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Introduction: The therapeutic interest of targeting B-cell activating factor (BAFF) in Sjögren's disease (SjD) can be suspected from the results of two phase II clinical trials but has not been evaluated in an animal model of the disease. We aimed to evaluate the therapeutic efficacy of this strategy on dryness and salivary gland (SG) infiltrates in the NOD mouse model of SjD., Material and Methods: Female NOD mice between ages 10 and 18 weeks were treated with a BAFF-blocking monoclonal antibody, Sandy-2 or an isotype control. Dryness was measured by the stimulated salivary flow. Salivary lymphocytic infiltrates were assessed by immunohistochemistry. Blood, SGs, spleen and lymph-node lymphocyte subpopulations were analysed by flow cytometry. SG mRNA expression was analysed by transcriptomic analysis., Results: BAFF inhibition significantly decreased SG lymphocytic infiltrates, which was inversely correlated with salivary flow. The treatment markedly decreased B-cell number in SGs, blood, lymph nodes and spleen and increased Foxp3 + regulatory and CD3 + CD4 - CD8 - double negative T-cell numbers in SGs., Conclusion: A monoclonal antibody blocking BAFF and depleting B cells had therapeutic effectiveness in the NOD mouse model of SjD. The increase in regulatory T-lymphocyte populations might underlie the efficacy of this treatment., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objectives: To date, no immunomodulatory drug has demonstrated its efficacy in primary SS (pSS). We sought to analyse potential commonalities between pSS transcriptomic signatures and signatures of various drugs or specific knock-in or knock-down genes., Methods: Gene expression from peripheral blood samples of patients with pSS was compared with that of healthy controls in two cohorts and three public databases. In each of the five datasets, we analysed the 150 most up- and downregulated genes between pSS patients and controls with regard to the differentially expressed genes resulting from the biological action on nine cell lines of 2837 drugs, 2160 knock-in and 3799 knock-down genes in the Connectivity Map database., Results: We analysed 1008 peripheral blood transcriptomes from five independent studies (868 patients with pSS and 140 healthy controls). Eleven drugs could represent potential candidate drugs, with histone deacetylases and PI3K inhibitors among the most significantly associated. Twelve knock-in genes were associated with a pSS-like profile and 23 knock-down genes were associated with a pSS-revert profile. Most of those genes (28/35, 80%) were interferon-regulated., Conclusion: This first drug repositioning transcriptomic approach in SS confirms the interest of targeting interferons and identifies histone deacetylases and PI3K inhibitors as potential therapeutic targets., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Objective: Innate lymphoid cells (ILCs) are a cell population implicated in the pathogenesis of various chronic inflammatory diseases, but little is known about their role in primary Sjögren's syndrome (pSS). The aim of this study was to assess the frequency of ILC subsets in peripheral blood (PB) and their quantity and location in minor salivary glands (MSGs) in pSS., Methods: The frequency of ILC subsets was analysed in the PB of patients with pSS and healthy controls (HCs) by flow cytometry. The amount and location of ILC subsets in MSGs were studied in patients with pSS and sicca controls by immunofluorescence assay., Results: In PB, the frequency of ILC subsets did not differ between patients with pSS and HCs. The circulating frequency of the ILC1 subset was increased in patients with pSS with positive anti-SSA antibodies and that of the ILC3 subset was reduced in patients with pSS with glandular swelling. In MSGs, the ILC3 number was higher in lymphocytic-infiltrated than non-infiltrated tissue in patients with pSS and normal glandular tissues in sicca controls. The ILC3 subset was preferentially located at the periphery of infiltrates and was more abundant in small infiltrates of recently diagnosed pSS., Conclusion: Altered ILC homeostasis mainly concerns salivary glands in pSS. Most ILCs in MSGs consist of the ILC3 subset, located at the periphery of lymphocytic infiltrates. The ILC3 subset is more abundant in smaller infiltrates and in recently diagnosed pSS. It might play a pathogenic role in the development of T and B lymphocyte infiltrates in the early stages of pSS., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

B and T lymphocyte attenuator (BTLA) is a co-inhibitory receptor that is expressed by lymphoid cells and regulates the immune response. Consistent with an inhibitory role for BTLA, the disease is exacerbated in BTLA-deficient lupus mice. We recently demonstrated that the BTLA pathway is altered in CD4 + T cells from lupus patients. In the present work, we aimed at delineating the expression pattern of BTLA on CD4 + T cell subsets suspected to play a key role in lupus pathogenesis, such as circulating follicular helper T cells (cT FH ) and regulatory T cells (Tregs). We did not detect significant ex vivo variations of BTLA expression on total CD4 + T cells (naive and memory), cT FH or T FH subsets between lupus patients and healthy controls. However, we interestingly observed that BTLA expression is significantly increased on activated Tregs, but not resting Tregs, from lupus patients, especially those displaying an active disease. Moreover, it correlates with the diminution of the Tregs frequency observed in these patients. We also showed that both BTLA mRNA and protein expression remain low after TCR stimulation of activated Tregs sorted from healthy donors and evidenced a similar dynamic of BTLA and HVEM expression profile by human Tregs and effector CD4 + T cells upon T cell activation than the one previously described in mice. Finally, we observed that the HVEM/BTLA ratio is significantly lower in Tregs from lupus patients compared to healthy controls, whereas ex vivo effector CD4 + T cells express higher BTLA levels. Our data suggest that an altered expression of BTLA and HVEM could be involved in an impaired regulation of autoreactive T cells in lupus. These results provide a better understanding of the BTLA involvement in lupus pathogenesis and confirm that BTLA should be considered as an interesting target for the development of new therapeutic strategies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Aubergeon, Sawaf, Felten, Gottenberg, Dumortier and Monneaux.)

Coinhibitory receptors play an important role in the prevention of autoimmune diseases, such as systemic lupus erythematosus (SLE), by limiting T cell activation. B and T lymphocyte attenuator (BTLA) is an inhibitory receptor, similar to cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD1), that negatively regulates the immune response. The role of BTLA in the pathogenesis of autoimmune diseases in humans and, more specifically, in SLE is largely unknown. We investigated BTLA expression on various T cell subsets, and we did not observe significant variations of BTLA expression between lupus patients and healthy controls. However, the enhancement of BTLA expression after activation was significantly lower in SLE patients compared with that in healthy controls. Furthermore, we found an impaired capacity of BTLA to inhibit T cell activation in SLE due to a poor BTLA recruitment to the immunological synapse following T cell stimulation. Finally, we demonstrated that defective BTLA function can be corrected by restoring intracellular trafficking and by normalizing the lipid metabolism in lupus CD4+ T cells. Collectively, our results evidence that the BTLA signaling pathway is altered in SLE T cells and highlight the potential of targeting this pathway for the development of new therapeutic strategies in lupus.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by B cell hyperactivity leading to the production of autoantibodies, some of which having a deleterious effect. Reducing autoantibody production thus represents a way of controlling lupus pathogenesis, and a better understanding of the molecular and cellular factors involved in the differentiation of B cells into plasma cells could allow identifying new therapeutic targets. Follicular helper T cells (TFH) represent a distinct subset of CD4(+) T cells specialized in providing help to B cells. They are required for the formation of germinal centers and the generation of long-lived serological memory and, as such, are suspected to play a central role in SLE. Recent advances in the field of TFH biology have allowed the identification of important molecular factors involved in TFH differentiation, regulation, and function. Interestingly, some of these TFH-related molecules have been described to be dysregulated in lupus patients. In the present review, we give an overview of the aberrant expression and/or function of such key players in lupus, and we highlight their potential as therapeutic targets.

Follicular helper T cells (TFH) represent a distinct subset of CD4(+) T cells specialized in providing help to B lymphocytes, which may play a central role in autoimmune diseases having a major B cell component such as systemic lupus erythematosus. Recently, TFH subsets that share common phenotypic and functional characteristics with TFH cells from germinal centers, have been described in the peripheral blood from healthy individuals. The aim of this study was to analyze the distribution of such populations in lupus patients. Circulating TFH cell subsets were defined by multicolor flow cytometry as TFH17 (CXCR3(-)CCR6(+)), TFH1 (CXCR3 (+) CCR6(-)) or TFH2 (CXCR3(-)CCR6(-)) cells among CXCR5 (+) CD45RA(-)CD4(+) T cells in the peripheral blood of 23 SLE patients and 23 sex and age-matched healthy controls. IL-21 receptor expression by B cells was analyzed by flow cytometry and the serum levels of IL-21 and Igs were determined by ELISA tests. We found that the TFH2 cell subset frequency is strongly and significantly increased in lupus patients with an active disease (SLEDAI score>8), while the TFH1 cell subset percentage is greatly decreased. The TFH2 and TFH1 cell subset frequency alteration is associated with the presence of high Ig levels and autoantibodies in patient's sera. Moreover, the TFH2 cell subset enhancement correlates with an increased frequency of double negative memory B cells (CD27(-)IgD(-)CD19(+) cells) expressing the IL-21R. Finally, we found that IgE levels in lupus patients' sera correlate with disease activity and seem to be associated with high TFH2 cell subset frequency. In conclusion, our study describes for the first time the distribution of circulating TFH cell subsets in lupus patients. Interestingly, we found an increased frequency of TFH2 cells, which correlates with disease activity. Our results suggest that this subset might play a key role in lupus pathogenesis.

A more complete understanding of the mechanism of action of TLR agonists has fueled the investigation of new synthetic immunoadjuvants. In this context, we designed and synthesized glycolipids of the type Pam(2)Cys-α-Galactose as novel immunoadjuvants. Their synthesis required modifying a hydrophobic tBoc-[2,3-bispalmitoyloxy-(2R)-propyl]-R-cysteinyl moiety, i.e. the minimal structure required for TLR2 agonist activity, by addition of a hydrophilic head, either an α-Galactosylpyranose or an α-Galactosylfuranose to gain respectively Pam(2)CGalp and Pam(2)CGalf. While preparing a carbohydrate building block, an unexpected stereoselectivity was observed during a halide ion-catalytic process on a protected galactofuranose: the alpha anomer was obtained with surprisingly high selectivity (α/β ratio>9) and with good isolated yield (51%). The TLR2 binding properties of Pam(2)CGalp and Pam(2)CGalf were then fully evaluated. Their efficiency in triggering the proliferation of BALB/c mouse splenocytes was also compared to that of Pam(2)CAG and Pam(3)CAG, two well-established ligands of TLRs. Moreover, the maturation state of murine dendritic cells previously incubated with either Pam(2)CGalp or Pam(2)CGalf was monitored by flow cytometry and compared to that induced by lipopolysaccharide. Pam(2)CGalp and Pam(2)CGalf were found to be equivalent TLR2 agonists, and induced splenocyte proliferation and DC maturation. With very similar activity, Pam(2)CGalp and Pam(2)CGalf were also 10-fold to 100-fold better than Pam(2)CAG and Pam(3)CAG at inducing B cell proliferation. This represents the first time a glucidic head has been added to the tBoc-[2,3-bispalmitoyloxy-(2R)-propyl]-R-cysteinyl moiety whilst maintaining the immunomodulating activity. This should greatly enrich the data available on Pam(2)C structure/activity relationships., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Systemic lupus erythematosus is a polymorphic and multigenic inflammatory autoimmune disease. Cyclic AMP (cAMP) modulates inflammation and the inhibition of cyclic nucleotide phosphodiesterase type 4 (PDE4), which specifically hydrolyzes cAMP, inhibits TNFα secretion. This study was aimed at investigating the evolution of PDE activity and expression levels during the course of the disease in MRL/lpr lupus-prone mice, and to evaluate in these mice the biological and clinical effects of treatments with pentoxifylline, denbufylline and NCS 613 PDE inhibitors. This study reveals that compared to CBA/J control mice, kidney PDE4 activity of MRL/lpr mice increases with the disease progression. Furthermore, it showed that the most potent and selective PDE4 inhibitor NCS 613 is also the most effective molecule in decreasing proteinuria and increasing survival rate of MRL/lpr mice. NCS 613 is a potent inhibitor, which is more selective for the PDE4C subtype (IC₅₀= 1.4 nM) than the other subtypes (PDE4A, IC₅₀= 44 nM; PDE4B, IC₅₀= 48 nM; and PDE4D, IC₅₀= 14 nM). Interestingly, its affinity for the High Affinity Rolipram Binding Site is relatively low (K(i) = 148 nM) in comparison to rolipram (K(i) = 3 nM). Finally, as also observed using MRL/lpr peripheral blood lymphocytes (PBLs), NCS 613 inhibits basal and LPS-induced TNFα secretion from PBLs of lupus patients, suggesting a therapeutic potential of NCS 613 in systemic lupus. This study reveals that PDE4 represent a potential therapeutic target in lupus disease.

Associated with the CD1d protein, KRN 7000, a potent synthetic α-galactosylceramide, is known to activate the invariant NKT immune cells. This stimulation then leads to the production of different cytokines modulating a T(H)1/T(H)2 immune response balance involved in protection against several pathologies such as autoimmune diseases and cancers. Various efforts have been made toward the synthesis of simple and more functionalized analogues in order to selectively induce T(H)1 or T(H)2-type cytokine production. Since the discovery of KRN 7000, structure-activity relationships, crystallographic and modelling studies have pointed to the potential of several GalCer analogues in term of selective bioactivity, and have highlighted interesting elements in order to better understand the recognition and activation mechanisms of immune iNKT cells. By presenting an up-to-date library of analogues, collecting recent breakthroughs done in crystallography and molecular modelling, and relating them to the available biological results, we hope that this review will highlight and help the scientific community in their KRN research.

Our goal in the search for potentially bioactive analogues of KRN 7000 was to design an easy synthetic approach to a library of analogues using a strategy recently developed in our laboratory based on a Nucleophilic addition followed by an Epoxide Opening (the NEO strategy). Through the use of a common pivotal structure, a new C-galactoside ester analogue (23) was synthesized which showed an encouraging T(H)2 biased response during preliminary biological tests., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Invariant natural killer T (iNKT) cells are a subset of T cells that recognize glycolipid antigens presented by the CD1d molecule. Accumulating evidences showed that iNKT cells are implicated in the regulatory mechanisms that control autoimmunity. We evaluated the number of circulating iNKT cells in patients with rheumatoid arthritis (RA) by flow cytometry and performed a longitudinal analysis of iNKT cell frequency in RA patients who were given an anti-CD20 therapy. Significantly lower iNKT cell numbers were measured in the blood from RA patients compared to healthy individuals (p<0.0001) and low iNKT cell frequencies were rather associated with an active disease. In RA patients who received rituximab treatment, iNKT cell number was increased in relation to the clinical outcome. We demonstrated that the number of iNKT cells is altered in RA patients and that following rituximab therapy, clinical remission of RA is associated with an increase of iNKT cell frequency., (2009 Elsevier Inc. All rights reserved.)

Crohn's disease is considered to be caused either by an excess of T-cell effector functions and/or by a defective regulatory T-cell compartment. The aim of this study was to assess in Crohn's disease the frequency of circulating CD4(+)CD25(high) T cells that possess regulatory T-cell functions and CD4(+)CD25(low) T cells that contain activated T cells. Flow cytometry of peripheral blood was used to assess CD4(+)CD25(high) and CD4(+)CD25(low) T-cell frequencies in a cohort of 66 patients with Crohn's disease in comparison to 19 patients with ulcerative colitis and 31 healthy individuals enrolled as controls. The CD4(+)CD25(high) T-cell frequency was significantly lowered in naïve Crohn's disease (P = 0.013) and in ulcerative colitis (P = 0.001). CD4(+)CD25(low) T-cell frequency was increased in Crohn's disease (P = 0.0001) and in ulcerative colitis (P = 0.0002). Both CD4(+)CD25(high) and CD4(+)CD25(low) T-cell frequencies are altered in naïve Crohn's disease resulting in an imbalance between both populations and a relative contraction of the CD4(+)CD25(high) T-cell population.

The prognosis of patients with systemic lupus erythematosus has greatly improved since treatment regimens combining corticosteroids and immunosuppressive medications have been widely adopted in therapeutic strategies given to these patients. Immune suppression is evidently efficient but also leads to higher susceptibility to infectious and malignant diseases. Toxic effects and sometimes unexpectedly dramatic complications of current therapies have been progressively reported. Identifying novel molecular targets therefore remains an important issue in the treatment of lupus. The aim of this review article is to highlight emerging pharmacological options and new therapeutic avenues for lupus with a particular focus on non-antibody molecular strategies.

Objective: To assess the safety, tolerability, and efficacy of spliceosomal peptide P140 (IPP-201101; sequence 131-151 of the U1-70K protein phosphorylated at Ser140), which is recognized by lupus CD4+ T cells, in the treatment of patients with systemic lupus erythematosus (SLE)., Methods: An open-label, dose-escalation phase II study was conducted in two centers in Bulgaria. Twenty patients (2 male and 18 female) with moderately active SLE received 3 subcutaneous (SC) administrations of a clinical batch of P140 peptide at 2-week intervals. Clinical evaluation was performed using approved scales. A panel of autoantibodies, including antinuclear antibodies, antibodies to extractable nuclear antigens (U1 RNP, SmD1, Ro/SSA, La/SSB), and antibodies to double-stranded DNA (anti-dsDNA), chromatin, cardiolipin, and peptides of the U1-70K protein, was tested by enzyme-linked immunosorbent assay (ELISA). The plasma levels of C-reactive protein, total Ig, IgG, IgG subclasses, IgM, IgA, and IgE, and of the cytokines interleukin-2 and tumor necrosis factor alpha were measured by ELISA and nephelometry., Results: IgG anti-dsDNA antibody levels decreased by at least 20% in 7 of 10 patients who received 3 x 200 microg IPP-201101 (group 1), but only in 1 patient in the group receiving 3 x 1,000 microg IPP-201101 (group 2). Physician's global assessment of disease activity scores and scores on the SLE Disease Activity Index were significantly decreased in group 1. The changes occurred progressively in the population of responders, increased in magnitude during the treatment period, and were sustained. No clinical or biologic adverse effects were observed in the individuals, except for some local irritation at the highest concentration., Conclusion: IPP-201101 was found to be safe and well tolerated by subjects. Three SC doses of IPP-201101 at 200 microg significantly improved the clinical and biologic status of lupus patients.

Objective: Naturally occurring CD4+,CD25+ Treg cells are central in the maintenance of peripheral tolerance. Impaired activity and/or a lower frequency of these cells is involved in the emergence of autoimmunity. We undertook this study to analyze relative proportions and functional alterations of Treg cells in MRL/lpr mice., Methods: The frequency of CD4+,CD25+ T cells in the peripheral blood of healthy and autoimmune mice was compared by flow cytometry. The capacity of CD4+,CD25+ T cells to inhibit the proliferation and cytokine secretion of CD4+,CD25- T cells was assessed after polyclonal activation., Results: MRL/lpr mice exhibited a normal percentage of CD4+,CD25 high T cells, and forkhead box P3 messenger RNA and protein expression in Treg cells was not altered. However, MRL/lpr Treg cells displayed a reduced capacity to suppress proliferation and to inhibit interferon-gamma secretion by syngeneic effector CD4+,CD25- T cells, as compared with syngeneic cocultures of CBA/J T cells. Moreover, effector MRL/lpr CD4+,CD25- T cells were substantially less susceptible to suppression even when cultured with CBA/J or MRL/lpr Treg cells. Crossover experiments led us to conclude that in MRL/lpr mice, each partner engaged in T cell regulation displays altered functions. Molecules involved in suppressive mechanisms (CTLA-4 and CD80/CD86) are underexpressed, and antigen-presenting cells (APCs) produce raised levels of interleukin-6, which is known to abrogate suppression., Conclusion: Our results suggest that although the frequency and phenotype of Treg cells in MRL/lpr mice are similar to those in normal mice, Treg cells in MRL/lpr mice are not properly stimulated by APCs and are unable to suppress proinflammatory cytokine secretion from effector T cells.

Apoptosis consists of highly regulated pathways involving post-translational modifications and cleavage of proteins leading to sequential inactivation of the main cellular processes. Here, we focused on the apoptotic processing of one of the essential components of the mRNA splicing machinery, the U1-70K snRNP protein. We found that at an early stage of apoptosis, before the cleavage of the C-terminal part of the protein by caspase-3, the basal phosphorylation of the Ser140 residue located within the RNA recognition motif, increases very significantly. A caspase-dependent, PP1-mediated dephosphorylation of other serine residues takes place in a subset of U1-70K proteins. The U1-70K protein phosphorylated at Ser140 is clustered in heterogeneous ectopic RNP-derived structures, which are finally extruded in apoptotic bodies. The elaborate processing of the spliceosomal U1-70K protein we identified might play an important role in the regulated breakdown of the mRNA splicing machinery during early apoptosis. In addition, these specific changes in the phosphorylation/dephosphorylation balance and the subcellular localization of the U1-70K protein might explain why the region encompassing the Ser140 residue becomes a central autoantigen during the autoimmune disease systemic lupus erythematosus.

The link between infection and autoimmunity is not yet well understood. This study was designed to evaluate if an acute viral infection known to induce type I interferon production, like influenza, can by itself be responsible for the breakdown of immune tolerance and for autoimmunity. We first tested the effects of influenza virus on B cells in vitro. We then infected different transgenic mice expressing human rheumatoid factors (RF) in the absence or in the constitutive presence of the autoantigen (human immunoglobulin G [IgG]) and young lupus-prone mice [(NZB x NZW)F(1)] with influenza virus and looked for B-cell activation. In vitro, the virus induces B-cell activation through type I interferon production by non-B cells but does not directly stimulate purified B cells. In vivo, both RF and non-RF B cells were activated in an autoantigen-independent manner. This activation was abortive since IgM and IgM-RF production levels were not increased in infected mice compared to uninfected controls, whether or not anti-influenza virus human IgG was detected and even after viral rechallenge. As in RF transgenic mice, acute viral infection of (NZB x NZW)F(1) mice induced only an abortive activation of B cells and no increase in autoantibody production compared to uninfected animals. Taken together, these experiments show that virus-induced acute type I interferon production is not able by itself to break down B-cell tolerance in both normal and autoimmune genetic backgrounds.

Introduction: The spliceosome, which is a particle containing a molecule of U-RNA and proteins that are specific to each U ribonuclear particle (U-snRNP) or common to every U-snRNPs, is one of the numerous nuclear targets recognized by the antibodies (Abs) and CD4+ T cells from patients with systemic lupus erythematosus and lupus mice., Exegesis: We recently characterized a peptide from the spliceosomal protein U1-70K (sequence 131-151), which is recognized by the Abs and CD4+ T cells from lupus mice and patients. This peptide contains a conserved RNP1 motif, which is also present in other spliceosomal proteins targeted by the Abs from individuals with lupus. We further showed that peptide 131-151 containing a phosphoserine at position 140 (peptide P140) possessed tolerogenic properties in lupus mice and was recognized by the Abs and CD4+ T cells from lupus patients., Conclusion: Thanks to its RNP1 motif, the peptide P140 might play an important role in the initiation and perpetuation steps of the humoral and cellular immune response diversification in lupus individuals. Therapeutic and particularly immunomodulating properties of P140 peptide are being evaluated in humans (a phase III clinical trial will be undertaken in the next weeks).

Regulatory T cells, especially CD4+CD25+ T cells, "natural killer" T cells and gammadelta T cells, are central in the maintenance of peripheral tolerance and the protection from the development of autoimmune diseases. Numerical or functional modifications of these cell populations were demonstrated to lead to the breakdown of tolerance and the emergence of autoimmunity. Involvement of regulatory T cells in the pathogenesis of systemic autoimmune diseases, such as systemic lupus erythematosus, might be of first importance. In murine models and patients with lupus, these regulatory T cells seem to be reduced in number. Functional deficiencies have also been described in a few studies. A better knowledge of regulatory T cell functional properties in systemic autoimmune diseases is essential to manipulate these cells and hopefully to restore immune tolerance.

Systemic lupus erythematosus (SLE) is a multisystem chronic inflammatory disease of multifactorial aetiology, characterized by inflammation and damage of various tissues and organs. Current treatments of the disease are mainly based on immunosuppressive drugs such as corticosteroids and cyclophosphamide. Although these treatments have reduced mortality and morbidity, they cause a non-specific immune suppression. To avoid these side effects, our efforts should focus on the development of alternative therapeutic strategies, which consist, for example in specific T cell targeting using autoantigen-derived peptides identified as sequences encompassing major epitopes.

We previously demonstrated the importance of the RNP1 motif-bearing region 131-151 of the U1-70K spliceosomal protein in the intramolecular T-B spreading that occurs in MRL/lpr lupus mice. Here, we analyze the involvement of RNP1 motif in the development and prevention of naturally-occurring intermolecular T-B cell diversification. We found that MRL/lpr peripheral blood lymphocytes proliferated in response to peptides containing or corresponding exactly to the RNP1 motif of spliceosomal U1-70K, U1-A and hnRNP-A2 proteins. We also demonstrated that rabbit antibodies to peptide 131-151 cross-reacted with U1-70K, U1-A and hnRNP-A2 RNP1-peptides. These antibodies recognized the U1-70K and U1-A proteins, and also U1-C and SmD1 proteins, which are devoid of RNP1 motif. Repeated administration of phosphorylated peptide P140 into MRL/lpr mice abolished T-cell response to several peptides from the U1-70K, U1-A and SmD1 proteins without affecting antibody and T-cell responses to foreign (viral) antigen in treated mice challenged with infectious virus. These results emphasized the importance of the dominant RNP1 region, which seems to be central in the activation cascade of B and T cells reacting with spliceosomal RNP1+ and RNP1- spliceosomal proteins. The tolerogenic peptide P140, which is recognized by lupus patients' CD4+ T cells and known to protect MRL/lpr mice, is able to thwart emergence of intermolecular T-cell spreading in treated animals.

A peptide encompassing residues 131-151 of the spliceosomal U1-70K protein and its analog phosphorylated at Ser140 were synthesized as potential candidates for the treatment of patients with lupus. Studies in the MRL/lpr and (NZB x NZW)F1 lupus models have demonstrated that these sequences contain a CD4+ T cell epitope but administration of the phosphorylated peptide only ameliorates the clinical manifestations of treated MRL/lpr mice. Binding assays with soluble HLA class II molecules and molecular modeling experiments indicate that both peptides behave as promiscuous epitopes and bind to a large panel of human DR molecules. In contrast to normal T cells and T cells from non-lupus autoimmune patients, we found that PBMCs from 40% of lupus patients selected randomly and CFSE-labeled CD4+ T cells proliferate in response to peptide 131-151. Remarkably, however, we observed that phosphorylation of Ser140 prevents CD4+ T cells proliferation but not secretion of regulatory cytokines, suggesting a striking immunomodulatory effect of phosphorylated analog on lupus CD4+ T cells that was unique to patients. The analog might act as an activator of regulatory T cells or as a partial agonist of TCR.

Objective: To analyze spontaneous T cell spreading against determinants of the U1-70K protein in young autoimmune MRL/lpr lupus mice, in comparison with the T cell spreading occurring in normal BALB/c mice immunized with peptide 131-151 of this protein., Methods: Peripheral blood lymphocytes (PBLs) from both unprimed MRL/lpr mice and immunized BALB/c mice were tested for their ability to proliferate ex vivo in response to 18 overlapping peptides of the U1-70K spliceosomal protein, using assays for lymphocyte proliferation and secretion of interleukin-2., Results: The proliferative response to peptides of the U1-70K protein evolved rapidly in MRL/lpr mice tested at different ages. At least 5 peptides were recognized by PBLs from 8-week-old autoimmune mice, whereas a different peptide was recognized by PBLs from MRL/lpr mice at 12 weeks of age. At 15 weeks, the proliferative response was weak or negative when assessed with any of the test peptides. At least 2 major peptides recognized by MRL/lpr PBLs were also recognized by PBLs generated in the BALB/c mice primed with peptide 131-151. We further demonstrated that, in preautoimmune MRL/lpr mice, repeated administration of phosphorylated peptide 131-151 (called P140), which was shown previously to be protective, transiently abolished T cell intramolecular spreading to other regions of the 70K protein., Conclusion: This is the first study to demonstrate that intramolecular T cell spreading effectively occurs in MRL/lpr mice with lupus, and that region 131-151 is important in the cascade of events observed in the murine lupus response. This sequence might originate a mechanism of tolerance spreading that leads to the beneficial effect observed in MRL/lpr mice after treatment with the phosphorylated peptide 131-151., (Copyright 2004 American College of Rheumatology)

Current drug-based therapy for systemic lupus erythematosus (SLE) are non-specific and often counterbalanced by adverse effects. Current research aims at developing specific treatments that target deleterious cells only and not the whole immune system. This strategy requires the identification of sequences derived from major lupus autoantigens, responsible for the activation of autoreactive B and T cells. This review summarizes the identification and characterization of peptides, which are able to modulate T cells ex vivo, and describes the promising results obtained after administration of some of these peptides in lupus mice. Although these therapeutic trials are encouraging, the precise mode of action of peptide-based immunotherapy is still elusive. Here, we discuss the possible mechanisms leading to T-cell tolerance induction and the feasibility of extending the success of peptide-based therapy from animal models to human.

Modifications of self antigens that occur during apoptosis might be involved in the generation of neo-antigens, which can break tolerance and induce autoimmunity. We have previously identified an epitope at residues 131-151 of the U1-70K snRNP protein, recognized by IgG antibodies and CD4+ T cells from at least two strains of lupus mice. With the aim of investigating the possible role of phosphorylation on the antigenicity of peptide 131-151 and to gain a better understanding of how this peptide can drive autoimmune response, we synthesized two peptides phosphorylated on Ser137 and 140, respectively. We show here that peptide P140 phosphorylated on Ser140 is recognized by both CD4+ T cells and antibodies from MRL/lpr mice. Furthermore, intravenous administration to lupus-prone MRL/lpr mice of P140 in saline (but not of the non-phosphorylated peptide) decreased proteinuria and anti-DNA antibody production, and significantly prolonged survival of treated mice. We further demonstrated that P140 is recognized by antibodies from lupus patients and binds to various HLA DR molecules, offering new hope for manipulating T cell response in humans.

(NZB x NZW)F(1) and MRL/Fas(lpr) lupus mice present a similar phenotype with a spectrum of autoantibodies associated with very severe nephritis. It is thought, however, that in contrast to other lupus-prone mice such as MRL/Fas(lpr) mice, (NZB x NZW)F(1) mice do not generate autoantibodies to ribonucleoproteins (RNP) Sm/RNP. In this study, we demonstrate that contrary to previous reports, the autoimmune response directed against Sm/RNP antigens also occurs in NZB x NZW mice. CD4(+) T cells from unprimed 10-week-old NZB x NZW mice proliferate and secrete IL-2 in response to peptide 131-151 of the U1-70K protein, which is known to contain a T(h) epitope recognized by CD4(+) T cells from MRL/Fas(lpr) mice. Peptide 131-151, which was found to bind I-A(k) and I-E(k) class II MHC molecules, also bound both I-A(d) and I-E(d) molecules. This result led us to also re-evaluate longitudinally the anti-Sm/RNP antibody response in NZB x NZW mice. We found that 25-week-old mice do produce antibodies reacting with several small nuclear and heterogeneous nuclear (hn) RNP proteins, such as SmD1, U1-70K and hnRNP A2/B1 proteins. The fine specificity of these antibodies was studied with overlapping synthetic peptides. The same antigenically positive and negative peptides were characterized in MRL/Fas(lpr) and NZB x NZW mice in the three proteins. This new finding can help to understand the mechanisms involved in the development of the anti-Sm/RNP antibody response and, particularly, the role played by non-MHC genes in this autoimmune response.

Immune spreading to multiple intracellular antigens is likely to be of primary importance in organ-specific and systemic autoimmune diseases. A number of mechanisms by which immune spreading may occur from only a single autoreactive epitope have been proposed. Search for an initiator or early epitope thus represents an important area of investigation. For example, many studies have focused on the identification of epitopes recognized by the antibodies from both patients with systemic lupus erythematosus (SLE) and lupus-prone mice. Recently, an autoepitope present in the 70K U1 ribonucleo protein (RNP) and recognized by CD4+ T cells from lupus mice has also been identified. Here, we analyze the results of B- and T-cell-epitope mapping studies of several RNPs present in the spliceosome and propose a model of epitope spreading. In this model, a consensus sequence (the RNP motif) conserved in many nuclear, nucleolar and cytoplasmic antigens, might play a role as 'driver' epitope. This hypothesis is based on the observation that this sequence is recognized by CD4+ T cells from lupus mice and is often targeted by autoantibodies, very early during the course of the disease. Targeting this region that is repeated in different self-antigens, might represent an interesting strategy to interfere with the continuous T-cell stimulation and exposure to specific antigens.

T cells play a critical role in both the immunological and clinical manifestations of systemic autoimmune diseases such as systemic lupus erythematosus (SLE). Although in normal mice multiple T cell epitopes have been characterized in several self-proteins, there is little information on the fine specificity of autoreactive T cells in lupus model mice and humans. In SLE-prone mice and humans, the only Th cell epitopes identified at the molecular level in self-antigens concern histones and nucleosomes, and the 70-kD U1-snRNP protein. T cell characterization in certain autoimmune mice such as MRL lpr/lpr and NZB/NZW mice has been largely impaired by their hyporesponsiveness in response to mitogen and minimal IL-2 secretion. In addition, MRL lpr/lpr mice also develop lymphadenopathy characterized by the progressive accumulation of functionally immature CD4(-) CD8(-) T cells. It is therefore important to optimize the methods used to measure T cell proliferation and cytokine production ex vivo in order to identify minimal activation in the presence of appropriate antigen. The protocol described in this article has been used for identifying in young MRL lpr/lpr and NZB/NZW mice a CD4(+) T cell epitope in the murine 70-kD U1-RNP protein.

Autoantibodies directed against spliceosomal heterogeneous nuclear ribonucleoproteins (hnRNPs) are a typical feature of rheumatoid arthritis, systemic lupus erythematosus, and mixed-connective tissue disease. With the aim of investigating a potential pathogenic role of these Abs, we have studied the Ab response to A2/B1 hnRNPs in different murine models of lupus. The specificity of anti-A2/B1 Abs was tested with a series of 14 overlapping synthetic peptides covering the region 1-206 of A2 that contains most of the epitopes recognized by patients' Abs. A major epitope recognized very early during the course of the disease by Abs from most of MRL lpr/lpr mice but not from other lupus mice and from mice of different MHC haplotypes immunized against B1 was identified in residues 50-70. This peptide contains a highly conserved sequence RGFGFVTF also present in other hnRNPs and small nuclear ribonucleoproteins. Abs reacting with a second A2 epitope identified in residues 35-55 were detectable several weeks later, suggesting an intramolecular B cell epitope spreading during the course of the disease. We identified several T cell epitopes within the region 35-175 that generated an effective Th cell response with IL-2 and IFN-gamma secretion in nonautoimmune CBA/J mice sharing the same MHC haplotype H-2k as MRL/lpr mice. None of the peptides stimulated T cells primed in vivo with B1. Because Abs to peptide 50-70 were detected significantly earlier than Abs reacting with other A2 peptides and the protein itself, it is possible that within the protein, this segment contains residues playing an initiator role in the induction of the anti-A2/B1 and antispliceosome Ab response.

Systemic lupus erythematosus is characterized by the presence of high titers of autoantibodies reacting with various components of the U1 small nuclear ribonucleoprotein particle (snRNP). It has been suggested that these antibodies are produced by an antigen-driven mechanism under the dependence of antigen-specific T cells. To investigate the role of T cell help in this process, we sought, with 20 overlapping peptides, the Th epitopes on the U1-70K snRNP in unprimed H-2(k) MRL / lpr lupus mice and immunized CBA normal mice. The peptide 131 - 151 was recognized by both IgG autoantibodies and CD4(+) T cells from 7 - 9-week-old MRL / lpr mice. In this test, antigen-presenting cells (APC) from MRL / lpr mice were required; APC from naive CBA mice failed to stimulate CD4(+) cells from MRL / lpr mice. The potential role of MRL / lpr B cells as APC, the expression of MHC class II molecules at their surface and their activation state (expression of CD69, CD80 / B7-1 and CD86 / B7-2 molecules) were studied. Peptide 131 - 151 bound both I-A(k) and I-E(k) class II molecules and favored an IL-2-positive T cell response but not IFN-gamma, IL-6 and IL-10 secretion. Segment 131 - 151 is localized within the RNP80 motif and contains residues that are highly conserved in many nuclear, nucleolar and cytoplasmic RNA binding proteins.