Expression of Hc fragment from Clostridium botulinum neurotoxin serotype B in Escherichia coli and its use as a good immunogen.

A good immunogen was developed as an effective recombinant vaccine candidate that protected mice against botulinum neurotoxin serotype B (BoNT/B) intoxication. The Hc fragment of Clostridium botulinum neurotoxin type B (rBoNT/B-Hc) was cloned into the bacterial expression vector pQE-30, and the resulting vector was successfully expressed in the Escherichia coli M15 strain. The purified rBoNT/B-Hc protein was used to vaccinate mice and evaluate their survival against challenge with native BoNT/B. The mice that received three subcutaneous injections of rBoNT/B-Hc immunogen doses ranging from 0.25 to 6.25 μg mixed with Freund's adjuvant were completely protected against an intraperitoneal (i.p.) administration of 10,000 50% lethal doses (LD50) of BoNT/B. A dose response was observed in both the ELISA antibody titers and protective efficacy with increasing dose of immunogen. The work presented here demonstrates that the purified rBoNT/B-Hc was a highly effective immunogen and able to protect against a high-dose neurotoxin challenge.