Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2012
Publication Date: 4/17/2013
Citation: Li, C., Wang, R., Su, B., Luo, Y., Terhune, J., Beck, B.H., Peatman, E. 2013. Evasion of mucosal defenses during Aeromonas hydrophila infection of channel catfish (Ictalurus punctatus) skin. Developmental and Comparative Immunology. 39(4):447-455. Interpretive Summary: The exterior surfaces of fish such as the skin and gill are rich with mucus. These mucosal surfaces make up the first layer of protection against infection from bacteria. Despite their importance little is known about the immune system in these surfaces, particularly at the genetic level. In the present study, we examined the immune response in the skin of channel catfish after exposure to a lethal bacterium called Aeromonas hydrophila. We used a molecular tool called a microarray that allowed for the detection of changes in the levels of immune related genes in healthy fish versus those exposed to Aeromonas hydrophila. In infected fish, we found robust changes in over 2000 different genes. From these data, we believe that many of the gene expression patterns observed are not protective responses, but instead, actually serve to enhance the ability of Aeromonas hydrophila to infect channel catfish. This research represents a novel approach to addressing one of the major disease issues affecting cultured catfish. Catfish producers and consumers could greatly benefit from the economic returns associated with reducing costly production losses due to Aeromonas hydrophila outbreaks.
Technical Abstract: The mucosal surfaces of fish serve as the first-line of defense against the myriad of aquatic pathogens present in the aquatic environment. The immune repertoire functioning at these interfaces is still poorly understood. The skin, in particular, must process signals from several fronts, sensing and integrating environmental, nutritional, social, and health cues. Pathogen invasion can disrupt this delicate homeostasis with profound impacts on signaling throughout the organism. Here, we investigated the transcriptional effects of virulent A. hydrophila infection in channel catfish skin, Ictalurus punctatus. We utilized an 8X60K Agilent microarray to examine gene expression profiles at critical early timepoints following challenge—2 h, 8 h, and 12 h. Expression of a total of 2,168 unique genes was significantly perturbed during at least one timepoint. We observed dysregulation of a number of genes involved in antioxidant, cytoskeletal, immune, junctional, and nervous system pathways. In particular, A. hydrophila infection rapidly altered a number potentially critical lectins, chemokines, interleukins, and other mucosal factors in a manner predicted to enhance its ability to adhere and invade the catfish host.