Purpose: Tilapia is an important agricultural fish that has been plagued by Group B streptococcus (GBS)
infections in recent years, some of them severe. It is well-known that surface immunogenicity protein
(Sip) is an effective vaccine against GBS.
Experimental design: Since Sip was not expressed in either E. coli BL21 or E. coli Rosetta, we removed
the N-terminal signal peptide and LysM of the virus to produce purified truncated Sip (tSip1), which
multiplied easily in an E. coli host. The antibody’s ability to recognize and combine with GBS was determined
by Western-blot and specific staining in vitro. The relative percentage of survival (RPS), antibody
titers, bacterial recovery, and pathologic morphology were monitored in vivo to evaluate the immune
effects. Freund’s incomplete adjuvant (FIA) plus tSip and aluminum hydroxide gel (AH) plus tSip were
also evaluated.
Results: It revealed that tSip mixed with FIA was an effective vaccine against GBS in tilapia, while AH is
toxic to tilapia.