C-Terminal Processing of Collagen XVII Induces Neoepitopes for Linear IgA Dermatosis Autoantibodies

Transmembrane collagen XVII (COL17) is a hemidesmosomal component of basal keratinocytes that can be targeted by autoantibodies in autoimmune blistering disorders, including linear IgA dermatosis (LAD). COL17 can be physiologically cleaved within the juxtamembranous extracellular NC16A domain, and LAD autoantibodies preferentially react with the processed ectodomains, indicating that the processing induces neoepitopes. However, the details of how neoepitopes develop have not been elucidated. In this study, we show that C-terminal processing of COL17 also plays a role in inducing neoepitopes for LAD autoantibodies. First, the mAb hC17-ect15 targeting the 15th collagenous domain of COL17 was produced, which showed characteristics similar to LAD autoantibodies. The mAbs preferentially reacted with C-terminally deleted (up to 682 amino acids) recombinant COL17, suggesting that C-terminal processing shows neoepitopes on the 15th collagenous domain. The LAD autoantibodies also react with C-terminal deleted COL17. Therefore, neoepitopes for LAD autoantibodies also develop after C-terminal processing. Finally, the passive transfer of the mAb hC17-ect15 into human COL17-expressing transgenic mice failed to induce blistering disease, suggesting that neoepitope-targeting antibodies are not always pathogenic. In summary, this study shows that C-terminal processing induces dynamic structural changes and neoepitopes for LAD autoantibodies on COL17.

Endoscopic findings of laryngopharyngeal and esophageal involvement in autoimmune bullous disease

BACKGROUND AND AIM

Autoimmune bullous disease (ABD) is induced by autoantibodies against cell adhesion molecules, and blistering may occur on the mucous membranes of the eyes, nose, mouth, oral cavity, laryngopharynx, and esophagus. Endoscopic prevalence and features of ABD-associated esophageal lesions are not well known. We conducted the present study to assess the endoscopic prevalence of ABD-associated mucosal lesions.

METHODS

Endoscopic prevalence of mucosal lesions, particularly laryngopharyngeal and esophageal lesions, was used as the primary endpoint to assess the significance of upper gastrointestinal endoscopy, and clinical and endoscopic features were secondary endpoints.

RESULTS

Of 123 ABD patients, 50.4% had apparent oral or laryngopharyngeal lesions and 30.8% had laryngopharyngeal lesions. Esophageal lesions were detected through normal observation in 16.8% of affected patients, whereas 40.6% exhibited epidermolysis or blood blisters by mechanical inducement, regardless of esophageal mucosal lesion detection by normal observation. Additionally, 56.0% exhibited the Nikolsky sign with mechanical inducement. Of the 123 patients, 29.2% did not have exposed skin lesions. Of these patients, 77.7% had oral cavity or laryngopharyngeal lesions, 36.1% had esophageal lesions, and 58.3% exhibited the Nikolsky sign on esophageal mucosa.

CONCLUSION

It is important to determine the endoscopic characteristics and findings of ABD. ABD can be suspected from endoscopic findings.

Validation of chemiluminescent enzyme immunoassay in detection of autoantibodies in pemphigus and pemphigoid

BACKGROUND

A novel chemiluminescent enzyme immunoassay (CLEIA) was recently developed to quantify autoantibodies specific for desmogleins (Dsgs) and BP180, the target antigens of pemphigus and pemphigoid. This assay is automated and highly accurate and efficient.

OBJECTIVE

To validate the use of the CLEIA for detection of autoantibodies during the clinical courses of patients with pemphigus and pemphigoid.

METHODS

To define cut-off values for Dsg1, Dsg3, and BP180, we evaluated 47 serum samples from patients with pemphigus foliaceus (PF), 59 from those with pemphigus vulgaris (PV), 52 from those with bullous pemphigoid (BP), and 995 from healthy individuals. We also evaluated any fluctuations in CLEIA titers according to disease activity during the clinical course of 10 cases each of PF, PV, and BP. We used clinical symptom scores, the pemphigus disease area index (PDAI) and the bullous pemphigoid disease area index (BPDAI), to evaluate disease activity.

RESULTS

The cut-off values for the CLEIA titers determined by the Youden index were 15.4U/mL for Dsg1, 14.9U/mL for Dsg3, and 16.8U/mL for BP180. CLEIA titers fluctuated in parallel with the PDAI/BPDAI scores in 28 of the 30 cases with PF, PV, or BP. Although the CLEIA and enzyme-linked immunosorbent assay (ELISA) values in the same samples differed substantially in some cases, the concordance rates of positive/negative results between the CLEIA and ELISA were 96% for Dsg1, 97% for Dsg3, and 96% for BP180.

CONCLUSION

The CLEIA, a newly developed, highly effective autoantibody detection system, is as reliable as ELISA for evaluation of the clinical courses of pemphigus and pemphigoid.

A randomized double-blind trial of intravenous immunoglobulin for bullous pemphigoid

BACKGROUND

Patients with steroid-resistant bullous pemphigoid (BP) require an appropriate treatment option.

OBJECTIVE

A multicenter, randomized, placebo-controlled, double-blind trial was conducted to investigate the therapeutic effect of high-dose intravenous immunoglobulin (IVIG; 400mg/kg/day for 5days) in BP patients who showed no symptomatic improvement with prednisolone (≥0.4mg/kg/day) administered.

METHODS

We evaluated the efficacy using the disease activity score on day15 (DAS15) as a primary endpoint, and changes in the DAS over time, the anti-BP180 antibody titer, and safety for a period of 57days as secondary endpoints.

RESULTS

We enrolled 56 patients in this study. The DAS15 was 12.5 points lower in the IVIG group than in the placebo group (p=0.089). The mean DAS of the IVIG group was constantly lower than that of the placebo group throughout the course of observation, and a post hoc analysis of covariance revealed a significant difference (p=0.041). Furthermore, when analyzed only in severe cases (DAS≥40), the DAS15 differed significantly (p=0.046). The anti-BP180 antibody titers showed no difference between the two groups.

CONCLUSION

IVIG provides a beneficial therapeutic outcome for patients with BP who are resistant to steroid therapy.

Autoantibody Profile Differentiates between Inflammatory and Noninflammatory Bullous Pemphigoid

Bullous pemphigoid (BP) is a major autoimmune blistering skin disorder, in which a majority of the autoantibodies (autoAbs) target the juxtamembranous extracellular noncollagenous 16A domain (NC16A) domain of hemidesmosomal collagen XVII. BP-autoAbs may target regions of collagen XVII other than the NC16A domain; however, correlations between epitopes of BP-autoAbs and clinical features have not been fully elucidated. To address correlations between the clinical features and specific epitopes of BP-autoAbs, we evaluated the epitope profiles of BP-autoAbs in 121 patients. A total of 87 patients showed a typical inflammatory phenotype with erythema and autoAbs targeting the anti-NC16A domain, whereas 14 patients showed a distinct noninflammatory phenotype, in which autoAbs specifically targeted the midportion of collagen XVII, but not NC16A. Interestingly, this group clinically showed significantly reduced erythema associated with scant lesional infiltration of eosinophils. Surprisingly, 7 of the 14 cases (50.0%) received dipeptidyl peptidase-IV inhibitors for the treatment of diabetes. Dipeptidyl peptidase-IV inhibitors were used in 3 of 76 (3.9%) typical cases of BP with autoAbs targeting NC16A; thus, dipeptidyl peptidase-IV inhibitors are thought to be involved in the development of atypical noninflammatory BP. This study shows that the autoAb profile differentiates between inflammatory and noninflammatory BP, and that noninflammatory BP may be associated with dipeptidyl peptidase-IV inhibitors.

Grading criteria for disease severity by pemphigus disease area index

Pemphigus is a group of autoimmune blistering diseases that affect the skin and mucous membranes. A reliable and accurate disease severity tool to assess pemphigus severity is crucial for managing pemphigus and for clinical trials. The purpose of this study was to compare the pemphigus disease area index activity score (PDAI), the Japanese pemphigus disease severity score (JPDSS) and the physician's subjective impression, and also to find appropriate severity grading cut-offs for the PDAI. We also evaluated the correlation between PDAI activity score and the JPDSS. Thirty-seven pemphigus patients and 110 assessments were analyzed in this study. The optimal points of pemphigus disease severity score in PDAI were: mild (0-8), moderate (9-24) and severe (≥25). In mild or moderate cases, the JPDSS was well correlated with the PDAI, but in severe cases the JPDSS reached a plateau at a PDAI score of approximately 30. The PDAI evaluates disease severity more accurately than the JPDSS, particularly in severe cases. The PDAI is not only a useful tool to measure the extent of cutaneous lesions, but also an excellent scoring system for evaluating pemphigus disease severity.

Low pathogenicity of anti-desmoglein 3 immunoglobulin G autoantibodies contributes to the atypical clinical phenotypes in pemphigus

The clinical phenotypes of pemphigus can be explained by the desmoglein (Dsg) compensation theory. However, some atypical cases such as cutaneous pemphigus vulgaris (cPV), in which patients have anti-Dsg3 antibodies without oral erosions, do not conform to this theory. To explain the discrepancy between clinical phenotypes and anti-Dsg antibody profiles, the pathogenic strength of immunoglobulin (Ig)G autoantibodies against Dsg3 must be taken into consideration. We analyzed the epitopes and blister-inducing pathogenic strength of the sera from three patients having IgG against Dsg3 without oral erosions with domain-swapped recombinant proteins and dissociation assay using cultured normal human epidermal keratinocytes. The results showed that all sera contained IgG directed against the amino terminal EC1 domain of Dsg3, as is found in most PV sera. However, dissociation assays revealed that the pathogenic strength of the anti-Dsg3 antibodies in all three cases was extremely lower than that of typical PV cases with mucosal involvement. In conclusion, when anti-Dsg3 IgG antibodies are not sufficient to inhibit the expression of Dsg3 in the oral mucosa, but can inhibit the expression in the skin, skin blisters can result. Therefore, the pathogenicity of anti-Dsg3 antibodies should be regarded as a key factor contributing to the clinical phenotype in pemphigus patients with conflicting antibody profiles.

Autoimmune reactivity against precursor form of desmoglein 1 in healthy Tunisians in the area of endemic pemphigus foliaceus

BACKGROUND

Desmoglein 1 (Dsg1), the pemphigus foliaceus (PF) antigen, is produced as a precursor (preDsg1) and is transported to the cell surface as the mature form (matDsg1). Recent studies show that B cells from North American individuals without pemphigus can potentially produce anti-preDsg1 IgG antibodies, but ELISA screening of large numbers of normal people in North America and Japan hardly ever shows circulating antibodies against preDsg1 or matDsg1. In contrast, in Tunisia, where PF is endemic, anti-Dsg1 IgGs are frequently detected in healthy individuals.

OBJECTIVE

To characterize these anti-Dsg1 antibodies from normal individuals in Tunisia.

METHODS

Sera from 16 healthy individuals and 9 PF patients in the endemic PF area in Tunisia, and sera from Japanese non-endemic PF patients were analyzed by immunoprecipitation-immunoblotting using recombinant proteins of preDsg1, matDsg1, and domain-swapped Dsg1/Dsg2 molecules.

RESULTS

Sera from normal Tunisian individuals reacted to preDsg1 alone (8/16) or more strongly to preDsg1 than to matDsg1 (7/16), while those from all Tunisian PF patients and Japanese non-endemic PF patients reacted similarly to preDsg1 and matDsg1, or preferentially to matDsg1. The epitopes recognized by anti-Dsg1 IgGs from normal Tunisian individuals were more frequently found in the C-terminal extracellular domains (EC3 to EC5), while those in Tunisian endemic PF patients were more widely distributed throughout the extracellular domains, suggesting IgGs against EC1 and EC2 developed during disease progression.

CONCLUSIONS

These findings indicate that IgG autoantibodies against Dsg1 are mostly raised against preDsg1 and/or C-terminal domains of Dsg1 in healthy Tunisians in the endemic area of PF.

Unilateral bullous pemphigoid without erythema and eosinophil infiltration in a hemiplegic patient

In this report, we describe an 88-year-old male stroke patient with unilateral bullous pemphigoid limited to the hemiplegic side. Physical examinations revealed multiple tense bullae with clear and/or bloody contents without apparent erythema on the right thigh and lower leg, accompanied by erosions on the right chest. Histopathologically, no eosinophils were infiltrated into and around the subepidermal bullae. Immunofluorescence revealed deposited and circulating immunoglobulin (Ig)G anti-basement membrane zone antibodies. Immunoblot assays using various antigen sources and enzyme-linked immunosorbent assay revealed that IgG antibodies in this case reacted with unique epitopes between NC16a and C-terminal domains on the 120-kDa LAD-1, the extracellular truncated form of BP180. Three observations were unique in our case. First, the distribution of bullae in our patient was limited to the hemiplegic side. Second, there was no apparent erythema clinically and no eosinophilic infiltration histopathologically. Third, the patient achieved remission without the use of oral corticosteroids. The unusual epitopes in this case may contribute to these phenomena.

Alopecia as a rare but distinct manifestation of pemphigus vulgaris

BACKGROUND

Pemphigus vulgaris (PV) patients may develop scalp erosions, however, the development of alopecia has been reported to be extremely rare.

OBJECTIVE

To delineate the clinicopathological features of alopecia in PV and provide insight into the pathogenesis of this rarely observed manifestation.

METHODS

A retrospective case note review was performed on five PV patients presenting with progressive hair loss and alopecic patches. Data were collected on demographics and clinical findings. Results for hair pull tests, direct immunofluorescence study of plucked hairs, established laboratory tests to detect anti-desmoglein 1 and 3 autoantibodies and scalp swab culture were recorded. A combination of vertical and horizontal sectioning technique enabled detailed histopathological analysis of alopecic patches. Clinical course was monitored.

RESULTS

Anagen hair follicles with the outer root sheath structure were easily pulled from perilesional scalp, with intercellular IgG deposition on the outer root sheath keratinocytes. Acantholysis between outer root sheath keratinocytes extending from the infundibulum to suprabalbar level was evident in anagen hair follicles of affected lesions. Perifollicular cell infiltration was observed in the lesions where scalp swabs detected micro-organisms. The bulge stem cell area was mostly intact. Alopecia was non-scarring and following 4 weeks of therapy hair re-growth was seen in all patients.

CONCLUSION

In PV, the combination of anti-desmoglein autoantibody-mediated acantholysis in conjunction with secondary factors, such as inflammatory changes due to infection, may cause weakening of hair follicle anchorage resulting in hair loss and alopecic patches. This unusual clinical phenotype should alert physicians to PV as a potential diagnosis.

Homologous regions of autoantibody heavy chain complementarity-determining region 3 (H-CDR3) in patients with pemphigus cause pathogenicity

Pemphigus is a life-threatening autoimmune disease in which antibodies specific for desmogleins (Dsgs) cause loss of keratinocyte cell adhesion and blisters. In order to understand how antibodies cause pathogenicity and whether there are commonalities among antibodies in different patients that could ultimately be used to target specific therapy against these antibodies, we characterized Dsg-specific mAbs cloned by phage display from 3 patients with pemphigus vulgaris and 2 with pemphigus foliaceus. Variable heavy chain gene usage was restricted, but similar genes were used for both pathogenic and nonpathogenic mAbs. However, the heavy chain complementarity-determining region 3 (H-CDR3) of most pathogenic, but not nonpathogenic, mAbs shared an amino acid consensus sequence. Randomization of the H-CDR3 and site-directed mutagenesis indicated that changes in this sequence could block pathogenicity but not necessarily binding. In addition, for 2 antibodies with longer H-CDR3s, a tryptophan was critical for pathogenicity but not binding, a result that is consistent with blocking the tryptophan acceptor site that is thought to be necessary for Dsg-mediated adhesion. These studies indicate that H-CDR3 is critical for pathogenicity of a human autoantibody, that a small region (even 1 amino acid) can mediate pathogenicity, and that pathogenicity can be uncoupled from binding in these antibodies.

Antibodies to the desmoglein 1 precursor proprotein but not to the mature cell surface protein cloned from individuals without pemphigus

In pemphigus foliaceus (PF), autoantibodies against desmoglein 1 (Dsg1) cause blisters. Using Ab phage display, we have cloned mAbs from a PF patient. These mAbs, like those from a previous patient, were directed against mature Dsg1 (matDsg1) on the cell surface of keratinocytes and precursor Dsg1 (preDsg1) in the cytoplasm. To determine whether individuals without pemphigus have B cell tolerance to Dsg1, we cloned mAbs from two patients with thrombotic thrombocytopenic purpura and a healthy person. We found mAbs against preDsg1, but not matDsg1. All but 1 of the 23 anti-preDsg1 mAbs from PF patients and those without PF used the VH3-09 (or closely related VH3-20) H chain gene, whereas no PF anti-matDsg1 used these genes. V(H) cDNA encoding anti-preDsg1 had significantly fewer somatic mutations than did anti-matDsg1 cDNA, consistent with chronic Ag-driven hypermutation of the latter compared with the former. These data indicate that individuals without PF do not have B cell tolerance to preDsg1 and that loss of tolerance to matDsg1 is not due to epitope shifting of anti-preDsg1 B cells (because of different V(H) gene usage). However, presentation of peptides from Dsg1 by preDsg1-specific B cells may be one step in developing autoimmunity in PF.

Anti-desmoglein IgG autoantibodies in patients with pemphigus in remission

BACKGROUND

Desmoglein (Dsg) enzyme-linked immunosorbent assay (ELISA) is a highly sensitive and specific method to detect anti-Dsg3 and anti-Dsg1 IgG autoantibodies in pemphigus vulgaris (PV) and pemphigus foliaceus (PF), respectively. Whereas ELISA index values fluctuate in parallel with disease activity, ELISA positivity during clinical remission has been observed.

OBJECTIVE

To determine the prevalence of positive Dsg ELISA index values during clinical remission. To ascertain how positive Dsg ELISA scores during remission compare with those during active disease.

METHODS

Dsg ELISA was performed on serum samples of PV and PF patients taken during remission (lesion-free >or= 3 months on <or= 15 mg or <or= 5 mg/day prednisolone) and active disease. We used a modified ELISA protocol with optimal serum dilutions in sera with very high initial index values, as we previously described.

RESULTS

When remission was defined as no eruption >or= 3 months with <or= 15 mg/day prednisolone, 20 of 43 PV patients (46.5%) and 4 of 12 PF patients (33.3%) showed Dsg3 and Dsg1 ELISA positivity, respectively. With <or= 5 mg/day, 6 of 17 PV (35.3%) and 1 of 6 PF patients (16.7%) showed Dsg3 and Dsg1 ELISA positivity, respectively. The index value of each ELISA-positive remission serum was consistently lower than that of its corresponding active disease serum. We observed consistent correlation between ELISA index values and indirect immunofluorescence titres.

CONCLUSIONS

Circulating anti-Dsg IgG autoantibodies are found in a considerable percentage of pemphigus patients in remission, who have high levels of antibody production during active stages.