Antibodies to brain integral membrane proteins in systemic lupus erythematosus

Anti-endothelial antibodies and neuropsychiatric systemic lupus erythematosus

The pathogenesis of neuropsychiatric systemic lupus erythematosus (NPSLE) has been attributed to autoantibody-mediated neural dysfunction, vasculopathy, and coagulopathy. Several autoantibodies specificities have been reported in serum and cerebrospinal fluid of NPSLE patients (i.e., antineuronal, antiribosomal P proteins, antiglial fibrillary acidic proteins, antiphospholipid, and anti-endothelial antibodies). We have recently demonstrated an association between serum anti-endothelial antibodies and psychosis or depression in patients with SLE. Subsequently, by screening a cDNA library from human umbilical artery endothelial cells with serum from a SLE patient with psychosis, one positive strongly reactive clone was identified encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. Anti-Nedd5 antibodies have been found significantly associated with psychiatric manifestations in SLE patients, strengthening the view of a possible implication of autoantibodies in the development of psychiatric disorders.

Novel brain reactive autoantibodies: Prevalence in systemic lupus erythematosus and association with psychoses and seizures

Autoantibodies can cause neuropsychiatric manifestations in lupus patients by altering the physiological function of neuronal cells. In this study, we identified Brain Reactive Autoantibodies (BRAAs) against murine neuronal membrane proteins (M.W. 27.5 and 29.5 kD) and found them correlating with psychosis and/or seizures in lupus patients. They were specific to neuronal membrane tissues of mammalian origin and are significantly associated with psychosis and/or seizures (p<0.0001). These membrane proteins mass spectrometry profiles did not match to any published protein sequences. These BRAAs may play important roles in the pathophysiology of neuropsychiatric lupus.

Central nervous system vasculitis

Vasculitis is inflammation of blood vessel walls, which produces dysfunction in both the peripheral and central nervous system (CNS). Cerebral ischemia is the major cause for neurological manifestations of CNS vasculitis. Unfortunately, a universally accepted classification of vasculitis has not emerged. Vasculitis affecting the CNS alone is referred to as primary angiitis of the CNS; secondary vasculitis occurs in association with a variety of conditions, including infections, drug abuse, lymphoproliferative disease and connective tissue diseases. The pathogenesis of vasculitis includes different immunological mechanisms. Recently, anti-neutrophil cytoplasmatic antibody (ANCA) has been demonstrated to play an active role in the immunopathogenesis of the vasculitis. Diagnosis of vasculitis depends on a combination of clinical, radiographic and pathologic features. A wide spectrum of clinical features may occur. The most typical clinical picture of CNS vasculitis is troke, encephalopathy or seizures. Assays for ANCA, serum cytokines, antibodies to endothelial cell antigens have been reported to be useful in diagnosing or monitoring the disease activity. The gold standard in diagnosis is confirmation of vasculitis in a biopsy specimen. Angiography may suggest the diagnosis but no abnormalities are pathognomonic. Ideally, the therapy of each vasculitis would focus on the specific immunologic mechanism causing the disease. Such specific interventions are not yet available. In general the most important approaches induce global immunosuppression. The goal of therapy, however, is to prevent recurrence of disease.

High resolution autoantibody detection by optimized protein G-horseradish peroxidase immunostaining in a western blotting assay

We report a procedure for optimisation of Western blotting using protein G-horseradish peroxidase (protein G-HRP) which avoids the false positive reactions often caused by second antibodies and increases the detection of autoantibodies by protein G conjugate. A number of modifications were investigated. Higher concentrations of serum and protein G-HRP at 1:5 to 1:10 and 1:100, respectively, increased the detection to the same order as that obtained with second antibody systems and gold staining with silver enhancement. The role of various detergents in the procedure was established. 3-[(3-Cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) in incubation with protein G-HRP increased the binding between protein G and immunoglobulin G. Addition of Tween-20 for blocking produced little background so that protein blockers could be avoided. Prolonged incubation with serum increased markedly the sensitivity of the procedure when compared with the recommended 2 h incubation period. Polyvinylidene difluoride membrane provided better transfer effect, lower background and higher mechanical strength than nitrocellulose membrane. The utilization of only one antibody-specific ligand increased the simplicity, reliability, economy, efficiency and specificity of the method. These modifications make this method significantly better for detection and screening for autoantibodies.

Controversies in lupus: nervous system involvement

What have we learned about CNS lupus in recent years? An enormous amount of knowledge on pathophysiology of antiphospholipid antibodies, in particular, has been gathered. Although hard evidence of a direct pathogenetic role of these antibodies in cerebral lupus is still lacking, it is generally felt that the multiple microinfarctions found in the brains of lupus patients are related to their presence. Better understanding of the pathogenesis of cerebral lupus will come from the study of experimental models, as it has been possible to develop an antiphospholipid antibody syndrome in mice. Because no specific laboratory test for CNS lupus is yet available, diagnosing the condition remains a challenge to every clinician. Techniques including neuropsychometric testing, quantitative EEG, and SPECT scans have taught us more about cognitive dysfunction and psychosis in patients with SLE. These categories remain the most difficult to define. The concept of hypercoagulability in SLE patients has diverted the direction of therapy from immunosuppression towards anticoagulation. It is of utmost importance that randomised trials are commenced in order to determine the optimal mode of anticoagulation for various groups of lupus patients. It will be necessary to conduct such trials under strict inclusion criteria, based on well defined patient categories. Such an enterprise will require international co-operation of investigators.

Nervous system lupus: pathogenesis and rationale for therapy

Several different pathogenic mechanisms appear to be involved in CNS lupus. These include: B-cell/autoantibody-mediated nervous system compromise; immune complex deposition and vasculitis; microthrombosis and vasculopathy; aberrant MHC Class II antigen expression with T-cell mediated disease (multiple-sclerosis model); and, cytokine-induced brain inflammation. These processes are not mutually exclusive: there exist in vitro and in vivo models for each of these. A number of autoantibodies, especially those with specificities for shared neuronal/lymphocyte antigens, are associated with certain forms of cognitive dysfunction or overt nervous system manifestations. In MRL/lpr mice, lymphoid infiltrates in the brain parenchyma are related to a neurobehavioural dysfunction which develops very early in the course of autoimmune disease. Recent results, both in animal models and in human studies on the therapeutic effects of corticosteroids, immunosuppressive drugs or anticoagulants on clinical and subclinical manifestations of CNS lupus are highlighted in an attempt to develop a rationale for intervention based upon presumed pathogenesis.

Brain reactive autoantibodies and cognitive impairment in systemic lupus erythematosus

Nervous system involvement in SLE encompasses a wide array of clinical manifestations which may reflect multiple etiologic factors including autoantibodies to nervous tissue antigens. The aim of the present study was to examine the association between autoantibodies to a wide range of brain antigens and cognitive abnormalities in an unselected population of 70 SLE patients. Using a battery of standardized neuropsychological tests, cognitive impairment was identified in 15/70 (21%) SLE patients compared with 1/25 (4%) patients with rheumatoid arthritis and 1/23 (4%) healthy subjects (P = 0.04). Integral membrane proteins were isolated from dissociated brain cells by temperature-induced phase separation with Triton X-114. Synaptosomes were isolated by differential centrifugation and membrane enriched fractions were prepared by lectin affinity chromatography. Western blotting identified IgG reactivity to a wide range of proteins (MW 22-52 K) in SLE patients. The proteins identified were distinct from well-characterized intracellular antigens including ribosomal P proteins. There was no significant difference in the prevalence of anti-brain antibodies between SLE patients who were cognitively impaired and those who were not impaired. Furthermore, there was no association between the presence of autoantibodies and subsets of cognitive dysfunction. These results suggest that circulating autoantibodies to brain antigens are not responsible for the abnormalities in cognitive function in SLE patients.