Interferon-α induces unabated production of short-lived plasma cells in pre-autoimmune lupus-prone (NZB×NZW)F1 mice but not in BALB/c mice.

IFN-α is known to play a critical role in the pathogenesis of systemic lupus erythematosus (SLE), but the mechanisms remain unclear. We previously showed that within weeks, exposure to IFN-α in vivo induces lupus in pre-autoimmune lupus-prone NZB×NZW F1 (NZB/W) but not in BALB/c mice. In the current study, we show that in vivo expression of IFN-α induces sustained B-cell proliferation in both BALB/c and NZB/W mice. In NZB/W but not BALB/c mice, B-cell proliferation was accompanied by a rapid and unabated production of autoantibody-secreting cells (ASCs) in secondary lymphoid organs, suggesting that a B-cell checkpoint is altered in the autoimmune background. The majority (>95%) of ASCs elicited in IFN-α-treated NZB/W mice were short-lived and occurred without the induction of long-lived plasma cells. A short course of cyclophosphamide caused a sharp drop in IFN-α-elicited short-lived plasma cells, but the levels recovered within days following termination of treatment. Thus, our work provides new insights into effectiveness and limitations of the current SLE therapies.

IFNalpha kinoid vaccine-induced neutralizing antibodies prevent clinical manifestations in a lupus flare murine model.

A major involvement of IFNalpha in the etiopathogenesis of systemic lupus erythematosus has been suggested by clinical observations, including the increase of serum levels of this cytokine in patients with active disease. Supporting this hypothesis, we have shown that expression of IFNalpha from a recombinant adenovirus (IFNalpha Adv) precipitates lupus manifestations in genetically susceptible New Zealand Black (NZB) x New Zealand White (NZW)F(1) mice (NZB/W) but not in BALB/c mice. In the present investigation, we have prepared an IFNalpha immunogen, termed IFNalpha kinoid, which, appropriately adjuvanted, induces transient neutralizing antibodies (Abs) but no cellular immune response to the cytokine and without apparent side effects. Using this preparation, we also showed that, in kinoid-vaccinated NZB/W mice, lupus manifestations, including proteinuria, histological renal lesions, and death triggered by IFNalpha Adv challenge were delayed/prevented as long as an effective threshold of anti-IFNalpha inhibitory capacity was present in the serum.

Systemic IFN-alpha drives kidney nephritis in B6.Sle123 mice.

The impact of IFN-alpha secretion on disease progression was assessed by comparing phenotypic changes in the lupus-prone B6.Sle1Sle2Sle3 (B6.Sle123) strain and the parental C57BL/6 (B6) congenic partner using an adenovirus (ADV) expression vector containing a recombinant IFN-alpha gene cassette (IFN-ADV). A comprehensive comparison of cell lineage composition and activation in young B6 and B6.Sle123 mice revealed a variety of cellular alterations in the presence and absence of systemic IFN-alpha. Most IFN-alpha-induced phenotypes were similar in B6 and B6.Sle123 mice; however, B6.Sle123 mice uniquely exhibited increased B1 and plasma cells after IFN-alpha exposure, although both strains had an overall loss of mature B cells in the bone marrow, spleen and periphery. Although most of the cellular effects of IFN-alpha were identical in both strains, severe glomerulonephritis occurred only in B6.Sle123 mice. Mice injected with IFN-ADV showed an increase in immune complex deposition in the kidney, together with an unexpected decrease in serum anti-nuclear antibody levels. In summary, the predominant impact of systemic IFN-alpha in this murine model is an exacerbation of mechanisms mediating end organ damage.

Type-I interferons and systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease characterized by the production of autoantibodies directed against nuclear antigens and chronic inflammation affecting multiple tissues. Complex genetic disorders are at the origin of the disease in humans and in SLE-prone mice, leading to the escape of auto-reactive B-lymphocytes from central and peripheral control checkpoints that operate normally in healthy organisms. Although necessary, autoimmune B-cells are not sufficient and additional mechanisms such as T-cell help are clearly needed for the disease to occur. The role of type-I interferons (type-I IFNs), and in particular IFNalpha, as prominent cofactors for SLE was suggested years ago. Leading observations in patients and recent data in SLE-prone mice have now established IFNalpha as a major actor in SLE. Several systemic clinical symptoms and laboratory findings can indeed be interpreted as downstream effects of a high IFNalpha production, and point to this cytokine as a link between the expansion of autoimmune B-cells and the stimulation of other components of the immune system. Consequently, a vicious circle is established with overt immune-cell activation and inflammatory infiltrates culminating in the selective destruction of tissue targets, notably the kidney. These notions can now be transplanted to the clinic and designate IFNalpha as a new promising therapeutic target.

Diagnostic value of anti-nucleosome antibodies in the assessment of disease activity of systemic lupus erythematosus: a prospective study comparing anti-nucleosome with anti-dsDNA antibodies.

OBJECTIVE: To determine the diagnostic value of anti-nucleosome antibodies in the assessment of clinically active systemic lupus erythematosus (SLE) and active nephritis. METHODS: A 12 month prospective study of 87 patients diagnosed with SLE. At each evaluation, disease activity was scored by SLE Disease Activity Index and Lupus Activity Criteria Count, and blood samples were collected for laboratory tests. Autoantibodies were detected by ELISA. RESULTS: Nearly all patients were female (96.6%). The mean age was 33 years and the mean disease duration was 60.7 months. About half the patients presented with nephritis (49.4%) and active SLE (50.6%) at the first clinical examination. During the study period, the prevalence of active SLE decreased from 50.6% to 29.1%. The prevalence of anti-nucleosome and anti-dsDNA antibodies was 40.0%-58.6% and 10.9%-21.8%, respectively, throughout the study period. The sensitivity of anti-nucleosome and anti-dsDNA antibodies for active SLE was 72.7%-100% and 31.3%-54.8%, respectively. The specificity of anti-nucleosome and anti-dsDNA antibodies for active SLE was 66.7%-83.7% and 88.7%-100%, respectively. The sensitivity and specificity of anti-nucleosome antibodies for active nephritis were 32.0%-67.5% and 46.2%-67.3%, respectively. The sensitivity and specificity for anti-dsDNA antibodies for active nephritis were 16.0%-35.4% and 85.1-97.5%, respectively. CONCLUSION: Anti-nucleosome antibodies are more sensitive than anti-dsDNA antibodies to active SLE and active nephritis. Thus, anti-nucleosome antibody reactivity may be a useful marker in the diagnosis and assessment of active SLE.

IFN-alpha induces early lethal lupus in preautoimmune (New Zealand Black x New Zealand White) F1 but not in BALB/c mice.

Recent studies indicate that IFN-alpha is involved in pathogenesis of systemic lupus erythematosus. However, direct proof that IFN-alpha is not only necessary, but also sufficient to induce lupus pathogenicity is lacking. In this study, we show that in vivo adenovector-mediated delivery of murine IFN-alpha results in preautoimmune (New Zealand Black (NZB) x New Zealand White (NZW))F(1), but not in normal, mice, in a rapid and severe disease with all characteristics of systemic lupus erythematosus. Anti-dsDNA Abs appeared as soon as day 10 after initiation of IFN-alpha treatment. Proteinuria and death caused by glomerulonephritis occurred in all treated mice within, respectively, approximately 9 and approximately 18 wk, at a time when all untreated (NZB x NZW)F(1) did not show any sign of disease. IFN-alpha in vivo induced an overexpression of B lymphocyte stimulator in circulation at similar levels in both the preautoimmune and the normal mouse strains. All effects elicited by IFN-alpha were dose dependent. (NZB x NZW)F(1) infused with purified murine IFN-alpha also showed acceleration of lupus. Thus, prolonged expression of IFN-alpha in vivo induces early lethal lupus in susceptible animals.

Nucleosomes in the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is characterized by the development of a large array of autoantibodies that primarily are directed against the whole chromatin (antinucleosome) and its individual components, dsDNA and histones. Apoptotic defects and impaired removal of apoptotic cells could contribute to an overload of autoantigens (and in particular of nucleosomes) in circulation or in target tissues that could become available to initiate an autoimmune response. In susceptible individuals, this can lead to autoantibody-mediated tissue damage. In addition to intrinsic or secondary apoptosis/apoptotic cell removal defects, certain apoptotic stimuli (eg, UV, viruses) could lead to posttranscriptional modifications that generate autoantigen cryptic fragments for which cells of the immune system have not been tolerized. Besides their role as a major immunogen in lupus, nucleosomes participate in antibody-mediated renal pathogenicity and act as a bridging molecule that recognizes heparin sulfate/collagen V components of the glomerular basement membrane. New tools that were developed to detect antinucleosome antibodies in the serum of patients (by ELISA) have shown the specificity and the high sensitivity of antinucleosome antibody reactivity in SLE. In particular, antinucleosome could be a useful marker of patients who have SLE and lack anti-dsDNA antibodies, a prognosis marker for imminent relapse, and a diagnosis marker of lupus nephritis.

Concomitant early appearance of anti-ribonucleoprotein and anti-nucleosome antibodies in lupus prone mice.

OBJECTIVE: To gain insights on initial stages of the autoimmune response in lupus prone mice taking advantage of new sensitive and quantitative techniques for the detection of autoantibodies specific for RNA- (ribonucleoproteins) and DNA-protein (chromatin) complexes. METHODS: DNA and nucleosome antibodies were detected by ELISA, antibodies to SmB, U1A-RNP, Ro52, Ro60 and La by a new radioligand assay, using de novo synthesized radio-labeled antigens. RESULTS: Analysis of anti-chromatin (including anti-nucleosome, anti-dsDNA and anti-histone antibodies) and of anti-snRNP antibodies (including anti-U1A-RNP, anti-SmB, anti-Ro52, anti-Ro60, anti-La antibodies) was performed in sequential sera from B/W, MRL+/+, MRL Yaa and MRL lpr/lpr mice. In a cohort of 105 MRL+/+ mice of different ages, 59, 51, and 57 mice were positive for anti-nucleosome, anti-SmB and anti-U1A-RNP, respectively. None of them was positive for anti-dsDNA. Importantly, antibody positivities were not randomly distributed but were significantly clustered in individual mice. Appearance of DNA- and RNA-protein complex antibodies started at approximately 18-20 weeks of age, preceding that of the anti-dsDNA (or anti-histone) antibodies that only started at 30-32 weeks. Anti-nucleosome, anti-SmB and anti-U1A-RNP antibody responses did not display any cross-reactivity as demonstrated by inhibition and adsorption experiments. CONCLUSION: These data indicate that anti-nucleosome and anti-snRNP antibodies appear early and concomitantly in lupus prone mice even though they do not share any cross-reactivity. These results fit with the assumption that their production is triggered by tightly physically associated nucleosomes and snRNP autoantigens contained in the same apoptotic bodies.