.85 nM). Furthermore, we found the Gly9 position can be substituted for D-Lys. This is a new potential site for attaching functional units for conjugation with IgG for the preparation of homogeneous antibody-drug conjugates.

Immunoglobulin G glycosylation and its alterations in aging-related diseases.

Immunoglobulin G (IgG) is an important serum glycoprotein and a major component of antibodies. Glycans on IgG affect the binding of IgG to the Fc receptor or complement C1q, which in turn affects the biological activity and biological function of IgG. Altered glycosylation patterns on IgG emerge as important biomarkers in the aging process and age-related diseases. Key aging-related alterations observed in IgG glycosylation include reductions in galactosylation and sialylation, alongside increases in agalactosylation, and bisecting GlcNAc. Understanding the role of IgG glycosylation in aging-related diseases offers insights into disease mechanisms and provides opportunities for the development of diagnostic and therapeutic strategies. This review summarizes five aspects of IgG: an overview of IgG, IgG glycosylation, IgG glycosylation with inflammation mediation, IgG glycan changes with normal aging, as well as the relevance of IgG glycan changes to aging-related diseases. This review provides a reference for further investigation of the regulatory mechanisms of IgG glycosylation in aging-related diseases, as well as for evaluating the potential of IgG glycosylation changes as markers of aging and aging-related diseases.

Direct Affinity Ligand Immobilization onto Bare Iron Oxide Nanoparticles Enables Efficient Magnetic Separation of Antibodies.

Magnetic separation is a promising alternative to chromatography for enhancing the downstream processing (DSP) of monoclonal antibodies (mAbs). However, there is a lack of efficient magnetic particles for successful application. Aiming to fill this gap, we demonstrate the suitability of bare iron oxide nanoparticles (BION) with physical site-directed immobilization of an engineered Protein A affinity ligand (rSpA) as an innovative magnetic material. The rSpA ligand contains a short peptide tag that enables the direct and stable immobilization onto the uncoated BION surface without commonly required laborious particle activation. The resulting BION@rSpA have beneficial characteristics outperforming conventional Protein A-functionalized magnetic particles: a simple, fast, low-cost synthesis, a particle size in the nanometer range with a large effective specific surface area enabling large immunoglobulin G (IgG) binding capacity, and a high magnetophoretic velocity advantageous for fast processing. We further show rapid interactions of IgG with the easily accessible rSpA ligands. The binding of IgG to BION@rSpA is thereby highly selective and not impeded by impurity molecules in perfusion cell culture supernatant. Regarding the subsequent acidic IgG elution from BION@rSpA@IgG, we observed a hampering pH increase caused by the protonation of large iron oxide surfaces after concentrating the particles in 100 mM sodium acetate buffer. However, the pH can be stabilized by adding 50 mM glycine to the elution buffer, resulting in recoveries above 85% even at high particle concentrations. Our work shows that BION@rSpA enable efficient magnetic mAb separation and could help to overcome emerging bottlenecks in DSP.

Proteomic profiling of circulating β-thalassaemia/haemoglobin E extra-cellular vesicles reveals that association with immunoglobulin induces membrane vesiculation.

Splenectomised β-thalassaemia/haemoglobin E (HbE) patients have increased levels of circulating microparticles or medium extra-cellular vesicles (mEVs). The splenectomised mEVs play important roles in thromboembolic complications in patients since they can induce platelet activation and endothelial cell dysfunction. However, a comprehensive understanding of the mechanism of mEV generation in thalassaemia disease has still not been reached. Thalassaemic mEVs are hypothesised to be generated from cellular oxidative stress in red blood cells (RBCs) and platelets. Therefore, a proteomic analysis of mEVs from splenectomised and non-splenectomised β-thalassaemia/HbE patients was performed by liquid chromatography with tandem mass spectrometry. A total of 171 proteins were identified among mEVs. Interestingly, 72 proteins were uniquely found in splenectomised mEVs including immunoglobulin subunits and cytoskeleton proteins. Immunoglobulin G (IgG)-bearing mEVs in splenectomised patients were significantly increased. Furthermore, complement C1q was detected in both mEVs with IgG binding and mEVs without IgG binding. Interestingly, the percentage of mEVs generated from RBCs with IgG binding was approximately 15-20 times higher than the percentage of RBCs binding with IgG. This suggested that the vesiculation of thalassaemia mEVs could be a mechanism of RBCs to eliminate membrane patches harbouring immune complex and may consequently prevent cells from phagocytosis and lysis.

Poor association between 13-valent pneumococcal conjugate vaccine-induced serum and mucosal antibody responses with experimental Streptococcus pneumoniae serotype 6B colonisation

BackgroundPneumococcal carriage is the primary reservoir for transmissionand a prerequisite for invasive pneumococcal disease. Pneumococcal Conjugate Vaccine 13 (PCV13) showed a 62% efficacy in protection against experimental Streptococcus pneumoniae serotype 6B (Spn6B) carriage in a controlled human infection model (CHIM) of healthy Malawian adults. We, therefore, measured humoral responses to experimental challenge and PCV-13 vaccination and determined the association with protection against pneumococcal carriage. MethodsWe vaccinated 204 young, healthy Malawian adults with PCV13 or placebo and nasally inoculated them with Spn6B at least four weeks post-vaccination to establish carriage. We collected peripheral blood and nasal lining fluid at baseline, 4 weeks post-vaccination (7 days pre-inoculation), 2, 7, 14 and > 1 year post-inoculation. We measured the concentration of anti-serotype 6B Capsular Polysaccharide (CPS) Immunoglobulin G (IgG) and IgA antibodies in serum and nasal lining fluid using the World Health Organization (WHO) standardised enzyme-linked immunosorbent assay (ELISA). ResultsPCV13-vaccinated adults had higher serum IgG and nasal IgG/IgA anti-Spn6B CPS-specific binding antibodies than placebo recipients 4 to 6 weeks post-vaccination, which persisted for at least a year after vaccination. Nasal challenge with Spn6B did not significantly alter serum or nasal anti-CPS IgG binding antibody titers with or without experimental pneumococcal carriage. Pre-challenge titers of PCV13-induced serum IgG and nasal IgG/IgA anti-Spn6B CPS binding antibodies did not significantly differ between those that got experimentally colonised by Spn6B compared to those that did not. ConclusionThis study demonstrates that despite high PCV13 efficacy against experimental Spn6B carriage in young, healthy Malawian adults, robust vaccine-induced systemic and mucosal anti-Spn6B CPS binding antibodies did not directly relate to protection.

Electric Field-Assisted Molecularly Imprinted Polymer-Modified QCM Sensor for Enhanced Detection of Immunoglobulin.

In this study, an electric-field-assisted molecularly imprinted polymer (EFAMIP) as an enhanced form of MIP was developed to improve the MIP-modified quartz crystal microbalance (QCM) biosensors. While exerting a vertical electric field, polymerization of methacrylic acid in the presence of immunoglobulin G (IgG) as the template was initiated, and later, after the template removal process, the EFAMIPs were obtained. The polymer surface characterization was conducted by using a scanning electron microscope. The impact of electric field direction on IgG binding sites, forming either EFAMIP-Fab or EFAMIP-Fc, was assessed. Next, the static measurement results in liquid for EFAMIP-modified QCM and MIP-modified QCM were compared. While encompassing IgG, EFAMIP-modified QCMs exhibited up to a 113.5% higher frequency shift than typical MIP in time-limited detection. The final frequency shift of EFAMIP, which determines the detection limit of IgG, was improved up to 12.5% compared to typical MIP. Moreover, the EFAMIP-Fab performance was promising for the selective detection of IgG in a solution containing different types of immunoglobulins.

A Chronic Increase in Blood-Brain Barrier Permeability Facilitates Intraneuronal Deposition of Exogenous Bloodborne Amyloid-Beta1-42 Peptide in the Brain and Leads to Alzheimer's Disease-Relevant Cognitive Changes in a Mouse Model.

Increased blood-brain barrier (BBB) permeability and amyloid-β (Aβ) peptides (especially Aβ1-42) (Aβ42) have been linked to Alzheimer's disease (AD) pathogenesis, but the nature of their involvement in AD-related neuropathological changes leading to cognitive changes remains poorly understood. To test the hypothesis that chronic extravasation of bloodborne Aβ42 peptide and brain-reactive autoantibodies and their entry into the brain parenchyma via a permeable BBB contribute to AD-related pathological changes and cognitive changes in a mouse model. The BBB was rendered chronically permeable through repeated injections of Pertussis toxin (PT), and soluble monomeric, fluorescein isothiocyanate (FITC)-labeled or unlabeled Aβ42 was injected into the tail-vein of 10-month-old male CD1 mice at designated intervals spanning ∼3 months. Acquisition of learned behaviors and long-term retention were assessed via a battery of cognitive and behavioral tests and linked to neuropathological changes. Mice injected with both PT and Aβ42 demonstrated a preferential deficit in the capacity for long-term retention and an increased susceptibility to interference in selective attention compared to mice exposed to PT or saline only. Immunohistochemical analyses revealed increased BBB permeability and entry of bloodborne Aβ42 and immunoglobulin G (IgG) into the brain parenchyma, selective neuronal binding of IgG and neuronal accumulation of Aβ42 in animals injected with both PT and Aβ42 compared to controls. Results highlight the potential synergistic role of BBB compromise and the influx of bloodborne Aβ42 into the brain in both the initiation and progression of neuropathologic and cognitive changes associated with AD.

Overview of the Safety Profile From Efgartigimod Clinical Trials in Participants With Diverse IgG-Mediated Autoimmune Diseases

Background Efgartigimod is a first-in-class, human immunoglobulin-G (IgG) Fc fragment that inhibits the neonatal Fc receptor (FcRn) and outcompetes endogenous IgG binding. FcRn inhibition by efgartigimod is a rational therapeutic option for IgG-mediated autoimmune disorders, including immune thrombocytopenia (ITP). Aims To determine the safety profile of efgartigimod for a variety of IgG-mediated autoimmune disorders, including ITP. Methods Intravenous efgartigimod safety was assessed in a phase 3 (ADVANCE) trial in ITP. It was also evaluated in generalized myasthenia gravis (gMG) in phase 2 and 3 (ADAPT) trials and a 3-year open-label extension (ADAPT+) along with an open-label phase 2 trial in pemphigus. Varying dosing regimens of efgartigimod (10-25 mg/kg) were used, including cyclical (gMG) and continuous weekly dosing (ITP, pemphigus). Results Across all indications and doses studied, efgartigimod demonstrated a consistent safety profile, with comparable treatment emergent adverse event (TEAE) rates to placebo (ADVANCE 93.0% efgartigimod vs. 95.6% placebo; ADAPT 77.4% efgartigimod vs. 84.3% placebo; 85% of participants in open label pemphigus study). Most TEAEs across studies were mild to moderate in severity. Discontinuation rates due to adverse events were low across studies (3.5% efgartigimod vs. 2.2% placebo in ADVANCE; 3.6% efgartigimod vs. 3.6% placebo in ADAPT; 3% in pemphigus). No increase in TEAE incidence rates or infections with repeated efgartigimod cycles (up to 19) in ADAPT+ was observed. In ADVANCE, no thromboembolic TEAEs were reported. Efgartigimod did not impair participant ability to generate new specific IgG responses to non-live vaccines, regardless of the timing of vaccinations however, there were transient reductions in specific IgG titers observed. Conclusions Efgartigimod was generally well tolerated across indications and doses studied. Most TEAEs, including infections, were mild or moderate in severity and did not increase in frequency with recurrent dosing. Non-live vaccine responsiveness was preserved. There were no thromboembolic events in those treated for ITP.

Heightened TLR7 signaling primes BCR-activated B cells in chronic graft-versus-host disease for effector functions

AbstractChronic graft-versus-host disease (cGVHD) is a debilitating, autoimmune-like syndrome that can occur after allogeneic hematopoietic stem cell transplantation. Constitutively activated B cells contribute to ongoing alloreactivity and autoreactivity in patients with cGVHD. Excessive tissue damage that occurs after transplantation exposes B cells to nucleic acids in the extracellular environment. Recognition of endogenous nucleic acids within B cells can promote pathogenic B-cell activation. Therefore, we hypothesized that cGVHD B cells aberrantly signal through RNA and DNA sensors such as Toll-like receptor 7 (TLR7) and TLR9. We found that B cells from patients and mice with cGVHD had higher expression of TLR7 than non-cGVHD B cells. Using ex vivo assays, we found that B cells from patients with cGVHD also demonstrated increased interleukin-6 production after TLR7 stimulation with R848. Low-dose B-cell receptor (BCR) stimulation augmented B-cell responses to TLR7 activation. TLR7 hyperresponsiveness in cGVHD B cells correlated with increased expression and activation of the downstream transcription factor interferon regulatory factor 5. Because RNA-containing immune complexes can activate B cells through TLR7, we used a protein microarray to identify RNA-containing antigen targets of potential pathological relevance in cGVHD. We found that many of the unique targets of active cGVHD immunoglobulin G (IgG) were nucleic acid–binding proteins. This unbiased assay identified the autoantigen and known cGVHD target Ro-52, and we found that RNA was required for IgG binding to Ro-52. Herein, we find that BCR-activated B cells have aberrant TLR7 signaling responses that promote potential effector responses in cGVHD.

SARS-CoV-2 mRNA Vaccines Induce Greater Complement Activation and Decreased Viremia and Nef Antibodies in Men With HIV-1.

Immune dysregulation in people with human immunodeficiency virus-1 (PWH) persists despite potent antiretroviral therapy and, consequently, PWH tend to have lower immune responses to licensed vaccines. However, limited information is available about the impact of mRNA vaccines in PWH. This study details the immunologic responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccines in PWH and their impact on HIV-1. We quantified anti-S immunoglobulin G (IgG) binding and neutralization of 3 SARS-CoV-2 variants of concern and complement activation in blood from virally suppressed men with HIV-1 (MWH) and men without HIV-1 (MWOH), and the characteristics that may impact the vaccine immune responses. We also studied antibody levels against HIV-1 proteins and HIV-1 plasma RNA. MWH had lower anti-S IgG binding and neutralizing antibodies against the 3 variants compared to MWOH. MWH also produced anti-S1 antibodies with a 10-fold greater ability to activate complement and exhibited higher C3a blood levels than MWOH. MWH had decreased residual HIV-1 plasma viremia and anti-Nef IgG approximately 100 days after immunization. MWH respond to SARS-CoV-2 mRNA vaccines with lower antibody titers and with greater activation of complement, while exhibiting a decrease in HIV-1 viremia and anti-Nef antibodies. These results suggest an important role of complement activation mediating protection in MWH.

Autoantibodies Which Bind to and Activate Keratinocytes in Systemic Sclerosis.

Systemic sclerosis (SSc) is a multisystem connective tissue disease characterised by pathological processes involving autoimmunity, vasculopathy and resultant extensive skin and organ fibrosis. Recent studies have demonstrated activation and aberrant wound healing responses in the epithelial layer of the skin in this disease, implicating the epithelial keratinocytes as a source of pro-fibrotic and inflammatory mediators. In this paper, we investigated the role of Immunoglobulin G (IgG) autoantibodies directed against epithelial cells, as potential initiators and propagators of pathological keratocyte activation and the ensuing SSc fibrotic cascade. A keratinocyte cell-based ELISA is used to evaluate the binding of SSc IgG. SSc skin biopsies were stained by immunofluorescence for the presence of IgG in the keratinocyte layer. Moreover, IgG purified from SSc sera was evaluated for the potential to activate keratinocytes in tissue culture and to induce TLR2 and 3 signalling in reporter cell lines. We demonstrate enhanced binding of SSc IgG to keratinocytes and the activation of these cells leading to the release of IL-1α, representing a potential initiating pathway in this disease.

Effect of efgartigimod on muscle group subdomains in participants with generalized myasthenia gravis: post hoc analyses of the phase 3 pivotal ADAPT study.

Generalized myasthenia gravis (gMG) is a rare, chronic, neuromuscular autoimmune disease mediated by pathogenic immunoglobulin G (IgG) autoantibodies. Patients with gMG experience debilitating muscle weakness, resulting in impaired mobility, speech, swallowing, vision and respiratory function. Efgartigimod is a human IgG1 antibody Fc fragment engineered for increased binding affinity to neonatal Fc receptor. The neonatal Fc receptor blockade by efgartigimod competitively inhibits endogenous IgG binding, leading to decreased IgG recycling and increased degradation resulting in lower IgG concentration. The safety and efficacy of efgartigimod were evaluated in the ADAPT study. Key efficacy outcome measures included Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. Efgartigimod demonstrated significant improvement in both the MG-ADL and QMG scores. This post hoc analysis aimed to determine whether all subdomains of MG-ADL and QMG improved with efgartigimod treatment. Individual items of MG-ADL and QMG were grouped into four subdomains: bulbar, ocular, limb/gross motor and respiratory. Change from baseline over 10 weeks in each subdomain was calculated for each group. Greater improvements from baseline were seen across MG-ADL subdomains in participants treated with efgartigimod compared with placebo. These improvements were typically observed 1 to 2 weeks after the first infusion and correlated with reductions in IgG. Similar results were observed across most QMG subdomains. These post hoc analyses of MG-ADL and QMG subdomain data from ADAPT suggest that efgartigimod is beneficial in improving muscle function and strength across all muscle groups, leading to the observed efficacy in participants with gMG.

Characterization of the antispike IgG immune response to COVID-19 vaccines in people with a wide variety of immunodeficiencies.

Research on coronavirus disease 2019 vaccination in immune-deficient/disordered people (IDP) has focused on cancer and organ transplantation populations. In a prospective cohort of 195 IDP and 35 healthy volunteers (HV), antispike immunoglobulin G (IgG) was detected in 88% of IDP after dose 2, increasing to 93% by 6 months after dose 3. Despite high seroconversion, median IgG levels for IDP never surpassed one-third that of HV. IgG binding to Omicron BA.1 was lowest among variants. Angiotensin-converting enzyme 2 pseudo-neutralization only modestly correlated with antispike IgG concentration. IgG levels were not significantly altered by receipt of different messenger RNA-based vaccines, immunomodulating treatments, and prior severe acute respiratory syndrome coronavirus 2 infections. While our data show that three doses of coronavirus disease 2019 vaccinations induce antispike IgG in most IDP, additional doses are needed to increase protection. Because of the notably reduced IgG response to Omicron BA.1, the efficacy of additional vaccinations, including bivalent vaccines, should be studied in this population.

Abstract P1040: An Engineered Human Cardiac Tissue Model Reveals The Potential Contribution Of Systemic Lupus Erythematosus Autoantibodies To Myocardial Injury

A considerable number of patients with systemic lupus erythematosus (SLE) develop myocardial injury. SLE patients have highly heterogenous populations of autoantibodies that may contribute to cardiac disease pathogenesis and heterogeneity; however, little is known about their direct role in myocardial injury. Here, we engineered a model of matured human cardiac tissue and used it to study SLE induced myocardial injury. To this end, we cultured tissues with immunoglobulin G (IgG) from SLE patients with and without myocardial injury. We found that IgG binding levels differed between patient groups and correlated with measures of myocardial inflammation and systolic function. Interestingly, IgG from a subset of patients with systolic dysfunction exerted functional effects on our model system in the absence of immune cells, suggesting a direct contribution to myocardial injury. This was demonstrated by altered calcium handling and cellular composition, impaired cellular respiration, and distinctive patterns of gene expression determined by RNA sequencing. We further harnessed this model to identify potential disease-contributing autoantibodies. We propose that this model can be used to improve risk stratification and therapeutic strategies for SLE patients with myocardial injury.

A Severe Acute Respiratory Syndrome Coronavirus 2 Anti-Spike Immunoglobulin G Assay: A Robust Method for Evaluation of Vaccine Immunogenicity Using an Established Correlate of Protection.

As the COVID-19 pandemic continues, variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continue to emerge. Immunogenicity evaluation of vaccines and identification of correlates of protection for vaccine effectiveness is critical to aid the development of vaccines against emerging variants. Anti-recombinant spike (rS) protein immunoglobulin G (IgG) quantitation in the systemic circulation (serum/plasma) is shown to correlate with vaccine efficacy. Thus, an enzyme-linked immunosorbent assay (ELISA)-based binding assay to detect SARS-CoV-2 (ancestral and variant strains) anti-rS IgG in human serum samples was developed and validated. This assay successfully met acceptance criteria for inter/intra-assay precision, specificity, selectivity, linearity, lower/upper limits of quantitation, matrix effects, and assay robustness. The analyte in serum was stable for up to 8 freeze/thaw cycles and 2 years in -80 °C storage. Similar results were observed for the Beta, Delta, and Omicron BA.1/BA.5/XBB.1.5 variant-adapted assays. Anti-rS IgG assay results correlated significantly with neutralization and receptor binding inhibition assays. In addition, usage of international reference standards allows data extrapolation to WHO international units (BAU/mL), facilitating comparison of results with other IgG assays. This anti-rS IgG assay is a robust, high-throughput method to evaluate binding IgG responses to S protein in serum, enabling rapid development of effective vaccines against emerging COVID-19 variants.

Fibromyalgia patients with elevated levels of anti-satellite glia cell immunoglobulin G antibodies present with more severe symptoms.

Transferring fibromyalgia patient immunoglobulin G (IgG) to mice induces pain-like behaviour, and fibromyalgia IgG binds mouse and human satellite glia cells (SGCs). These findings suggest that autoantibodies could be part of fibromyalgia pathology. However, it is unknown how frequently fibromyalgia patients have anti-SGC antibodies and how anti-SGC antibodies associate with disease severity. Here, we quantified serum or plasma anti-SGC IgG levels in 2 fibromyalgia cohorts from Sweden and Canada using an indirect immunofluorescence murine cell culture assay. Fibromyalgia serum IgG binding to human SGCs in human dorsal root ganglia tissue sections was also assessed by immunofluorescence. In the cell culture assay, anti-SGC IgG levels were increased in both fibromyalgia cohorts compared with control group. Elevated anti-SGC IgG was associated with higher levels of self-reported pain in both cohorts, and higher fibromyalgia impact questionnaire scores and increased pressure sensitivity in the Swedish cohort. Anti-SGC IgG levels were not associated with fibromyalgia duration. Swedish fibromyalgia (FM) patients were clustered into FM-severe and FM-mild groups, and the FM-severe group had elevated anti-SGC IgG compared with the FM-mild group and control group. Anti-SGC IgG levels detected in culture positively correlated with increased binding to human SGCs. Moreover, the FM-severe group had elevated IgG binding to human SGCs compared with the FM-mild and control groups. These results demonstrate that a subset of fibromyalgia patients have elevated levels of anti-SGC antibodies, and the antibodies are associated with more severe fibromyalgia symptoms. Screening fibromyalgia patients for anti-SGC antibodies could provide a path to personalized treatment options that target autoantibodies and autoantibody production.

Immunoglobulin G-dependent inhibition of inflammatory bone remodeling requires pattern recognition receptor Dectin-1

Immunoglobulin G (IgG) antibodies are major drivers of inflammation during infectious and autoimmune diseases.In pooled serum IgG (IVIg), however, antibodies have a potent immunomodulatory and anti-inflammatory activity, but how this is mediated is unclear. We studied IgG-dependent initiation of resolution ofinflammation in cytokine- and autoantibody-driven models of rheumatoid arthritis and found IVIg sialylation inhibited joint inflammation, whereas inhibition of osteoclastogenesis was sialic acid independent. Instead, IVIg-dependent inhibition of osteoclastogenesis was abrogated in mice lacking receptors Dectin-1 or FcγRIIb. Atomistic molecular dynamics simulations and super-resolution microscopy revealed that Dectin-1 promoted FcγRIIb membrane conformations that allowed productive IgG binding and enhanced interactions with mouse and human IgG subclasses. IVIg reprogrammed monocytes via FcγRIIb-dependent signaling that required Dectin-1. Our data identify a pathogen-independent function of Dectin-1 as a co-inhibitory checkpoint for IgG-dependent inhibition of mouse and human osteoclastogenesis. These findings may have implications for therapeutic targeting of autoantibody and cytokine-driven inflammation.

Unraveling cross-reactivity of anti-glycan IgG responses in filarial nematode infections.

Parasitic nematodes responsible for filarial diseases cause chronic disablement in humans worldwide. Elimination programs have substantially reduced the rate of infection in certain areas, but limitations of current diagnostics for population surveillance have been pointed out and improved assays are needed to reach the elimination targets. While serological tests detecting antibodies to parasite antigens are convenient tools, those currently available are compromised by the occurrence of antibodies cross-reactive between nematodes, as well as by the presence of residual antibodies in sera years after treatment and clearance of the infection. We recently characterized the N-linked and glycosphingolipid derived glycans of the parasitic nematode Brugia malayi and revealed the presence of various antigenic structures that triggered immunoglobulin G (IgG) responses in infected individuals. To address the specificity of IgG binding to these glycan antigens, we screened microarrays containing Brugia malayi glycans with plasma from uninfected individuals and from individuals infected with Loa loa, Onchocerca volvulus, Mansonella perstans and Wuchereria bancrofti, four closely related filarial nematodes. IgG to a restricted subset of cross-reactive glycans was observed in infection plasmas from all four species. In plasma from Onchocerca volvulus and Mansonella perstans infected individuals, IgG binding to many more glycans was additionally detected, resulting in total IgG responses similar to the ones of Brugia malayi infected individuals. For these infection groups, Brugia malayi, Onchocerca volvulus and Mansonella perstans, we further studied the different IgG subclasses to Brugia malayi glycans. In all three infections, IgG1 and IgG2 appeared to be the major subclasses involved in response to glycan antigens. Interestingly, in Brugia malayi infected individuals, we observed a marked reduction in particular in IgG2 to parasite glycans post-treatment with anthelminthic, suggesting a promising potential for diagnostic applications. Thus, we compared the IgG response to a broad repertoire of Brugia malayi glycans in individuals infected with various filarial nematodes. We identified broadly cross-reactive and more specific glycan targets, extending the currently scarce knowledge of filarial nematode glycosylation and host anti-glycan antibody response. We believe that our initial findings could be further exploited to develop disease-specific diagnostics as part of an integrated approach for filarial disease control.

The role of anti-E. coli antibody from maternal colostrum on the colonization of newborn dairy calves gut with Escherichia coli and the development of clinical diarrhea

Escherichia coli (E. coli) is an early organism in the colonization of mucosal tissue and has an influence on the development of mucosal and systemic inflammatory responses. To understand the impact of transfer of Immunoglobulin G (IgG), E. coli-specific antibody and general immune factors to the calf on the gut microbiota, an observational study that followed the temporal colonization of the intestine with E. coli as correlated with the total quantity of IgG and the antibody recognizing E. coli, was conducted in newborn Holstein calves. The calves were subjected to the “gold standard” of colostrum management, including dam vaccination prior to delivery to prime colostrum. Twenty Holstein dams, producing an adequate quantity of good-quality colostrum following uncomplicated deliveries of healthy female offspring, were utilized in this study. Each calf was monitored and scored daily for diarrhea. Blood and fecal samples were collected from calves on day (D) D1 (before colostrum intake), then D3, D7, D14 and D28 after colostrum feeding. E. coli isolated from fecal samples of the calves were assessed for virulence genes and the quantity per gram of feces using conventional Polymerase chain reaction and Real-time polymerase chain reaction quantitative, respectively. The total quantity of plasma IgG and the titer of E. coli-binding antibody were measured by enzyme-linked immunosorbent assay. The peak in diarrhea in the calves was observed on D12. No IgG or E. coli-binding antibody were detected prior to colostrum intake (D1). Both total IgG and binding antibody sharply increased by D3. Total and binding IgG declined with calf age. The total number of bacteria (16S rRNA) in feces was similar between D1 and D14. The number of total bacteria increased over the period from D14 to D28. The number of E. coli was minimal on D1. The number of E. coli increased during the period D3-D7. A decrease in the number of E. coli per gram of feces declines between D14and D28. The stable toxin gene was frequently identified in the E. coli isolated from the calves. Further, E. coli K99 was not identified in this study. While the gut was colonized by E. coli early in life corresponding to the peak level of IgG and specific antibody, a decreasing number of E. coli were observed as the passive immunity waned. This suggests that the function of the passive antibody may be to control colonization and seed innate immune function that then stabilizes the level of E. coli in the digestive tract of calves.