Pellett Sabine, Tepp William H, Scherf Jacob M, Pier Christina L, Johnson Eric A
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
Toxicon. 2015 Jul;101:63-9. doi: 10.1016/j.toxicon.2015.04.015. Epub 2015 Apr 30.
Botulinum Neurotoxin type D (BoNT/D) causes periodic outbreaks of botulism in cattle and horses, but is rarely associated with human botulism. Previous studies have shown that humans responded poorly to peripheral injection of up to 10U of BoNT/D. Isolated human pyramidalis muscle preparations were resistant to BoNT/D, whereas isolated human intercostal muscle preparations responded to BoNT/D similarly as to other BoNT serotypes. In vitro data indicate that BoNT/D does not cleave human VAMP1 efficiently, and differential expression of the VAMP 1 and 2 isoforms may be responsible for the above observations. Here we examined sensitivity of cultured human neurons derived from human induced pluripotent stem cells to BoNT/D. Our data indicate that BoNT/D can enter and cleave VAMP 2 in human neurons, but at significantly lower efficiency than other BoNT serotypes. In addition, BoNT/D had a short duration of action in the cultured neurons, similar to that of BoNT/E. In vivo analyses indicated a slower time to death in mice, as well as a later onset and shorter duration of action than BoNT/A1. Finally, examination of BoNT/D activity in various rodent and human cell models resulted in dramatic differences in sensitivity, indicating a unique cell entry mechanism of BoNT/D.
D型肉毒杆菌神经毒素（BoNT/D）可引发牛和马的肉毒中毒周期性暴发，但很少与人类肉毒中毒相关。先前的研究表明，人类对外周注射高达10单位的BoNT/D反应不佳。分离出的人类锥状肌制剂对BoNT/D具有抗性，而分离出的人类肋间肌制剂对BoNT/D的反应与对其他BoNT血清型的反应相似。体外数据表明，BoNT/D不能有效地切割人类VAMP1，VAMP 1和2亚型的差异表达可能是上述观察结果的原因。在这里，我们检测了源自人类诱导多能干细胞的培养人类神经元对BoNT/D的敏感性。我们的数据表明，BoNT/D可以进入并切割人类神经元中的VAMP 2，但效率明显低于其他BoNT血清型。此外，BoNT/D在培养的神经元中的作用持续时间较短，与BoNT/E相似。体内分析表明，小鼠死亡时间较慢，且起效时间较晚，作用持续时间比BoNT/A1短。最后，在各种啮齿动物和人类细胞模型中检测BoNT/D活性，结果显示敏感性存在显著差异，这表明BoNT/D具有独特的细胞进入机制。
