Missense Variant c.3301C>T (p.R1101W) in von Willebrand Factor A Sequence in a Patient with Recessive Dystrophic Epidermolysis Bullosa Pruriginosa with Compound Heterozygous COL7A1 Variants

Dystrophic epidermolysis bullosa (DEB) pruriginosa is a rare subtype of DEB characterized by multiple, violaceous, and severe pruritic lichenified nodules along with blisters. Here, we report the case of a Korean male who, since the age of 3 years, had multiple pruritic nodules with blisters on both lower extremities. Genetic testing is required to diagnose DEB pruriginosa because its clinical and histologic features are inconclusive. We identified compound heterozygous COL7A1 variants of c.5797C>T (p.R1933*) and c.3301C>T (p.R1101W) in the patient, leading to a diagnosis of recessive DEB pruriginosa. Among the variants identified, c.3301C>T is a novel missense variant that has not been reported previously. This variant is in exon 26, which encodes von Willebrand factor A (vWFA) in collagen type VII. vWFA is known to preserve normal dermal structures by interacting with dermal collagens and basement membranes. Considering that this variant contradicts the general concept that autosomal dominant inheritance is more common and that variants typically occur in the triple helical collagenous domain of COL7A1 in DEB pruriginosa, we focus on the rarity of this case and the possible pathogenic role of the c.3301C>T (p.R1101W) variant.

A postulated model for photoimmunopathogenesis of chronic actinic dermatitis around adaptive immunity, including Th17 cells, Tregs, TRMs, cytotoxic T cells, and/or common-γ chain receptor+ cells

BACKGROUND/PURPOSE

The pathogenesis of chronic actinic dermatitis (CAD) is more complicated than other photodermatoses. However, the relationship between the clinical severity of CAD and the offending photocontact or contact allergens or both, and the correlations of CAD immunopathogenesis with the immunoregulatory molecules involved in adaptive immunity are yet to be investigated.

METHODS

We performed phototesting with broad-spectrum ultraviolet (UV) B, UVA, and visible light to establish the presence of photosensitivity in 121 patients with CAD, together with photopatch and contact patch testing. Nine patients with CAD were selected according to their clinical severity score for CAD (CSS-CAD), and triple direct immunofluorescence analysis was performed with paraffin-embedded skin biopsy samples.

RESULTS

As CSS-CAD was closely correlated with the multiplicity of photo(contact) allergens, particularly photoallergens, three or more photoallergens were detected in the severe CAD group (52.5%); less in the moderate group (32.8%); and only one in the mild group (14.8%; P = .025). In the groups showing greater severity of disease, the absolute numbers of IFN-γ⁺ , IL-17⁺ , CD4+, CD8+, common-γ chain receptor (common-γCR)⁺ , and CD69⁺ tissue-resident memory cells increased on average; there was also an increase in the CD4+/CD8+ cell ratio, with the more severely affected groups. However, the levels of TNF-α⁺ and FoxP3⁺ regulatory T (Treg) cells and the mean IL-17/IFN-γ cell ratio decreased in the more severely affected CSS-CAD subgroups.

CONCLUSIONS

Based on the clinical analysis and immunopathogenic results, avoidance of excessive sun exposure, and topical and systemic blocking agents for photo(contact) allergens are recommended. Additionally, conventional immunomodulators and emerging agents including JAK-STAT inhibitors may be administered for CAD treatment in the future.

Structural analysis of the conformational domains involved in neutralization of bovine coronavirus using deletion mutants of the spike glycoprotein S1 subunit expressed by recombinant baculoviruses

Two conformation-dependent neutralizing epitopes, A and B, have been mapped to the S1 subunit of the S spike glycoprotein of bovine coronavirus (BCV). In order to characterize the structure of these antigenic sites, we constructed a series of cDNA clones encoding deleted or truncated S1 derivatives and expressed the modified genes in insect cells using recombinant baculoviruses. Monoclonal antibodies directed against epitopes A and B recognized only the mutant S1 polypeptides containing amino acids 324-720, as demonstrated by immunoprecipitation and Western blot analysis in the absence of beta-mercaptoethanol. In addition, two domains within this region were identified and only mutants containing both domains were immunoreactive, indicating that both were critical in the formation of the antigenic determinants. One domain was localized between residues 324 and 403 and the other at residues 517-720. Deletion of either domain inhibited extracellular secretion of the mutant proteins whereas mutants containing both or none of the domains were secreted efficiently. This observation suggests a vital function of the native conformation of the S1 protein in both antigenic structure and intracellular transport. Antigenic determinants A and B were not distinguished, but these determinants appeared to require both domains for epitope formation. Our results suggest that the antigenic determinants formed by two domains are likely associated with the probable polymorphic region of the BCV S1 subunit.

The S2 subunit of the spike glycoprotein of bovine coronavirus mediates membrane fusion in insect cells

The hemagglutinin/esterase (HE), spike precursor (S) and the S1 and S2 subunits of the spike precursor protein of bovine coronavirus were expressed in Spodoptera frugiperda (Sf9) cells, and the cell-fusing activity of each recombinant glycoprotein was examined. Extensive syncytia formation was observed in cells infected with the S2 recombinant but not with the HE or S1 recombinant baculoviruses. Fusion of Sf9 cells expressing the intact S protein precursor was evident after trypsin treatment. These results demonstrate that proteolytic cleavage of the S spike precursor is required for fusion induction and that the fusion is mediated by the S2 subunit. These observations may reflect the biological role of the S2 subunit in fusion-penetration during bovine coronavirus infection.