Cytokeratin expression and distribution pattern of epithelioid macrophages in animals with different pathological forms of bovine paratuberculosis (PTB): potential role in resilience to PTB

ALEJANDRA ISABEL NAVARRO LEÓN^1,2MARTA MUÑOZ¹CRISTINA BLANCO VÁZQUEZ¹Tania Iglesias-Cabo³María Canive⁴Gerard Badia-Bringué⁴MARTA ALONSO-HEARN⁴Ana Balseiro⁵ROSA CASAIS^1*

• ¹Servicio Regional de Investigación y Desarrollo Agroalimentario (SERIDA), Animal Biotechnology Center., GIJON, Spain
• ²Universidad de Oviedo, Oviedo, Spain
• ³Universidad de Oviedo - Campus de Gijon, Gijón, Spain
• ⁴NEIKER Nekazaritza Ikerketa eta Garapenerako Euskal Erakundea SA Derioko Zentroa, Derio, Spain
• ⁵Universidad de Leon, León, Spain

Paratuberculosis (PTB) is a chronic enteritis caused by Mycobacterium avium subsp. paratuberculosis (Map). Genome-wide association studies revealed a significant enrichment of the keratinisation pathway in cattle with multifocal lesions, suggesting a potential role of cytokeratins (CKs) in PTB resilience mechanisms. To confirm this, the amount of, CK-expressing cells was analysed in granulomas from distal jejunum (DJE) and jejunal lymph nodes (DJELN) of animals with focal, multifocal, and diffuse lesions, and in control animals without lesions. Quantitative double-immunohistochemical analysis, (using Iba1 (ionized calcium-binding adapter molecule-1) and CK, as specific markers of macrophages and epithelial cells, respectively, showed that animals with multifocal lesions had the highest numbers of double-Iba1/CK positive cells (epithelioid macrophages (EMs)). Significant differences were observed with the focal (p<0.001), diffuse (p=0.038) and control groups (p<0.001) in JELN. Likewise, these animals showed higher numbers of single-CK expressing cells in JELN and DJE. Two EMs distribution patterns were observed. In Pattern 1, mostly observed in animals with multifocal lesions (low Map load, no clinical signs), EMs form a barrier-like arrangement around the granuloma, while in Pattern 2, mainly found in animals with diffuse lesions (high Map load, clinical signs), EMs have a diffuse arrangementthroughout the granuloma. These findings suggest that animals with multifocal lesions might represent a resilient phenotype that controls Map infection and disease progression through formation of ordered granulomas that prevent Map dissemination and maintain tissue integrity, characteristic features of resilient animals. CK could be considered as a potential biomarker of PTB resilience.