Michael Kasperkiewicz

Pemphigoid diseases: Pathogenesis, diagnosis, and treatment

Pemphigoid diseases (including bullous pemphigoid, mucous membrane pemphigoid, pemphigoid gestationis, linear IgA dermatosis, lichen planus pemphigoides, and anti-p200 pemphigoid) are a subgroup of autoimmune bullous skin diseases characterized by an autoantibody response toward structural components of the hemidesmosome resulting in subepidermal blistering. By the use of different in vitro systems and experimental animal models, the pathogenic relevance of these autoantibodies has been demonstrated. Recent advances in the understanding of autoantibody responses have led to novel diagnostic tools and a more differentiated therapeutic approach for these disorders. This review covers the most recent understanding of the pathophysiology, diagnosis, and treatment of this group of autoimmune diseases.

Broad requirement for terminal sialic acid residues and FcγRIIB for the preventive and therapeutic activity of intravenous immunoglobulins in vivo

Intravenous immunoglobulin (IVIg) therapy is widely used to treat a variety of autoimmune diseases including immunothrombocytopenia, chronic inflammatory demyelinating polyneuropathy, and more recently autoimmune skin blistering diseases. Despite this well‐documented clinical success, the precise molecular and cellular mechanisms underlying this immunomodulatory activity are discussed controversially. In particular, the clinically relevant therapeutic pathway of IVIg‐mediated immune modulation has not been studied in detail. In the present study, we use four independent in vivo model systems of auto‐Ab‐mediated autoimmune disease to identify a common pathway explaining IVIg activity under therapeutic conditions in vivo. We show that irrespective of the in vivo model system, IVIg activity is strictly dependent on the presence of terminal sialic acid residues and the inhibitory FcγRIIB under preventive as well as therapeutic treatment conditions. In contrast, specific ICAM3 grabbing nonintegrin related 1, previously demonstrated to be essential under preventative treatment conditions, showed a disease‐specific impact on IVIg‐mediated resolution of established autoimmune disease.

Genetic identification and functional validation of FcγRIV as key molecule in autoantibody-induced tissue injury†

Autoantibody‐mediated diseases are clinically heterogeneous and often fail conventional therapeutic strategies. Gene expression profiling has helped to identify new molecular pathways in these diseases, although their potential as treatment targets largely remains to be functionally validated. Based on weighted gene co‐expression network analysis, we determined the transcriptional network in experimental epidermolysis bullosa acquisita (EBA), a paradigm of an antibody‐mediated organ‐specific autoimmune disease characterized by autoantibodies directed against type VII collagen. We identified 33 distinct and differentially expressed modules, including Fcγ receptor (FcγR) IV and components of the neutrophil‐associated enzyme system in autoantibody transfer‐induced EBA. Validation experiments, including functional analysis, demonstrated that FcγRIV expression on neutrophils crucially contributes to autoantibody‐induced tissue injury in the transfer model of EBA. Mice lacking the common γ‐chain of activating FcγRs, deficient in FcγRIV or treated with FcγRIV function blocking antibody, but not mice deficient in FcγRI, FcγRIIB, FcγRIII or both FcγRI and FcγRIII, were effectively protected from EBA. Skin disease was restored in γ‐chain‐deficient mice locally reconstituted with neutrophils from wild‐type, but not from γ‐chain‐deficient, mice. Our findings both genetically and functionally identify a novel disease‐related molecule, FcγRIV, in an autoantibody‐mediated disorder, which may be of importance for the development of novel targeted therapies. Copyright

Generation of antibodies of distinct subclasses and specificity is linked to H2s in an active mouse model of epidermolysis bullosa acquisita.

Epidermolysis bullosa acquisita (EBA) is an autoimmune blistering disease, characterized by antibodies to type VII collagen (COL7). EBA can be induced in mice by immunization with a fragment of the non-collagenous 1 domain of murine COL7. Contrary to other autoimmune diseases, e.g., rheumatoid arthritis, little is known about the genetic susceptibility for EBA. We therefore used the EBA mouse model to address the hypothesis that disease induction depends on the major histocompatibility complex (MHC) haplotype. Mice from different inbred strains were immunized with recombinant murine COL7. Five distinct responses were observed: induction of (i) severe disease in SJL/J (H2s) and female MRL/MpJ (H2k), (ii) mild and transient disease in C57Bl/10.s (H2s), (iii) microscopic blistering in DBA/1J (H2q), (iv) only presence of non-pathogenic autoantibodies in C57Bl/6J (H2b), NZM2410/J (H2z), BXD2 (H2b), and male MRL/MpJ, and (v) complete resistance to EBA in NOD/ShiLtJ (H2g7) and C57Bl/10.q (H2q) mice. Overall, susceptibility to EBA was strongly associated with H2s. In addition, the diseased phenotype was associated with autoantibodies to specific regions of COL7. Our findings show that induction of antibodies with a distinct specificity is linked to the MHC haplotype in experimental EBA. Furthermore, our data are the basis for future studies with the goal of identifying non-MHC EBA susceptibility genes.

Current therapy of the pemphigus group.

Treatment of pemphigus patients is still challenging and, in some cases, conventional therapy with systemic corticosteroids in combination with adjuvant corticosteroid-sparing immunosuppressive drugs is not sufficient to induce clinical remission. More recently, high-dose intravenous immunoglobulins, immunoadsorption, and the monoclonal anti-CD20 antibody, rituximab, have been established as additional successful therapeutic options. This contribution covers both conventional therapies and most current treatment strategies for pemphigus.

Current treatment of autoimmune blistering diseases.

Autoimmune bullous diseases are a heterogeneous group of disorders that can be subdivided according to the level of split formation in the intraepidermal blistering pemphigus diseases and subepidermal bullous disorders, latter including pemphigoid diseases, epidermolysis bullosa acquisita, and dermatitis herpetiformis. In the majority of autoimmune bullous disorders, disease activity can be sufficiently controlled by systemic corticosteroids in combination with further immunosuppressants/immunomodulants such as dapsone, doxycycline, methotrexate, azathioprine, or mycophenolate mofetil. In contrast, in pemphigus, mucous membrane pemphigoid, and epidermolysis bullosa acquisita, treatment is challenging and only in a minority of patients, conventional immunosuppressive therapy induces clinical remission. Since only a few years ago, only cyclophosphamide and high-dose intravenous immunoglobulin were available as potent second-line therapies. Meanwhile, immunoadsorption and the monoclonal anti-CD20 antibody rituximab have been established as further therapeutic options. Here, both conventional therapies and novel treatment regimens for autoimmune blistering diseases are discussed.

Improvement of treatment-refractory atopic dermatitis by immunoadsorption: a pilot study.

CCDs. Similar to previous studies, about 50% of patients with DP had IgE to CCDs, explaining DP at least in some patients. In current clinical practice immunotherapy with both BVand VV, is usually performed in patients who had not identified the culprit insect but display DP to venom extracts, especially in patients without IgE to CCDs. The present study, however, demonstrates that only a minority of CCD-negative patients with DP to venom extracts (8/33 [24%]) display a genuine sensitization to both SSMAs, whereas the majority (22/33 [66%]) present a sensitization only to one of the SSMAs (Fig 1). In the latter group immunotherapy only with venom from the primary sensitizing insect should be sufficient, and it is unlikely that immunotherapy with the second venom would be of additional benefit. In conclusion, detection of specific IgE to rApi m 1 and rVes v 5 is a reliable diagnostic method that enables us discriminate between genuine double sensitization and cross-reactivity in patients with double-positive IgE results to conventional venom extracts. This way it allows us to optimize patient selection for immunotherapy and to avoid unnecessary treatment protocols with both insect venoms. Silke C. Hofmann, MD* Nikolai Pfender* Steffi Weckesser, MD Johannes Huss-Marp, MD Thilo Jakob, MD

Serological diagnosis of autoimmune bullous skin diseases: Prospective comparison of the BIOCHIP mosaic-based indirect immunofluorescence technique with the conventional multi-step single test strategy

BackgroundVarious antigen-specific immunoassays are available for the serological diagnosis of autoimmune bullous diseases. However, a spectrum of different tissue-based and monovalent antigen-specific assays is required to establish the diagnosis. BIOCHIP mosaics consisting of different antigen substrates allow polyvalent immunofluorescence (IF) tests and provide antibody profiles in a single incubation.MethodsSlides for indirect IF were prepared, containing BIOCHIPS with the following test substrates in each reaction field: monkey esophagus, primate salt-split skin, antigen dots of tetrameric BP180-NC16A as well as desmoglein 1-, desmoglein 3-, and BP230gC-expressing human HEK293 cells. This BIOCHIP mosaic was probed using a large panel of sera from patients with pemphigus vulgaris (PV, n = 65), pemphigus foliaceus (PF, n = 50), bullous pemphigoid (BP, n = 42), and non-inflammatory skin diseases (n = 97) as well as from healthy blood donors (n = 100). Furthermore, to evaluate the usability in routine diagnostics, 454 consecutive sera from patients with suspected immunobullous disorders were prospectively analyzed in parallel using a) the IF BIOCHIP mosaic and b) a panel of single antibody assays as commonly used by specialized centers.ResultsUsing the BIOCHIP mosaic, sensitivities of the desmoglein 1-, desmoglein 3-, and NC16A-specific substrates were 90%, 98.5% and 100%, respectively. BP230 was recognized by 54% of the BP sera. Specificities ranged from 98.2% to 100% for all substrates. In the prospective study, a high agreement was found between the results obtained by the BIOCHIP mosaic and the single test panel for the diagnosis of BP, PV, PF, and sera without serum autoantibodies (Cohen’s κ between 0.88 and 0.97).ConclusionsThe BIOCHIP mosaic contains sensitive and specific substrates for the indirect IF diagnosis of BP, PF, and PV. Its diagnostic accuracy is comparable with the conventional multi-step approach. The highly standardized and practical BIOCHIP mosaic will facilitate the serological diagnosis of autoimmune blistering diseases.

Treatment of severe pemphigus with a combination of immunoadsorption, rituximab, pulsed dexamethasone and azathioprine/mycophenolate mofetil: a pilot study of 23 patients

Background  It has been previously shown in a relatively small group of patients that a combination of immunoadsorption (IA) and rituximab with daily use of high‐dose oral corticosteroids and azathioprine/mycophenolate mofetil may induce a rapid and durable remission in severe, treatment‐resistant pemphigus.

Heat-shock protein 90 inhibition in autoimmunity to type VII collagen: evidence that nonmalignant plasma cells are not therapeutic targets.

Blocking heat-shock protein 90 (Hsp90) induces death of malignant plasma cells by activation of the unfolded protein response, a signaling pathway activated by accumulation of misfolded proteins within the endoplasmic reticulum. We hypothesized that nontransformed plasma cells are also hypersensitive to Hsp90 inhibition because of their high amount of protein biosynthesis. To investigate this hypothesis, 2 different Hsp90 inhibitors, the geldanamycin derivative 17-DMAG and the nontoxic peptide derivative TCBL-145, were applied to mice with experimental epidermolysis bullosa acquisita, an autoimmune bullous disease characterized by autoantibodies against type VII collagen of the dermal-epidermal junction. Both inhibitors ameliorated clinical disease of type VII collagen-immunized mice, suppressed auto-antibody production, and reduced dermal neutrophilic infiltrate. Interestingly, total plasma cell numbers, type VII collagen-specific plasma cells, and germinal center B cells were unaffected by anti-Hsp90 treatment in vivo. However, T-cell proliferation was potently inhibited, as evidenced by the reduced response of isolated lymph node cells from immunized mice to in vitro restimulation with anti-CD3/CD28 antibody or autoantigen in the presence of Hsp90 inhibitors. Our results suggest that Hsp90 blockade has no impact on normal or autoreactive plasma cells in vivo and indentify T cells as targets of anti-Hsp90 treatment in autoimmunity to type VII collagen.