A non-toxic recombinant bivalent chimeric protein rETXCSA as a potential vaccine candidate against enterotoxemia and braxy

Clostridium perfringens epsilon toxin (ETX) and Clostridium septicum alpha toxin (CSA) are lethal and necrotizing toxins, which play key roles in enterotoxemia and braxy of ruminants, respectively. In the present study, we synthesized a bivalent chimeric protein rETXCSA comprising ETX (Y30A/H106P/Y196A) and CSA (C86L/N296A/H301A/W342A and a deletion of residues 212 to 222). Compared with recombinant ETX and recombinant CSA, rETXCSA showed no cytotoxicity in Madin-Darby Canine Kidney cells and was not fatal to mice. Moreover, rETXCSA could protect immunized mice against 10 × mouse LD of crude ETX or 3 × mouse LD of crude CSA without obvious histopathologic difference. Most importantly, both rabbits and sheep immunized with rETXCSA produced high titers of neutralizing antibody which protected the animals against the challenge with crude ETX or crude CSA. These data suggest that genetically detoxified rETXCSA is a potential subunit vaccine candidate against enterotoxemia and braxy.