title: Botulinum neurotoxins and botulism: a novel therapeutic approach.
abstract: Specific treatment is not available for human botulism. Current remedial mainstay is the passive administration of polyclonal antibody to botulinum neurotoxin (BoNT) derived from heterologous species (immunized animal or mouse hybridoma) together with supportive and symptomatic management. The antibody works extracellularly, probably by blocking the binding of receptor binding (R) domain to the neuronal receptors; thus inhibiting cellular entry of the holo-BoNT. The antibody cannot neutralize the intracellular toxin. Moreover, a conventional antibody with relatively large molecular size (150 kDa) is not accessible to the enzymatic groove and, thus, cannot directly inhibit the BoNT zinc metalloprotease activity. Recently, a 15-20 kDa single domain antibody (V(H)H) that binds specifically to light chain of BoNT serotype A was produced from a humanized-camel VH/V(H)H phage display library. The V(H)H has high sequence homology (>80%) to the human VH and could block the enzymatic activity of the BoNT. Molecular docking revealed not only the interface binding between the V(H)H and the toxin but also an insertion of the V(H)H CDR3 into the toxin enzymatic pocket. It is envisaged that, by molecular linking the V(H)H to a cell penetrating peptide (CPP), the CPP-V(H)H fusion protein would be able to traverse the hydrophobic cell membrane into the cytoplasm and inhibit the intracellular BoNT. This presents a novel and safe immunotherapeutic strategy for botulism by using a cell penetrating, humanized-single domain antibody that inhibits the BoNT by means of a direct blockade of the groove of the menace enzyme.
authors: Laboratory for Research and Technology Development, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, 2 Prannok Road, Bangkok-noi, Bangkok 10700, Thailand. gskmu@hotmail.com
authors: Jeeraphong
authors: J
authors: Thanongsaksrikul
authors: Wanpen
authors: W
authors: Chaicumpa
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000627:therapeutic use*; D001904:Botulinum Antitoxin / Q000627:therapeutic use*; D001905:Botulinum Toxins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000276:immunology / Q000633:toxicity; D001906:Botulism / Q000188:drug therapy* / Q000276:immunology; D006801:Humans; D009498:Neurotoxins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000276:immunology / Q000633:toxicity; D061905:Single-Domain Antibodies / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D001904:Botulinum Antitoxin; D009498:Neurotoxins; D061905:Single-Domain Antibodies; D001905:Botulinum Toxins