Immunization with recombinant bivalent chimera r-Cpae confers protection against alpha toxin and enterotoxin of Clostridium perfringens type A in murine model

• A rationally designed structural chimera r-Cpae was assessed for protective efficacy.
• Mice immunized with r-Cpae elicited significant levels of systemic and mucosal immunity.
• Active immunization with r-Cpae provided protection against native toxin challenge.
• Anti-r-Cpae sera neutralized αC and CPE in in vitro toxin neutralization assays.
• Passive immunization with anti-r-Cpae sera protected mice from native toxins.

Clostridium perfringens type A, an anaerobic pathogen is the most potent cause of soft tissue infections like gas gangrene and enteric diseases like food poisoning and enteritis. The disease manifestations are mediated via two important exotoxins, viz. myonecrotic alpha toxin (αC) and enterotoxin (CPE). In the present study, we synthesized a bivalent chimeric protein r-Cpae comprising C-terminal binding regions of αC and CPE using structural vaccinology rationale and assessed its protective efficacy against both alpha toxin (αC) and enterotoxin (CPE) respectively, in murine model. Active immunization of mice with r-Cpae generated high circulating serum IgG (systemic), significantly increased intestinal mucosal s-IgA antibody titres and resulted in substantial protection to the immunized animals (100% and 75% survival) with reduced tissue morbidity when administered with 5 × LD100 doses of αC (intramuscular) and CPE (intra-gastric gavage) respectively. Mouse RBCs and Caco-2 cells incubated with a mixture of anti-r-Cpae antibodies and αC and CPE respectively, illustrated significantly higher protection against the respective toxins. Passive immunization of mice with a similar mixture resulted in 91–100% survival at the end of the 15 days observation period while mice immunized with a concoction of sham sera and respective toxins died within 2–3 days. This work demonstrates the efficacy of the rationally designed r-Cpae chimeric protein as a potential sub unit vaccine candidate against αC and CPE of C. perfringens type A toxemia.