MAb Passive Vaccination against Acinetobacter baumannii

项目摘要/摘要 从美国ICU分离的鲍曼不动杆菌中有50%是极端耐药(XDR)，远远高于其他 病原体。这些感染导致10,000和30,000人死亡，额外医疗费用为3.9亿美元， 美国和全球每年7.42亿美元。此外，与其他耐药细菌相比，几乎没有 治疗鲍曼氏XDR杆菌的抗生素正在研发中。迫切需要新的治疗方法。 我们建立了两个单抗，C8和39，它们共同结合62个临床分离株中的90%。 鲍曼尼测试。我们在致死性鲍曼不动杆菌菌败血症的小鼠模型中发现了疗效。 和吸入性肺炎，这是鲍曼不动杆菌感染最常见的两个部位。此外，C8还展示了 在延迟治疗致命性鲍曼不动杆菌感染期间，与粘菌素有实质性的协同作用(39项尚未测试)。 还提出了其他尚未确定特征的单抗。我们将定义单抗的最佳混合 广泛针对菌株，并定义保护机制，以支持未来的人性化和临床试验。 具体目标1：确定关于表面结合和体外杀伤多个 鲍曼不动杆菌临床分离株。我们将定义单抗与同种类型对照的表面结合，以广泛地 鲍曼不动杆菌临床分离株的多样性。我们亦会研究细菌清除的机制。 单抗、细菌逃逸突变的可能性和频率，以及单抗对抗生素的影响 敏感度。最后，我们将建立单抗的抗原靶向。 具体目标2：确定最佳单抗在3种感染和抗病毒模型中的体内效应 使用和不使用抗生素的多种鲍曼不动杆菌。我们将比较单一药物在体内的疗效 在3个公认的感染模型中，延迟治疗期间单抗组合与同型对照的比较； 小鼠细菌性败血症、小鼠肺炎、大鼠伤口感染。我们将对抗MAb进行评估 老鼠体内的抗体。然后，我们将确定在感染前多早进行单抗预防是有效的，以及如何预防。 感染后长期单抗治疗仍然有效，且多剂量单抗在延长治疗期间的影响 心理治疗。最后，我们将在每个模型中定义单抗和抗菌治疗之间的相互作用。 具体目标3：确定最佳单抗被动免疫的保护机制。我们会 通过野生型与小鼠的最佳单抗对照与同型对照来确定体内疗效的机制 选择性地耗尽宿主效应物(例如补体、巨噬细胞、中性粒细胞)，并激活FcR与 抑制性FcRII)。结果测量将包括存活率、细菌密度和炎症。这些结果 将为未来优化人源化单抗效力的努力提供信息，并确定替代效力分析。 针对鲍曼不动杆菌感染的新解决方案是一个关键的未得到满足的需求。我们将确定一种最佳的单抗方案 跨多个感染部位(血液、肺、软组织)的保护，定义体外保护相关因素，以及 确定保护机制，这将使人源化单抗的未来功效最优化。

Project Summary/Abstract Fifty percent of A. baumannii isolates from US ICUs are extreme drug resistant (XDR), far higher than for other pathogens. These infections result in 10,000 and 30,000 deaths and excess healthcare costs of $390 million and $742 million in the US and globally, annually. Furthermore, in contrast to other resistant bacteria, virtually no antibiotics are in the pipeline to deal with XDR A. baumannii. New treatments are critically needed. We established two MAbs, C8 and 39, that collectively bind to 90% of the 62 clinical isolates of A. baumannii tested. We have found efficacy in lethal murine models of XDR A. baumannii bacteremic sepsis and aspiration pneumonia, the two most common sites of A. baumannii infection. Furthermore, C8 exhibits substantial synergy with colistin during delayed therapy for lethal A. baumannii infection (39 is not yet tested). Other MAbs have also been raised that are not yet characterized. We will define an optimal mixture of MAbs to target strains broadly, and define mechanisms of protection to support future humanization and clinical trials. Specific Aim 1: Define optimal MAbs with respect to surface binding and in vitro killing of multiple clinical isolates of A. baumannii. We will define surface binding of the MAbs vs. isotype controls to broadly diverse clinical isolates of A. baumannii. We will also identify the mechanism of bacterial clearance by the MAbs, the potential for and frequency of bacterial escape mutants, and the impact of MAbs on antibiotic susceptibility. Finally, we will establish the antigenic targets of the MAbs. Specific Aim 2: Define the in vivo effects of the optimal MAbs in 3 models of infection and against multiple strains of A. baumannii, with and without antibiotics. We will compare in vivo efficacy of single vs. combination MAbs vs. isotype control during delayed therapy in 3 well-established models of infection; mouse bacteremic sepsis, mouse pneumonia, and rat wound infection. We will evauate for anti-MAb antibodies in rats. We will then determine how early prior to infection MAb prophylaxis is effective, and how long post-infection MAb therapy remains effective, and the impact of multiple doses of MAbs during prolonged therapy. Finally, we will define interactions between MAbs and antibacterial therapy in each model. Specific Aim 3: Define the mechanisms of protection of optimal MAb passive vaccination. We will define the in vivo mechanisms of efficacy by treating with optimal MAb vs. isotype control in wild-type vs. mice with selective depletion of host effectors (e.g., complement, macrophages, neutrophils, and activating FcR vs. inhibitory FcRII). Outcome measures will include survival, bacterial density, and inflammation. These results will inform future efforts to optimize the efficacy of humanized MAbs, and identify surrogate efficacy assays. Novel solutions for A. baumannii infections are a critical unmet need. We will identify an optimal MAb regimen protective across multiple sites of infection (blood, lung, soft tissue), define in vitro correlates of protection, and determine the mechanisms of protection, which will enable future efficacy optimization of humanized MAbs.