Genetic complementation results in augmented autoantibody responses to lupus-associated antigens

A Central Role for HLA-DR3 in Anti-Smith Antibody Responses and Glomerulonephritis in a Transgenic Mouse Model of Spontaneous Lupus

MHC, especially HLA-DR3 and HLA-DR2, is one of the most important genetic susceptibility regions for systemic lupus erythematosus. Human studies to understand the role of specific HLA alleles in disease pathogenesis have been hampered by the presence of strong linkage disequilibrium in this region. To overcome this, we produced transgenic mice expressing HLA-DR3 (DRβ1*0301) and devoid of endogenous class II (both I-A and I-E genes, AE(0)) on a lupus-prone NZM2328 background (NZM2328.DR3(+)AE(0)). Both NZM2328 and NZM2328.DR3(+)AE(0) mice developed anti-dsDNA and glomerulonephritis, but anti-dsDNA titers were higher in the latter. Although kidney histological scores were similar in NZM2328 and NZM2328.DR3(+)AE(0) mice (7.2 ± 4.3 and 8.6 ± 5.7, respectively, p = 0.48), the onset of severe proteinuria occurred earlier in NZM2328.DR3(+)AE(0) mice compared with NZM2328 mice (median, 5 and 9 mo respectively, p < 0.001). Periarterial lymphoid aggregates, classic wire loop lesions, and occasional crescents were seen only in kidneys from NZM2328.DR3(+)AE(0) mice. Interestingly, NZM2328.DR3(+)AE(0) mice, but not NZM2328 mice, spontaneously developed anti-Smith (Sm) Abs. The anti-Sm Abs were seen in NZM2328.DR3(+)AE(0) mice that were completely devoid of endogenous class II (AE(-/) (-)) but not in mice homozygous (AE(+/+)) or heterozygous (AE(+/-)) for endogenous MHC class II. It appears that only HLA-DR3 molecules can preferentially select SmD-reactive CD4(+) T cells for generation of the spontaneous anti-Sm immune response. Thus, our mouse model unravels a critical role for HLA-DR3 in generating an autoimmune response to SmD and lupus nephritis in the NZM2328 background.

Assessment of the translational value of mouse lupus models using clinically relevant biomarkers

Lupus is an autoimmune disease with a poorly understood etiology that manifests with a diverse pathology. This heterogeneity has been a challenge to clinical drug development efforts. A related difficulty is the uncertain translational power of animal models used for evaluating potential drug targets and candidate therapeutics, because it is unlikely that any 1 preclinical model will recapitulate the spectrum of human disease. Therefore, multiple models, along with an understanding of the immune mechanisms that drive them, are necessary if we are to use them to identify valid drug targets and evaluate candidate therapies successfully. To this end, we have characterized several different mouse lupus models and report their differences with respect to biomarkers and symptoms that are representative of the human disease. We compared the pristane-induced mouse lupus disease model using 3 different strains (DBA/1, SJL, BALB/c), and the spontaneous NZB x NZW F1(NZB/W) mouse model. We show that the models differ significantly in their autoantibody profiles, disease manifestations such as nephritis and arthritis, and expression of type I interferon-regulated genes. Similar to the NZB/W model, pristane-induced disease in SJL mice manifests with nephritis and proteinuria, whereas the pristane-treated DBA/1 mice develop arthritis and an interferon-driven gene signature that closely resembles that in human patients. The elucidation of each model's strengths and the identification of translatable biomarkers yields insight for basic lupus research and drug development, and should assist in the proper selection of models for evaluating candidate targets and therapeutic strategies.

HLA-DR3 restricted T cell epitope mimicry in induction of autoimmune response to lupus-associated antigen SmD

Although systemic lupus erythematosus (SLE) is a multigenic autoimmune disorder, HLA-D is the most dominant genetic susceptibility locus. This study was undertaken to investigate the hypothesis that microbial peptides bind HLA-DR3 and activate T cells reactive with lupus autoantigens. Using HLA-DR3 transgenic mice and lupus-associated autoantigen SmD protein, SmD(79-93) was identified to contain a dominant HLA-DR3 restricted T cell epitope. This T cell epitope was characterized by using a T-T hybridoma, C1P2, generated from SmD immunized HLA-DR3 transgenic mouse. By pattern search analysis, 20 putative mimicry peptides (P2-P21) of SmD(79-93,) from microbial and human origin were identified. C1P2 cells responded to SmD, SmD(79-93) and a peptide (P20) from Vibro cholerae. Immunization of HLA-DR3 mice with P20 induced T cell responses and IgG antibodies to SmD that were not cross-reactive with the immunogen. A T-T hybridoma, P20P1, generated from P20 immunized mice, not only responded to P20 and SmD(79-93), but also to peptides from Streptococcus agalactiae (P17) and human-La related protein (P11). These three T cell mimics (P20, P11 and P17) induced diverse and different autoantibody response profiles. Our data demonstrates for the first time molecular mimicry at T cell epitope level between lupus-associated autoantigen SmD and microbial peptides. Considering that distinct autoreactive T cell clones were activated by different microbial peptides, molecular mimicry at T cell epitope level can be an important pathway for the activation of autoreactive T cells resulting in the production of autoantibodies. In addition, the novel findings reported herein may have significant implications in the pathogenesis of SLE.

The worldwide gradient of autoimmune conditions

Among the numerous consequences of globalization, the dissemination of scientific research allows real-time comparisons of clinical and basic experimental data between different geographical areas. As a result, the field of geoepidemiology is now vigorously supported by multiple lines of evidence. This special issue of Autoimmunity Reviews is dedicated to the 2010 International Congress on Autoimmunity and aims to provide a state-of-the-art representation of what is currently known in the field of geoepidemiology for autoimmune diseases. The obvious implications of these observations is a role for environmental factors. We will herein review selected publications from prominent scientific journals to provide the bases to understand some of the lines of evidence proposed in the subsequent papers of this comprehensive volume. The ultimate goal is thus to define whether geoepidemiology should be considered a new challenge for autoimmunologists.