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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATION OF NUTRITIONAL, GENETIC AND PHYSIOLOGICAL APPROACHES TO IMPROVE PRODUCTION EFFICIENCY OF RAINBOW TROUT Title: Quantitative Expression of Immunological Factors in Rainbow Trout (Oncorhynchus Mykiss) after Infection with Either Flavobacterium Psychrophilum, Aeromonas Salmonicida, Or Infectious Hematopietic Necrosis Virus (Ihnv)

Authors
item Overturf, Kenneth
item Lapatra, Scott - CLEAR SPRINGS FOODS, BUHL

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2006
Publication Date: April 6, 2006
Citation: Overturf, K.E., Lapatra, S. 2006. Quantitative expression of immunological factors in rainbow trout (oncorhynchus mykiss) after infection with either flavobacterium psychrophilum, aeromonas salmonicida, or infectious hematopietic necrosis virus (ihnv). Journal of Fish Diseases. 29:215-224.

Interpretive Summary: To further enhance our understanding of immunological health in rainbow trout during stress or after infection with disease organisms, a molecular assay was developed. Separate groups of rainbow trout were infected with either of three microorganisms known to cause disease in rainbow trout. Each disease organism was given to experimental groups of rainbow trout at three different doses and samples from infected and mock infected fish were taken after infection. Ten fish were sampled at each time point for individual sections of liver, spleen and head kidney. Organ specimens from 5 of the fish were used to reisolate and quantitate the disease organism at the time the samples were taken. Trout genetic material was extracted from the organs of the remaining 5 animals. Using a newly developed molecular assay the genetic material from these organs was examined for the level of several different immune factors. Infection with one of the disease organisms produced a much greater change in expression level of all the immunological related factors examined in this study. The same disease organism also elicited the best dose response profile which was typically seen at 5 days post infection for the immune factors examined. Infection with the other two disease microorganisms showed elevated but variable expression levels for several of the genes tested.

Technical Abstract: To further enhance our understanding of immunological gene expression in rainbow trout (Oncorhynchus mykiss) during stress or after infection with naturally occurring pathogens, a series of probes and primers were developed for the quantification of immune factors. Separate groups of specific-pathogen-free rainbow trout were infected with either Flavobacterium psychrophilum, Aeromonas salmonicida, or infectious hematopoetic necrosis virus (IHNV). Each pathogen was dosed at three different concentrations and samples from infected and mock infected fish were taken at either 1 or 5 d after infection. Ten fish were sampled at each time point for individual sections of liver, spleen and head kidney. Organ specimens from 5 of the fish were used to reisolate and quantitate the pathogen at the time the samples were taken. Total RNA was extracted from the organs of the remaining 5 animals. Using real-time polymerase chain reaction (PCR) with fluorescent labeled probes the RNA from these organs was examined for the level of expression of the following immunological factors including an interferon related protein (MX-1), interleukin 8 (IL-8), the cytotoxic T-cell marker CD-8, and complement factor C-3 (C-3). They were also measured for the level of B-actin which was used as a standardization control for cellular RNA expression. Infection with IHNV produced the greatest change in expression level of all the immunological related factors examined in this study. IHNV elicited the best dose response profile which was typically seen at 5 days post infection for MX-1, C-3, IL-8 and CD-8. Infection with A. salmonicida and F. psychrophylum showed elevated but variable expression levels for several of the genes tested.

Last Modified: 10/20/2014
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