Recombinant Botulinum Neurotoxin Hc Subunit (BoNT Hc) and Catalytically Inactive Clostridium botulinum Holoproteins (ciBoNT HPs) as Vaccine Candidates for the Prevention of Botulism

Abstract

There are few available medical countermeasures against botulism and the discontinuation of the pentavalent botulinum toxoid vaccine by the Centers for Disease Control and Prevention in 2011 has resulted in the need for a safe and effective prophylactic alternative. Advances in genetic engineering have resulted in subsequent vaccine efforts being primarily focused on the production of highly purified recombinant protein antigens representing one or more domains of the botulinum neurotoxin. Recombinant subunit vaccines based on the carboxy one-third of the toxin (Hc) developed in our lab against serotypes A-F have been shown to be safe and effective. However, in response to the identification of an ever increasing number of BoNT subtypes with significant amino acid heterogeneity, we have developed catalytically inactive BoNT holoproteins (ciBoNT HPs) in an attempt to elicit greater protective immunity to address these toxin variants. Here we report the production of ciBoNT/B1 HP, ciBoNT/C1 HP, ciBoNT/E1 HP and ciBoNT/F1 HP and compare the immunological and protective abilities of ciBoNT HPs and BoNT/A Hc, BoNT/B Hc, BoNT/C Hc, BoNT/E Hc and BoNT/F Hc vaccines when challenged with homologous and heterologous toxins. Our results suggest the ciBoNT HP vaccines exhibit superior potency after single vaccinations but multiple vaccinations with BoNT/Hc antigens resulted in increased survival rates at the toxin challenge levels used.

Immunogenicity of a Bivalent Non-Purified Recombinant Vaccine against Botulism in Cattle

“…Although these are effective on conferring protection, toxoids are time-consuming to prepare and are potentially hazardous during detoxification [ 11 ]. Therefore, the development of recombinant subunit vaccines has been evaluated as a mean of solving these problems [ 12 , 16 , 19 , 22 , 23 ].…”

Engineering of Botulinum Neurotoxins for Biomedical Applications

“…The most mature application of this technology is appears to be the application of atoxic BoNT derivatives to elicit protective immunity or generate antibodies. These recombinant atoxic BoNT derivates have been successfully produced in E. coli , C. botulinum , yeast and insect cell culture-based expression systems [ 43 , 44 , 51 , 52 ]. The catalytically inert BoNTs have been demonstrated to have significantly reduced toxicity ( Table 1 ) that is far above the minimal therapeutic doses required as effective vaccines.…”

“…Webb reported the use of Pichia pastoris codon-optimized, full length open reading frames (ORFs) encoding BoNT/A1, /B1, /C1, and /E1. These catalytically inactive BoNTs (ciBoNTs) were engineered with neutralizing mutations in the conserved LC active site HEXXH motif in which histidine and glutamic acid moieties were substituted with non-reactive alanine residues ( Table 1 ) [ 43 , 44 ]. The ciBoNT HPs were purified with a combination of ion exchange (IEC) and hydrophobic interaction chromatography (HIC) techniques, employing no affinity purification tags.…”

Confronting the threat of bioterrorism: realities, challenges, and defensive strategies

“…New recombinant botulism vaccines are being developed, in addition to vaccines against glanders and Rift Valley fever. [117][118][119] Efforts are ongoing to greatly shorten the time required to develop and produce new vaccines and other immune approaches. Improved technologies are important for rapid scale-up and production of new treatment regimens, particularly following an attack with a contagious agent.…”