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

描述(申请人提供)：原发性肺泡蛋白沉积症(PAP)的特征是肺内表面活性物质逐渐积聚，导致呼吸衰竭，以及占可归因性死亡18%的肺部和全身感染的增加。由于GM-CSF基因敲除(GM-/-)小鼠发生PAP并增加感染死亡率，以及人类PAP与高水平的中和抗GM-CSF抗体相关，因此GM-CSF信号的缺失似乎是疾病发病的核心。我们报道，GM-CSF在小鼠和人类中都需要刺激肺泡巨噬细胞(AM)的终末分化，并且主要通过造血细胞转录因子PU.1来实现。在PAP患者和GM-/-小鼠中，中性粒细胞和单核细胞计数是正常的，这表明GM-CSF在肺中起关键作用，但在造血中不起作用。我们的初步数据显示，在无疾病、健康的个体中，存在低水平的抗GM-CSF抗体，并与中性粒细胞功能呈负相关；在GMA/A小鼠和PAP患者中，中性粒细胞功能受损。这一建议试图检验以下一般假设：GM-CSF在先天免疫中具有关键的全身作用，髓系细胞的刺激机制决定了基础水平的抗菌素和其他功能。具体地说，我们假设(1)高水平的抗GM-CSF抗体是PAP临床表现的原因，而不是微生物并发感染的附带现象或结果；(2)低水平的抗GM-CSF抗体可能通过结合和灭活循环中的GM-CSF而发挥重要的生理作用，从而调节髓系细胞的基础免疫应答。在目标1中，我们将确定抗GM-CSF抗体调节包括AM、单核细胞和中性粒细胞在内的髓系细胞功能的机制(S)。在目标2中，通过将PAP患者的抗GM-CSF抗体转移到非人类灵长类动物中，在健康受试者中重现PAP，满足Koch的第二和第三假设。在目标3中，我们将利用一种新的PAP小鼠免疫模型来确定体内消除GM-CSF生物活性的抗GM-CSF抗体的临界阈值，并确定髓系细胞功能障碍的动力学和药效学以及PAP的发生和消退。预期的结果将确定抗GM-CSF抗体导致PAP患者的临床表现，并将确定髓系细胞功能障碍的潜在机制。这些结果对GM-CSF在PAP以外的粘膜屏障功能中的作用在健康和疾病中都具有生物学意义。PAP疗法和基于抗GM-CSF抗体的疗法治疗严重的炎症性疾病具有临床意义，这一方法现在已经出现了重大的商业兴趣和开发。

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.