Immunoreactive circulating alpha-interferon is low in Sjögren's syndrome

Association between type I interferon pathway activation and clinical outcomes in rheumatic and musculoskeletal diseases: a systematic literature review informing EULAR points to consider

BACKGROUND

Type I interferons (IFN-I) contribute to a broad range of rheumatic and musculoskeletal diseases (RMDs). Compelling evidence suggests that the measurement of IFN-I pathway activation may have clinical value. Although several IFN-I pathway assays have been proposed, the exact clinical applications are unclear. We summarise the evidence on the potential clinical utility of assays measuring IFN-I pathway activation.

METHODS

A systematic literature review was conducted across three databases to evaluate the use of IFN-I assays in diagnosis and monitor disease activity, prognosis, response to treatment and responsiveness to change in several RMDs.

RESULTS

Of 366 screened, 276 studies were selected that reported the use of assays reflecting IFN-I pathway activation for disease diagnosis (n=188), assessment of disease activity (n=122), prognosis (n=20), response to treatment (n=23) and assay responsiveness (n=59). Immunoassays, quantitative PCR (qPCR) and microarrays were reported most frequently, while systemic lupus erythematosus (SLE), rheumatoid arthritis, myositis, systemic sclerosis and primary Sjögren's syndrome were the most studied RMDs. The literature demonstrated significant heterogeneity in techniques, analytical conditions, risk of bias and application in diseases. Inadequate study designs and technical heterogeneity were the main limitations. IFN-I pathway activation was associated with disease activity and flare occurrence in SLE, but their incremental value was uncertain. IFN-I pathway activation may predict response to IFN-I targeting therapies and may predict response to different treatments.

CONCLUSIONS

Evidence indicates potential clinical value of assays measuring IFN-I pathway activation in several RMDs, but assay harmonisation and clinical validation are urged. This review informs the EULAR points to consider for the measurement and reporting of IFN-I pathway assays.

Advances in Pathogenesis of Sjögren's Syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease of unknown etiology that mainly involves exocrine glands. Patients present with dry mouth and eyes, fever, arthralgia, and other systemic symptoms. In severe cases, the quality of life of patients is affected. At present, there is no cure for SS, and the treatment options are extremely limited. In recent years, studies of patients and animal models have identified abnormalities of immune cell function and cytokines to be involved in SS. A systematic review of the literature may clarify the etiology and pathogenesis of SS, as well as provide a theoretical basis for the development of new drugs for the treatment of SS.

Dysfunction of lacrimal and salivary glands in Sjögren's syndrome: nonimmunologic injury in preinflammatory phase and mouse model

Sjögren's syndrome (SjS) is a chronic autoimmune disorder characterized by dry eyes and dry mouth due to dacryoadenitis and sialoadenitis with SS-A/Ro and/or SS-B/La autoantibodies in genetically predisposed individuals. Destruction of lacrimal and salivary glands by autoimmune reactions may lead to clinical manifestation. However, the mechanisms behind the decreased volume of secretions in tears and saliva are complex and are not fully understood. Exocrine gland dysfunction may precede autoimmunity (acquired immunity) or represent a process independent from inflammation in the pathogenesis of SjS. The preceded functional and morphologic changes of those tissues by nonimmunologic injury before the development of inflammation at the sites of target organs have been implicated. This paper focuses on the several factors and components relating to glandular dysfunction and morphologic changes by nonimmunologic injury during the preinflammatory phase in mouse model, including the factors which link between innate immunity and adaptive immunity.

Cytokines in Sjogren's syndrome: potential therapeutic targets

The dysregulated cytokine network in Sjögren's Syndrome (SS) is reflected by local and systemic overexpression of pro-inflammatory cytokines and absent or low levels of anti-inflammatory cytokines. To date, the use of cytokine based therapies in SS has been disappointing. Oral administration of low dose interferon (IFN) alpha showed inconsistent efficacy in various studies and failed to achieve the primary endpoint in a pivotal randomised controlled trial. Similarly, neither of the two tumour necrosis factor (TNF)-alpha blockers tested (etanercept and infliximab) showed efficacy in placebo controlled trials. Although the rationale for low dose oral IFN treatment has not been firmly established, TNF blockade was based on solid preclinical data. Therefore, the reason for the lack of efficacy is unclear, but recent data suggest that unexpected biological effects of TNF antagonists may have contributed to this. Cytokines, given their central role in the pathogenesis of SS, remain attractive targets for future treatments, despite the disappointing early results. Inflammatory cytokines are obvious candidates, and agents against several of them are available or under development for other autoimmune diseases similar to SS. New candidate cytokines such as IL-17 and IL-12 and/or IL-23 may provide promising targets for SS. Additionally, as an alternative to systemic treatment, which has the risk of potentially severe side effects, the use of local cytokine directed therapy should be explored.

Opening the flood gates: interferon-alpha treatment for Sjögren's syndrome

Interferon (IFN)-alpha is the main IFN produced in response to viral infection. Low levels of IFNalpha can be detected in nasal secretions after exposure to viruses in vivo. Radioimmunoassay has shown that endogenous IFNalpha is low in children, reaches a peak in young adults, and gradually declines with aging. Importantly, this endogenous IFNalpha is significantly decreased in patients with Sjögren's syndrome (SS). IFNalpha has been tested as a therapeutic agent in patients with SS. Intramuscular human leucocyte IFNalpha increases saliva production significantly in patients with SS. Improvements have been noted in lacrimal function and in dryness symptoms. Since IFNalpha infrequently induces autoimmune phenomena and high dose IFNalpha treatment sometimes has a serious adverse event profile, treatment focus has shifted to use of low dose orally-administered IFNalpha. In a single-masked controlled trial, 60 patients with SS randomly received natural human IFNalpha 150IU 3 times a day in an oral lozenge formulation or sucralfate as control for 6 months. At study end, 15 (50%) of the 30 IFNalpha-treated patients had saliva production increases at least 100% above baseline. IFNalpha treatment was well tolerated and no patients withdrew. Labial minor salivary gland biopsies indicated significant decreases in lymphocytic infiltration accompanied by a significant increase in intact salivary gland tissue after 6 months of treatment. In another 12-week double-masked, randomised, placebo-controlled trial, stimulated saliva production in patients with SS receiving IFNalpha lozenges 150IU 3 times daily was significantly increased. This dosage was also suggestive of benefit for 5 of 7 subjective measures of oral and ocular comfort. The tolerability profile of these low dose oral IFNalpha lozenges is excellent; no serious adverse events have been recorded. Adverse effects were generally mild and there were no clinically significant changes in laboratory or clinical safety measures. Low oral doses of natural human IFNalpha thus appear to improve secretory function and relieve dryness in patients with SS without causing significant adverse events. Endogenous or orally administered IFNalpha may activate oropharyngeal lymphoid and epithelial cells and induce production of potent soluble factors which could mediate immunological reactivity. It has been suggested that IFNalpha/beta potentiates clonal expansion and survival of CD8 T cells. Stimulating effects have also been demonstrated on natural killer cell activity, which has been shown to be depressed in patients with SS. It is likely that some combination of these immunological effects results in anti-inflammatory activity and ameliorates signs and symptoms of SS.

Cytokines in Sjögren's syndrome

Cytokines play a central role in the regulation of immunity and are often found to be deregulated in autoimmune diseases. Sjögren's syndrome is a chronic autoimmune disease characterized by inflammation and loss of secretory function of the salivary and lachrymal glands. This review highlights the current knowledge of the expression and the function of pro- and anti-inflammatory cytokines both locally and systemically in Sjögren's syndrome patients. In the salivary glands, saliva and serum of these patients, many pro-inflammatory cytokines are upregulated. Concomitantly, most anti-inflammatory cytokines are not detectable or are expressed at low levels. Besides a role in inflammation, cytokines are also thought to be involved in salivary gland dysfunction by directly interfering with the epithelial cells in the glands. Future research on the role of novel cytokines in Sjögren's syndrome in combination with a better understanding of the effect of cytokines on exocrine dysfunction will aide the identification of the best therapeutic targets for Sjögren's syndrome.

Cytokine Expression in Labial Salivary Glands from Patients with Primary Sjöugren's Syndrome

The presence and distribution of 7 cytokines was examined immunohistologically in labial salivary gland (LSG) specimens from patients with primary Sjögren's syndrome (SS) and control subjects. The cytokines interleukin (IL)-1 beta IL-6, tumor necrosis factor (TNF) alpha and interferon (IFN) gamma were identified in defined parts of LSG from patients but not in the corresponding parts of control glands: (a) LSG acinar epithelium expressed IL-1 beta, (b) blood vessels located in both normal LSG stroma and within lymphocytic infiltrates expressed IL-1 beta, IL-6 and IFN gamma, and (c) lymphocytic infiltrates expressed IL-1 beta, IL-6 and TNF alpha. All four cytokines were expressed by salivary ducts within both patient and control specimens, but with generally greater intensity in patients. IL-1 alpha, IL-4 and TNF beta (lymphotoxin) could not be detected in any of the specimens from patients or controls. The locations of cytokines in LSG suggests possible mechanisms of immunologically mediated parenchymal damage in primary SS.

A pilot study to test the efficacy of oral administration of interferon-alpha lozenges to patients with Sjögren's syndrome

BACKGROUND

Complications from Sjögren's syndrome-induced xerostomia may cause a significant disruption in daily routines such as speech and eating habits. In addition, the reduction in salivary output may lead to increased incidence of caries, oral ulcers, sialadenitis, periodontal problems, and Candida infections. Interferon-alpha has been suggested as an effective drug therapy to increase salivary output.

OBJECTIVE

The objective was to test the efficacy of interferon-alpha lozenges in relieving the symptoms of dry mouth and dry eyes when administered orally to patients with Sjögren's syndrome in double-blind placebo-controlled and open-label trials.

STUDY DESIGN

Twelve patients with a diagnosis of primary Sjögren's syndrome were provided an Institutional Review Board-approved, written informed-consent form. During the double-blind placebo-controlled study they were randomized to receive 150 IU of interferon-alpha (8 patients) or placebo (4 patients) for 24 weeks with 6-week reevaluations. Five patients who received interferon-alpha in the double-blind placebo-controlled trial were treated in an open-label study for another 24 weeks. Whole saliva was measured during each visit, and symptoms were assessed by questionnaires and visual analog scales. The Wilcoxon signed rank test was used to detect significant changes for each variable.

RESULTS

The results indicated that, by the end of 24 weeks, patients who received interferon-alpha had a statistically significant improvement in unstimulated salivary flow rate (P < .05), and statistically significant changes were observed in the median ocular dryness visual analog scale (P < .05) and oral dryness visual analog scale (P < .05). No significant changes were observed among the placebo patients. By the end of 48 weeks, medicated patients had better results than they had at the end of the double-blind placebo-controlled study and showed improvements in whole stimulated salivary flow rate, conditions of throat, and swallowing dry food.

CONCLUSION

Oral administration of 150 IU interferon-alpha 3 times a day for the patients with primary Sjögren's syndrome improved saliva production, relieved symptoms of xerostomia and xerophthalmia, and was well tolerated by the patients.

Biochemical deficiency of pyridoxine does not affect interleukin-2 production of lymphocytes from patients with Sjögren's syndrome

BACKGROUND

There is evidence that pyridoxine deficiency may alter the immune response. It is not known whether a deficiency of this vitamin is evident in subjects with primary Sjögren's syndrome (SS).

OBJECTIVE

We studied whether subjects with primary SS showed a biochemical deficiency of pyridoxine, and if it is associated with abnormal production of interleukin-2 from lymphocytes stimulated in vitro with phytohemagglutinin (PHA).

DESIGN

Two studies were conducted, (i) biochemical and nutritional assessments were performed in a cross-over study in subjects with primary SS, who were supplemented with 25 mg/day of pyridoxine or placebo for 3 months. After 1 month washout, they were supplemented for 3 months with placebo, (ii) patients with SS and matched controls received pyridoxine or placebo for 45 days, and a blood sample was obtained to study IL-2 production and expression in T-lymphocytes stimulated with PHA.

RESULTS

Subjects with primary SS showed limited dietary intake of pyridoxine and biochemical deficiency of this vitamin assessed through the activation coefficient of the erythrocyte aspartate aminotransferase. The biochemical deficiency did not affect production nor mRNA expression of IL-2 from T-lymphocytes stimulated in vitro with PHA compared with the control group. Supplementation of subjects with primary SS with 25 mg/day with pyridoxine for 45 days did not produce any significant change as compared to those patients supplemented with placebo.

CONCLUSIONS

Subjects with primary SS showed biochemical deficiency of pyridoxine, possibly due to limited intake of this vitamin which was corrected by supplementation with pyridoxine. However, IL-2 production and mRNA expression from stimulated lymphocytes were unaffected by supplementation, probably because the deficiency was not severe enough to affect the immune system.

SPONSORSHIP

This work was supported by the National Council of Science and Technology (CONACYT), Mexico, grant no. 212226-5-0902PM.

Oral administration of interferon-alpha induces a transient decline in oral mucosal immunoglobulins and an increase in interleukin-5

Although administration of interferon-alpha (IFN-alpha) via the oral-mucosal route has shown efficacy in a variety of human and animal diseases, the mechanism of action of orally administered IFN is not clearly understood. To assess the possibility that IFN-alpha given via a lozenge alters the local mucosal immune system, immunoglobulins (Ig) and cytokines were measured in salivary secretions. Volunteers were given low doses of IFN-alpha and saliva was collected over a 24-h period. IgA and precursor IgM were measured by sandwich enzyme-linked immunosorbent assay (ELISA). Salivary concentrations of interleukin-5 (IL-5), the T helper cytokine primarily responsible for the switch from IgM to IgA, were also determined. After oral administration of IFN-alpha, there was an initial decline in IgM and IgA followed by a return to baseline levels by 8-24 h. This change in Ig concentration was associated with a gradual increase in IL-5, consistent with the return of Ig to baseline as a result of modulation by Ig-mediating cytokines.

Single-blinded controlled trial of low-dose oral IFN-alpha for the treatment of xerostomia in patients with Sjögren's syndrome

A single-blinded controlled trial was conducted to test the efficacy of low-dose oral human interferon-alpha (IFN-alpha) to improve salivary function in patients with Sjögren's syndrome. Fifty-six outpatients with primary and 4 patients with secondary Sjögren's syndrome were assigned randomly into treatment groups of either IFN-alpha or sucralfate (control). The IFN-alpha (150 IU) or sucralfate (250 mg) was given orally three times a day for 6 months. Saliva was quantitated monthly by the Saxon test. After 6 months of treatment, 15 of 30 (50%) IFN-alpha-treated patients had saliva production increases at least 100% above baseline, whereas only 1 of 30 (3.3%) sucralfate patients had a comparable increase (p < 0.001). The increase in saliva production, by treatment group, was significantly greater (p < 0.01) in the IFN-alpha treated group at every month after treatment. Serial labial salivary gland biopsies of 9 IFN-alpha responder patients showed that lymphocytic infiltration was significantly decreased (p < 0.02) and the proportion of intact salivary gland tissue was significantly increased (p = 0.004) after the IFN-alpha treatment. In this study, IFN-alpha therapy significantly improved Sjögren's syndrome salivary gland dysfunction.

Primary Sjögren's syndrome--clinical and laboratory markers of disease activity

Primary Sjögren's syndrome is a chronic autoimmune disorder of the lacrimal and salivary glands, reflecting general involvement of the exocrine tissues and leading to functional impairment. This polyglandular disease is often associated with systemic extraglandular manifestations, and laboratory tests usually indicate polyclonal B-lymphocyte hyperactivity. Clinical and laboratory markers monitoring the disease processes are needed for improved management of primary Sjögren's syndrome. However, incomplete knowledge of the long-term course of inflammation as well as of clinical manifestations makes precise and simple directions for monitoring disease activity in primary Sjögren's syndrome difficult. This review describes potential primary (eg, salivary gland histopathology, autoantibodies, soluble interleukin-2 receptors, and beta 2-microglobulin) and secondary disease activity markers (clinical and laboratory signs of glandular and extraglandular organ damage) and their known associations. The importance of genetic characteristics, patient age, and symptom duration for the disease activity markers is indicated. The systematic use of primary and secondary disease activity markers will improve our understanding of primary Sjögren's syndrome and help create better guidelines for monitoring the disease.

Production of human alpha- and gamma-interferon is dependent on age and sex and is decreased in rheumatoid arthritis: a simple method for a large-scale assay

We examined host ability to produce alpha- and gamma-interferon on a large scale by culturing 2 ml of peripheral blood for 20 hr with Sendai virus or concanavalin A as inducer of alpha- or gamma-interferon, respectively. Production of gamma- but not alpha-interferon was lower in females (n = 351) than in males (n = 531) (P less than 0.001). Both alpha- and gamma-interferon production declined gradually with ageing. The production of alpha-interferon (3,233 +/- 1,773 IU/ml) and gamma-interferon (19 +/- 20 IU/ml) in rheumatoid arthritis patients was significantly lower than the values found in total and age-matched healthy donors (P less than 0.01). These results suggest that interferon production is dependent on age and sex and is significantly lower in patients with rheumatoid arthritis.