ARS | Publication request: Intestinal immune gene response to bacterial challenge in rainbow trout (Oncorhynchus mykiss)

Submitted to: Annual Eastern Fish Health Workshop
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2011
Publication Date: March 28, 2011
Citation: Evenhuis, J., Cleveland, B.M. 2011. Intestinal immune gene response to bacterial challenge in rainbow trout (Oncorhynchus mykiss) [abstract]. Annual Eastern Fish Health Workshop. Paper No. 001.

Technical Abstract: The mucosal immune system of fish is poorly understood and defined models for studying this system 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 RT-PCR. In general, the magnitude of infection was positively correlated with the amplitude of change in immune gene transcript abundance. We found that innate immune response genes SAA, IL-8, INF-g and TNF-a, as well as the acquired immune gene IgM, were all up-regulated in intestinal tissue in both challenge paradigms. A 500-fold increase was observed in SAA transcript abundance and 20-fold increase of IL-8 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 transcript between 3 through 10 days post-infection. These findings demonstrate that measurable changes in immune gene expression occur in the lower intestine of rainbow trout following either bath challenge with Y. ruckeri or injection challenge with F. psychrophilum.