Insight into the mechanism of the acquired antibody auto-reactivity

Mechanistic Insight into Poly-Reactivity of Immune Antibodies upon Acid Denaturation or Arginine Mutation in Antigen-Binding Regions

The poly-reactivity of antibodies is defined as their binding to specific antigens as well as to related proteins and also to unrelated targets. Poly-reactivity can occur in individual molecules of natural serum antibodies, likely due to their conformation flexibility, and, for therapeutic antibodies, it plays a critical role in their clinical development. On the one hand, it can enhance their binding to target antigens and cognate receptors, but, on the other hand, it may lead to a loss of antibody function by binding to off-target proteins. Notably, poly-reactivity has been observed in antibodies subjected to treatments with dissociating, destabilizing or denaturing agents, in particular acidic pH, a common step in the therapeutic antibody production process involving the elution of Protein-A bound antibodies and viral clearance using low pH buffers. Additionally, poly-reactivity can emerge during the affinity maturation in the immune system, such as the germinal center. This review delves into the underlying potential causes of poly-reactivity, highlighting the importance of conformational flexibility, which can be further augmented by the acid denaturation of antibodies and the introduction of arginine mutations into the complementary regions of antibody-variable domains. The focus is placed on a particular antibody's acid conformation, meticulously characterized through circular dichroism, differential scanning calorimetry, and sedimentation velocity analyses. By gaining a deeper understanding of these mechanisms, we aim to shed light on the complexities of antibody poly-reactivity and its implications for therapeutic applications.

Enhanced Anti-Diabetogenic Effect of Intravenous Immune Globulin Modified by Ferrous Ion Exposure

The aim of this study was to investigate the immunomodulatory capacity of native and Fe(II)-exposed intravenous immune globulin (IVIg) in multiple low dose streptozotocin-induced diabetes and to delineate the mechanisms of their influence on immune cell functions. Optimal doses (200–600mg/kg) of IVIg prevented the development of hyperglycemia, glycosuria and attenuated mononuclear cell infiltration in pancreatic islets. Fe(II) exposure of IVIg decreased their optimal therapeutic dose to 100mg/kg which significantly decreased the serum levels of proinflammatory cytokines compared to the same dose of native IVIg. This was accompanied by lower numbers of TNF-α, IFN-γ and IL-17 producing CD4+ T cells and increased frequencies of CD4+IL-10+ and CD4+IL-4+ T cells in the pancreatic lymph nodes and islets on day 16 after diabetes induction. Ferrous ion-exposed IVIg enhanced the bias towards Th2 response while the regulatory Foxp3+ T cells were not affected.

The avidity of anti-β2-glycoprotein I antibodies in patients with or without antiphospholipid syndrome: a collaborative study in the frame of the European forum on antiphospholipid antibodies

Objective. The objective of this study was to extend the findings of the preliminary study by measuring the avidity of IgG anti-β2-glycoprotein I antibodies (anti-β2-GPI) on a larger group of patients with primary or secondary antiphospholipid syndrome (APS) and anti-β2-GPI positive patients without APS in the frame of the European Forum on antiphospholipid antibodies (aPL).

Methods. Serum from 137 patients with primary APS, APS associated with autoimmune diseases, and patients with autoimmune diseases other than APS from five EU rheumatology centres were tested for anti-β2-GPI antibodies. The 109 patients who were sera positive for anti-β2-GPI by the in-house anti-β2-GPI enzyme-linked immunosorbent assay (ELISA) at the Immunology Laboratory, UMC Ljubljana were selected for further testing on avidity with chaotropic anti-β2-GPI ELISA.

Results. High, low and heterogeneous avidity IgG anti-β2-GPI was found in 32/109, 17/109 and 60/109 patients respectively. Significantly more patients with APS were in the high avidity than in the low avidity anti-β2-GPI group, while the opposite was observed for non-APS (both p < 0.001). The most common clinical feature among patients with high avidity anti-β2-GPI was thrombosis, mainly due to venous thrombosis ( p < 0.01 and p < 0.001, versus low avidity anti-β2-GPI group).

Conclusion. Patients with or without APS had anti-β2-GPI of high, low or heterogeneous avidity. High avidity anti-β2-GPI was associated with thrombosis and APS, while in the low avidity anti-β2-GPI group non-APS (predominantly SLE) patients prevailed. Determination of anti-β2-GPI avidity should be considered in the analytical strategies for further differentiation of patients with anti-β2-GPI antibodies.

Natural autoantibodies to myeloperoxidase, proteinase 3, and the glomerular basement membrane are present in normal individuals

Anti-neutrophil cytoplasmic antibodies (ANCAs) have a pathogenic role in ANCA-associated vasculitis. The origin of ANCAs and anti-glomerular basement membrane (GBM) antibodies, however, is unknown. In this study, we determined whether natural autoantibodies against myeloperoxidase (MPO), proteinase 3 (PR3), and GBM were present in each of 10 healthy Chinese and Swedish individuals, negative for all three antigens by routine ELISA. Antibodies were purified from isolated IgG by antigen-specific affinity columns. Natural anti-GBM autoantibodies gave a linear staining pattern along the GBM of human renal sections. On ethanol-fixed granulocytes, both natural anti-MPO and anti-PR3 autoantibodies gave cytoplasmic staining. The titers of natural anti-MPO/PR3 autoantibodies were significantly lower than those from patients with vasculitis. In competition ELISA, the binding of natural anti-MPO autoantibodies could be inhibited by MPO, but not by PR3 or noncollagenous domains from type IV collagen. The same specificity results were found for natural anti-PR3 and anti-GBM autoantibodies. Overall, individuals of the Chinese origin had more natural autoantibodies than did those of the Swedish origin, but no other differences were found. Hence, our study shows that healthy individuals have masked circulating, noncross-reactive, antigen-specific natural autoantibodies against MPO, PR3, and GBM in their serum and IgG fractions. Further studies are needed to determine their role if any in the etiology of ANCA-associated vasculitis and anti-GBM disease.

Autoantibody potential of cancer therapeutic monoclonal antibodies

We and others have reported that multiple autoantibodies are unmasked in human polyclonal antibody preparations after exposure to physiological oxidizing agents (hemin) or electromotive force. We now have asked if oxidation unmasks autoantibody reactivities in monoclonal antibodies (mAb). To do this, we have studied 9 FDA approved mAb used therapeutically, including 4 chimeric, 4 humanized and 1 chemically modified chimeric Fab that were exposed to the physiological oxidizing agent hemin at 36 degrees C for 20 hr. These mAb were studied for autoantibody activity to phospholipids and DNA before and after oxidation with hemin and found to develop autoantibody activities after oxidation, while retaining their original specificity as measured by mAb anti-glycophorin A binding of erythrocytes, CD 19 binding to B lymphocytes and anti-HLA-A29 binding to A29-positive lymphocytes. The finding that certain mAb have the potential to unmask autoantibody activities as a consequence of exposure to physiological redox reactions in vitro gives pause to our present understanding of the immunological basis of tolerance and concern for potential autoimmune side effects in patients receiving mAb for diagnosis or treatment.

Protein destabilizing agents induce polyreactivity and enhanced immunomodulatory activity in IVIg preparations

Normal pooled human IVIg are produced using various blood protein fractionation technologies and as a result they may well differ in their biological properties. We have demonstrated that exposure of IVIg, for a period as short as 15 min, to protein-destabilizing agents like acidic pH, ROS or pro-oxidative ferrous ions dramatically increases the panel of recognized Ag including pro-inflammatory cytokines. We now show that exposure of IVIg to ferrous ions modifies some IgG molecules without denaturating them and enhances the protective activity of the preparation in experimental septic shock.

Gene therapy in autoimmune diseases: challenges and opportunities

Clinical treatment of autoimmune disorders presents a special challenge. For decades, most clinical regimens in autoimmunity has been largely symptomatic and non-disease specific. Although data from vigorous research has lead to accumulating knowledge on the pathogenic and immunological mechanisms of many autoimmune diseases, their direct clinical applications have been sparse. Advances in biotechnology have laid the groundwork for potent and specific molecular targeting therapies by gene therapy, and have just begun to be investigated in the treatment of autoimmune disorders. Such work has been largely based on the availability of well-established animal models of common autoimmune disorders, and the efficacy of strategic approaches initially investigated and validated in these models. Although these preclinical animal model studies have provided the proof-of-concept for multiple potential applications, human clinical trials on gene therapy in autoimmunity are still at its infancy. The recent success of Phase I/II clinical trials of gene therapy in rheumatoid arthritis and multiple sclerosis, development of cutting edge technology in target identification, as well as gene delivery systems have now set the stage for a more thorough and vigorous pace in the near future to advance this exciting field.