|FAN, YONGFENG - University Of California|
|BARASH, JASON - California Department Of Public Health|
|CONRAD, FRASER - University Of California|
|LOU, JIANLONG - University Of California|
|Cheng, Luisa Wai Wai|
|ARNON, STEPHEN - California Department Of Health|
|MARKS, JAMES - University Of California|
Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2019
Publication Date: 12/20/2019
Citation: Fan, Y., Barash, J.R., Conrad, F., Lou, J., Tam, C.C., Cheng, L.W., Arnon, S.S., Marks, J.D. 2019. The novel Clostridial neurotoxin produced by strain IBCA10-7060 is immunologically equivalent to BoNT/HA. Toxins. 12(1):9. https://doi.org/10.3390/toxins12010009.
Interpretive Summary: Botulinum neurotoxins (BoNTs) are some of the most lethal bacterial toxins. Seven serotypes, BoNT/A-G, have been identified via DNA sequence and antibody neutralization. In 2014, a new chimeric serotype was reported and named BoNT/HA. However, this new H serotype displayed properties similar to BoNT serotypes F and A. In this study, new human monoclonal antibodies were developed against this toxin. The antibodies specifically recognized BoNT/H and no other serotypes indicating that BoNT/H is indeed a new serotype. Identification and determination of a new BoNT serotype has significant implications for future biosafety risk assessments and development of countermeasures.
Technical Abstract: Background: Botulinum neurotoxins (BoNTs) comprise seven agreed on serotypes, A through G. In 2014, a novel chimeric neurotoxin produced by strain IBCA10-7060 was reported as BoNT/H, with subsequent names of BoNT/FA or BoNT/HA based on sequence homology and neutralization studies. The purpose of this study was to define the immunologic identity of the novel BoNT. Methods: BoNT/H specific mAbs were generated by using antibody repertoire cloning and yeast display after immunization with either BoNT/H LC-HN or BoNT/F LC-HN. Results: 21 unique BoNT/H LC-HN specific mAbs were obtained; 15 from the BoNT/H LC-HN immunized library (KD 0.78 nM to 182 nM) and six from the BoNT/F-immunized libraries (KD 20.5 nM to 1490 nM). 15 of 21 mAbs also bound catalytically inactive BoNT/H (BoNT/Hi) holotoxin. The mAbs bound nine non-overlapping epitopes on the BoNT/H LC-HN. None of the mAbs showed binding to BoNT serotypes A-G, nor did they bind any of the seven subtypes of BoNT/F, except for one LC-specific mAb that weakly bound BoNT/F5. Conclusions: The results, combined with the chimeric structure and neutralization by anti-A, but not anti-F antitoxin indicate that immunologically the novel BoNT is BoNT/HA. This determination has significant implications for existing countermeasures and potential vulnerabilities.