Production and Purification of Polyclonal Antibodies against Diphtheria Toxin

Abstract

Diphtheria is a fatal disease caused by exotoxin of <em>Corynebacterium diphtheria</em>. This toxin consists of two chains, catalytic chain (A) and binding (B) chain. By binding chain (B), the toxin binds to its receptor on numerous body cells such as myocardial, kidney and peripheral nerve cells. After entering, catalytic chain (A) inhibits protein synthesis and finally can cause cell death. At this time, the toxoid form of diphtheria toxin is used as vaccine. The aim of this study was the immunological analysis of the mutated synthetic catalytic subunit of diphtheria toxin in laboratory animals as a vaccine candidate, in addition to polyclonal antibody production and purification against diphtheria toxin. For this purpose the Dtx recombinant protein (with two mutant: A158G and G52E) was expressed using pET28a/DtxA plasmid in <em>E. coli</em> Bl21DE3 host. Then, recombinant protein, as a candidate vaccine, was extracted and purified. After evaluating and confirming the protein by SDS-PAGE and western blotting, immunization carried out in laboratory animals. Finally, followed by antibody titration by ELISA, antibody purification performed as well.The mutated recombinant protein prepared from an optimized expression was extracted and purified. Then, this protein was confirmed by SDS-PAGE and western blotting. ELISA results showed a satisfactory immunization of animals by this protein. Polyclonal antibody production and purification against diphtheria toxin was performed by G protein column and confirmed by ELISA. ELISA results showed a high titer of polyclonal antibody against diphtheria toxin in animal's serum after immunization by recombinant DTx protein.