Epitope regions in the heavy chain of Clostridium botulinum type E neurotoxin recognized by monoclonal antibodies

Seventeen monoclonal antibodies (MAbs) were previously established against the heavy chain (He) of botulinum type E neurotoxin in BALB/c mice immunized with the type E toroid, Five MAbs (LE15-5, LE34-6, EK19-7, EK21-4, and AE27-9) showed toxin-neutralizing activity in mice, Two of the five MAbs, EK19-7 and EK21-4, recognized the regions located at amino acid positions 731 to 787 and 811 to 897, respectively, One of the remaining three antibodies (LE34-6) reacted with the amino acid sequence VIKAIN, at amino acid positions 663 to 668, closed by the ion channel-forming domain, It is suggested that the ion channel-forming domain may also be associated with the blocking of acetylcholine release, Furthermore, the amino acid sequence YLTHMRD within 30 residues of the C-terminal region of the He component seemed to be recognized by LE15-5, It has been reported that the binding domain of the type E toxin is located on the C-terminal half of the He component, Therefore, the neutralizing activity of LE15-5 antibody may be attributed to its ability to block the binding of neurotoxin to the receptor of target cells.