Immune-relevant (including acute phase) genes identified in the livers of rainbow trout, Oncorhynchus mykiss, by means of suppression subtractive hybridization

To develop tools for analysis of the acute phase response, we used suppression subtractive hybridization of cDNAs from the livers of trout in an unchallenged state and in the course of a response to injection with a Vibrio bacterin emulsified in Freund's Incomplete Adjuvant. The resulting cDNA library contains 300-600bp long fragments of 25 or more immune-relevant genes. Fifteen were previously unreported for salmonids, and 12 were not known from any fish species. Known acute phase proteins include serum amyloid A, transferrin and precerebellin-like protein; trout C-polysaccharide-binding protein 1 is probably also an acute phase protein. Components of both the complement system (n=5) and the clotting system (n=3), as well as lectins, various binding proteins, a putative antibacterial peptide, a chemotaxin, an anti-oxidant enzyme, as well as some likely cell-surface receptors and metabolic and lysosomal enzymes are represented in the library. One clone closely resembles a group of Toll-like receptors, including the human IL-1 receptor. Three cDNAs appear to represent complete open reading frames.