Fishing for biomarkers with antigen mimics

A review on the effect of prolyl isomerization on immune response aberration and hypersensitivity reactions: A unifying hypothesis

Little is known about the causes and mechanisms of ectopic immune responses, including different types of hypersensitivity, superantigens, and cytokine storms. Two of the most questionable phenomena observed in immunology are why the intensity and extent of immune responses to different antigens are different, and why some self-antigens are attacked as foreign. The secondary structure of the peptides involved in the immune system, such as the epitope-paratope interfaces plays a pivotal role in the resulting immune responses. Prolyl cis/trans isomerization plays a fundamental role in the form of the secondary structure and the folding of proteins. This review covers some of the emerging evidence indicating the impact of prolyl isomerization on protein conformation, aberration of immune responses, and the development of hypersensitivity reactions.

Emerging technologies in autoantibody testing for rheumatic diseases

Testing for the presence of antinuclear antibodies (ANAs) is a key step in the diagnosis of systemic lupus erythematosus (SLE) and other systemic autoimmune rheumatic diseases (SARD). The standard slide-based indirect immunofluorescence (IIF) test is widely used, but is limited by a relative lack of specificity for SLE and not all SARD-ANAs are detected. Alternative immunoassays that might offer enhanced diagnostic and prognostic information have evolved, and some of these have entered clinical practice. This review summarizes the current state of ANA testing and multiplex techniques for detecting other autoantibodies, the possibility of point-of-care testing, and approaches for applications in early disease stages.

[Screening for Potential Drug Targets by Comprehensive Identification of Disease-specific Antigens Incorporated into Immune Complexes in Patients with Immunological Diseases]

Our immune system resembles an intelligent security system, which continually monitors for foreign invaders (infectious diseases); however, in some cases, this system recognizes healthy parts as something harmful or foreign and then attacks them (autoimmune diseases). The defining characteristics of an autoimmune disease are the existence of T- and B-cell autoreactivity against self proteins (autoantigens). In addition to autoimmune diseases, aberrant host proteins that occur during a certain state of diseases (e.g., cancer) can be recognized as an autoantigen. Immune complexes (ICs) are produced during an immune response and may reflect some aspects of an ongoing immune response. Therefore, the identity of antigens incorporated into ICs provides the information that in the future may aid in the development of diagnosis and treatment strategies for autoimmune diseases, infection, cancer, and transplantation therapy, and this information might be more relevant than information on free antigens. We developed a novel proteomic strategy (immune complexome analysis) in which ICs are separated from serum, followed by direct tryptic digestion and nano-liquid chromatography-tandem mass spectrometry for the identification and profiling of antigens in circulating ICs. We applied this strategy to the analysis of circulating ICs in autoimmune diseases (rheumatoid arthritis, anti-neutrophil cytoplasmic antibody-associated vasculitis, Takayasu's arteritis, mixed connective tissue disease, dermatomyositis, Sjögren's syndrome, systemic scleroderma, and systemic lupus erythematosus), infectious diseases and cancers. In this review, we mainly discuss the results for autoimmune diseases.

Epitope imprinted polyethersulfone beads by self-assembly for target protein capture from the plasma proteome

Self-assembly techniques were applied to fabricate epitope imprinted polyethersulfone beads for target protein capture from the plasma proteome.

Immune complexome analysis

Immune complexes (ICs) are produced during an immune response and may reflect some aspects of an ongoing immune response. Therefore, the identity of antigens incorporated into ICs provides the information that in the future may aid in the development of diagnosis and treatment strategies for autoimmune diseases, infection, cancer, and transplantation therapy, and this information might be more relevant than the information on free antigens. Because ICs may contain many antigens, comprehensive identification and profiling of such antigens are more effective than immunoblotting detection. Here, we introduced mass spectrometry (MS)-based two approaches (immunoproteomics and immune complexome analysis) to comprehensively identify the antigens. Immunoproteomics is a concept to identify disease-associated antigens that elicit immune responses by combining protein separation (two-dimensional electrophoresis, gel-free separation), immunological detection (Western blotting), and MS or by combining immunocapture and MS. Immune complexome analysis is designed for identifying antigens in circulating ICs and consists of ICs separation from serum and direct tryptic digestion followed by nano-liquid chromatography-tandem MS.

Development of robust and standardized cantilever sensors based on biotin/NeutrAvidin coupling for antibody detection

A cantilever-based protein biosensor has been developed providing a customizable multilayer platform for the detection of antibodies. It consists of a biotin-terminated PEG layer pre-functionalized on the gold-coated cantilever surface, onto which NeutrAvidin is adsorbed through biotin/NeutrAvidin specific binding. NeutrAvidin is used as a bridge layer between the biotin-coated surface and the biotinylated biomolecules, such as biotinylated bovine serum albumin (biotinylated BSA), forming a multilayer sensor for direct antibody capture. The cantilever biosensor has been successfully applied to the detection of mouse anti-BSA (m-IgG) and sheep anti-BSA(s-IgG) antibodies. As expected, the average differential surface stress signals of about 5.7 ± 0.8 × 10⁻³ N/m are very similar for BSA/m-IgG and BSA/s-IgG binding, i.e., they are independent of the origin of the antibody. A statistic evaluation of 112 response curves confirms that the multilayer protein cantilever biosensor shows high reproducibility. As a control test, a biotinylated maltose binding protein was used for detecting specificity of IgG, the result shows a signal of bBSA layer in response to antibody is 5.8 × 10⁻³ N/m compared to bMBP. The pre-functionalized biotin/PEG cantilever surface is found to show a long shelf-life of at least 40 days and retains its responsivity of above 70% of the signal when stored in PBS buffer at 4 °C. The protein cantilever biosensor represents a rapid, label-free, sensitive and reliable detection technique for a real-time protein assay.

Toward a new autoantibody diagnostic orthodoxy: understanding the bad, good and indifferent

Rapid advances in diagnostic technologies used to detect autoantibodies have made it difficult for even the most modern laboratory to keep abreast of the changing approaches and platforms, not to mention the clinicians who are hard pressed to keep abreast of evolving diagnostic paradigms attended by these newer techniques. While autoantibody testing is traditionally considered to be primarily serving the realm of diagnostic medicine, there is little doubt that autoantibodies are also being recognized as an approach to providing prognostic and therapeutic information. Accordingly, along with related proteomics, genomics and metabolomics, it is taking on increasing importance in the realm of personalized medicine. In today's world of autoantibody diagnostics, overarching concerns about false-negative and false-positive autoantibodies tests cannot be summarily dismissed by citing pros or cons of any one technology or diagnostic platform, but often point to persisting gaps in our knowledge about, and understanding of, the origin and roles of autoantibodies. Before we can hope to completely understand the enigmas that attend the results of autoantibody diagnostic tests, perhaps it is time to step back and re-examine long-accepted paradigms and beliefs. This review will address some of the issues that impact on autoantibody detection technologies and some of the considerations and issues that will attend a new orthodoxy of autoantibody diagnostics. These issues will be addressed in the context of "bad" (pathogenic), "good" (protective) or "indifferent" (no apparent role in disease) autoantibodies.

Application of immunosignatures to the assessment of Alzheimer's disease

OBJECTIVE

Accurate assessment of Alzheimer's disease (AD), both presymptomatically and at different disease stages, will become increasingly important with the expanding elderly population. There are a number of indications that the immune system is engaged in AD. Here we explore the ability of an antibody-profiling technology to characterize AD and screen for peptides that may be used for a simple diagnostic test.

METHODS

We developed an array-based system to profile the antibody repertoire of transgenic mice with cerebral amyloidosis (TG) and elderly individuals with or without AD. The array consists of 10,000 random sequence peptides (20-mers) capable of detecting antibody binding patterns, allowing the identification of peptides that mimic epitopes targeted by a donor's serum.

RESULTS

TG mice exhibited a distinct immunoprofile compared to nontransgenic littermates. Further, we show that dementia patients, including autopsy-confirmed AD subjects, have distinguishable profiles compared to age-matched nondemented people. Using antibodies to different forms of Aβ peptide and blocking protocols, we demonstrate that most of this signature is not due to the subject's antibodies raised against Aβ.

INTERPRETATION

We propose that "immunosignaturing" technology may have potential as a diagnostic tool in AD.