Characterization of a highly neutralizing single monoclonal antibody to botulinum neurotoxin type A

Compared to conventional antisera strategies, monoclonal antibodies (mAbs) represent an alternative and safer way treat botulism, a fatal flaccid paralysis due botulinum neurotoxins (BoNTs). In addition, mAbs offer the advantage be produced in reproducible manner. We previously identified unique potent mouse mAb (TA12) targeting BoNT/A1 with high affinity neutralizing activity. this study, we characterized molecular basis of TA12 neutralization by combining Hydrogen/Deuterium eXchange Mass Spectrometry (HDX-MS) site-directed mutagenesis functional studies. found that recognizes conformational epitope located at interface between HCN HCC subdomains receptor-binding domain (HC ). The TA12-binding shares common structural features ciA-C2 VHH lies on face opposite recognized ciA-C2- CR1/CR2-neutralizing mAbs. single substitution N1006 was sufficient affect binding HC confirming position epitope. further uncovered overlaps BoNT/A1-binding site for both neuronal cell surface receptor synaptic vesicle glycoprotein 2 isoform C (SV2C) GT1b ganglioside. Hence, potently blocks entry into neurons interfering simultaneously SV2C lower extent GT1b. Our study reveals mechanism emphasizes potential using treatment botulism type A.