Generation and characterization of a monoclonal antibody against FGFR3 that protects mice from BoNT/A

Botulinum neurotoxin serotype A (BoNT/A) can cause flaccid paralysis of muscles, an illness fatal to human, by entering neurons and blocking neurotransmitter release. The process was mediated by three receptors. A specific monoclonal antibody anti-D23, designated as ML419, targeting the ectodomain (D23) of fibroblast growth factor receptor 3 (FGFR3), one of the three receptors, was screened and capable of disturbing the recognition of BoNT/A and FGFR3. ML419 was screened from 14 stable positive hybridoma cell lines, and was subcloned, sequenced, and classified as IgG2a(κ) subclass. ML419 binds the D23 domain of FGFR3 with high affinity (K_D∼0.26 nM), and prevents the BoNT/A from entering Neuro-2a cells effectively. In vivo data showed that, 200 μg of ML419 could completely protect all the mice against with 5 MLD₅₀ BoNT/A, while 100 μg of ML419 could protected 60% of the mice. Collectively, our results indicated that ML419 served as a good candidate for further development of therapeutics for BoNT/A.