Croatian Journal of Fisheries (Oct 2012)
VACCINATION OF HYBRID STRIPED BASS: GROWTH, IMMUNE REACTION AND GENE EXPRESSION
Abstract
Hybrid striped bass (42.6+4.9 g wet wt; 139.3+6.1 mm length), were randomly stocked into one of 6 tanks (n=6 tank-1) of a custom designed, recirculating life support system (RLSS). Water quality was as follows: DO2 (6.50.6 mg l-1), pH (7.70.5), TAN (0.06-1.31 mg l-1), nitrite (0.06-0.60 mg l-1) and nitrate (2.0-32.1 mg l-1), salinity 5 ppt, temperature 28±1 oC. A 12:12 photophase:scotophase was used, with a 30 min. dusk-dawn dimming of lights. Fish were fed at 4% body wt d-1 as two separate feedings (08.00 and 16.00 h). Dietary crude protein and lipid levels were 40% and 10% respectively. Tanks were randomly paired and fish either left untreated, vaccinated, or sham injected. The vaccine employed was an experimental formalin killed Streptococcus iniae oil-in-water adjuvanted bacterin. Fish were weighed and measured bimonthly for 8 wk with group weights being employed to adjust feeding rates. At trial termination, all animals were weighed and measured, and their condition factor (CF) and feed conversion ratios (FCR) calculated. Visceral somatic (VSI) and hepatosomatic (HSI) indices and intraperitoneal fat (IPF) and muscle ratios (MR) were also assessed. Blood was taken from anaesthetized fish and hematocrit recorded. Blood was allowed to clot overnight at 5 oC after which serum protein levels were recorded and lysozyme activity measured. Livers were prepared for microarray evaluation using standard techniques using a Danio rerio genechip to assess global changes in gene expression. No differences were observed with respect to final weights, lengths, CF, FCR, or HSI although differences (P < 0.001) were determined for VSI, which was higher in control animals. Packed cell volume and serum protein levels were similar across groups (P > 0.05). Time-course of changes in serum lysozyme activity described an initial reduction in lysozyme activity followed by a rebounding in activity which peaked 25 days post-treatments. Evaluation of lysozyme activity among time-points revealed differences (P < 0.05) between 11 and 25 days post-vaccination. Examination of the hepatic microarray datasets revealed only four immune-discrete genes that were impacted 53-days following vaccination when compared against control fish. These included the up-regulated TCIRG1, or T-cell immune regulator 1 (P < 0.0467) and IL20RA, or interleukin 20 receptor alpha (P < 0.0433), and down-regulated cytokine inducible kinase, plk3 (P < 0.01) and mouse immune responsive protein, IRG1 (P < 0.01).
