Project description:Introduction: Pediatric systemic lupus erythematosus (pSLE) patients often initially present with more active and severe disease than adults, including a higher frequency of lupus nephritis. Specific autoantibodies, including anti-C1q, anti-DNA and anti-alpha-actinin, have been associated with kidney involvement in SLE, and DNA antibodies are capable of initiating early stage lupus nephritis in severe combined immunodeficiency (SCID) mice. Over 100 different autoantibodies have been described in SLE patients, highlighting the need for comprehensive autoantibody profiling. Knowledge of the antibodies associated with pSLE and proliferative nephritis will increase the understanding of SLE pathogenesis, and may aid in monitoring patients for renal flare. Methods: We used autoantigen microarrays composed of 140 recombinant or purified antigens to compare the serum autoantibody profiles of new-onset pSLE patients (n=45) to healthy controls (n=17). We also compared pSLE patients with biopsy-confirmed class III or IV proliferative nephritis (n=23) and without significant renal involvement (n=18). We performed ELISA with selected autoantigens to validate the microarray findings. We created a multiple logistic regression model, based on the ELISA and clinical information, to predict whether a patient had proliferative nephritis, and used a validation cohort (n=23) and longitudinal samples (88 patient visits) to test its accuracy. Results: Fifty autoantibodies were at significantly higher levels in the sera of pSLE patients compared to healthy controls, including anti-B-cell activating factor (BAFF). High levels of anti-BAFF were associated with active disease. Thirteen serum autoantibodies were present at significantly higher levels in pSLE patients with proliferative nephritis than those without, and we confirmed five autoantigens (dsDNA, C1q, collagens IV & X and aggrecan) by ELISA. Our model, based on ELISA measurements and clinical variables, correctly identified patients with proliferative nephritis with 91% accuracy. Conclusions: Autoantigen microarrays are an ideal platform for identifying autoantibodies associated with both pSLE and specific clinical manifestations of pSLE. Using multiple regression analysis to integrate autoantibody and clinical data permits accurate prediction of clinical manifestations with complex etiologies in pSLE.

Project description:We previously reported the establishment of a rabbit (Oryctolagus cuniculus) model of Systemic Lupus Erythematosus (SLE) in which peptide immunization led to lupus-like autoantibody production including anti-Sm, -RNP, -SS-A, -SS-B and -dsDNA. Some neurological symptoms in form of seizures and nystagmus were observed. The animals used in the previous and in the present study were from a National Institute of Allergy and Infectious Diseases colony of rabbits that were pedigreed, immunoglobulin allotype-defined but not inbred. Their genetic heterogeneity may correspond to that found among patients of a given ethnicity. We extended the information about this rabbit model of SLE by microarray based expression profiling. We first demonstrated that human expression arrays could be used with rabbit RNA to yield information on molecular pathways. We then designed a study evaluating gene expression profiles in 8 groups of control and SLE rabbits (46 rabbits in total). Genes significantly upregulated in SLE rabbits were associated with NK cytotoxicity, antigen presentation, leukocyte migration, cytokine activity, protein kinases, RNA spliceosomal ribonucleoproteins, intracellular signaling cascades, and glutamate receptor activity. These results link increased immune activation with up-regulation of components associated with neurological and anti-RNP responses, demonstrating the utility of the rabbit SLE model to uncover biological pathways related to SLE-induced clinical symptoms, including Neuropsychiatric Lupus. Our finding of distinct gene expression patterns in rabbits that made anti-dsDNA compared to those that only made other anti-nuclear antibodies should be further investigated in subsets of SLE patients with different autoantibody profiles. An important goal of biomedical research is to translate basic findings into clinical applications. Models in inbred mice that spontaneously develop SLE, along with various mutant, transgenic and knockout models have documented a variety of genetic defects leading to SLE, but from the clinical perspective, the degree to which these findings using the inbred or homogeneous artificially mutated strains apply to individuals in heterogeneous outbred human populations is open to question. Given that there is still no cure available for SLE, it is important that we continue to explore possibilities using new animal models of SLE including neuropsychiatric lupus (NPSLE). The gene expression study reported here was conducted to expand our understanding of SLE and in particular NPSLE using our rabbit model. We reported earlier that immunization of rabbits with the SM- or GR-MAP peptides led to development of anti-nuclear autoantibodies, including anti-dsDNA, as well as neurological symptoms in the form of seizures and nystagmus in some rabbits. After establishing that it was possible to use the Affymetrix U95 human microarray for the rabbit gene expression studies, through comparative hybridization of identically prepared cRNA from human and rabbit PWBC, the human microarray was used due to lack of rabbit-specific microarrays. We describe unique gene expression changes associated with lupus like serological patterns in immunized rabbits. Our results also demonstrate that caution must be applied when choosing the structure of the carrier Multiple Antigen Peptide (MAP-peptide) for immunization. We discovered that using MAP-4 rather than MAP-8 significantly altered patterns of immune response and gene expression. Currently, microarrays specific for study of gene expression profiles are not available for rabbits. Therefore, we first conducted studies that compared identically prepared rabbit and human cRNA binding to the Affymetrix U95 microarray available for human gene expression analyses. It was determined that the human microarray could be used with rabbit cRNA to yield information on genetic pathways activated and/or suppressed in autoantibody-producing immunized rabbits. In the current report, gene expression profiles of a total of 46 rabbits, from 4 generations within a pedigreed group of control and immunized rabbits, were obtained and analyzed.

Project description:Systemic lupus erythematosus is a chronic autoimmune disease with multifactorial ethiopathogenesis. The complement system is involved in both the early and late stages of disease development and organ damage. To better understand autoantibody mediated complement consumption the GAPAID consortium examined ex vivo immune complex formation on autoantigen arrays. We recruited patients with SLE (n=211), with other systemic autoimmune diseases (n=65) and non-autoimmune control subjects (n=149) in two rheumatology tertiary care centers. Standard clinical and laboratory data were collected from all subjects and serum complement levels were determined in SLE patients. The genotype of SNP rs1143679 in the ITGAM gene was also determined. On-chip formation of immune complexes was examined using a functional immunoassay on autoantigen microarray. The amount of antigen-bound IgM, IgG and complement C4 and C3 was quantified on autoantigens comprising nucleic acids, proteins and lipids. Our results show that the relatively high complement consumption of nucleic acids is further increased upon binding of IgM and IgG. This is true even when serum complement levels are decreased due to complement consumption in SLE patients. A negative correlation between serum complement levels and ex vivo complement deposition on nucleic acid autoantigens is demonstrated. On the contrary, most protein and lipid autoantigens show positive correlation with C4 and C3 levels. Genetic analysis reveals that the non-synonymous variant rs1143679 in complement receptor type 3 is associated with an increased production of anti-dsDNA IgG antibodies. Notwithstanding, homozygous carriers of the previously reported susceptible allele (AA) have lower levels of dsDNA specific IgM among SLE patients. Regarding organ involvement we find that besides anti-C1q IgG, low levels of dsDNA specific IgM and low complement C4 binding to C1q are also associated with renal injury. In summary, nucleic acids maintain a skewed complement deposition balance when bound by IgG and IgM, depleting the early classical complement pathway from other physiological processes. Dysfunction of the receptor responsible for complement-mediated apoptotic debris removal promotes the development of autoantibodies targeting nucleic acids. These observations provide serological and genetic evidence for complement-mediated clearance deficiency of apoptotic debris in lupus.

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RNA-seq study reveals unique transcriptome expression in systemic lupus erythematosus patients with distinct autoantibody profile

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