Fig. 6.

Protection by vaccine candidate BL21(DE3)/pETGA+pUTaBE in turbot against A. hydrophila challenge. The fish (30 fish in each group, divided into three parallel groups) were vaccinated i.p. with E. coli BL21(DE3)/pETGA+pUTaBE (10⁷ CFU per fish), E. coli BL21(DE3)/pETGA+pUTa (10⁷ CFU per fish), purified GAPDH antigen with an equal volume of Freund's complete adjuvant (Sigma) (20 μg per fish), or PBS as a control (0.1 ml per fish). Four weeks after immunization, the four groups were injected i.p. with wild-type A. hydrophila LSA34 (5.0 × 10⁷ CFU per fish). The significant difference and the relative percent survival (RPS) were calculated by using Fisher's exact test and the formula RPS = [1 − (% mortality in vaccinated fish/% mortality in control fish)] × 100, respectively.