The effect of pH on recombinant C-terminal domain of Botulinum Neurotoxin type E (rBoNT/E-HCC)

Recombinant proteins are tending to be the most favorable vaccine-candidates against botulism. Recombinant Carboxy-terminal of botulinum neurotoxin serotype E (rBoNT/E-HCC) has been introduced as an efficient vaccine against botulism type E. In this report, we made an effort to investigate the effect of different pH on protein structure to assess if rBoNT/E-HCC could be used as a vaccine for oral administration. Initially, rBoNT/E-HCC was expressed and purified. Structural changes of rBoNT/E-HCC at several pH conditions were studied by various techniques including circular dichroism (CD), fluorescence, aggregation and UV-Vis spectroscopy. The results showed the more compact and more stable structure for rBoNT/E-HCC at acidic pH, and loosely folded structure at alkaline pH. Our finding as the first step of rBoNT/E-HCC evaluation, hopefully introduce it as a suitable vaccine candidate for oral administration.