DEVELOPMENT OF A RECOMBINANT VACCINE FOR RICIN TOXIN

描述（由申请人提供）：蓖麻毒素是已知最有效的生物毒素之一，过去曾被用作生物武器。由于在2003年期间几起广为宣传的事件中发现并记录了蓖麻毒素的痕迹，因此，最近将注意力集中在实际使用蓖麻毒素的潜在威胁上。目前，还没有获得许可的疫苗来防止蓖麻毒素在潜在的恐怖袭击中被气溶胶使用，或在战场上被用作武器。这一拟议项目的目的是通过生产过程和中间规模扩大阶段开发肌肉注射蓖麻毒素疫苗，直至并包括小瓶佐剂配方，以供最终发布用于人类临床研究。该项目的团队包括来自工业界（DOR Biopharmaceuticals, Inc. [DOR]和Cambrex Biosciences， Inc. [CAMB]）、学术界（德克萨斯大学西南医学中心[UTSWMC]和堪萨斯大学[UK]）和非营利研究机构（斯坦福研究所[SRI]）的代表。除了未来的I/II期临床试验外，预计至少有几千人剂量的生产目标，足以进行稳定性和毒性试验。该候选疫苗是从大肠杆菌宿主菌株产生的蓖麻毒素a链中提取的重组多肽。拟议的努力将集中在开发先前描述的遗传灭活蓖麻毒素a链上，该链在导致毒性丧失的位点上包含非冗余结构突变。为实现具体目标所涉及的活动将包括最大化大肠杆菌的表达水平、提高工艺产量、开发和验证工艺方法、测定和稳定性指示试验。在制定用于临床使用的疫苗时，将解决影响溶液中抗原稳定性的几个因素。此外，开发的批次将在动物模型中进行功效测试，并解决潜在的毒性问题。开发抗蓖麻毒素中毒疫苗的一个关键问题是动物保护反应与人类保护反应的相关性，因为在开发期间不能进行人体挑战/功效研究。根据初步数据，这种特殊的疫苗抗原在某些条件下聚集，可能影响效力和稳定性。在疫苗储存期间，多肽结构的保存也将通过在蛋白稳定受体中配制候选疫苗来解决。

DESCRIPTION (provided by applicant): Ricin is one of the most potent biological toxins known and has been used as a biological weapon in the past. Much attention has been recently focused on the potential threat of actual ricin use, since traces of ricin have been found and documented in several well publicized incidents during 2003. Currently, there is no licensed vaccine to protect against the possibility of the aerosol use of ricin in a potential terrorist attack or as a weapon on the battlefield. The purpose of this proposed project is to develop an intramuscularly administered ricin vaccine through process and intermediate scale-up stages of manufacturing, up to and including formulation with adjuvant in vials for final release for human clinical studies. The team for this project includes representatives from industry (DOR Biopharmaceuticals, Inc. [DOR] and Cambrex Biosciences, Inc. [CAMB]), academe (University of Texas Southwestern Medical Center [UTSWMC] and the University of Kansas [UK]) and a non-profit research organization (Stanford Research Institute [SRI]). A production goal of at least several thousand human doses sufficient for stability and toxicity testing, in addition to future Phase I/II clinical testing, is projected. The vaccine candidate is a recombinant polypeptide derived from the A chain of ricin toxin produced in an E. coli host strain. The proposed efforts will focus on the development of a previously characterized genetically inactivated ricin A chain that contains non-redundant structural mutations in sites resulting in loss of toxicity. The activities involved in executing the specific aims will include maximization of expression levels in E. coli, improvement of process yields, and development and validation of process methods, assays, and stability-indicating tests. Several factors that contribute to the stability of the antigen in solution will be addressed in formulating the vaccine for clinical use. Further, the developed lots will be tested in animal models for efficacy and potential toxicity issues will be addressed. A key issue in the development of a vaccine to combat ricin intoxication will be the correlation of animal protective responses with human protective responses, since no human challenge/efficacy studies can be performed during development. Based on preliminary data, this particular vaccine antigen aggregates under certain conditions, potentially affecting potency and stability. Preservation of the polypeptide structure during storage of the vaccine will also be addressed by formulating the vaccine candidate in protein stabilizinq recipients.