Sexual dimorphism in an animal model of Sjögren's syndrome: a potential role for Th17 cells

The First Case Report of Preschool-Onset SS/SLE Coexisting With NMOSD of Chinese Origin

Systemic lupus erythematosus (SLE) is an autoimmune connective tissue disease (CTD), the main features of which are multiple serum autoantibodies and extensive involvement of multiple systems. The onset age of patients varies from childhood to middle age, with nearly 1/5 in childhood. Sjogren’s syndrome (SS) is also an autoimmune disease characterized by high-degree lymphocytic infiltration of exocrine glands, usually occurring in middle-aged and older women, and rarely in childhood. Neuromyelitis optica spectrum disorder (NMOSD) is an immune-mediated inflammatory demyelinating disease of the central nervous system (CNS) mainly involving the optic nerve and spinal cord. The coexistence of NMOSD and SLE and/or SS is well recognized by both neurologists and rheumatologists, but cases in children have been rarely reported. In this paper, we reported a case of a girl with onset at age 5 clinically featured by recurrent parotid gland enlargement, pancytopenia, hypocomplementemia, multiple positive serum antibodies, and cirrhosis. She was initially diagnosed with SS/SLE overlap syndrome at age 5. Four years later, the patient suffered a sudden vision loss and was examined to have positive AQP4 antibodies in serum and cerebrospinal fluid (CSF), and long segmental spinal swelling, in line with the diagnostic criteria for NMOSD. Up to now, the current patient is of the youngest onset age to develop SS/SLE coexisting with NMOSD, also with cirrhosis. It is important for clinicians to be aware of the possibility of CTDs coexisting with NMOSD in children, especially in those with positive anti-multiple autoantibodies, and to decrease the rate of missed diagnosis.

Blocking IAg7 class II major histocompatibility complex by drug-like small molecules alleviated Sjögren's syndrome in NOD mice

BACKGROUND

Sjögren's syndrome (SjS) is an autoimmune disease with a strong genetic association. To date, no vaccine or therapeutic agent exists to cure SjS, and patients must rely on lifelong therapies to treat symptoms. Human leukocyte antigens (HLA) are primary susceptibility loci that form the genetic basis for many autoimmune diseases, including SjS. In this study, we sought to determine whether blocking MHC class II IAg7 antigen presentation in the NOD mouse would alleviate SjS by preventing the recognition of autoantigens by pathogenic T cells.

METHODS

Mapping of the antigenic epitopes of Ro60 autoantigen to IAg7 of the NOD mice was performed using structural modeling and in-vitro stimulation. Tetraazatricyclo-dodecane (TATD) and 8-Azaguanine (8-Aza) were previously identified as potential binders to IAg7 of the NOD mice using in silico drug screening. Mice were treated with 20mgs/kg via IP every day five days/week for 23 weeks. Disease profiling was conducted.

FINDINGS

Specific peptides of Ro60 autoantigen were identified to bind to IAg7 and stimulated splenocytes of the NOD mice. Treating NOD mice with TATD or 8-Azaguanine alleviated SjS symptoms by improving salivary and lacrimal gland secretory function, decreasing the levels of autoantibodies, and reducing the severity of lymphocytic infiltration in the salivary and lacrimal glands.

INTERPRETATION

This study presents a novel therapeutic approach for SjS by identifying small molecules capable of inhibiting T cell response via antigen-specific presentation.

FUNDING

CQN is supported financially in part by PHS grants AI130561, DE026450, and DE028544 from the National Institutes of Health.

Stimulation of regulatory T cells with Lactococcus lactis expressing enterotoxigenic E. coli colonization factor antigen 1 retains salivary flow in a genetic model of Sjögren's syndrome

BACKGROUND

Sjögren's syndrome (SjS), one of the most common autoimmune diseases, impacts millions of people annually. SjS results from autoimmune attack on exocrine (salivary and lacrimal) glands, and women are nine times more likely to be affected than men. To date, no vaccine or therapeutic exists to treat SjS, and patients must rely on lifelong therapies to alleviate symptoms.

METHODS

Oral treatment with the adhesin from enterotoxigenic Escherichia coli colonization factor antigen I (CFA/I) fimbriae protects against several autoimmune diseases in an antigen (Ag)-independent manner. Lactococcus lactis, which was recently adapted to express CFA/I fimbriae (LL-CFA/I), effectively suppresses inflammation by the induction of infectious tolerance via Ag-specific regulatory T cells (Tregs), that produce IL-10 and TGF-β. To test the hypothesis that CFA/I fimbriae can offset the development of inflammatory T cells via Treg induction, oral treatments with LL-CFA/I were performed on the spontaneous, genetically defined model for SjS, C57BL/6.NOD-Aec1Aec2 mice to maintain salivary flow.

RESULTS

Six-week (wk)-old C57BL/6.NOD-Aec1Aec2 mice were orally dosed with LL-CFA/I and treated every 3 wks; control groups were given L. lactis vector or PBS. LL-CFA/I-treated mice retained salivary flow up to 28 wks of age and showed significantly reduced incidence of inflammatory infiltration into the submandibular and lacrimal glands relative to PBS-treated mice. A significant increase in Foxp3+ and IL-10- and TGF-β-producing Tregs was observed. Moreover, LL-CFA/I significantly reduced the expression of proinflammatory cytokines, IL-6, IL-17, GM-CSF, and IFN-γ. Adoptive transfer of CD4+ T cells from LL-CFA/I-treated, not LL vector-treated mice, restored salivary flow in diseased SjS mice.

CONCLUSION

These data demonstrate that oral LL-CFA/I reduce or halts SjS progression, and these studies will provide the basis for future testing in SjS patients.

Impact of comorbid Sjögren syndrome in anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders

BACKGROUND

Neuromyelitis optica spectrum disorders (NMOSD) are autoimmune neurological diseases of the central nervous system, which are characterized by the presence of serum anti-aquaporin-4 autoantibodies (AQP4-IgG). An association between Sjögren syndrome (SjS) and AQP4-IgG-positive NMOSD has been proposed, but the rate of coexistence has not been determined.

METHODS

In this study, 4,447 patients suspected of having NMOSD with acute neurological episodes were evaluated for the positivity of serum AQP4-IgG, serum SS-A/Ro antibody, and the presence of SjS-related symptoms (dry eye, dry mouth).

RESULTS

Of the 4,447 patients, 1,651 were positive for serum AQP4-IgG, and the remaining 2,796 were negative. A significantly higher proportion of AQP4-IgG-positive patients were positive for serum anti-SSA/Ro antibody (26.3 vs. 4.5%; p < 0.0001) and anti-SSB/La antibody (7.2 vs. 1.2%; p < 0.0001) and had dry eye (9.1 vs .4.9%; p < 0.0001) and dry mouth symptoms (8.9 vs. 3.7%; p < 0.0001). More than 80% of the patients with SjS with acute neurological events such as myelitis or optic neuritis were AQP4-IgG positive. AQ4-IgG-positive patients with comorbid SjS showed a higher female rate (97.1 vs. 89.0%; p = 0.0062), a higher positivity rate for oligoclonal bands (15.4 vs. 7.5%; p = 0.029), and a higher relapse frequency (p = 0.027) than AQP4-IgG-positive patients without comorbid SjS.

CONCLUSIONS

The prevalence of SjS is higher among AQP4-IgG-positive than AQP4-IgG-negative patients, with the potential prevalence of 10-20% at the diagnosis of AQP4-IgG-positive NMOSD. Comorbid SjS is more prevalent in females, and it has a higher relapse frequency among AQP4-IgG-positive patients.

Sex-mediated elevation of the specialized pro-resolving lipid mediator levels in a Sjögren's syndrome mouse model

Our previous results showed that the specialized pro-resolving mediator (SPM) Resolvin D1 (RvD1) promotes resolution of inflammation in salivary glands in non-obese diabetic (NOD)/ShiLtJ, a mouse model for Sjögren's syndrome (SS). Additionally, mice lacking the RvD1 receptor ALX/FPR2 show defective innate and adaptive immune responses in salivary glands. Particularly, ALX/FPR2 KO mice exhibit exacerbated inflammation in their salivary glands in response to systemic LPS treatment. Moreover, female ALX/FPR2 KO mice show increased autoantibody production and loss of salivary gland function with age. Together, these studies suggest that an underlying SPM dysregulation could be contributing to SS progression. Therefore, we investigated whether SPM production is altered in NOD/ShiLtJ using metabololipidomics and enzyme-linked immunosorbent assay (ELISA). Our results demonstrate that SPM levels were broadly elevated in plasma collected from NOD/ShiLtJ female mice after disease onset, whereas these drastic changes did not occur in male mice. Moreover, gene expression of enzymes involved in SPM biosynthesis were altered in submandibular glands (SMG) from NOD/ShiLtJ female mice after disease onset, with 5-LOX and 12/15-LOX being downregulated and upregulated, respectively. Despite this dysregulation, the abundances of the SPM products of these enzymes (ie, RvD1 and RvD2) were unaltered in freshly isolated SMG cells suggesting that other cell populations (eg, lymphocytes) may be responsible for the overabundance of SPMs that we observed. The elevation of SPMs noted here appeared to be sex mediated, meaning that it was observed only in one sex (females). Given that SS primarily affects females (roughly 90% of diagnosed cases), these results may provide some insights into the mechanisms underlying the observed sexual dimorphism.

Estrogen, estrogen-like molecules and autoimmune diseases

In western countries, the slope of autoimmune disease (AD) incidence is increasing and affects 5-8% of the population. Mainly prevalent in women, these pathologies are due to thymic tolerance processes breakdown. The female sex hormone, estrogen, is involved in this AD female susceptibility. However, predisposition factors have to act in concert with unknown triggering environmental factors (virus, microbiota, pollution) to initiate AD. Individuals are exposed to various environmental compounds that display endocrine disruption abilities. The cellular effects of some of these molecules may be mediated through the aryl hydrocarbon receptor (AhR). Here, we review the effects of these molecules on the homeostasis of the thymic cells, the immune tolerance intrinsic factors (transcription factors, epigenetic marks) and on the immune tolerance extrinsic factors (microbiota, virus sensibility). This review highlights the contribution of estrogen and endocrine disruptors on the dysregulation of mechanisms sustaining AD development.

Salivary-gland-protective regulatory T-cell dysfunction underlies female-specific sialadenitis in the non-obese diabetic mouse model of Sjögren syndrome

Immune cell-mediated destruction of salivary glands is a hallmark feature of Sjögren syndrome. Similar to the female predominance in humans, female non-obese diabetic (NOD) mice develop spontaneous salivary gland autoimmunity. However, in both humans and mice it is unclear what factors contribute to the initial immune infiltration of the salivary glands. Here, we used an adoptive transfer model of Sjögren syndrome to determine if female mice harbor a sex-specific defect in salivary-gland-protective regulatory T (Treg) cells. Transfer of cervical lymph node (LN) cells from female NOD mice into sex-matched NOD-severe combined immunodeficient (SCID) recipients resulted in sialadenitis, regardless of the presence or absence of Treg cells. In contrast, transfer of cervical LN cells from male NOD mice into sex-matched NOD-SCID recipients only resulted in sialadenitis when Treg cells were depleted before transfer, suggesting that male NOD mice have functional salivary-gland-protective Treg cells. Notably, the host environment affected the ability of Treg cells to prevent sialadenitis with testosterone promoting salivary gland protection. Treg cells from male mice did not protect against sialadenitis in female recipients. Testosterone treatment of female recipients of bulk cervical LN cells decreased sialadenitis, and Treg cells from female mice were capable of protecting against development of sialadenitis in male recipients. Hence, our data demonstrate that female NOD mice develop sialadenitis through a defect in salivary-gland-protective Treg cells that can be reversed in the presence of testosterone.

The G-Protein-Coupled Receptor ALX/Fpr2 Regulates Adaptive Immune Responses in Mouse Submandibular Glands

Lipoxin receptor (ALX)/N-formyl peptide receptor (FPR)-2 is a G-protein-coupled receptor that has multiple binding partners, including the endogenous lipid mediators resolvin D1, lipoxin A₄, and the Ca²⁺-dependent phospholipid-binding protein annexin A1. Previous studies have demonstrated that resolvin D1 activates ALX/Fpr2 to resolve salivary gland inflammation in the NOD/ShiLtJ mouse model of Sjögren syndrome. Moreover, mice lacking the ALX/Fpr2 display an exacerbated salivary gland inflammation in response to lipopolysaccharide. Additionally, activation of ALX/Fpr2 has been shown to be important for regulating antibody production in B cells. These previous studies indicate that ALX/Fpr2 promotes resolution of salivary gland inflammation while modulating adaptive immunity, suggesting the need for investigation of the role of ALX/Fpr2 in regulating antibody production and secretory function in mouse salivary glands. Our results indicate that aging female knockout mice lacking ALX/Fpr2 display a significant reduction in saliva flow rates and weight loss, an increased expression of autoimmune-associated genes, an up-regulation of autoantibody production, and increased CD20-positive B-cell population. Although not all effects were noted among the male knockout mice, the results nonetheless indicate that ALX/Fpr2 is clearly involved in the adaptive immunity and secretory function in salivary glands, with further investigation warranted to determine the cause(s) of these between-sex differences.

Anti-IL-7 receptor-α treatment ameliorates newly established Sjögren's-like exocrinopathy in non-obese diabetic mice

The levels of interleukin (IL)-7 and its receptor are elevated in the salivary glands of patients with Sjögren's syndrome (SS). Our previous study indicates that IL-7 plays a critical pathogenic role in the development and onset of SS in a mouse model of this disease. The present study aims at determining whether IL-7 also plays a role in sustaining SS pathologies after the disease onset, by using the non-obese diabetic (NOD) model. Intraperitoneal administration of a blocking antibody against the IL-7 receptor α chain (IL-7Rα) to female NOD mice aged 10 weeks, which exhibited newly onset clinical SS, for the duration of 3 weeks significantly ameliorated characteristic SS pathologies including hyposalivation and leukocyte infiltration of the submandibular glands (SMGs). These changes were accompanied by a decrease in IFN-γ-producing CD4 T- and CD8 T cells, B cells, and lymphocyte chemoattractants CXCL9, -10, -11 and -13 in the SMGs. Anti-IL-7Rα treatment markedly diminished the amount of TNF-α in the SMGs and increased the level of claudin-1 and aquaporin 5, two molecules critical for normal salivary secretion. Furthermore, neutralization of IFN-γ and TNF-α, individually or in combination, considerably improved salivary secretion, reduced leukocyte infiltration and down-regulated CXCL9 and -13 expression in the SMGs. Collectively, the results indicate that endogenous IL-7R signals promote Th1 and Tc1 responses and IFN-γ- and TNF-α production to sustain the persistence of SS-like sialadenitis in NOD mice. These findings suggest that IL-7 and Th1 cytokines could serve as promising therapeutic targets for this prevalent autoimmune disease.

Unique glandular ex-vivo Th1 and Th17 receptor motifs in Sjögren's syndrome patients using single-cell analysis

Primary Sjögren's syndrome (pSS) is an autoimmune disease in which the underlying cause has yet to be elucidated. The main objective of this study was to determine the T cell receptor (TCR) repertoires of individual infiltrating T helper (Th)-1 and 17 cells of pSS patients using single-cell analysis. Single-cell analysis of ex-vivo infiltrating T cells demonstrated that pSS patients had higher frequencies of activated Th17 cells. Single-cell TCR sequencing revealed that TCRβ variable (TRBV)3-1/joint (J)1-2 (CLFLSMSACVW) and TRBV20-1/J1-1 (SVGSTAIPP*T) were expressed by activated Th1 and Th17 cells in both cohorts. Uniquely, TCRα variable (TRAV)8-2/J5 (VVSDTVLETAGE) was expressed by Th1 cells present only in patients and complementarity-determining region (CDR)3α-specific motif (LSTD*E) present in both Th1/Th17 cells. The study demonstrates that both activated Th1 and Th17 cells of pSS patients showed restricted clonal diversities of which two CDR3 motifs were present in controls and patients, with another two motifs unique to pSS.

Single-cell analysis reveals sexually dimorphic repertoires of Interferon-γ and IL-17A producing T cells in salivary glands of Sjögren's syndrome mice

The development of Sjögren's syndrome (SjS) is a dynamic and temporal process with a female predilection. Following the initial influx of immune cells, T cell clusters develop, accelerating the pathology in the salivary glands. Proinflammatory cytokines, IFN-γ and IL-17A, produced by T cells contribute synergistically to the disease. In this study, we examined the sexual dimorphism in cellular infiltrates of the salivary glands by using functional single-cell microengraving analysis. Using high-throughput sequencing, we investigated the clonal diversity of the T cell receptors (TCRs) of infiltrating IFN-γ and IL-17A-producing T cells in male and female SjS-susceptible (SjSs) C57BL/6.NOD-Aec1Aec2 mice. There were elevated frequencies of IFN-γ and IL-17A-producing effector T cell populations in female SjSS mice compared to male SjSS mice. MEME analysis shows high frequency and unique, sexually dimorphic motifs in the TCR hypervariable regions in the SjSS mice. Male mice selected for TRAV8/TRAJ52 (CATDLNTGANTGKLTFG) TCR genes in Th1 cells and TRBV16/(TRBD1/2)TRBJ1-7 (CGGKRRLESIFR) in Th1 and Th17 cells. Female SjSS mice selected for TRAV8/TRAJ52 (CATDLNTGANTGKLTFG), TRAV13D-2/TRAJ23 (CVYLEHHFE), and TRBV23/(TRBD2)TRBJ2-2 (CRKLHSCATCALNFL) in Th1 cells. These findings suggest that there is an elevated prevalence of pathogenic effector T cells in the glands with a sexually dimorphic selection bias of TCR repertoires.

What can Sjögren's syndrome-like disease in mice contribute to human Sjögren's syndrome?

For decades, Sjögren's syndrome (SS) and Sjögren's syndrome-like (SS-like) disease in patients and mouse models, respectively, have been intensely investigated in attempts to identify the underlying etiologies, the pathophysiological changes defining disease phenotypes, the nature of the autoimmune responses, and the propensity for developing B cell lymphomas. An emerging question is whether the generation of a multitude of mouse models and the data obtained from their studies is actually important to the understanding of the human disease and potential interventional therapies. In this brief report, we comment on how and why mouse models can stimulate interest in specific lines of research that apparently parallel aspects of human SS. Focusing on two mouse models, NOD and B6·Il14α, we present the possible relevance of mouse models to human SS, highlighting a few selected disease-associated biological processes that have baffled both SS and SS-like investigations for decades.

Sexual dimorphic function of IL-17 in salivary gland dysfunction of the C57BL/6.NOD-Aec1Aec2 model of Sjögren's syndrome

Interleukin (IL)-17 is one of the critical inflammatory cytokines that plays a direct role in development of Sjögren’s syndrome (SjS), a systemic autoimmune disease characterized by a progressive chronic attack against the exocrine glands. The expression levels of IL-17 are correlated with a number of essential clinical parameters such as focus score and disease duration in human patients. Significantly immunological differences of Th17 cells were detected at the onset of clinical disease in female SjS mice compared to males. To further define the role of IL-17 in SjS and elucidate its involvement in the sexual dimorphism, we examined the systemic effect of IL-17 by genetically ablating Il-17 in the C57BL/6.NOD-Aec1Aec2, spontaneous SjS murine model. The results indicate that IL-17 is a potent inflammatory molecule in the induction of chemoattractants, cytokines, and glandular apoptosis in males and females. Elimination of IL-17 reduced sialadenitis more drastically in females than males. IL-17 is highly involved in modulating Th2 cytokines and altering autoantibody profiles which has a greater impact on changing plasma cells and germinal center B cell populations in females than males. The result supports a much more important role for IL-17 and demonstrates the sexual dimorphic function of IL-17 in SjS.