These data demonstrate that this combination of M2 and M4 is promising in terms of a foundation for new human therapeutics for BoNT/B intoxication. Keywords: and related species cause botulism, a neuroparalytic disease with high mortality [1,2]. BoNT/B1, BoNT/B2, and BoNT/B6. These data demonstrate that the combination of M2 and M4 is usually promising in terms of a foundation for new human therapeutics for BoNT/B intoxication. Keywords: and related species cause botulism, a neuroparalytic disease with high mortality [1,2]. BoNTs have been classified as category A brokers by the Centers of Disease Control and Prevention (CDC) and are listed among the six brokers at highest risk of being used as bioweapons [3]. Originally, seven serotypes, designated A to G, have been identified, and four of these, namely A, B, E, and F, cause human botulism [2]. Additionally, BoNT/DC, which is considered a mosaic toxin between BoNT/D and BoNT/C, has been reported [4,5]. Recently, BoNT/H was reported [6,7], and subsequent studies have described that this toxin is usually a hybrid-toxin of BoNT/A1 and BoNT/F5 [8,9,10] and that its light chain and N-terminal of Hydroxyflutamide (Hydroxyniphtholide) its heavy chain are immunologically unique [11,12]. More recently, the novel serotype BoNT/X [13] Hydroxyflutamide (Hydroxyniphtholide) and BoNT-like toxin, BoNT/Wo [14] and BoNT/En (BoNT/J) [15,16], were also reported [17]. Each BoNT is usually Hydroxyflutamide (Hydroxyniphtholide) synthesized as a single polypeptide chain (150 kDa) that is proteolytically activated by cleavage into a light chain (L chain, 50 kDa) and a heavy chain (H chain, 100 kDa), which are linked by a disulfide bond [1]. The L chain acts as a zinc metalloprotease. The H chain consists of two functionally distinct regions: the C-terminal, or receptor-binding, domain name (HC), and the N-terminal, or translocation, domain name (HN). Food-borne and infant botulism are the primary forms of human botulism [18], and are caused by intestinal absorption of BoNT. BoNT in the gastrointestinal lumen crosses the intestinal barrier [19], enters the blood stream, and reaches the neuromuscular junction. There, BoNT binds via HC to the receptors present on presynaptic nerve terminals. BoNT/A, BoNT/D, BoNT/E, and BoNT/F bind to synaptic vesicle protein 2 (SV2) and polysialogangliosides [20,21,22], whereas BoNT/B and Hydroxyflutamide (Hydroxyniphtholide) BoNT/G bind to synaptotagmin and polysialogangliosides [23,24]; all serotypes subsequently enter neuronal cells by endocytosis. In the acidified synaptic vesicles, HN induces translocation of the L chain into the cytosol [25,26,27]. The metalloprotease domain name of the L chain cleaves the soluble = 5 per group. (B) Neutralization of BoNT/B1 with two combinations of CLG4B HuMAbs. A dose of 10 i.p. LD50 of BoNT/B1 was incubated with a mixture of HuMAbs (5.0 g each) and administered by i.p. injection into mice. Control mice (Cnt) were treated with PBS instead of HuMAbs. Mice were observed for morbidity and mortality for 2 weeks. Cnt, = 10 per group, M2+M4, = 5 per group, M2+S1, = 5 per group, M4+S1, = 5 per group. (C) Synergistic effect of M2+M4. A dose of 10 i.p. LD50 of BoNT/B1 was incubated with a M2 (0.5 g), M4 (0.5 g), or mixture of M2 and M4 (0.5 g each) and then administered by i.p. injection into mice. Control mice (Cnt) were treated with PBS instead of HuMAbs. Mice were observed for morbidity and mortality for 2 weeks. Cnt, = 12 per group, M2 0.5 g, = 6 per group, M4 0.5 g, = 6 per group, 0.5 g each, = 7 per group. (D) Neutralization of BoNT/B1 with M2+M4. A dose of 80 i.p. LD50 of BoNT/B1 was incubated with a mixture of HuMAbs (0.5 g each or 1.25 g each) and administered by i.p. injection into mice. Hydroxyflutamide (Hydroxyniphtholide) Control mice (Cnt) were treated with PBS instead of HuMAbs. Mice were observed for morbidity and mortality for.