Comparative evaluation of a vaccine candidate expressing enterotoxigenic Escherichia coli (ETEC) adhesins for colibacillosis with a commercial vaccine using a pig model

In this study, a comparative evaluation of a novel live vaccine candidate expressing enterotoxigenic Escherichia coli (ETEC) fimbriae and a commercial ETEC vaccine was carried out in suckling to weaned piglets. The E. coli K88ab, K88ac, K99, FasA and F41 fimbrial genes were individually inserted into an expression/secretion plasmid, pBP244. These plasmids were subsequently transfected into attenuated Salmonella, which were used as the vaccine candidate. Eighteen pregnant sows and 107 of their piglets were used in this comparative study. All the vaccinated groups of sows and piglets exhibited significantly increased antibody levels relative to specific antigens when compared with those in the unimmunized control. The experimental piglets with the vaccine candidate did not experience diarrhea following challenge with the virulent ETEC strains. However, diarrhea was observed in 36.8% of the piglets in the group immunized with the commercial vaccine and in 50% of the control group after challenge with the ETEC strains. These findings indicate that immunization of sows with the candidate vaccine can effectively protect their young pigs against colibacillosis.