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Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/13/2012 Publication Date: 3/15/2012 Citation: Evenhuis, J., Cleveland, B.M. 2012. Modulation of rainbow trout (Oncorhynchus mykiss) intestinal immune gene expression following bacterial challenge. Veterinary Immunology and Immunopathology. 146(1):8-17. Interpretive Summary: The intestinal immune response to bacterial challenges is poorly understood in rainbow trout. Two challenge model systems, one which introduces infection by immersion in a solution containing bacteria and the other by direct injection of bacteria, were used to observe changes in the expression of important immune genes in the lower intestine. Several immune genes representing both innate and acquired responses showed increases in expression for both types of challenges. This demonstrates that significant changes in immune gene expression occur in the lower intestine in response to two different bacterial infection pathways. Therefore, understanding the immune response of this tissue may be important for developing methods for disease prevention. Technical Abstract: The mucosal immune system of fish is still poorly understood, and defined models for studying natural host-pathogen interaction are lacking. The objective of this study was to evaluate different challenge paradigms and pathogens to examine the magnitude of change in intestinal immune gene expression. Rainbow trout were exposed by immersion to Yersinia ruckeri or by intraperitoneal injection with Flavobacterium psychrophilum. At 3, 9, or 10 days post-challenge, pathogen load was quantified by plate count and intestinal tissue was removed and immune gene expression measured by real-time PCR. In general, the magnitude of infection was correlated with change in immune gene transcript abundance. We found that message for the innate immune molecules, SAA, IL-8, INF-gamma and TNF-alpha, as well as the message for IgM, were up-regulated in intestinal tissue in both challenge paradigms. A >250-fold increase was observed in SAA and 20-fold increase of IL-8 gene transcript abundance occurred on day 10 following challenge with F. psychrophilum. Within individual fish, there was a positive correlation between bacteria load in the spleen and the increase of immune gene message between 3 to 10 days post-infection. These findings demonstrate that measurable changes in immune gene expression occur in the lower intestine of rainbow trout following bath challenge with Y. ruckeri or injection challenge with F. psychrophilum. |
