Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2006
Publication Date: 7/1/2006
Citation: Wiens, G.D., Lapatra, S., Palti, Y., Rexroad III, C.E., Yao, J., Welch, T.J. 2006. Gene expression and cellular immune response of rainbow trout (Oncorhynchus mykiss) exposed to Yersinia ruckeri: A model system for understanding mechanisms of teleost protective immunity. 10th International Congress, International Society of Developmental and Comparative Immunology, July 1 - 6, 2006. Meeting Abstract. Page 249. Interpretive Summary:
Technical Abstract: The formalin-killed enteric redmouth bacterin is one of the most successful aquaculture vaccines developed, and millions of rainbow trout have been vaccinated each year since the 1950s. Cell-mediated immunity is important for vaccine efficacy; however, the molecular mechanisms of protection are poorly understood. In order to better define bacterial pathogenesis and the host response, a green fluorescent protein expressing strain of Y. ruckeri, YRNC10, was created. After bath or intra-peritoneal challenge, intracellular bacteria were detected in peripheral blood (1.6%), spleen (1.1%) and anterior kidney leukocytes (0.4%) by flow cytometry and fluorescence microscopy. In addition, persistence of viable Y. ruckeri within adherent spleen cells was observed in the presence of gentamicin, an antibiotic that is bactericidal for extracellular bacteria. Leukocyte redistribution within trout tissues was observed within 48 hr of challenge. The percentage of large, granular cells increased 3-fold in the spleen while they decreased 2-fold in the anterior kidney. To examine gene expression in these tissues, 6691 sequences were determined from a subtracted library. The most abundant transcripts found included acute phase serum amyloid protein A, lysozyme C, and the CD209-like protein. Real-time PCR identified increased TNFa1, INF-g, IL-1b2, and CXCd mRNA in the spleen and no change or decreased transcript abundance of TLR3 and TNFSF13b. Similarly, bath vaccination induced increases in TNFa1, IL-1b2, and CXCd mRNA in the spleen but not the skin indicating the generation of systemic immunity. In summary, Y. ruckeri has a tropism for lymphoid tissues and survives within phagocytic cells similar to mammalian pathogenic Yersinia spp. The Y. ruckeri-rainbow trout interaction is a robust system for defining mechanisms of protective immunity to a pathogen with an extracellular and putative intracellular phase of infection.