Pathfinder: Determining the efficacy of plasmapheresis as a treatment for patients with chronic Pseudomonas infections and inhibitory antibodies

慢性铜绿假单胞菌肺部感染发生在患有囊性纤维化（CF）、非CF支气管扩张和慢性阻塞性肺病（COPD）的患者中。此类感染导致慢性炎症、肺功能恶化以及发病率和死亡率增加。一旦建立定殖，假单胞菌几乎不可能通过当前方法去除。改善感染的方法对患者的生活质量和寿命有积极的影响，抗体通常可以保护患者免受感染。然而，最近我们发现，一些慢性假单胞菌肺部感染的患者有一种抗体，实际上可以保护他们的殖民细菌免受免疫系统的杀死。发现这些抑制性抗体防止血清和细胞杀死患者的假单胞菌同源菌株。抑制性抗体被鉴定为对脂多糖特异性的IgG 2，特别是O-抗原组分。我们假设这些抗体通过将补体沉积远离细菌膜防止膜攻击复合物插入或通过阻断保护性抗体的进入来发挥其抑制作用。重要的是，我们发现高滴度抑制性抗体的患者比血清杀伤正常的假单胞菌感染患者的肺功能更差。根据我们的数据，我们选择了一个激进的治疗方案，为一个重症患者谁有抑制性抗体。使用血浆置换法，我们去除了所有的血清蛋白，包括抑制性IgG 2，并将其替换为IVIg，我们已经证明IVIg可以介导患者分离株的血清杀伤。患者在血浆置换后显著改善，痰中假单胞菌在相当长的一段时间内无法检测到。第二名重症患者最近接受了类似的治疗方案，取得了类似的成功。接受这种治疗的患者需要更少的住院天数，更少的治疗干预措施，如静脉注射抗生素，并报告症状水平大大降低。令人兴奋的是，这为具有抑制性抗体的重症患者提供了一种新的治疗方法，但许多重要问题仍未得到解答。该项目对于确定慢性假单胞菌肺部感染患者中抑制性抗体的临床相关性以及确定血浆置换是否是这一新问题的可行治疗选择至关重要。该项目将使用两种方法来实现这一点;首先，通过确定CF和非CF支气管扩张患者的大队列中抑制性抗体的患病率。这将确定问题的规模，并彻底调查抑制性抗体和健康退化之间的联系。其次，该项目将通过对目前接受血浆置换治疗的患者进行纵向研究来调查治疗方案。我们将确定先前的血浆置换治疗是否仅由于去除抑制性抗体而成功，或者是否有其他因素在起作用。我们将研究IgG 2的增加是否与菌株的重现和疾病的恶化相关。我们还将使用下一代测序来确定菌株替换是否由血浆置换术驱动，因为这将支持抑制性抗体的去除对免疫系统控制血浆置换后感染的能力产生积极影响的理论。最后，该项目旨在优化用于检测抑制性抗体存在的诊断测试。

Chronic Pseudomonas aeruginosa lung infections occur in patients suffering from cystic fibrosis (CF), non-CF bronchiectasis and chronic obstructive pulmonary disorder (COPD). Such infections lead to chronic inflammation, deteriorating lung function and increased morbidity and mortality. Once colonisation is established, Pseudomonas is almost impossible to remove by current methods. Methods to ameliorate infection would positively impact on patient quality of life and longevity.Antibody normally protects against infection. However, recently we identified that some patients with chronic Pseudomonas lung infections had a type of antibody that actually protects their colonising bacteria from killing by the immune system. These inhibitory antibodies were found to prevent both serum and cell killing of patient's Pseudomonas cognate strains. The inhibitory antibodies were identified as IgG2 specific to lipopolysaccharide, specifically the O-antigen component. We hypothesise that these antibodies exert their inhibitory effect either by depositing complement away from the bacterial membrane preventing membrane attack complex insertion or by blocking access of protective antibody. Importantly, we found patients with high titres of inhibitory antibodies had worse lung function than patients infected with Pseudomonas who had normal serum killing. Based on our data, we opted for a radical treatment programme for one critically ill patient who had inhibitory antibodies. Using plasmapheresis we removed all serum protein, including the inhibitory IgG2, and replaced it with IVIg that we had demonstrated could mediate serum killing of the patient's isolate. The patient improved dramatically after plasmapheresis and Pseudomonas remained undetectable in the sputum for a significant period of time. A second critically ill patient has recently undergone a similar treatment regime with similar success. Patients receiving this treatment required fewer days in hospital, fewer treatment interventions such as intravenous antibiotics and reported a much reduced level of symptoms. Excitingly, this offers a novel treatment for critically ill patients with inhibitory antibodies, however many vital questions remain unanswered. This project is vital to determine the clinical relevance of inhibitory antibodies in patients with chronic Pseudomonas lung infections and to identify whether plasma exchange is a viable treatment option for this novel problem. The project will do this using two approaches; first, by determining the prevalence of inhibitory antibodies in a large cohort of patients with both CF and non-CF bronchiectasis. This will determine the scale of the problem as well as thoroughly investigate the link between inhibitory antibodies and health degradation. Secondly, the project will investigate the treatment option by conducting a longitudinal study on patients currently being treated by plasma exchange. We will identify if previous plasma exchange treatments were successful due to removal of inhibitory antibodies alone, or if other factors were at play. We will investigate whether increases in IgG2 correlate with reappearance of the strain and worsening disease. We will also use next-generation sequencing to determine if strain replacement is being driven by plasmapheresis, as this would support the theory that the removal of inhibitory antibody is having a positive impact on the ability of the immune system to control infection post plasma exchange. Finally, this project aims to optimise a diagnostic test for detecting the presence of inhibitory antibodies.