Salivary desmoglein enzyme-linked immunosorbent assay for diagnosis of pemphigus vulgaris: a noninvasive alternative test to serum assessment

Current status and prospects for the diagnosis of pemphigus vulgaris

Introduction: Pemphigus vulgaris (PV) is an intraepidermal autoimmune bullous disease (AIBD) characterized by autoantibodies against desmosomal adhesion proteins, most commonly desmoglein (Dsg)3, leading to the suprabasal cleft formation and acantholysis.Areas covered: Direct immunofluorescence (DIF) and indirect immunofluorescence (IIF) studies display the intercellular deposition of IgG/C3 throughout the epidermis and presence of circulating autoantibodies respectively, as a net-like pattern. However, the target antigen remains unknown using immunofluorescence techniques. Thanks to the development of Dsg ELISA, using recombinant technology, circulating antibodies against Dsg1 and 3 could be detected sensitively. It is possible to differentiate PV from pemphigus foliaceus (PF) using this assay. BIOCHIP mosaic and multivariant ELISA are two novel serologic methods with the added value of the ability to screen several AIBDs simultaneously.Non-Dsg1/3 antigens are also involved in the pathogenesis of PV and investigated more deeply thanks to the protein microarrays technique. Additionally, patients with high values of anti-Dsg1/3 may be lesion-free, suggesting the presence of nonpathogenic autoantibodies.Expert opinion: Newer diagnostic methods to replace traditional techniques should possess high sensitivity and specificity and be widely available, noninvasive, and relatively cheap. The newly developed methods need to be further evaluated before being recommended for routine use.

Saliva Proteomics as Fluid Signature of Inflammatory and Immune-Mediated Skin Diseases

Saliva is easy to access, non-invasive and a useful source of information useful for the diagnosis of serval inflammatory and immune-mediated diseases. Following the advent of genomic technologies and -omic research, studies based on saliva testing have rapidly increased and human salivary proteome has been partially characterized. As a proteomic protocol to analyze the whole saliva proteome is not currently available, the most common aim of the proteomic analysis is to discriminate between physiological and pathological conditions. The salivary proteome has been initially investigated in several diseases: oral squamous cell carcinoma and oral leukoplakia, chronic graft-versus-host disease, and Sjögren's syndrome. Otherwise, salivary proteomics studies in the dermatological field are still in the initial phase, thus the aim of this review is to collect the best research evidence on the role of saliva proteomics analysis in immune-mediated skin diseases to understand the direction of research in this field. The results of PRISMA analysis reported herein suggest that human saliva analysis could provide significant data for the diagnosis and prognosis of several immune-mediated and inflammatory skin diseases in the next future.

Immunological methods for the diagnosis of oral mucosal diseases

Immunological methods, which have been widely used in autoimmune blistering diseases (AIBDs) of the oral mucosa, can also be adopted as auxiliary diagnostic tools in oral lichen planus (OLP) and discoid lupus erythematosus (DLE). AIBDs, characterized by autoantibodies against structural proteins of keratinocytes or the basement membrane zone, clinically present as blisters and erosions of the oral mucosa. When atypical lesions occur, OLP or DLE may be confused with AIBDs. The improvement of diagnostic accuracy is necessary due to the significant differences in treatment and prognosis among these diseases. A variety of immunological methods are used for qualitative and quantitative detection of target antigens and autoantibodies. These methods can evaluate efficacy of treatment, monitor diseases and guide treatment decisions. In this review, we discuss the application of immunofluorescence, biochemical tests, and protein microarrays for AIBDs, OLP and DLE, as well as the differential diagnostic methods using immunological tests.

New biochip immunofluorescence test for the serological diagnosis of pemphigus vulgaris and foliaceus: A review of the literature

The immunoassays that are available for the serological diagnosis of the more common subtypes of autoimmune blistering diseases such as pemphigus vulgaris (PV) and pemphigus foliaceus (PF) include enzyme-linked immunosorbent assay (ELISA) testing to specific antigens desmoglein (Dsg)1 and Dsg3, direct immunofluorescence (DIF), indirect immunofluorescence (IIF), and immunoblotting. A review of the literature on the biochip assay was conducted. Six studies investigated the validity of a new biochip, mosaic-based, IIF test in patients with pemphigus and demonstrated its relatively high sensitivity and specificity (Dsg3: 97.62-100%, 99.6-100%; Dsg1: 90%, 100%) in comparison with ELISA (Dsg3: 81-100%, 94-100%; Dsg1: 69-100%, 61.1-100%), and/or IIF (PV: 75-100%, 91.8-100%; PF: 67-100%) using suitable substrates. So far, validation studies of the biochip have been conducted in four countries (Germany, Italy, Turkey, and Poland) but none in the southern hemisphere. Caucasian patients were recruited as normal controls for these studies; thus, the diagnostic value of the biochip remains uncertain in population groups of other ethnicities. A range of disease control patients were recruited including patients with linear immunoglobulin A dermatosis, psoriasis, discoid lupus erythematosus, lichen planus, and noninflammatory skin diseases (e.g., squamous cell carcinoma, basal cell carcinoma, and vascular leg ulcers). Prospective studies with control patients from a diverse range of ethnicities are needed to better validate the biochip.

Oral mucosa biology and salivary biomarkers

Although the surfaces of both the skin and oral mucosa are protected by squamous epithelial cells and fall within the scope of dermatologic practice, the oral cavity contains highly specialized structures and functions distinct from other skin biology and pathologic conditions and are also the purview of clinicians who care for patients with skin and mucosal diseases. We describe the distinct features of the tongue, mucosa, and salivary glands. In particular, we examine the composition and function of the saliva, with special focus on salivary biomarkers. Within the oral cavity, saliva shows great promise as a noninvasive and sensitive marker for many systemic diseases. Biomarkers are being used as diagnostic or monitoring tools for a wide variety of diseases, including systemic lupus erythematosus, Sjögren disease, Behçet disease, and autoimmune blistering disorders, as well as premalignant and malignant lesions of the mouth.

Correlation between salivary and serum anti-desmoglein 1 and 3 antibody titres using ELISA and between anti-desmoglein levels and disease severity in pemphigus vulgaris

ELISA for anti-desmoglein antibodies (Dsg) is commonly used for diagnosis and assessment of treatment response in pemphigus vulgaris (PV). The present study was conducted to assess the relationship between salivary and serum Dsg1 and Dsg3 levels, and whether salivary Dsg1 and Dsg3 levels correlate with clinical disease severity of oral mucosal lesions in PV. In total 43, patients with PV with predominantly mucosal involvement were recruited. Both serum and salivary samples were collected from the cases, and salivary samples were also collected from five controls. There was a statistically significant correlation between serum and salivary Dsg1 levels and between serum and salivary Dsg3 levels. There was no correlation between serum or salivary Dsg1 and Dsg3 levels with the objective component of the oral mucosal Autoimmune Bullous Skin Disorder Intensity Score (ABSIS). Serum Dsg1 levels significantly correlated with cutaneous ABSIS, but there was no correlation between cutaneous ABSIS and either salivary Dsg1, salivary Dsg3 or serum Dsg3. As salivary Dsg titres correlate with serum levels, saliva can serve as a simple and noninvasive alternative to serum for Dsg ELISA.

Salivary Samples for the Diagnosis of Pemphigus vulgaris Using the BIOCHIP Approach: a Pilot Study

Pemphigus vulgaris (PV) is a rare autoimmune intraepithelial blistering skin disease characterized by the presence of circulating autoantibodies against desmoglein 3 (DSG3) and desmoglein 1 (DSG1), resulting in loss of the normal epithelial cell-to-cell adhesion, through a process called acantholysis. In recent years, a BIOCHIP-based indirect immunofluorescence technique for the determination of anti-DSG3 and anti-DSG1 autoantibodies has been described. Even though, the use of saliva anti-DSG3 and anti-DSG1 ELISA for the diagnosis of PV has been already reported, there are no studies concerning the utilization of saliva by the BIOCHIP approach. In the present pilot study, ELISA and BIOCHIP were performed, using salivary and serum samples from the same patients to investigate if the detection of anti-desmoglein autoantibodies in salivary samples by BIOCHIP could be used as a test for the diagnosis of PV. There was a strong correlation between ELISA and BIOCHIP results both for anti-DSG3 and anti-DSG1 serum autoantibodies. Autoantibodies to DSG3 were detected in 8 out of 8 salivary samples by ELISA and in 6 out of 8 salivary samples by the BIOCHIP approach. Autoantibodies to DSG1 were negative in all salivary samples using both ELISA and BIOCHIP. There were no positive results in the negative control group. In conclusion, the results of this pilot study indicate lack of correlation between serum and salivary results using both ELISA and BIOCHIP, indicating that saliva may not be the ideal substrate for the laboratory diagnosis of PV using these approaches.

Serum and salivary IgG and IgA antibodies to desmoglein 3 in mucosal pemphigus vulgaris

BACKGROUND

The use of saliva for the diagnosis of pemphigus vulgaris (PV) by enzyme-linked immunosorbent assay (ELISA) using desmoglein (Dsg)3 antigen has not been extensively documented, nor has the detection of serum IgA antibodies to Dsg3.

OBJECTIVES

(i) To establish whether whole saliva might provide a suitable alternative to serum for diagnosing and monitoring PV; (ii) to investigate whether anti-Dsg3 IgA antibodies can be detected in serum and saliva and (iii) to establish whether there is an association between serum or saliva anti-Dsg3 antibodies and disease severity.

METHODS

Precoated Dsg3 ELISA plates were used to test serum and/or saliva for IgG and IgA antibodies. Matched serum and whole saliva samples were collected from 23 patients with PV, 17 healthy subjects and 19 disease controls. All patients with PV, disease controls and six healthy controls provided matched parotid saliva.

RESULTS

Whole saliva IgG antibodies to Dsg3 were detected in 14 of 23 patients (61%) and serum IgG antibodies were detected in 17 of 23 (74%) with a strong positive correlation. Serum IgA antibodies were detected in 14 of 23 patients with PV (61%) with a combined positivity (IgG and/or IgA antibodies to Dsg3) of 78% (18 of 23). We were unable to show IgA anti-Dsg3 antibodies in either whole or parotid saliva of patients with PV. Sequential samples showed that changes in IgG antibody titres in whole saliva were associated with a change in disease severity scores.

CONCLUSIONS

Assay of salivary IgG antibodies to Dsg3 offers a diagnostic alternative to serum in the diagnosis and monitoring of PV. The role of anti-Dsg3 IgA antibodies requires further elucidation in the pathogenesis of PV.

Salivary IgA and IgG antibodies to bullous pemphigoid 180 noncollagenous domain 16a as diagnostic biomarkers in mucous membrane pemphigoid

BACKGROUND

Mucous membrane pemphigoid (MMP) is an uncommon mucocutaneous immunobullous disorder. Use of saliva for diagnosis by enzyme-linked immunosorbent assay (ELISA) using the noncollagenous (NC) domain 16a of bullous pemphigoid antigen II (BP180) is not well described.

OBJECTIVE

To establish whether whole or parotid saliva is a suitable alternative to serum for diagnosis of MMP.

METHODS

Precoated BP180-NC16a ELISA plates were used to test serum, and whole and parotid saliva for IgG, IgA and secretory IgA antibodies. Patients with MMP (n = 64) provided matched serum and whole saliva. In addition 18 of the MMP patients also provided matched parotid saliva. Healthy controls (n = 50) provided matched serum and whole saliva and 6 of these additionally provided matched parotid saliva. An additional 16 disease controls provided matched serum, and whole and parotid saliva.

RESULTS

In whole saliva, IgG antibodies were detected in 11/64 (17%), IgA in 23/64 (36%) and a combined positivity in 29/64 (45%). In parotid saliva, IgA antibodies were found in 8/18 (44%). Serum IgG antibodies were detected in 27/64 (42%), serum IgA antibodies in 18/64 (28%) and a combined positivity in 33/64 (52%). Combined use of serum and saliva increased detection of specific antibodies by 30%. Control samples were all negative (positive predictive value of 100% for all tests). The negative predictive values were 62% for IgA saliva, 65% for IgG serum, 59% for IgA serum and 56% for IgG saliva.

CONCLUSIONS

IgG and IgA antibodies may provide a suitable diagnostic marker in MMP. Assay of salivary IgA antibodies to NC16a offers a similar diagnostic predictive value to serum.