A peptide based on the CDR3 of an anti-DNA antibody of experimental SLE origin is also a dominant T-cell epitope in (NZBXNZW)F1 lupus-prone mice

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.

Downsizing antibodies: Towards complementarity-determining region (CDR)-based peptide mimetics

Monoclonal antibodies emerged as an important therapeutic drug class with remarkable specificity and binding affinity. Nonetheless, these heterotetrameric immunoglobulin proteins come with high manufacturing and therapeutic costs which can take extraordinary proportions, besides other limitations such as their limited in cellulo access imposed by their molecular size (ca. 150 kDa). These drawbacks stimulated the development of downsized functional antibody fragments (ca. 15-50 kDa), together with smaller synthetic peptides (ca. 1-3 kDa) derived from the antibodies' crucial complementarity-determining regions (CDR). Despite the general lack of success in the literal translation of CDR loops in peptide mimetics, rational structure-based and computational approaches have shown their potential for obtaining functional CDR-based peptide mimetics. In this review, we describe the efforts made in the development of antibody and nanobody paratope-derived peptide mimetics with particular focus on the used design strategies, in addition to highlighting the challenges associated with their development.

Peptides from antibodies to DNA elicit cytokine release from peripheral blood mononuclear cells of patients with systemic lupus erythematosus: relation of cytokine pattern to disease duration

Peptides from VH regions of antibodies to DNA drive immune responses in systemic lupus erythematosus (SLE). We studied peptide-induced cytokine release by peripheral blood mononuclear cells (PBMC) of patients, the influence of peptide concentration, disease characteristics and HLA-D haplotypes. Cells secreting cytokines (IFNg, IL-2, IL-4 and IL-10) were measured by ELISPOT in PBMC from 31 patients with SLE and 20 matched healthy controls in response to seven peptides (A-G) from the CDR1/FR2 to CDR2/FR3 VH regions of human anti-DNA MAbs. Disease activity was assessed by SELENA-SLEDAI. HLA-DR and -DQ alleles were determined by molecular typing techniques. PBMC from significantly higher proportions of SLE patients than controls responded to VH peptides by generating IFNg and IL-10. Type of cytokines released in response to at least one peptide (D) depended on antigen concentration. Cytokine release was not associated with clinical features of SLE except for disease duration. A shift occurred from IFNg, IL-4 and IL-10 production in early disease to IL-4 and IL-10 in late disease (suggesting increasing TH2-like responses over time). Three peptides (B, D, G) were more stimulatory in the SLE patients than controls. Although none of the peptides was restricted by any particular MHC class II allele, among responders there was increased prevalence of HLA-DQB1 0201 and/or DRB1 0301, alleles known to predispose to SLE. Thus, responses to some VH peptides are more frequent in SLE and vary with disease duration. Increased responses in individuals with HLA class II genotypes that predispose to SLE suggest that peptide presentation by those molecules permits brisker peripheral blood cell responses to autoantibody peptides, thus increasing risk for disease.

Idiotype-specific Th cells support oligoclonal expansion of anti-dsDNA B cells in mice with lupus

Systemic lupus erythematosus (SLE) is marked by a Th cell-dependent B cell hyperresponsiveness, with frequent germinal center reactions and hypergammaglobulinemia. The specificity of Th cells in lupus remains unclear, but B cell Ids have been suggested. A hallmark is the presence of anti-dsDNA, mutated IgG autoantibodies with a preponderance of arginines in CDR3 of the Ig variable H chain (IgVH). B cells can present V region-derived Id peptides on their MHC class II molecules to Id-specific Th cells. We show that Id-specific Th cells support the proliferation of anti-dsDNA Id(+) B cells in mice suffering from systemic autoimmune disease with SLE-like features. Mice developed marked clonal expansions of B cells; half of the IgVH sequences were clonally related. Anti-dsDNA B cells made up 40% of B cells in end-stage disease. The B cells expressed mutated IgVH with multiple arginines in CDR3. Hence, Id-driven T cell-B cell collaboration supported the production of classical anti-dsDNA Abs, recapitulating the characteristics of such Abs in SLE. The results support the concept that Id-specific Th cells may trigger the development of SLE and suggest that manipulation of the Id-specific T cell repertoire could play a role in treatment.

T cell tolerance to germline-encoded antibody sequences in a lupus-prone mouse

The BCR V region has been implicated as a potential avenue of T cell help for autoreactive B cells in systemic lupus erythematosus. In principle, either germline-encoded or somatically generated sequences could function as targets of such help. Preceding studies have indicated that class II MHC-restricted T cells in normal mice attain a state tolerance to germline-encoded Ab diversity. In this study, we tested whether this tolerance is intact in systemic lupus erythematosus-prone (New Zealand Black x SWR)F1 mice (SNF1). Using a hybridoma sampling approach, we found that SNF1 T cells were tolerant to germline-encoded Ab sequences. Specifically, they were tolerant to germline-encoded sequences derived from a lupus anti-chromatin Ab that arose spontaneously in this strain. This was true both for diseased and prediseased mice. Thus, there does not appear to be a global defect in T cell tolerance to Ab V regions in this autoimmune-prone strain either before or during autoimmune disease.

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.

Modulation of autoreactive responses of peripheral blood lymphocytes of patients with systemic lupus erythematosus by peptides based on human and murine anti-DNA autoantibodies

Two peptides, based on the sequences of the complementarity-determining regions (CDR) 1 and 3 of a pathogenic murine monoclonal anti-DNA autoatibody that bears the 16/6 idiotype (Id), were shown to either prevent or treat an already established systemic lupus erythematosus (SLE) in two murine models of lupus. Two additional peptides based on the human monoclonal anti-DNA, 16/6 Id were synthesized. This study was undertaken in order to investigate the ability of the CDR-based peptides to immunomodulate SLE-associated responses of peripheral blood lymphocytes (PBL) of SLE patients. PBL of 24 of the 62 SLE patients tested proliferated in vitro following stimulation with the human 16/6 Id. Peptides based on the CDRs of both the human and murine anti-DNA autoantibodies inhibited efficiently and specifically the 16/6 Id-induced proliferation and IL-2 production. The latter inhibitions correlated with an up-regulated production (by 2.5-3.5-fold) of the immunosuppressive cytokine, TGF-beta. Overall, the results of our study demonstrate that the CDR-based peptides are capable of down-regulating in vitro autoreactive T cell responses of PBL of SLE patients. Thus, these peptides are potential candidates for a novel specific treatment of SLE patients.

Molecular identification of pathogenetic IdLNF+1 autoantibody idiotypes derived from the NZBxSWR F1 model for systemic lupus erythematosus

The acceleration of nephritis in SNF(1) mice by CD4(+) T-cell clones reactive with a nephritogenic idiotype, Id(LN)F(1) [1], as well as the ability of anti-Id(LN)F(1) antisera to down-regulate the production of Id(LN)F(+)(1) immunoglobulin (Ig) in vivo and delay nephritis [2], suggests that dysregulation of this idiotype may contribute to the development of SNF(1) nephritis. Herein, we show that a monoclonal Id(LN)F(1)-expressing antibody, 540, significantly (P< or = 0.01) stimulated Id(LN)F(1)-reactive T-cell clones B6 and D2 to proliferate, while other Id(LN)F+1 antibodies did not. Further, injection of 540-producing hybridoma cells into nonautoimmune (SWRxBalb/c)F(1) mice resulted in the deposition of Id(LN)F(+)(1) Ig in the kidneys, in a pattern indicative of early nephritis. To identify the pathogenetic Id(LN)F(1) epitope(s) at the molecular level, we compared the deduced amino acid sequences of the heavy and light chain variable regions of pathogenetic and non-pathogenetic Id(LN)F(1)-expressing Igs 540, 317, and 533. Two overlapping peptides derived from the V(H) sequence of 540 (aa 54-66 and 62-73), which both contain the triple basic amino acid motif K(X)K(X)K, stimulated SNF(1) T cells and T-cell clones B6 and D2. These results further support the involvement of a subset of Id(LN)F(1)-expressing Ig in SNF(1) nephritis.

Disabling erbB receptors with rationally designed exocyclic mimetics of antibodies: structure-function analysis

Overexpression of the HER2 receptor is observed in about 30% of breast and ovarian cancers and is often associated with an unfavorable prognosis. We have recently designed an anti-HER2 peptide (AHNP) based on the structure of the CDR-H3 loop of the anti-HER2 rhumAb 4D5 and showed that this peptide can mimic some functions of rhumAb 4D5. The peptide disabled HER2 tyrosine kinases in vitro and in vivo similar to the monoclonal antibody (Park, B.-W. et al. Nat. Biotechnol. 2000, 18, 194--198). AHNP has been shown to selectively bind to the extracellular domain of the HER2 receptor with a submicromolar affinity in Biacore assays. In the present paper, we demonstrate that in addition to being a structural and functional mimic of rhumAb 4D5, AHNP can also effectively compete with the antibody for binding to the HER2 receptor indicating a similar binding site for the peptide and the parental antibody. To further develop AHNP as an antitumor agent useful for preclinical trials and as a radiopharmaceutical to be used for tumor imaging, a number of derivatives of AHNP have been designed. Structure--function relationships have been studied using surface plasmon resonance technology. Some of the AHNP analogues have improved binding properties, solubility, and cytotoxic activity relative to AHNP. Residues in the exocyclic region of AHNP appear to be essential for high-affinity binding. Kinetic and equilibrium analysis of peptide-receptor binding for various AHNP analogues revealed a strong correlation between peptide binding characteristics and their biological activity. For AHNP analogues, dissociation rate constants have been shown to be better indicators of peptide biological activity than receptor-binding affinities. This study demonstrates a possibility of mimicking the well-documented antibody effects and its applications in tumor therapy by much smaller antibody-based cyclic peptides with potentially significant therapeutic advantages. Strategies used to improve binding properties of rationally designed AHNP analogues are discussed.

Immunization with a bacterial ATP-binding cassette transporter fragment suppresses autoimmunity and prolongs survival in MRL/lpr lupus-prone mice

The present study was undertaken to better define the role of the U1 70 kDa antigen in a spontaneous murine model of systemic lupus erythematosus (SLE) by testing whether immunization with the U1 70 kDa polypeptide could alter the production of antibodies against U1 70 kDa or against other small nuclear ribonucleoproteins (snRNP), modify disease expression or alter survival. We found that, while immunization with a U1 70 kDa derived fusion protein (70 KFP) tended to delay the development of anti-snRNP antibodies in the sera of MRL/lpr mice, it had no effect on autoimmune-mediated renal disease or survival. Unexpectedly, it was found that MRL/lpr mice immunized with a 367 amino acid fragment of a bacterial ATP-binding cassette transporter, MFP, had prolonged survival compared to saline injection or U1 70 kDa immunization and that this was associated with a delay in the onset of SLE-like proliferative glomerulonephritis. This is the first study, to our knowledge, in which a bacterial ATP-binding cassette transporter was shown to be beneficial in treating a murine model of SLE. We report that MFP significantly prolonged longevity in the MRL/lpr murine model of SLE compared to saline injection or 70 KFP immunization and that improved survival was associated with a delay in the onset of SLE-like glomerulonephritis.

A peptide based on the sequence of the CDR3 of a murine anti-DNA mAb is a better modulator of experimental SLE than its single amino acid-substituted analogs

A peptide based on the complementarity determining region (CDR) 3 of a pathogenic anti-DNA 16/6 Id(+) monoclonal antibody was previously shown to be a dominant T-cell epitope in experimental SLE, and to be capable of inhibiting SLE-associated proliferative responses. Single amino acid-substituted analogs of pCDR3 were designed and analyzed for their ability to stimulate or inhibit the proliferation of a pCDR3-specific T-cell line. Alterations in positions 9 and 10 neutralized the proliferative potential of pCDR3, whereas alterations in positions 6-8 and 11-15 retained the proliferative potential of the peptides. Similar to pCDR3, its analogs Ala11 and Nle13 inhibited efficiently the in vivo priming of lymph node cells either to pCDR3 or to the human monoclonal anti-DNA 16/6 Id(+) antibody. Substituting both positions 11 (Tyr --> Ala) and 13 (Met --> Nle) reduced this inhibitory capacity compared to the single substituted analogs. Also, truncation of pCDR3 at the C- and/or N-terminus obliterated the inhibitory activities of the peptide. Analogs Ala11 and Nle13 immunomodulated serological and clinical smanifestations of experimental SLE. Nevertheless, the original pCDR3 was a more efficient modulator of the disease.

The potential use of peptides and vaccination to treat systemic lupus erythematosus

Studies in humans and mice with systemic lupus erythematosus (SLE) suggest that the development of autoantibodies and disease is dependent on T helper (Th) cells. This review highlights recent efforts to identify the antigens that activate such autoreactive Th cells. Various laboratories are using different approaches to identify the autoantigenic epitopes, which appear to be derived from diverse sources such as nucleosome core histones, ribonucleoproteins, and immunoglobulin variable regions. Identification of the putative autoantigenic epitopes has raised the possibility of peptide-specific vaccination as therapy for SLE. Indeed, vaccination of prenephritic lupus-susceptible mice with such peptides delays the development of autoantibodies and nephritis, and prolongs survival. Recent data suggest that peptide treatment can also influence established disease in older lupus mice. These studies offer new hope for a similar treatment approach in patients with SLE. Studies have begun to identify T cell epitopes in human disease.