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

Humanized Mouse Models of Systemic Lupus Erythematosus: Opportunities and Challenges

Animal models have played a crucial role in the understanding of the mechanisms and treatments of human diseases; however, owing to the large differences in genetic background and disease-specific characteristics, animal models cannot fully simulate the occurrence and progression of human diseases. Recently, humanized immune system mice, based on immunodeficient mice, have been developed that allow for the partial reconstruction of the human immune system and mimic the human in vivo microenvironment. Systemic lupus erythematosus (SLE) is a complex disease characterized by the loss of tolerance to autoantigens, overproduction of autoantibodies, and inflammation in multiple organ systems. The detailed immunological events that trigger the onset of clinical manifestations in patients with SLE are still not well known. Two methods have been adopted for the development of humanized SLE mice. They include transferring peripheral blood mononuclear cells from patients with SLE to immunodeficient mice or transferring human hematopoietic stem cells to immunodeficient mice followed by intraperitoneal injection with pristane to induce lupus. However, there are still several challenges to be overcome, such as how to improve the efficiency of reconstruction of the human B cell immune response, how to extend the lifespan and improve the survival rate of mice to extend the observation period, and how to improve the development of standardized commercialized models and use them. In summary, there are opportunities and challenges for the development of humanized mouse models of SLE, which will provide novel strategies for understanding the mechanisms and treatments of SLE.

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.

Amelioration of lupus manifestations by a peptide based on the complementarity determining region 1 of an autoantibody in severe combined immunodeficient (SCID) mice engrafted with peripheral blood lymphocytes of systemic lupus erythematosus (SLE) patients

A peptide based on the complementarity determining region (CDR)1 of a human monoclonal anti-DNA autoantibody (hCDR1) was shown to either prevent or treat an already established murine lupus in systemic lupus erythematosus (SLE)-prone mice or in mice with induced experimental SLE. The present study was undertaken to determine the therapeutic potential of hCDR1 in a model of lupus in severe combined immunodeficient (SCID) mice engrafted with peripheral blood lymphocytes (PBL) of patients with SLE. To this end, PBL obtained from lupus patients were injected intraperitoneally into two equal groups of SCID mice that were treated either with the hCDR1 (50 micro g/mouse) once a week for 8 weeks, or with a control peptide. Mice were tested for human IgG levels, anti-dsDNA autoantibodies, anti-tetanus toxoid antibodies and proteinuria. At sacrifice, the kidneys of the successfully engrafted mice were assessed for human IgG and murine complement C3 deposits. Of the 58 mice transplanted with PBL of SLE patients, 38 (66%) were engrafted successfully. The mice that were treated with the control peptide developed human dsDNA-specific antibodies. Treatment with hCDR1 down-regulated the latter significantly. No significant effect of the treatment on the levels of anti-tetanus toxoid antibodies could be observed. Treatment with hCDR1 resulted in a significant amelioration of the clinical features manifested by proteinuria, human IgG complex deposits as well as deposits of murine complement C3. Thus, the hCDR1 peptide is a potential candidate for a novel specific treatment of SLE patients.

Lupus manifestations in severe combined immunodeficient (SCID) mice and in human/mouse radiation chimeras

The objective of this study was to develop a human lupus model. To this end we have established and compared two models: (1) severe combined immunodeficient (SCID) mice reconstituted with peripheral blood lymphocytes (PBL) of either systemic lupus erythematosus (SLE) patients or healthy controls and (2) lethally irradiated BALB/c mice radioprotected with bone marrow of SCID mice, to which human PBL were transferred (human/mouse chimera). Engraftment was successful in most (78.4%) recipient mice as determined by the levels of human IgG measured. In about 50% of either SCID mice or human/mouse chimeras that were successfully engrafted with PBL of SLE patients, significant anti-dsDNA autoantibodies, mostly of the IgG1 and IgG2 isotypes, were determined. Interestingly, in a significant number (84.5%) of recipients of PBL of the healthy controls, anti-dsDNA antibodies were observed as well, suggesting that PBL of at least some of the healthy controls have the potential to develop SLE-associated autoantibodies under the appropriate stimulatory conditions. Glomerular immune deposits (human IgG, mouse C3) were detected in 70-80% of SCID mice with human DNA specific antibodies and in a third of the human/mouse chimeras. Thus, SLE serology and glomerular pathology were reproducibly demonstrated in two models of human SLE. These models should allow the evaluation of potential therapies for the treatment of lupus patients.

Chemically modified ribozyme targeting TNF-alpha mRNA regulates TNF-alpha and IL-6 synthesis in synovial fibroblasts of patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is chronic polyarthritis in which a variety of inflammatory cytokines play a role. Since tumor necrosis factor-alpha (TNF-alpha) is one of the most important cytokines in the pathogenesis of RA, we evaluated the feasibility of ribozymes as a therapeutic agent to control the inflammatory process of RA synovium. A hammerhead ribozyme against TNF-alpha was chemically modified to increase nuclease resistance and added to RA fibroblastlike cell cultures without using a delivery system. The cellular uptake of fluorescent-labeled ribozyme into synovial cells was found to last at least 48 hr by confocal laser scanning microscopy. The ribozyme targeting TNF-alpha gene inhibited both the expression of TNF-alpha mRNA and the secretion of TNF-alpha and IL-6. The cytotoxic effect by the ribozyme on synovial cells was negligible when determined by an alamar blue assay. Chemically modified ribozymes designed to suppress the TNF-alpha gene may be potential as a therapeutic agent for rheumatoid arthritis.