Characterization of antibody titer and immunogenic feature of light chain of botulinum neurotoxin type A

The botulinum neurotoxins (BoNTs), the most toxic biological compounds, are known to cause muscle paralysis. These toxins are enzymatic properties which inhibit the release of the acetylcholine. The purposes of this study are the recombinant expression of light chain (LC) of botulinum toxin types A (rBoNT/A-LC) with high purity, the evaluation of its antibody titer yield and its immunogenicity, and finally the evaluation of in vitro reorganization of BoNT/A-holotoxin by produced antibody. BoNT/A light chain gene sequences were obtained from the NCBI genome database. After codon optimization of target gene to better express in E. coli, the target gene was ordered to be synthesized in pET-28a (+). E. coli BL21 (DE3) was transformed by the mentioned vector containing the gene. The expression process was performed in standard conditions. In order to express the recombinant protein in soluble form, optimization of host cell culture and expression process was performed. The protein was purified by affinity chromatography (Ni-NTA column) and was confirmed with specific antibodies. In this study, the highest expression of soluble protein was obtained at 0.5 mM IPTG, cell culture optical density of 0.5, and the induction time of 18 h at 18 °C. Western blot analysis confirmed the target protein. The results showed that rBoNT/A-LC was highly expressed in soluble form and highly purified using affinity chromatography. Immunology results showed that the immune mice with rBoNT/A-LC are able to endurance up to 100 LD50 of BoNT/A. The results also indicated that the produced antibodies can recognize up to 200 ng of BoNT/A-holotoxin.