Fully Human Monoclonal Antibodies Effectively Neutralizing Botulinum Neurotoxin Serotype B.

Takuhiro Matsumura,Masahiro Yutani,Anariwa Du,Ryo Misaki,Sho Amatsu,Kazuyoshi Ikuta,Yukako Fujinaga,Kazuhito Fujiyama,Tomoko Kohda

doi:10.3390/toxins12050302

Abstract

Botulinum neurotoxin (BoNT) is the most potent natural toxin known. Of the seven BoNT serotypes (A to G), types A, B, E, and F cause human botulism. Treatment of human botulism requires the development of effective toxin-neutralizing antibodies without side effects such as serum sickness and anaphylaxis. In this study, we generated fully human monoclonal antibodies (HuMAbs) against serotype B BoNT (BoNT/B1) using a murine–human chimera fusion partner cell line named SPYMEG. Of these HuMAbs, M2, which specifically binds to the light chain of BoNT/B1, showed neutralization activity in a mouse bioassay (approximately 10 i.p. LD50/100 µg of antibody), and M4, which binds to the C-terminal of heavy chain, showed partial protection. The combination of two HuMAbs, M2 (1.25 µg) and M4 (1.25 µg), was able to completely neutralize BoNT/B1 (80 i.p. LD50) with a potency greater than 80 i.p. LD50/2.5 µg of antibodies, and was effective both prophylactically and therapeutically in the mouse model of botulism. Moreover, this combination showed broad neutralization activity against three type B subtypes, namely BoNT/B1, BoNT/B2, and BoNT/B6. These data demonstrate that the combination of M2 and M4 is promising in terms of a foundation for new human therapeutics for BoNT/B intoxication.

Highlights

Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum and related species cause botulism, a neuroparalytic disease with high mortality [1,2]
We found that M2 and S1 bound to the L chain of BoNT/B1, and M4 bound to the HC
Plasma antibody titers against BoNT/A1 or BoNT/B1 were measured by enzyme-linked immunosorbent assay (ELISA)

Summary

Introduction

Botulinum neurotoxins (BoNTs) produced by the anaerobic bacterium Clostridium botulinum and related species cause botulism, a neuroparalytic disease with high mortality [1,2]. BoNT/DC, which is considered a mosaic toxin between BoNT/D and BoNT/C, has been reported [4,5]. BoNT/H was reported [6,7], and subsequent studies have described that this toxin is a hybrid-toxin of BoNT/A1 and BoNT/F5 [8,9,10] and that its light chain and N-terminal of its heavy chain are immunologically unique [11,12]. The novel serotype BoNT/X [13] and BoNT-like toxin, BoNT/Wo [14] and BoNT/En (BoNT/J) [15,16], were reported [17]

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Results

Discussion

Conclusion