[ODP-126] Characterization of neutralizing human antibody against botulinum neurotoxin type E
Botulinum neurotoxin serotype E (BoNT/E) is one of the major causes of human botulism, which is a life-threatening disease with flaccid paralysis of muscles. Recently we have developed a mouse monoclonal antibody (mE9-4) which can neutralize BoNT/E without any other antibodies. To develop antibody -based immunotherapies for human botulinum using this antibody, we introduced the complementary-determining region of mE9-4 to human antibody framework and obtained fully humanized mE9-4 (hmE9-4). hmE9-4 expressed by the Expi293 expression system exhibited the same level of binding activity against BoNT/E as the parental antibody, and it efficiently neutralized BoNT/E in a mouse bioassay (>4,000 LD50/mg antibody). Moreover, it blocked cleavage of SNAP-25 by BoNT/E in a mouse neuronal cell-based assay. Because hmE9-4 bound to the light chain (LC) of BoNT/E that contains protease domain, it could directly interfere with the catalytic activity of LC. To elucidate the mechanism of the unique neutralization activity of hmE9-4, identification of the binding epitope and structural analysis of the BoNT/E-hmE9-4 complex are now underway. The insights into the neutralization mechanisms of hmE9-4 gained by this study may potentially provide useful information to therapeutic strategies for other serotypes.
[非会員共同研究者：片平 じゅん（大府大・生命環境・細胞分子生物学）]