Role of Anti-GM-CSF Antibodies in Myeloid Cell Function & Innate Immunity

描述（由申请方提供）：原发性肺泡蛋白沉积症（PAP）的特征是肺中表面活性剂的进行性蓄积，导致呼吸衰竭以及肺部和全身感染增加，占归因死亡率的18%。GM-CSF信号传导的消除似乎是疾病发病机制的中心，因为GM-CSF敲除（GM-/-）小鼠发展PAP并且具有增加的感染死亡率，并且因为人类中的PAP与高水平的中和性抗GM-CSF抗体相关。我们报道了GM-CSF是刺激小鼠和人类肺泡巨噬细胞（AM）终末分化所必需的，并且主要通过造血转录因子PU.1来实现。PAP患者和GM-/-小鼠的中性粒细胞和单核细胞计数正常，表明GM-CSF在肺中发挥关键作用，但在造血中不起作用。我们的初步数据显示，低水平的抗GM-CSF抗体存在于无疾病的健康个体中，并且与中性粒细胞功能呈负相关;并且在GMA/A小鼠和PAP患者中中性粒细胞功能受损。该提案旨在测试以下一般假设：GM-CSF在先天免疫中具有关键的全身作用，刺激骨髓细胞中的机制，确定抗微生物和其他功能的基础水平。具体而言，我们假设（1）高水平的抗GM-CSF抗体是PAP临床表现的原因，而不是并发微生物感染的附带现象或后果;（2）低水平的抗GM-CSF抗体可能通过结合和灭活循环GM-CSF，从而调节骨髓细胞的基础免疫应答，发挥重要的生理作用。在目的1中，我们将确定抗GM-CSF抗体调节骨髓细胞（包括AM、单核细胞和中性粒细胞）功能的机制。在目标2中，通过将来自PAP患者的抗GM-CSF抗体转移到非人灵长类动物中，在健康受试者中重现PAP，满足Koch的第2和第3假设。在目标3中，我们将利用小鼠中PAP的新型免疫模型来确定在体内消除GM-CSF生物活性的抗GM-CSF抗体的临界阈值水平，并确定骨髓细胞功能障碍的动力学和药效学以及PAP的发作和消退。预期结果将确定抗GM-CSF抗体导致PAP患者的临床表现，并将确定骨髓细胞功能障碍的潜在机制。结果具有生物学意义的作用，GM-CSF的粘膜屏障功能超越PAP在健康和疾病。PAP疗法以及基于抗GM-CSF抗体的治疗严重炎性病症的疗法存在临床意义，这是一种现已出现重大商业兴趣和发展的方法。

DESCRIPTION (provided by applicant): Primary pulmonary alveolar proteinosis (PAP) is characterized by progressive accumulation of surfactant in the lungs resulting in respiratory failure as well as increased pulmonary and systemic infections that account for 18% of attributable mortality. Abrogation of GM-CSF signaling appears to be central to disease pathogenesis because GM-CSF knockout (GM-/-) mice develop PAP and have increased mortality from infection and because PAP in humans is associated with high levels of neutralizing anti-GM-CSF antibodies. We reported that GM-CSF is required to stimulate the terminal differentiation of alveolar macrophages (AMs) in mice and likely also in humans, and does so primarily via the hematopoietic transcription factor, PU.1. Neutrophil and monocyte counts are normal in PAP patients and GM-/- mice, suggesting GM-CSF has a critical role in the lung but not in hematopoiesis. Our Preliminary Data now show that low levels of anti-GM-CSF antibodies are present in disease-free, healthy individuals, and correlate inversely with neutrophil function; and that neutrophils are functionally impaired in both GMA/A mice and PAP patients. This proposal seeks to test the following general hypothesis: GM-CSF has a critical systemic role in innate immunity, stimulating mechanisms in myeloid cells determining basal levels of antimicrobial and other functions. Specifically, we hypothesize that (1) high levels of anti-GM-CSF antibodies are the cause of the clinical manifestations in PAP and not an epiphenomenon or a consequence of intercurrent microbial infection; and (2) low levels of anti-GM-CSF antibodies may play an important physiological role by binding and inactivating circulating GM-CSF, thereby modulating the basal immune responsiveness of myeloid cells. In Aim 1, we will determine the mechanism(s) by which anti-GM-CSF antibodies regulate functions in myeloid cells, including AMs, monocytes and neutrophils. In Aim 2, PAP will be recapitulated in healthy subjects by transfer of anti-GM-CSF antibodies from PAP patients into non-human primates, satisfying Koch's 2nd & 3rd postulates. In Aim 3, we will utilize a novel immune model of PAP in mice to determine the critical threshold level of anti-GM-CSF antibodies that abrogate GM-CSF bioactivity in vivo and determine the kinetics and pharmacodynamics of myeloid cell dysfunction and onset and resolution of PAP. Expected results will establish that anti-GM-CSF antibodies cause the clinical manifestations in PAP patients, and will determine underlying mechanisms of myeloid cell dysfunction. Results have biological implications for the role of GM-CSF in mucosal barrier function beyond PAP in both health and disease. Clinical implications exist for PAP therapies, and also for anti-GM-CSF antibody-based therapies to treat serious inflammatory disorders, an approach for which significant commercial interest and development have now emerged.