Targeted intracellular delivery of therapeutic proteins remains a significant unmet challenge in biotechnology. A promising approach is to leverage the intrinsic capabilities of bacterial toxins like diphtheria toxin (DT) to deliver a potent cytotoxic enzyme into cells with an associated membrane translocation moiety. Despite showing promising clinical efficacy, widespread deployment of DT-based therapeutics is complicated by the prevalence of pre-existing antibodies in the general population arising from childhood DT toxoid vaccinations, which impact the exposure, efficacy, and safety of these potent molecules. Here, we describe the discovery and characterization of a distant DT homolog from the ancient reptile pathogen Austwickia chelonae that we have dubbed chelona toxin (ACT). We show that ACT is comparable to DT structure and function in all respects except that it is not recognized by pre-existing anti-DT antibodies circulating in human sera. Furthermore, we demonstrate that ACT delivers heterologous therapeutic cargos into target cells more efficiently than DT. Our findings highlight ACT as a promising new chassis for building next-generation immunotoxins and targeted delivery platforms with improved pharmacokinetic and pharmacodynamic properties.

中文翻译：

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一种基于远处白喉毒素同源物的增强型细胞内递送平台，可逃避预先存在的抗毒素抗体。


治疗性蛋白质的靶向细胞内递送仍然是生物技术中一个尚未解决的重大挑战。一种有前途的方法是利用白喉毒素 （DT） 等细菌毒素的内在能力，将有效的细胞毒性酶递送到具有相关膜易位部分的细胞中。尽管显示出有希望的临床疗效，但由于儿童 DT 类毒素疫苗接种引起的普通人群中预先存在的抗体的普遍存在，基于 DT 的疗法的广泛部署变得复杂，这会影响这些强效分子的暴露、疗效和安全性。在这里，我们描述了从古老的爬行动物病原体 Austwickia chelonae 中发现和表征一种远距离的 DT 同源物，我们称之为 chelona 毒素 （ACT）。我们表明，ACT 在所有方面都与 DT 的结构和功能相当，只是它不能被人血清中循环的预先存在的抗 DT 抗体识别。此外，我们证明 ACT 比 DT 更有效地将异源治疗货物递送到靶细胞中。我们的研究结果强调 ACT 是构建下一代免疫毒素和靶向递送平台的有前途的新底盘，具有改进的药代动力学和药效学特性。