Roy Chad J, Brey Robert N, Mantis Nicholas J, Mapes Kelly, Pop Iliodora V, Pop Laurentiu M, Ruback Stephen, Killeen Stephanie Z, Doyle-Meyers Lara, Vinet-Oliphant Heather S, Didier Peter J, Vitetta Ellen S
Department of Microbiology and Immunology, Tulane School of Medicine, New Orleans, LA 70112; Divisions of Microbiology, Comparative Pathology, and Veterinary Medicine, Tulane National Primate Research Center, Covington, LA 70433;
Soligenix, Inc., Princeton, NJ 08540;
Proc Natl Acad Sci U S A. 2015 Mar 24;112(12):3782-7. doi: 10.1073/pnas.1502585112. Epub 2015 Mar 9.
Ricin toxin (RT) is the second most lethal toxin known; it has been designated by the CDC as a select agent. RT is made by the castor bean plant; an estimated 50,000 tons of RT are produced annually as a by-product of castor oil. RT has two subunits, a ribotoxic A chain (RTA) and galactose-binding B chain (RTB). RT binds to all mammalian cells and once internalized, a single RTA catalytically inactivates all of the ribosomes in a cell. Administered as an aerosol, RT causes rapid lung damage and fibrosis followed by death. There are no Food and Drug Administration-approved vaccines and treatments are only effective in the first few hours after exposure. We have developed a recombinant RTA vaccine that has two mutations V76M/Y80A (RiVax). The protein is expressed in Escherichia coli and is nontoxic and immunogenic in mice, rabbits, and humans. When vaccinated mice are challenged with injected, aerosolized, or orally administered (gavaged) RT, they are completely protected. We have now developed a thermostable, aluminum-adjuvant-containing formulation of RiVax and tested it in rhesus macaques. After three injections, the animals developed antibodies that completely protected them from a lethal dose of aerosolized RT. These antibodies neutralized RT and competed to varying degrees with a panel of neutralizing and nonneutralizing mouse monoclonal antibodies known to recognize specific epitopes on native RTA. The resulting antibody competition profile could represent an immunologic signature of protection. Importantly, the same signature was observed using sera from RiVax-immunized humans.
蓖麻毒素（RT）是已知的第二大致死性毒素；美国疾病控制与预防中心（CDC）已将其指定为特定生物制剂。RT由蓖麻植物产生；作为蓖麻油的副产品，估计每年生产5万吨RT。RT有两个亚基，即具有核糖体毒性的A链（RTA）和结合半乳糖的B链（RTB）。RT能与所有哺乳动物细胞结合，一旦内化，单个RTA就能催化使细胞内所有核糖体失活。以气溶胶形式给药时，RT会导致肺部迅速损伤和纤维化，随后导致死亡。目前尚无美国食品药品监督管理局批准的疫苗，治疗仅在接触后的最初几小时有效。我们开发了一种具有V76M/Y80A两个突变的重组RTA疫苗（RiVax）。该蛋白在大肠杆菌中表达，在小鼠、兔子和人类中无毒且具有免疫原性。用注射、雾化或口服（灌胃）RT对接种疫苗的小鼠进行攻击时，它们能得到完全保护。我们现在已经开发出一种热稳定的、含铝佐剂的RiVax制剂，并在恒河猴身上进行了测试。三次注射后，这些动物产生了抗体，能完全保护它们免受致死剂量的雾化RT攻击。这些抗体中和了RT，并与一组已知能识别天然RTA上特定表位的中和及非中和小鼠单克隆抗体在不同程度上发生竞争。由此产生的抗体竞争图谱可能代表一种保护的免疫特征。重要的是，使用来自RiVax免疫的人类血清也观察到了相同的特征。
