Orf-induced pemphigoid with antilaminin-332 antibodies

Keratinocyte footprint assay discriminates antilaminin-332 pemphigoid from all other forms of pemphigoid diseases

Background

Antilaminin‐332 mucous membrane pemphigoid is a chronic severe pemphigoid disease characterized by autoantibodies to laminin‐332. At present no commercial assay is available to demonstrate antilaminin‐332 antibodies, and diagnosis relies on in‐house techniques with limited sensitivities.

Objectives

In order to move, keratinocytes cultured in vitro secrete laminin‐332 to attach to the culture dish. In that way, they leave behind a unique footprint trail of laminin‐332. We aimed to develop a sensitive and specific laboratory assay to determine antilaminin‐332 autoantibodies in patient serum based on binding of patient IgG to these unique footprints.

Methods

Normal human keratinocytes were grown on glass coverslips and incubated with patient or control serum for 1 h. The binding of IgG was then investigated by immunofluorescence. After validating the test for its ability to identify antilaminin‐332 autoantibodies it was converted into a daily available test based on binding of IgG to dried coverslips that can be stored frozen. The staining patterns of sera from patients with antilaminin‐332 pemphigoid were then compared with those of sera from patients with other autoimmune bullous diseases and normal human sera.

Results

IgG of all antilaminin‐332 pemphigoid sera (n = 16) bound to laminin‐332 footprints, while all normal human controls (n = 55) were negative. From the sera of patients with other diseases (n = 72) four sera tested positive. The footprint assay was also positive for sera that were negative by salt‐split skin analysis, demonstrating that it is a very sensitive technique.

Conclusions

The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin‐332 autoantibodies.

What's already known about this topic?

Antilaminin‐332 mucous membrane pemphigoid is a severe form of pemphigoid, and patients may have an increased risk of malignancies.

The diagnosis of antilaminin‐332 mucous membrane pemphigoid is complicated by the lack of specific commercial tests for antilaminin‐332 antibodies and can be confirmed only in specialized laboratories.

Keratinocytes in culture need laminin‐332 for adhesion and migration and therefore deposit it on the bottom of the culture dish.

What does this study add?

The keratinocyte footprint assay detects antilaminin‐332 autoantibodies in patient serum using the native laminin‐332 produced by cultured keratinocytes.

What is the translational message?

The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin‐332 autoantibodies.

Linked Comment: https://doi.org/10.1111/bjd.18372.

https://doi.org/10.1111/bjd.18761 available online

Human orf complicated by epidermolysis bullosa acquisita

Orf is a DNA parapoxvirus transmitted to humans by contact with infected goats and sheep. Many complications have been reported after orf infection, including erythema multiforme. A few cases of autoimmune bullous dermatosis complicating orf disease have been reported to date. They are usually characterized by tense blister eruptions with or without mucosal involvement; linear deposition of C3, IgG and/or IgA along the basement membrane; and negativity of indirect immunofluorescence analysis and enzyme-linked immunosorbent assay (ELISA) (performed in four of 11 reported cases). These analyses have targeted antigens of bullous pemphigoid, mucous membrane pemphigoid or epidermolysis bullosa acquisita, except one case of mucosal pemphigoid with antilaminin-332 antibodies. We describe the case of a patient who presented with an ulceration on his finger 10 days after direct contact with a lamb during Eid al-Adha. Four weeks later he developed a severe tense blistering eruption associated with mucous membrane erosions. Indirect immunofluorescence analysis using the patient's serum revealed circulating antibasement membrane IgG that bound the dermal side of salt-split skin. ELISA was positive for recombinant immunodominant NC1 domain of type VII collagen. We finally diagnosed epidermolysis bullosa acquisita complicating probable human orf infection.