JIANG, Qiong*; GOETZ, Frederick W.; PHILLIPS, Ruth; PLACE, Allen R.; Center of Marine Biotechnology, Baltimore, MD; Marine Biological Laboratory, Program in Scientific Aquaculture, Woods Hole, MA 02543; Washington State University, Vancouver, WA ; Center of Marine Biotechnology, Baltimore, MD: Chitinase- A New Member In The Fish Innate Immunity Repertoires

Chitin is an unbranched homopolymer of &beta-(1, 4) linked N-acetyl glucosamine (NAG) residues and is the second most abundant carbon polymer, after cellulose, on earth. Chitin and its deacetylated derivative, chitosan, have been shown to possess immunostimulating properties in plants, mammals, and fish. Specifically, chitin and chitosan enhance T-cell functionality, natural killer (NK) cell activity, and interferon (IFN) production from activated NK cells. In addition, they induce macrophages to produce interleukins (IL-1&beta, IL-12 and IL-18), tumor necrosis factor (TNF-&alpha), macrophage stimulating factor (MAF) and colony-stimulating factor (CSF). Vertebrates possess an enzyme in gastric tissue that specifically recognizes and hydrolyses chitin-releasing dimers from the nonreducing end of the polymer. We have purified and cloned the gastric chitinase (Onmy-CHIT.01) from rainbow trout (Onchorhynchus mykiss) and found a second form locating in myeloid cells of rainbow trout. The second form, Onmy-CHIT.02, displays 58% identity with the gastric ortholog and possesses all the characteristic protein motifs found in the18 glycosyl hydrolyase family (E.C 3.2.1.14), which is secreted upon stimulation. The tissue distribution of the two transcripts as assessed by quantitative real-time PCR, showed that the gastric chitinase was expressed exclusively in the stomach while the myeloid cell chitinase was found predominantly in the head kidney, kidney and spleen. We also screened a rainbow trout BAC library and found both genes located on chromosome 17 of the rainbow trout. The gene regulatory mechanisms are currently under investigation.