Immunization with a nontoxic naturally occurring Clostridium perfringens alpha toxin induces neutralizing antibodies in rabbits.

Clostridium perfringens alpha toxin, encoded by plc gene, has been implicated in gas gangrene, a life threatening infection. Vaccination is considered one of the best solutions against Clostridium infections. Although studies have identified many low quality clostridial vaccines, the use of recombinant proteins has been considered a promising alternative. Previously, a naturally occurring alpha toxin isoform (αAV1b) was identified with a mutation at residue 11 (His/Tyr), which can affect its enzymatic activity. The aim of the present study was to evaluate whether the mutation in the αAV1b isoform could result in an inactive toxin and was able to induce protection against the native alpha toxin. We used recombinant protein techniques to determine whether this mutation in αAV1b could result in an inactive toxin compared to the active isoform, αZ23. Rabbits were immunized with the recombinant toxins (αAV1b and αZ23) and with native alpha toxin. αAV1b showed no enzymatic and hemolytic activities. ELISA titration assays showed a high titer of both anti-recombinant toxin (anti-rec-αAV1b and anti-rec-αZ23) antibodies against the native alpha toxin. The alpha antitoxin titer detected in the rabbits' serum pool was 24.0 IU/mL for both recombinant toxins. These results demonstrate that the inactive naturally mutated αAV1b is able to induce an immune response, and suggest it can be considered as a target for the development of a commercial vaccine against C. perfringens alpha toxin.

Molecular cloning and functional characterization of recombinant Loxtox from Loxosceles similis venom.

Loxoscelism is a recognized public health problem in Brazil, but the venom from Loxosceles similis, which is widespread in Brazil due to its adaptability to the urban environment, remains poorly characterized. Loxtox is a family of phospholipase D enzymes (PLDs), which are the major components of Loxosceles venom and are responsible for the clinical effects of loxoscelism. Loxtox toxins correspond to 15% of L. similis venom gland transcripts, but the Loxtox family of L. similis has yet to be fully described. In this study, we cloned and functionally characterized recLoxtox s1A and recLoxtox s11A. These recombinant toxins exhibited different in vitro activities depending on pH, and recLoxtox s1A had more intense effects on rabbit skin than did recLoxtox s11A in vivo. Both recombinant toxins were used in immunization protocols, and mapping of their epitopes revealed different immunological reactions for the produced immune serums. Additionally, polyclonal antibodies raised against recLoxtox s1A had greater capacity to significantly reduce the in vitro and in vivo effects of L. similis venom. In summary, we obtained and characterized two novel Loxtox isoforms from L. similis venom, which may be valuable biotechnological and immunological tools against loxoscelism.