Single-chain antibody countermeasures for the Radiation GI Syndrome

描述(由申请人提供)：在胃肠道血管内皮细胞(GI)内对神经酰胺介导的细胞死亡的遗传或药物抑制可保护小鼠免受放射性GI综合征(RGS)的死亡。预防性给予抗神经酰胺抗体可减少内皮细胞的凋亡，从而显著保护肠道干细胞和动物在致死性辐射暴露后的存活。照射后24小时给药同样保护隐窝干细胞，并显著提高存活率，表明抗神经酰胺抗体是致死性RGS小分子缓释剂的第一有效抗体。为了提高抗神经酰胺抗体的疗效，我们建议选择一种含有已知的抗神经酰胺抗体神经酰胺结合区的重组单链抗体融合蛋白作为一种新的医学放射对策。单链抗体融合蛋白是全长抗体的较小衍生物，因此与全长抗体相比，它具有快速进入血液并增加对组织的渗透的优势。此外，单链抗体融合蛋白可以通过一般的克隆技术进行修饰，以显示更好的靶向结合，从产品开发的角度来看，这些融合蛋白可以很容易地以最低的成本生产。虽然在某些情况下，单链抗体融合蛋白可能不能保持亲本抗体的全部活性，但我们的初步数据表明，通过酶消化人源化抗神经酰胺抗体而获得的类似抗体片段可以显著保护和减轻辐射诱导的隐窝干细胞的致死性，即使在高单剂量暴露后24小时也是如此。这些数据表明，单链抗体融合蛋白足以诱导神经酰胺的治疗性中和。因此，中和抗神经酰胺单链抗体融合蛋白是实现生物盾牌计划任务的有希望的候选者，该计划旨在开发对策，在核灾难发生后的第一个24小时内减轻急性辐射综合征。

DESCRIPTION (provided by applicant): Genetic or pharmacologic inhibition of ceramide-mediated cell death within the vascular endothelium of the gastrointestinal tract (GI) protects mice from death from the Radiation GI Syndrome (RGS). Prophylactic administration of anti-ceramide antibody attenuates endothelial apoptosis, resulting in significant protection of intestinal stem cells and animal survival following lethal radiation exposure. Administration 24 h post radiation exposure similarly protects crypt stem cells and dramatically improves survival, indicating that anti-ceramide antibody represents the first effective antibody of small molecule mitigator of lethal RGS. To improve upon the efficacy of anti-ceramide antibody, we propose to select a recombinant single-chain antibody fusion protein containing the known ceramide-binding regions of anti-ceramide antibody as a novel Medical Radiation Countermeasure. Single-chain antibody fusion proteins are smaller derivatives of full length antibodies, and thus offer the advantage of rapid entering into the bloodstream and increased penetration into tissue compared to full-length antibodies. Additionally, single-chain antibody fusion proteins can be modified by general cloning techniques to display preferred target binding, and from a product development standpoint these fusion proteins can be produced easily and at minimal cost. While in some cases single-chain antibody fusion proteins may not retain full activity of the parent antibody, our preliminary data indicates that similar antibody fragments derived by enzymatic digestion of humanized anti-ceramide antibody results in significant protection and mitigation of radiation-induced crypt stem cell lethality, even 24 h after high single-dose exposure. These data indicate that a single-chain antibody fusion protein can be sufficient to induce therapeutic neutralization of ceramide. As such, a neutralizing anti-ceramide single-chain antibody fusion protein represents a promising candidate to fulfill the Project BioShield mandate for development of countermeasures to mitigate acute radiation syndromes within the first 24 h after a nuclear disaster.