Investigating the epithelial barrier and immune signatures in the pathogenesis of equine insect bite hypersensitivity.
Authors: Cvitas Iva, Oberhänsli Simone, Leeb Tosso, Dettwiler Martina, Müller Eliane, Bruggman Remy, Marti Eliane Isabelle
Journal: PloS one
Summary
Equine insect bite hypersensitivity (IBH) represents a Th2-driven, IgE-mediated allergic response to Culicoides bites that parallels human atopic dermatitis, yet the underlying mechanisms linking epithelial barrier dysfunction to immune dysregulation have remained poorly characterised. Cvitas and colleagues employed transcriptomic analysis of lesional and non-lesional skin from affected horses compared to healthy controls, alongside separate examination of isolated epidermis, to map the molecular landscape of IBH pathogenesis. Lesional skin showed substantial downregulation of tight junction genes, altered keratin expression, and marked upregulation of Th2 cytokines—particularly interleukin-13—alongside unexpected Th1 immune signatures and hypoxic pathway involvement; notably, non-lesional skin from IBH horses displayed intermediate gene expression patterns between healthy and lesional tissue, suggesting a predisposed epidermal state. The epidermis of unaffected skin in IBH horses exhibited distinct alterations in lipid metabolism genes and IL25 expression, implicating barrier impairment as a predisposing rather than reactive feature. These findings suggest that both structural epithelial weakness and dysregulated local immunity drive IBH susceptibility, potentially opening avenues for targeted therapeutic interventions beyond current anti-inflammatory approaches, whilst reinforcing equine IBH's value as a naturally occurring model for human allergic skin disease.
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Practical Takeaways
- •IBH appears rooted in a fundamentally compromised skin barrier rather than just immune overreaction—management should focus on barrier repair and lipid supplementation, not just itch suppression
- •Even clinically normal-looking skin in IBH-affected horses shows abnormal gene expression, suggesting systemic skin dysfunction requires year-round preventive care
- •The shared mechanisms between equine IBH and human atopic dermatitis may allow cross-translation of human dermatology treatments and prevention strategies to equine practice
Key Findings
- •IBH lesional skin showed downregulation of tight junction genes and keratin alterations, indicating epithelial barrier impairment as a predisposing factor
- •IL-13 was substantially upregulated in IBH lesional skin alongside mixed Th-1 and Th-2 immune signatures
- •Non-lesional epidermis from IBH horses showed dysregulation of epidermal lipid metabolism and IL-25 expression even in absence of visible lesions
- •Equine IBH shares multiple transcriptional features with human atopic dermatitis, validating horses as a natural model for skin allergy research