Immunization with a novel Clostridium perfringens epsilon toxin mutant rETX(Y196E)-C confers strong protection in mice

Epsilon toxin (ETX) is produced by toxinotypes B and D of Clostridium perfringens. It can induce lethal enterotoxemia in domestic animals, mainly in sheep, goats and cattle, causing serious economic losses to global animal husbandry. In this study, a novel and stable epsilon toxin mutant rETX(Y196E)-C, obtained by substituting the 196th tyrosine (Y196) with glutamic acid (E) and introducing of 23 amino acids long C-terminal peptide, was determined as a promising recombinant vaccine candidate against enterotoxemia. After the third vaccination, the antibody titers against recombinant wild type (rETX) could reach 1:10(5) in each immunized group, and the mice were completely protected from 100 × LD(50) (50% lethal dose) of rETX challenge. The mice in 15 μg subcutaneously immunized group fully survived at the dose of 500 × LD(50) of rETX challenge and 80% of mice survived at 180 μg (1000 × LD(50)) of rETX administration. In vitro, immune sera from 15 μg subcutaneously immunized group could completely protect MDCK cells from 16 × CT(50) (50% lethal dose of cells) of rETX challenge and protect against 10 × LD(50) dose (1.8 μg) of rETX challenge in mice. These data suggest that recombinant protein rETX(Y196E)-C is a potential vaccine candidate for future applied researches.