Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2012
Publication Date: 3/5/2013
Citation: Li, C., Beck, B.H., Su, B., Terhune, J., Peatman, E. 2013. Early mucosal responses in blue catfish (Ictalurus furcatus) skin to Aeromonas hydrophila infection. Fish and Shellfish Immunology. 34(3):920-928. Interpretive Summary: The external mucosal surfaces of fish represent the first layer of immune protection against infection from disease-causing bacteria. Despite the obvious importance of the mucosal immune system in fish, the particular genetic events that determine sensitivity or resistance to bacterial disease remain unclear. Here, we examined the immune response in the skin of blue catfish after a laboratory infection with the disease-causing bacterium Aeromonas hydrophila. Using a molecular tool called a microarray, we were able to examine changes in the levels of immune related genes in healthy blue catfish versus those exposed to Aeromonas hydrophila. In exposed fish, we found large-scale changes in over 1100 different genes. We believe that many of these changes in gene expression may not serve to protect fish against disease, but instead, actually function to enhance the ability of Aeromonas hydrophila to adhere to and invade blue catfish. These findings greatly enhance our understanding of the mucosal immune system present in blue catfish. This new knowledge will function to reduce costly production losses associated with Aeromonas hydrophila outbreaks, which will benefit catfish farmers and consumers alike, in the form of improved economic returns and better catfish products.
Technical Abstract: Bacterial pathogens are well-equipped to detect, adhere to, and initiate infection in their finfish hosts. The mucosal surfaces of fish, such as the skin, function as the front line of defense against such bacterial insults that are routinely encountered in the aquatic environment. While recent progress has been made, and despite the obvious importance of mucosal surfaces, the precise molecular events that occur soon after encountering bacterial pathogens remain unclear. Indeed, these early events are critical in mounting appropriate responses that ultimately determine host survival or death. In the present study, we investigated the transcriptional consequences of a virulent Aeromonas hydrophila challenge in the skin of blue catfish, Ictalurus furcatus. We utilized an 8×60K Agilent microarray to examine gene expression profiles at key early timepoints following challenge (2 h, 12 h, and 24 h). A total of 1155 unique genes were significantly altered during at least one timepoint. We observed dysregulation in a number of genes involved in diverse pathways including those involved in antioxidant responses, apoptosis, cytoskeletal rearrangement, immunity, and extracellular matrix protein diversity and regulation. Taken together, A. hydrophila coordinately modulates mucosal factors across numerous cellular pathways in a manner predicted to enhance its ability to adhere to and infect the blue catfish host.