Characterization of autoantibodies from patients with Goodpasture's disease using a resonant mirror biosensor

Basement membranes and autoimmune diseases

Basement membrane components are targets of autoimmune attack in diverse diseases that destroy kidneys, lungs, skin, mucous membranes, joints, and other organs in man. Epitopes on collagen and laminin, in particular, are targeted by autoantibodies and T cells in anti-glomerular basement membrane glomerulonephritis, Goodpasture's disease, rheumatoid arthritis, post-lung transplant bronchiolitis obliterans syndrome, and multiple autoimmune dermatoses. This review examines major diseases linked to basement membrane autoreactivity, with a focus on investigations in patients and animal models that advance our understanding of disease pathogenesis. Autoimmunity to glomerular basement membrane type IV is discussed in depth as a prototypic organ-specific autoimmune disease yielding novel insights into the complexity of anti-basement membrane immunity and the roles of genetic and environmental susceptibility.

Performance evaluation of a novel chemiluminescence assay for detection of anti-GBM antibodies: an international multicenter study

BACKGROUND

Autoantibodies to the non-collagen region (NC1) of the alpha-3 subunit of collagen IV represent a serological hallmark in the diagnosis of Goodpasture's syndrome (GPS). The objective of our study was to carefully analyze the performance characteristics of a novel anti-glomerular basement membrane (GBM) chemiluminescence immunoassay (CIA).

METHODS

Sera from patients with GPS (n = 90) were collected from four clinical centers. Samples from different disease groups (n = 397) and healthy individuals (n = 400) were used as controls. All samples were tested for anti-GBM antibodies by a rapid, random access CIA (QUANTA Flash™ GBM). Most of the samples were also tested using other methods including different commercial anti-GBM IgG assays and research assays for anti-GBM IgA and IgM.

RESULTS

The sensitivity and specificity of the novel CIA was 95.6% [95% confidence interval (CI) 89.0-98.8%] and 99.6% (95% CI 98.9-99.9%), respectively. Receiver operating characteristic analysis showed good discrimination between GPS patients and controls. The area under the curve was 0.98 (CI 0.96-1.0). The three anti-GBM antibody-positive samples from the control group were from two healthy individuals and one human immunodeficiency virus (HIV)-infected patient. All three individuals had low levels of anti-GBM antibodies [20, 24 and 25 chemiluminescent unit (CU), cutoff 20 CU]. When the results of the new CIA were compared to other methods, good agreement was observed: 95.8% (kappa = 0.92) versus EliA™ GBM, 97.4% (kappa = 0.95) versus both BINDAZYME™ Anti-GBM and QUANTA Lite® GBM. Anti-GBM IgA was detectable in low concentrations in patients with GPS and was associated with anti-GBM IgG but was less useful in discriminating GPS patients and controls. No discrimination was found for anti-GBM IgM.

CONCLUSION

The novel QUANTA Flash™ GBM CIA demonstrated good sensitivity and specificity and had good agreement with other methods. Our data confirm that ∼5% of patients with GPS do not have detectable levels of anti-GBM antibodies.

Internal reflection ellipsometry in air and water ambient

We measured a multilayer sample in air and water ambient below the critical angle of incidence based on internal reflection ellipsometry (IRE). Measurements with varying incident angle and varying wavelength both provided values by the fitting for refractive indices and thicknesses of layers consistent with design or theoretical ones. This verified that IRE is useful in measurement and analysis of thin films on transparent substrates and especially effective to study thin films at transparent substrate-liquid interfaces.

Nanotechnologies in proteomics

Progress in proteomic researches is largely determined by development and implementation of new methods for the revelation and identification of proteins in biological material in a wide concentration range (from 10(-3) M to single molecules). The most perspective approaches to address this problem involve (i) nanotechnological physicochemical procedures for the separation of multicomponent protein mixtures; among these of particular interest are biospecific nanotechnological procedures for selection of proteins from multicomponent protein mixtures with their subsequent concentration on solid support; (ii) identification and counting of single molecules by use of molecular detectors. The prototypes of biospecific nanotechnological procedures, based on the capture of ligand biomolecules by biomolecules of immobilized ligate and the concentration of the captured ligands on appropriate surfaces, are well known; these are affinity chromatography, magnetic biobeads technology, different biosensor methods, etc. Here, we review the most promising nanotechnological approaches for selection of proteins and kinetic characterization of their complexes based on these biospecific methods with subsequent MS/MS identification of proteins and protein complexes. Two major groups of methods for the analysis and identification of individual molecules and their complexes by use of molecular detectors will be reviewed: scanning probe microscopy (SPM) (including atomic-force microscopy) and cryomassdetector technology.

Avidity of anti-glomerular basement membrane autoantibodies was associated with disease severity

Anti-glomerular basement membrane (GBM) antibody-mediated diseases are characterized by the binding of autoantibodies to GBM, leading to rapidly progressive glomerulonephritis that often results in irreversible loss of renal function. The nephrotoxic potential of anti-GBM antibodies has been demonstrated in animal experiments. We questioned whether high avidity leads to persistent deposition of anti-GBM antibodies, thereby perpetuating inflammation and renal damage. To address the hypothesis, sera from 32 patients and serial samples from 11 patients with anti-GBM disease were collected. Purified bovine alpha chain non-collagen 1 domains of type IV collagen [alpha(IV)NC1] were employed to exam avidity of anti-GBM antibodies using antigen-inhibition enzyme-linked immunosorbent assay. The amount of alpha(IV)NC1 needed for 50% inhibition of antibody binding was compared among patients with different clinical and pathological parameters. After the sera were diluted to give equivalent concentration of anti-GBM antibodies, the amount of alpha(IV)NC1 used for 50% inhibition was prominently different among patients, from 0.02 microg to 20 microg, with an average at 0.666 microg. A significant correlation was observed between the amount of alpha(IV)NC1 used and the percentage of glomeruli which had crescents (P=0.001). Higher avidity of anti-GBM antibodies predicted higher percentage of glomerular crescents (R2=0.58, P<0.001). No obvious change of avidity was observed in the serial samples. The results suggested that affinity maturation might have been completed by the time that patients presented with anti-GBM disease. The avidity of anti-GBM antibodies was associated with the degree of renal damage and might play a key role in the pathogenesis of anti-GBM disease.

A survey of the year 2002 commercial optical biosensor literature

We have compiled 819 articles published in the year 2002 that involved commercial optical biosensor technology. The literature demonstrates that the technology's application continues to increase as biosensors are contributing to diverse scientific fields and are used to examine interactions ranging in size from small molecules to whole cells. Also, the variety of available commercial biosensor platforms is increasing and the expertise of users is improving. In this review, we use the literature to focus on the basic types of biosensor experiments, including kinetics, equilibrium analysis, solution competition, active concentration determination and screening. In addition, using examples of particularly well-performed analyses, we illustrate the high information content available in the primary response data and emphasize the impact of including figures in publications to support the results of biosensor analyses.

ANCA and anti-GBM antibodies in diagnosis and follow-up of vasculitic disease

In the last decade, serological detection of anti-neutrophil cytoplasmic antibodies (ANCA) and of anti-glomerular basement membrane (GBM) antibodies has tremendously facilitated the diagnosis of small vessel vasculitides. Once diagnosed, these diseases have proven to be treatable. However, in contrast to anti-GBM disease, ANCA-associated vasculitides are chronic diseases with a high relapse rate. Since morbidity in ANCA-associated vasculitides is dictated by the frequency and severity of relapses, much health benefit would be achieved if a relapse could be prevented or early treatment started. Increases in ANCA titers and persistently high ANCA levels indicate a high risk of relapse and warrant clinical evaluation of the patient for signs of relapse. This review will focus on the value of ANCA and anti-GBM antibody testing in diagnosis and on the importance of these tests in follow-up of disease.

Pulmonary-renal vasculitic disorders: differential diagnosis and management

Pulmonary-renal syndrome (PRS) is a combination of diffuse pulmonary hemorrhage and glomerulonephritis. Pulmonary-renal syndrome is not a single entity and is caused by a variety of conditions, including Goodpasturés syndrome associated with autoantibodies to the glomerular and alveolar basement membranes, various forms of primary systemic vasculitis associated with serum positivity for antineutrophil cytoplasmic antibodies (ANCA), cryoglobulinemia, systemic lupus erythematosus, systemic sclerosis, antiphospholipid syndrome, environmental factors, and drugs. The majority of cases of PRS are associated with ANCAs. The antigen target in Goodpasturés syndrome is the alpha-3 chain of type IV collagen. The antigen target in PRS associated with systemic vasculitis is proteinase-3 and myeloperoxidase. Pulmonary-renal syndrome has been observed from the first to the ninth decade of life. The widespread adoption of serologic testing performed in an appropriate clinical context hopefully will limit diagnostic delay. The goals of treatment in PRS are to remove the circulating antibodies, to stop further production of autoantibodies, and to remove any antigen that stimulates antibody production. Treatment is based on plasmapheresis, steroids, and cyclophosphamide; however, infections are frequent contributors to death, and less toxic alternatives may improve outcome and prognosis resulting in a long-term survival. The degree of renal function and the percent of crescents on renal biopsy are better predictors of outcome. Renal transplantation can be safely carried out in PRS.