ABSTRACT: 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.
