Genetically modified Shiga toxin 2e (Stx2e) producing Escherichia coli is a vaccine candidate for porcine edema disease

Porcine edema disease (ED) is an enterotoxaemia in pigs after weaning, caus ed by Shiga toxin 2e (Stx2e) producing Escherichia coli. Recently in Japan, outbreaks of ED are re-emerging in pig production. In this study we constr ucted a mutant that retained immunogenicity but lost Vero cell cytotoxicity , which produced genetically modified toxin (Stx2e*) by replacing glutamate with glutamine at position 167 and arginine with leucine at position 170 o f the A subunit. The stx(2e)* gene was replaced with the stx(2e) gene of th e wild type virulent strain by homologous recombination. As the parent wild strain was pathogenic to pigs but the mutant was not, the mutant named as YT106 was given to the pigs to examine its protective immunity against ED. All 20 pigs vaccinated with YT106 survived, but only eight of the 20 non-va ccinated pigs survived after the challenge with a wild strain. Also, the ei ght pigs that survived had decreased rates of gain relative to those of the controls. Blood IgG and intestinal IgA titres increased 3.3 and 1.6 times more than the control, respectively, showing that YT106 might be a good can didate of a live attenuated vaccine strain to protect against ED. (C) 2001 Academic Press.