Renibacterium salmoninarum iron‐acquisition mechanisms and ASK cell line infection: Virulence and immune response

• Published in: Journal of Fish Diseases
• Main Authors: Bethke, Jorn, Arias‐Muñoz, Eloisa, Yáñez, Alejandro, Avendaño‐Herrera, Ruben
• Other Authors: Comisión Nacional de Investigación Científica y Tecnológica
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Atlantic salmon
• Online Access: http://dx.doi.org/10.1111/jfd.13051; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fjfd.13051; https://onlinelibrary.wiley.com/doi/pdf/10.1111/jfd.13051; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jfd.13051

Abstract Renibacterium salmoninarum is the aetiological agent of bacterial kidney disease (BKD) in salmonid farms. This pathogen possesses at least three iron‐acquisition mechanisms, but the link between these mechanisms and virulence is unclear. Therefore, this study used RT‐qPCR to assess the effects of normal and iron‐limited conditions on iron‐uptake genes controlled by IdeR and related to iron acquisition in Chilean R. salmoninarum strain H‐2 and the type strain DSM20767 T . Further evaluated was the in vitro immune‐related response of the Atlantic Salmon Kidney (ASK) cell line, derived from the primary organ affected by BKD. R. salmoninarum grown under iron‐limited conditions overexpressed genes involved in haemin uptake and siderophore transport, with overexpression significantly higher in H‐2 than DSM20767 T . These overexpressed genes resulted in higher cytotoxicity and an increased immune response (i.e., TNF‐α, IL‐1β, TLR1 and INF‐γ) in the ASK cell line. This response was significantly higher against bacteria grown under iron‐limited conditions, especially H‐2. These observations indicate that iron‐acquisition mechanisms are possibly highly related to the virulence and pathogenic capacity of R. salmoninarum . In conclusion, treatments that block iron‐uptake mechanisms or siderophore synthesis are attractive therapeutic approaches for treating R. salmoninarum , which causes significant aquaculture losses.