Induction of Oral Tolerance in Experimental Sjogren's Syndrome Autoimmunity

How to focus on autoantigen-specific lymphocytes: a review on diagnosis and treatment of Sjogren's syndrome

Sjogren's syndrome (SS) is an autoimmune epithelitis characterized by focal lymphocytic infiltration against self-antigens leading to progressive glandular dysfunction, which can develop to multisystem manifestation. The classification criteria for SS emphasizes glandular lymphocyte infiltrates and anti-SSA/SSB seropositivity, which is usually manifested in advanced patients. Therapeutically, apart from symptomatic treatment, treatment of SS is based on glucocorticoids and conventional synthetic disease-modifying antirheumatic drugs with global immunosuppression, but the efficacy of biologic or targeted synthetic therapies is still sparse. Currently, emerging studies focus on autoantigen-specific immunotherapies to treat autoimmune disorders by directly eliminating autoreactive cell subsets and inducing tolerance by increasing the autoreactive regulatory lymphocytes. Herein, we summarize the current state of research on the autoantigen-specific approaches for detecting autoreactive lymphocytes and outline the current autoantigen-specific immunotherapies in other autoimmune disorders and their attempts in treatment of SS. Last, we discuss the potential value of focusing on autoantigen-specific lymphocytes in the early diagnosis, monitoring, and targeted treatment of SS. Potential strategies for targeting autoreactive lymphocytes need to be confirmed in SS.

Autoimmunity-Basics and link with periodontal disease

Autoimmune reactions reflect an imbalance between effector and regulatory immune responses, typically develop through stages of initiation and propagation, and often show phases of resolution (indicated by clinical remissions) and exacerbations (indicated by symptomatic flares). The fundamental underlying mechanism of autoimmunity is defective elimination and/or control of self-reactive lymphocytes. Periodontal diseases are characterized by inflammatory conditions that directly affect teeth-supporting structures, which are the major cause of tooth loss. Several studies have demonstrated the involvement of autoimmune responses in periodontal disease. Evidence of involvement of immunopathology has been reported in periodontal disease. Bacteria in the dental plaque induce antibody formation. Autoreactive T-cells, natural killer cells, ANCA, heat shock proteins, autoantibodies, and genetic factors are reported to have an important role in the autoimmune component of periodontal disease. The present review describes the involvement of autoimmune responses in periodontal diseases and also the mechanisms underlying these responses.

Mouse Models of Primary Sjogren's Syndrome

Sjogren's syndrome (SjS) is a chronic autoimmune disorder characterized by immune cell infiltration and progressive injury to the salivary and lacrimal glands. As a consequence, patients with SjS develop xerostomia (dry mouth) and keratoconjunctivitis sicca (dry eyes). SjS is the third most common rheumatic autoimmune disorder, affecting 4 million Americans with over 90% of patients being female. Current diagnostic criteria for SjS frequently utilize histological examinations of minor salivary glands for immune cell foci, serology for autoantibodies, and dry eye evaluation by corneal or conjunctival staining. SjS can be classified as primary or secondary SjS, depending on whether it occurs alone or in association with other systemic rheumatic conditions, respectively. Clinical manifestations typically become apparent when the disease is relatively advanced in SjS patients, which poses a challenge for early diagnosis and treatment of SjS. Therefore, SjS mouse models, because of their close resemblance to the human SjS, have been extremely valuable to identify early disease markers and to investigate underlying biological and immunological dysregulations. However, it is important to bear in mind that no single mouse model has duplicated all aspects of SjS pathogenesis and clinical features, mainly due to the multifactorial etiology of SjS that includes numerous susceptibility genes and environmental factors. As such, various mouse models have been developed in the field to try to recapitulate SjS. In this review, we focus on recent mouse models of primary SjS xerostomia and describe them under three categories of spontaneous, genetically engineered, and experimentally induced models. In addition, we discuss future perspectives highlighting pros and cons of utilizing mouse models and current demands for improved models.

Significantly reduced lymphadenopathy, salivary gland infiltrates and proteinuria in MRL-lpr/lpr mice treated with ultrasoluble curcumin/turmeric: increased survival with curcumin treatment

Objectives

Commercial curcumin (CU), derived from food spice turmeric (TU), has been widely studied as a potential therapeutic for a variety of oncological and inflammatory conditions. Lack of solubility/bioavailability has hindered curcumin's therapeutic efficacy in human diseases. We have solubilised curcumin in water applying heat/pressure, obtaining up to 35-fold increase in solubility (ultrasoluble curcumin (UsC)). We hypothesised that UsC or ultrasoluble turmeric (UsT) will ameliorate systemic lupus erythematosus (SLE) and Sjögren's syndrome (SS)-like disease in MRL-lpr/lpr mice.

Methods

Eighteen female MRL-lpr/lpr (6 weeks old) and 18 female MRL-MpJ mice (6 weeks old) were used. Female MRL-lpr/lpr mice develop lupus-like disease at the 10th week and die at an average age of 17 weeks. MRL-MpJ mice develop lupus-like disease around 47 weeks and typically die at 73 weeks. Six mice of each strain received autoclaved water only (lpr-water or MpJ-water group), UsC (lpr-CU or MpJ-CU group) or UsT (lpr-TU or MpJ-TU group) in the water bottle.

Results

UsC or UsT ameliorates SLE in the MRL-lpr/lpr mice by significantly reducing lymphoproliferation, proteinuria, lesions (tail) and autoantibodies. lpr-CU group had a 20% survival advantage over lpr-water group. However, lpr-TU group lived an average of 16 days shorter than lpr-water group due to complications unrelated to lupus-like illness. CU/TU treatment inhibited lymphadenopathy significantly compared with lpr-water group (p=0.03 and p=0.02, respectively) by induction of apoptosis. Average lymph node weights were 2606±1147, 742±331 and 385±68 mg, respectively, for lpr-water, lpr-CU and lpr-TU mice. Transferase dUTP nick end labelling assay showed that lymphocytes in lymph nodes of lpr-CU and lpr-TU mice underwent apoptosis. Significantly reduced cellular infiltration of the salivary glands in the lpr-TU group compared with the lpr-water group, and a trend towards reduced kidney damage was observed in the lpr-CU and lpr-TU groups.

Conclusions

These studies show that UsC/UsT could prove useful as a therapeutic intervention in SLE/SS.

SDS-PAGE to Immunoblot in One Hour

An ultra-rapid method for electrophoresing proteins on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transfer of proteins to nitrocellulose membranes, and immunoblotting is described here. Electrophoresis of the autoantigens La and Ro60, as well as molecular weight standards on a 4-20 % gradient gel, was performed in about 10 min using heated (70-75 °C) normal Laemmli running buffer. Electrophoretic transfer of these proteins was achieved in 7 min using a semidry transfer method. Finally, immunoblotting of La and Ro60 was carried out in 30 min. Thus, the entire process of electrophoresis, electrotransfer, and immunoblotting could be carried out in 1 h.

Role of autoimmune responses in periodontal disease

Periodontal diseases are characterized by localized infections and inflammatory conditions that directly affect teeth supporting structures which are the major cause of tooth loss. Several studies have demonstrated the involvement of autoimmune responses in periodontal disease. Evidences of involvement of immunopathology have been reported in periodontal disease. Bacteria in the dental plaque induce antibody formation. Autoreactive T cells, natural killer cells, ANCA, heat shock proteins, autoantibodies, and genetic factors are reported to have an important role in the autoimmune component of periodontal disease. The present review describes the involvement of autoimmune responses in periodontal diseases and also the mechanisms underlying these responses. This review is an attempt to throw light on the etiopathogenesis of periodontal disease highlighting the autoimmunity aspect of the etiopathogenesis involved in the initiation and progression of the disease. However, further clinical trials are required to strengthen the role of autoimmunity as a cause of periodontal disease.

The value of animal models to study immunopathology of primary human Sjögren's syndrome symptoms

Sjögren's syndrome (SjS) is a complex chronic autoimmune disease of multifactorial etiology that results in eventual loss of secretory function in the exocrine glands. The challenges towards finding a therapeutic prevention or treatment for SjS are due primarily to a lack of understanding in the pathophysiological and clinical progression of the disease. In order to circumnavigate this problem, there is a need for appropriate animal models that resemble the major phenotypes of human SjS and deliver a clear underlying biological or molecular mechanism capable of defining various aspects for the disease. Here, we present an overview of SjS mouse models that are providing insight into the autoimmune process of SjS and advance our focus on potential diagnostic and therapeutic targets.

Animal models in autoimmune diseases: lessons learned from mouse models for Sjögren's syndrome

The mouse model is the one of the most frequently used and well-established animal models, and is currently used in many research areas. To date, various mouse models have been utilized to elucidate underlying causes of multifactorial autoimmune conditions, including pathological immune components and specific signaling pathways. This review summarizes the more recent mouse models for Sjögren's syndrome, a systemic autoimmune disease characterized by lymphocytic infiltration in the exocrine glands, such as the salivary and lacrimal glands, and loss of secretory function, resulting in dry mouth and dry eyes in patients. Although every Sjögren's syndrome mouse model resembles the major symptoms or phenotypes of Sjögren's syndrome conditions in humans, the characteristics of each model are variable. Moreover, to date, there is no single mouse model that can completely replicate the human conditions. However, unique features of each mouse model provide insights into the roles of potential etiological and immunological factors in the development and progression of Sjögren's syndrome. Here, we will overview the Sjögren's syndrome mouse models. Lessons from these mouse models will aid us to understand underlying immune dysregulation in autoimmune diseases in general, and will guide us to direct future research towards appropriate diagnostic and therapeutic strategies.

Oral tolerance

The gut-associated lymphoid tissue is the largest immune organ in the body and is the primary route by which we are exposed to antigens. Tolerance induction is the default immune pathway in the gut, and the type of tolerance induced relates to the dose of antigen fed: anergy/deletion (high dose) or regulatory T-cell (Treg) induction (low dose). Conditioning of gut dendritic cells (DCs) by gut epithelial cells and the gut flora, which itself has a major influence on gut immunity, induces CD103(+) retinoic acid-dependent DC that induces Tregs. A number of Tregs are induced at mucosal surfaces. Th3 type Tregs are transforming growth factor-β dependent and express latency-associated peptide (LAP) on their surface and were discovered in the context of oral tolerance. Tr1 type Tregs (interleukin-10 dependent) are induced by nasal antigen and forkhead box protein 3(+) iTregs are induced by oral antigen and by oral administration of aryl hydrocarbon receptor ligands. Oral or nasal antigen ameliorates autoimmune and inflammatory diseases in animal models by inducing Tregs. Furthermore, anti-CD3 monoclonal antibody is active at mucosal surfaces and oral or nasal anti-CD3 monoclonal antibody induces LAP(+) Tregs that suppresses animal models (experimental autoimmune encephalitis, type 1 and type 2 diabetes, lupus, arthritis, atherosclerosis) and is being tested in humans. Although there is a large literature on treatment of animal models by mucosal tolerance and some positive results in humans, this approach has yet to be translated to the clinic. The successful translation will require defining responsive patient populations, validating biomarkers to measure immunologic effects, and using combination therapy and immune adjuvants to enhance Treg induction. A major avenue being investigated for the treatment of autoimmunity is the induction of Tregs and mucosal tolerance represents a non-toxic, physiologic approach to reach this goal.

The complexity of Sjögren's syndrome: novel aspects on pathogenesis

In Sjögren's syndrome, like in most other autoimmune diseases, the enigma leading to a pathogenic attack against self has not yet been solved. By definition, the disease must be mediated by specific immune reactions against endogenous tissues to qualify as an autoimmune disease. In Sjögren's syndrome the autoimmune response is directed against the exocrine glands, which, as histopathological hallmark of the disease, display persistent and progressive focal mononuclear cell infiltrates. Clinically, the disease in most patients is manifested by two severe symptoms: dryness of the mouth (xerostomia) and the eyes (keratoconjunctivitis sicca). A number of systemic features have also been described and the presence of autoantibodies against the ubiquitously expressed ribonucleoprotein particles Ro (Sjögren's-syndrome-related antigen A - SSA) and La (SSB) further underline the systemic nature of Sjögren's syndrome. The original explanatory concept for the pathogenesis of Sjögren's syndrome proposed a specific, self-perpetuating, immune mediated loss of acinar and ductal cells as the principal cause of salivary gland hypofunction. Although straightforward and plausible, the hypothesis, however, falls short of accommodating several Sjögren's syndrome-related phenomena and experimental findings. Consequently, researchers considered immune-mediated salivary gland dysfunction prior to glandular destruction and atrophy as potential molecular mechanisms underlying the symptoms of dryness in Sjögren's syndrome. Accordingly, apoptosis, fibrosis and atrophy of the salivary glands would represent consequences of salivary gland hypofunction. The emergence of advanced bio-analytical platforms further enabled the identification of potential biomarkers with the intent to improve Sjögren's syndrome diagnosis, promote the development of prognostic tools for Sjögren's syndrome and the long-term goal to identify possible processes for therapeutic treatment interventions. In addition, such approaches allowed us to glimpse at the apparent complexity of Sjögren's syndrome.

Sjögren's syndrome: studying the disease in mice

Sjögren's syndrome (SS), a systemic autoimmune disease, is characterized by inflammation of exocrine tissues accompanied by a significant loss of their secretory function. Clinical symptoms develop late and there are no diagnostic tests enabling early diagnosis of SS. Thus, particularly to study these covert stages, researchers turn to studying animal models where mice provide great freedom for genetic manipulation and testing the effect of experimental intervention. The present review summarizes current literature pertaining to both spontaneous and extrinsic-factor induced SS-like diseases in mouse models, discussing advantages and disadvantages related to the use of murine models in SS research.

Current concepts: mouse models of Sjögren's syndrome

Sjögren's syndrome (SjS) is a complex chronic autoimmune disease of unknown etiology which primarily targets the exocrine glands, resulting in eventual loss of secretory function. The disease can present as either primary SjS or secondary SjS, the latter of which occurs concomitantly with another autoimmune disease such as rheumatoid arthritis, systemic lupus erythematosus, scleroderma, or primary biliary cirrhosis. Current advancements in therapeutic prevention and treatment for SjS are impeded by lack of understanding in the pathophysiological and clinical progression of the disease. Development of appropriate mouse models for both primary and secondary SjS is needed in order to advance knowledge of this disease. This paper details important features, advantages, and pitfalls of current animal models of SjS, including spontaneous, transgenic, knockout, immunization, and transplantation chimera mouse models, and emphasizes the need for a better model in representing the human SjS phenotype.

Heat-solubilized curry spice curcumin inhibits antibody-antigen interaction in in vitro studies: a possible therapy to alleviate autoimmune disorders

Chronic and complex autoimmune diseases, currently treated palliatively with immunosuppressives, require multi-targeted therapy for greater effectiveness. The naturally occurring polyphenol curcumin has emerged as a powerful "nutraceutical" that interacts with multiple targets to regress diseases safely and inexpensively. Up to 8 g/day of curcumin for 18 months was non-toxic to humans. However, curcumin's utility is limited by its aqueous insolubility. We have demonstrated a heat-mediated 12-fold increase in curcumin's aqueous solubility. Here, we show by SDS-PAGE and surface plasmon resonance that heat-solubilized curcumin binds to proteins. Based on this binding we hypothesized that heat-solubilized curcumin or turmeric would prevent autoantibody targeting of cognate autoantigens. Heat-solubilized curcumin/turmeric significantly decreased binding of autoantibodies from Sjögren's syndrome (up to 43/70%, respectively) and systemic lupus erythematosus (up to 52/70%, respectively) patients as well as an animal model of Sjögren's syndrome (up to 50/60%, respectively) to their cognate antigens. However, inhibition was not specific to autoimmunity. Heat-solubilized curcumin/turmeric also inhibited binding of commercial polyclonal anti-spectrin to spectrin (50/56%, respectively). Thus, we suggest that the multifaceted heat-solubilized curcumin can ameliorate autoimmune disorders. In addition, the non-toxic curcumin could serve as a new protein stain in SDS-PAGE even though it is less sensitive than the Coomassie system which involves toxic chemicals.

Periodontal Disease and Sjögren Syndrome: A Possible Correlation?

Sjögren syndrome (SS) is a chronic autoimmune rheumatic disease characterized by a progressive lymphocytic infiltration of exocrine glands, especially salivary and lachrymal ones, leading to xerostomia, parotid gland enlargement, and xerophthalmia. The aim of this study is to describe the capillaroscopic pattern of the interdental papilla in patients with SS and to evaluate a possible correlation with periodontal disease. Methods: A total of 25 patients affected by SS and 25 healthy controls were examined. The patients with conditions that compromise microcirculation, such as diabetes, hypertension, hyperlipidemia, or some pharmacological treatments, were not included in the study. All the patients were nonsmokers. Periodontal capillaroscopy has been used to investigate the features of microcirculation. Visibility, course, tortuosity, as well as the possible presence of microhemorrhage, the average caliber of the capillary loops, and the number of visible capillary loops per square millimeter were evaluated for each patient. Results: The results show evident alterations to the capillaries and a typical conformation of the interdental papilla microcirculation in patients with SS; it was possible to observe a reduced caliber of capillaries, as well as a greater number and tortuosity of capillary loops. Conclusion: This study shows that capillary alterations to patients with SS occur in gingival microcirculation.

Mucosal administration of alpha-fodrin inhibits experimental Sjögren's syndrome autoimmunity

Introduction

α-Fodrin is an autoantigen in Sjögren's syndrome. We hypothesized that mucosal administration of α-fodrin might prevent the disease.

Methods

Four-week-old NOD mice were immunized (intranasal) with a 1 μg or 10 μg dose of α-fodrin every other day. PBS 10 μl/dose and Glutathione transferase (GST 10 μg/dose (control mice) were intranasally administrated by the same procedure. The salivary flow was maintained in immunized animals. The animals were analyzed for the presence of anti-Sjögren's syndrome A, anti-Sjögren's syndrome B, rheumatoid factor and antinuclear, anti-α-fodrin, and anti-type 3 muscarinic acetylcholine receptor polypeptide (anti-M3RP) by immunofluorescence or ELISA. The cytokines IFNγ and IL-10 were measured by ELISA. Salivary glands were examined by H&E staining and immunohistochemical analysis. The water-volume intake was calculated for each group. The induction of regulatory T cells was assessed by fluorescence-activated cell sorting analysis for the frequency of Foxp3⁺ cells among peripheral CD4⁺CD25⁺ T cells.

Results

The appearance of anti-α-fodrin and anti-M3RP antibodies was delayed in mice immunized with α-fodrin. The titers of anti-α-fodrin and anti-M3RP antibodies were lower in immunized mice (P < 0.05), but there was no significant difference between the low-dose or high-dose immunization groups. Five out of eight mice in the GST group, five of eight mice in the PBS group, two of eight mice in the α-fodrin 1 μg/dose group, and three out of eight mice in the α-fodrin 10 μg/dose were positive for antinuclear antibodies. The levels of serum IFNγ in mice immunized with 1 μg/dose or 10 μg/dose α-fodrin, with PBS, and with GST were 41.9 ± 16.2 pg/ml, 37.1 ± 15.4 pg/ml, 86.8 ± 17.8 pg/ml and 71.6 ± 11.1 pg/ml, respectively, while we found no difference in the levels of serum IL-10 among the groups. The number of Foxp3⁺ CD4⁺CD25⁺ regulatory T cells was higher in the α-fodrin groups compared with the PBS and GST control groups (P < 0.05). Lymphocytic infiltration and expression of α-fodrin in the salivary glands was decreased in α-fodrin-treated groups. The fluid intake of mice in the 1 μg/dose α-fodrin, 10 μg/dose α-fodrin, PBS, and GST groups was 39.2 ± 2.1 ml, 40.4 ± 2.5 ml, 49.3 ± 3.1 ml and 51.6 ± 2.8 ml, respectively.

Conclusion

Mucosal administration of α-fodrin effectively inhibited the progression of experimental Sjögren's syndrome autoimmunity.

Oral manifestations of Sjögren's syndrome

Sjögren's syndrome is a common autoimmune rheumatic disease. The most common symptoms of Sjögren's syndrome are extreme tiredness, along with dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia). Saliva plays an essential role in numerous functions of the mouth. Xerostomia can be caused by medications, chronic diseases like Sjögren's syndrome, and medical treatments, such as radiation therapy and bone marrow transplant. Xerostomia can eventually lead to difficulty in swallowing, severe and progressive tooth decay, or oral infections. Despite having excellent oral hygiene, individuals with Sjögren's syndrome have elevated levels of dental caries, along with the loss of many teeth, early in the disease. Sjögren's syndrome alters the protein profile and brings about a change in the composition of saliva. There is an increase in the levels of lactoferrin, beta(2)-microglobulin, sodium, lysozyme C, and cystatin C, and a decrease in salivary amylase and carbonic anhydrase. Up to 90% of individuals with Sjögren's syndrome have antibodies targeting the Ro 60 and La autoantigens. Natural aging, regardless of Sjögren's syndrome, is also another factor that brings about a significant change in the composition of saliva. The most prevailing cause of xerostomia in elderly persons is the use of anticholinergic medications. Currently, there is no cure for Sjögren's syndrome, and treatment is mainly palliative.

Animal models of Sjögren's syndrome

Sjögren's syndrome is an autoimmune, chronic inflammatory disease characterized by focal mononuclear cell infiltration of exocrine tissues, accompanied by loss of secretory function. The pathogenesis of autoimmune diseases is complex and, therefore, difficult to study in vitro. As of today, the role of initiating factors remains obscure, clinical symptoms develop late, and there are no tests for early diagnosis of SS. Hence, the disease is difficult to detect and treat. Animal models may provide insights into the identification of target antigens, narrowing the relevant pathological immune mechanisms, and to study the evolution of tissue pathology. This review summarizes current knowledge on murine strains, both spontaneous and induced models, used to study Sjögren's syndrome. Special attention is paid to the characteristics of different strains regarding their properties to mimic specific aspects or stages of the disease.

Primary Sjogren's syndrome: current and prospective therapies

OBJECTIVE

To summarize data on existing and experimental therapies for primary Sjogren's syndrome (pSS), referring both to sicca syndrome and to other systemic disease manifestations.

METHODS

Relevant English and non-English articles acquired through Medline were reviewed.

RESULTS

pSS usually has a benign clinical course, centered on sicca features and general musculoskeletal manifestations, and is managed symptomatically. However, a subset of patients develops more severe extraglandular disease that warrants close monitoring and aggressive treatment. For dry eyes and mouth, nonpharmacologic measures to preserve secretions, and tear and saliva substitutes, offer some symptomatic relief. Muscarinic agonists and topical cyclosporine yield well-documented improvement in ocular sicca features. Although traditional antirheumatic drugs are used empirically for polyarthritis and other Sjogren's symptoms, their efficacy in pSS overall and as disease-modifying agents is limited. For the potential severe, nonexocrine manifestations complicating pSS, standard high-dose immunosuppression is used. Among the biologic agents already examined in pSS, those targeting tumor necrosis factor (TNF)-alpha failed to demonstrate significant benefit. Nonetheless, rituximab and other B-cell-depleting therapies appear promising.

CONCLUSIONS

Treatment of pSS patients with severe extraglandular disease should differ from that of patients with predominantly sicca features and/or general muscoloskeletal manifestations. pSS treatment is mainly symptomatic, primarily directed against sicca complaints. The traditional anti-rheumatic agents show limited efficacy in the systemic process and use of systemic TNF-alpha inhibitors has been very disappointing. B cell depleting treatments and other newer biologic therapies appear more promising.

The management of Sjögren's syndrome

Sjögren's syndrome is a chronic autoimmune disorder, characterized by lymphocytic infiltration and malfunction of the exocrine glands, resulting in dry mouth and eyes. The syndrome can present either alone (primary Sjögren's syndrome) or in the context of an underlying connective tissue disease (secondary Sjögren's syndrome). Systemic features, resulting from cutaneous, respiratory, renal, hepatic, neurologic, and vascular involvement, often occur. Two types of primary Sjögren's syndrome are currently recognized: a benign disease that affects quality of life, and a systemic syndrome associated with increased morbidity and mortality owing to a high risk of malignant transformation, and that requires close follow-up. Ocular involvement, manifested as keratoconjunctivitis sicca, is managed with local and systemic stimulators of tear secretion and supportive surgical procedures. Treatment of oral manifestations includes intense oral hygiene, prevention and treatment of oral infections, use of saliva substitutes, and local and systematic stimulation of salivary secretion. Cholinergic agents, such as pilocarpine and cevimeline, are helpful in patients with residual salivary function, and ciclosporin ocular drops seem to be of some benefit. Systemic immunosuppressives are reserved for treatment of severe extraglandular manifestations of Sjögren's syndrome. Anti-B-cell therapy is a new potential therapy for the glandular and extraglandular manifestations, such as glomerulonephritis or vasculitis, in addition to the management of lymphoma associated with Sjögren's syndrome. Induction of oral tolerance and gene-transfer modalities were recently attempted in animal models, with promising results.

Gene therapeutics in Sjögren's syndrome

Sjögren's syndrome (SS) is a complex autoimmune disorder, characterised by mononuclear cell infiltration of exocrine glands, principally the lacrimal and salivary glands. Both cellular, in the form of autoreactive immune cells, and humoral factors, such as autoantibodies, contribute to the expression of the disease. SS can also occur as a systemic disease affecting several organs, and approximately 5% of the patients develop malignant lymphoproliferation. Today SS is considered uncurable. The treatment available is only palliative, and the treatment goals are to manage symptoms and prevent or limit tissue damage. This may involve both local and systemic measures. However, the existing systemic treatment of chronic inflammatory autoimmune diseases has several limitations and unwanted side effects. In recent years the possibility to treat diseases with gene therapy has gained interest and has become a subject of investigation. Given the multitude of factors contributing to the pathogenesis of SS, gene therapy is a major challenge, but may elicit great benefits if successful. Keeping this in mind, the possibility for gene therapeutics in SS in general and potential targets for gene therapy are discussed.

Oral tolerance

Multiple mechanisms of tolerance are induced by oral antigen. Low doses favor active suppression, whereas higher doses favor clonal anergy/deletion. Oral antigen induces T-helper 2 [interleukin (IL)-4/IL-10] and Th3 [transforming growth factor (TGF)-beta] T cells plus CD4+CD25+ regulatory cells and latency-associated peptide+ T cells. Induction of oral tolerance is enhanced by IL-4, IL-10, anti-IL-12, TGF-beta, cholera toxin B subunit, Flt-3 ligand, and anti-CD40 ligand. Oral (and nasal) antigen administration suppresses animal models of autoimmune diseases including experimental autoimmune encephalitis, uveitis, thyroiditis, myasthenia, arthritis, and diabetes in the non-obese diabetic (NOD) mouse, plus non-autoimmune diseases such as asthma, atherosclerosis, graft rejection, allergy, colitis, stroke, and models of Alzheimer's disease. Oral tolerance has been tested in human autoimmune diseases including multiple sclerosis (MS), arthritis, uveitis, and diabetes and in allergy, contact sensitivity to dinitrochlorobenzene (DNCB), and nickel allergy. Although positive results have been observed in phase II trials, no effect was observed in phase III trials of CII in rheumatoid arthritis or oral myelin and glatiramer acetate (GA) in MS. Large placebo effects were observed, and new trials of oral GA are underway. Oral insulin has recently been shown to delay onset of diabetes in at-risk populations, and confirmatory trials of oral insulin are being planned. Mucosal tolerance is an attractive approach for treatment of autoimmune and inflammatory diseases because of lack of toxicity, ease of administration over time, and antigen-specific mechanisms of action. The successful application of oral tolerance for the treatment of human diseases will depend on dose, developing immune markers to assess immunologic effects, route (nasal versus oral), formulation, mucosal adjuvants, combination therapy, and early therapy.