Somatic mutation in autoantibody-associated VH genes of circulating IgM+IgD+ B cells

Therapeutic Approaches for the Management of Autoimmune Disorders via Gene Therapy: Prospects, Challenges, and Opportunities

BACKGROUND

Autoimmune diseases are the diseases that result due to the overactive immune response, and comprise systemic autoimmune diseases like rheumatoid arthritis (RA), sjӧgren's syndrome (SS), and organ-specific autoimmune diseases like type-1 diabetes mellitus (T1DM), myasthenia gravis (MG), and inflammatory bowel disease (IBD). Currently, there is no long-term cure; but, several treatments exist which retard the evolution of the disease, embracing gene therapy, which has been scrutinized to hold immense aptitude for the management of autoimmune diseases.

OBJECTIVE

The review highlights the pathogenic mechanisms and genes liable for the development of autoimmune diseases, namely T1DM, type-2 diabetes mellitus (T2DM), RA, SS, IBD, and MG. Furthermore, the review focuses on investigating the outcomes of delivering the corrective genes with their specific viral vectors in various animal models experiencing these diseases to determine the effectiveness of gene therapy.

METHODS

Numerous review and research articles emphasizing the tremendous potential of gene therapy in the management of autoimmune diseases were procured from PubMed, MEDLINE, Frontier, and other databases and thoroughly studied for writing this review article.

RESULTS

The various animal models that experienced treatment with gene therapy have displayed regulation in the levels of proinflammatory cytokines, infiltration of lymphocytes, manifestations associated with autoimmune diseases, and maintained equilibrium in the immune response, thereby hinder the progression of autoimmune diseases.

CONCLUSION

Gene therapy has revealed prodigious aptitude in the management of autoimmune diseases in various animal studies, but further investigation is essential to combat the limitations associated with it and before employing it on humans.

Deep Characterization of the Human Antibody Response to Natural Infection Using Longitudinal Immune Repertoire Sequencing

Human antibody response studies are largely restricted to periods of high immune activity (e.g. vaccination). To comprehensively understand the healthy B cell immune repertoire and how this changes over time and through natural infection, we conducted immune repertoire RNA sequencing on flow cytometry-sorted B cell subsets to profile a single individual's antibodies over 11 months through two periods of natural viral infection. We found that 1) a baseline of healthy variable (V) gene usage in antibodies exists and is stable over time, but antibodies in memory cells consistently have a different usage profile relative to earlier B cell stages; 2) a single complementarity-determining region 3 (CDR3) is potentially generated from more than one VJ gene combination; and 3) IgG and IgA antibody transcripts are found at low levels in early human B cell development, suggesting that class switching may occur earlier than previously realized. These findings provide insight into immune repertoire stability, response to natural infections, and human B cell development.

Understanding the immunopathogenesis of autoimmune diseases by animal studies using gene modulation: A comprehensive review

Autoimmune diseases are clinical syndromes that result from pathogenic inflammatory responses driven by inadequate immune activation by T- and B-cells. Although the exact mechanisms of autoimmune diseases are still elusive, genetic factors also play an important role in the pathogenesis. Recently, with the advancement of understanding of the immunological and molecular basis of autoimmune diseases, gene modulation has become a potential approach for the tailored treatment of autoimmune disorders. Gene modulation can be applied to regulate the levels of interleukins (IL), tumor necrosis factor (TNF), cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), interferon-γ and other inflammatory cytokines by inhibiting these cytokine expressions using short interfering ribonucleic acid (siRNA) or by inhibiting cytokine signaling using small molecules. In addition, gene modulation delivering anti-inflammatory cytokines or cytokine antagonists showed effectiveness in regulating autoimmunity. In this review, we summarize the potential target genes for gene or immunomodulation in autoimmune diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel diseases (IBD) and multiple sclerosis (MS). This article will give a new perspective on understanding immunopathogenesis of autoimmune diseases not only in animals but also in human. Emerging approaches to investigate cytokine regulation through gene modulation may be a potential approach for the tailored immunomodulation of some autoimmune diseases near in the future.

The endoplasmic reticulum stress-inducible protein, Herp, is a potential triggering antigen for anti-DNA response

Anti-dsDNA Abs are highly specific indicators of systemic lupus erythematosus (SLE) and play a pathogenic role in lupus nephritis. Human anti-dsDNA Abs are most likely generated by an Ag-driven mechanism. However, the Ag responsible for triggering anti-dsDNA Ab production has not been identified. To search for proteins that are cross-reactive with anti-dsDNA Abs, we screened a cDNA library from a patient with SLE with single-chain Fv of O-81 human anti-ss/dsDNA mAb by using a two-hybrid system. Homocysteine-induced ER protein (Herp), an endoplasmic reticulum (ER) stress-inducible ER membrane protein, was identified and shown to bind to original O-81 Ab and human lupus anti-dsDNA Abs. Some IgG purified from patients with active SLE by Herp-immobilized affinity chromatography bound to dsDNA. BALB/c mice immunized with Herp showed IgG anti-dsDNA Abs, IgG anti-nucleosome Abs, and glomerular IgG deposition. Herp reactivity was strongly positive in a proportion of PBLs from patients with active SLE, but undetectable in those from healthy controls. Moreover, activation of caspases was observed in the Herp-positive cells, implying that ER stress-induced apoptosis likely occurs in patients with active SLE. Herp is exposed on blebs of ER stress-induced apoptotic cells, suggesting that Herp can be recognized by immune cells. These results indicate that Herp mimics structural determinants of DNA immunologically and can be immunogenic in vivo. Thus, Herp represents a candidate autoantigen for anti-DNA Abs. This study may help explain how common environmental factors induce the production of anti-DNA Abs and contribute the development of SLE.

[The role of cell stress in systemic autoimmune disease]

Anti-DNA antibody is a characteristic feature of systemic lupus erythematosus (SLE) and plays an important role in pathogenesis of lupus nephritis. However, the mechanism of anti-DNA antibody production, which may directly link to the etiology of SLE, remains uncertain. Mammalian DNA alone is not immunogenic. However, some anti-DNA antibodies cross-react with self antigens, and immunization of mice with a certain peptide could induce anti-DNA antibodies. These facts raise a question as to whether an antigenic trigger of anti-DNA antibodies production is DNA itself. Therefore, molecular mimicry of DNA by non DNA antigen is a possibility for the initial production of anti-DNA antibodies. We found that the human monoclonal nephritogenic anti-DNA antibody, O-81, specifically bound to an endoplasmic reticulum stress response protein, Herp. This suggests that lupus nephritogenic anti-DNA antibody cross-react with Herp and an epitope on Herp mimics DNA. Each time cells receive stress (for example, viral infection), the synthesis of Herp protein is induced. If the epitope is immunogenic, repetitive cell stress can be a trigger of anti-DNA antibodies production.

Histogenesis of CD5-positive and CD5-negative B-cell neoplasms on the aspect of somatic mutation of immunoglobulin heavy chain gene variable region

The immunoglobulin heavy chain (IgH) gene of B-cells dramatically alters twice in their differentiation to memory or plasma cells; VDJ recombination at B-cell precursor and somatic hypermutation, class switch recombination and receptor revision at germinal center (GC) B-cells. Among them, somatic hypermutation of the IgH gene variable region (VH gene) is a powerful tool for detection of B cell differentiation. B-cells and B-cell neoplasms have been divided into following; 1) pre-GC B-cells and neoplasms with a germline VH gene and 2) GC and post-GC B-cells and neoplasms with a somatically mutated VH gene. In this article, we review normal B-cell differentiation and histogenesis of various types of B-cell neoplasms on the aspect of somatic mutation of the rearranged VH gene. In particular, differences between CD5+ and CD5- B-cell neoplasms, using our own data of over 100 cases with B-cell neoplasms, are discussed. Although CD5+ B-cells are included in pre-GC B-cells for the reason of germline VH gene in most of CD5+ B-cells, an about 5% of CD5+ B-cells show somatically mutated VH gene. The rearranged VH gene of CD5+ B-cell neoplasms shows heterogeneity, whereas CD5- B-cell neoplasms possess somatically mutated VH gene with a mean of 8 approximately 12%. Both CD5+ B-cell chronic lymphocytic leukemia and CD5+ diffuse large B-cell lymphoma display that about half of cases show a germline or low frequency of somatic mutation and the others possess somatically mutated VH gene. CD5+ mantle cell lymphoma constitutes most cases with germline and a small number of cases with mutated VH gene. Therefore, CD5- B-cells & CD5- B-cell neoplasms are distinct from CD5+ B-cells and CD5+ B-cell neoplasms in somatic mutation of VH gene. It suggests that each of CD5- and CD5+ B-cells independently has its own differentiation.

Benzodiazepine-induced superoxide signals B cell apoptosis: mechanistic insight and potential therapeutic utility

The properties of a proapoptotic 1,4-benzodiazepine, Bz-423, identified through combinatorial chemistry and phenotype screening are described. Bz-423 rapidly generated superoxide (O(2)(-)) in transformed Ramos B cells. This O(2)(-) response originated from mitochondria prior to mitochondrial transmembrane gradient collapse and opening of the permeability transition pore. Bz-423-induced O(2)(-) functioned as an upstream signal that initiated an apoptotic program characterized by cytochrome c release, mitochondrial depolarization, and caspase activation. Pretreatment of cells with agents that either block the formation of Bz-423-induced O(2)(-) or scavenge free radicals attenuated the death cascade, which demonstrated that cell killing by Bz-423 depends on O(2)(-). Parallels between Ramos cells and germinal center B cells prompted experiments to determine whether Bz-423 had therapeutic activity in vivo. This possibility was tested using the (NZB x NZW)F(1) murine model of lupus, in which the pathologically enhanced survival and expansion of germinal center B cells mediate disease. Administration of Bz-423 for 12 weeks specifically controlled germinal center hyperplasia and reduced the histological evidence of glomerulonephritis. Collectively, these studies define a new structure-function relationship for benzodiazepines and point to a new target and mechanism that could be of value for developing improved drugs to manage systemic lupus erythematosus and related disorders.

Chemically modified ribozyme to V gene inhibits anti-DNA production and the formation of immune deposits caused by lupus lymphocytes

A variety of autoantibodies is responsible for the tissue injury in autoimmune diseases. We have demonstrated that the human anti-DNA Ab O-81, of which Ids are commonly detected in renal glomeruli of active lupus nephritis, uses the V3-7 gene. We tried to develop a new therapy for lupus nephritis by using chemically modified ribozymes to specifically inhibit the expression of the mRNA of Ig V gene. The transfection of hammerhead ribozyme or the addition of chemically modified ribozyme against the flanking region of V3-7 caused a potent and selective inhibition of anti-DNA production in V3-7-using B cell clones, but not in irrelevant V gene-using clones in vitro. Chemically modified ribozyme was long-acting and resistant to RNase, and nonspecific cytotoxicity of the ribozyme was negligible. To know the efficacy of the ribozyme in vivo, we used a model of immune complex nephritis in SCID mice in which 5 x 10(6) PBLs from patients with active lupus nephritis (lupus PBL) were transferred twice. The injection of lupus PBL in combination with chemically modified ribozyme to increase resistance to RNase significantly reduced anti-DNA Ab levels in blood and decreased levels of urinary protein in the immune deposit models. Immunofluorescence study also revealed a marked decrease in IgG deposits at renal glomeruli in the ribozyme-treated group. These results indicate an efficacy of chemically modified ribozyme therapy for autoantibody-mediated immune diseases.