Patient-derived Granulocyte/Macrophage Colony–Stimulating Factor Autoantibodies Reproduce Pulmonary Alveolar Proteinosis in Nonhuman Primates

Abstract

Rationale: Granulocyte/macrophage colony-stimulating factor (GM-CSF) autoantibodies (GMAb) are strongly associated with idiopathic pulmonary alveolar proteinosis (PAP) and are believed to be important in its pathogenesis. However, levels of GMAb do not correlate with disease severity and GMAb are also present at low levels in healthy individuals. Objectives: Our primary objective was to determine whether human GMAb would reproduce PAP in healthy primates. A secondary objective was to determine the concentration of GMAb resulting in loss of GM-CSF signaling in vivo (i.e., critical threshold). Methods: Nonhuman primates (Macaca fascicularis) were injected with highly purified, PAP patient-derived GMAb in dose-ranging (2.2-50 mg) single and multiple administration studies, and after blocking antihuman immunoglobulin immune responses, in chronic administration studies maintaining serum levels greater than 40 mg/ml for up to 11 months. Measurements and Main Results: GMAb blocked GM-CSF signaling causing (1) a milky-appearing bronchoalveolar lavage fluid containing increased surfactant lipids and proteins; (2) enlarged, foamy, surfactant-filled alveolar macrophages with reduced PU.1 and PPARg mRNA, and reduced tumor necrosis factor-a secretion; (3) pulmonary leukocytosis; (4) increased serum surfactant protein-D; and (5) impaired neutrophil functions. GM-CSF signaling varied inversely with GMAb concentration below a critical threshold of 5 mg/ml, which was similar in lungs and blood and to the value observed in patients with PAP. Conclusions: GMAb reproduced the molecular, cellular, and histopathologic features of PAP in healthy primates, demonstrating that GMAb directly cause PAP. These results have implications for therapy of PAP and help define the therapeutic window for potential use of GMAb to treat other disorders.

Pulmonary Alveolar Proteinosis

“…8 The strong association of GM-CSF antibodies in human autoimmune pulmonary alveolar proteinosis is further supported by the recent observation of pathology findings similar to human pulmonary alveolar proteinosis in nonhuman primates (Macaca fascicularis) after passively transferring highly purified GM-CSF autoantibodies from a patient with pulmonary alveolar proteinosis. 6,7 Thus, the final common pathway appears to be the deficiency of functionally active GM-CSF. Additionally, the discovery of GM-CSF antibody in an indium tin oxide worker with pulmonary alveolar proteinosis raises the possible role of inhaled agents in the triggering and development of autoimmune pulmonary alveolar proteinosis, though this is speculative and needs confirmation.…”

“…127 Healthy individuals can have low levels of GM-CSF autoantibodies, but the risk of pulmonary alveolar proteinosis is increased if the GM-CSF antibody level is Ͼ 5 g/ mL. 7 The latex agglutination test is the most widely used test for the detection of GM-CSF antibodies. It has diagnostic sensitivity and specificity of 100% and 98%, respectively, so it is the test of choice for autoimmune pulmonary alveolar proteinosis.…”

“…The resultant disturbance leads to clinical manifestation ranging from asymptomatic disease to life-threatening respiratory failure. 2 New insights gained from knockout mice models, [3][4][5] nonhuman primates, 6,7 and granulocyte macrophage colony stimulating factor (GM-CSF) autoantibodies in human pulmonary alveolar proteinosis suggest a causal role of GM-CSF in the pathogenesis. 8,9 Although ongoing studies are still evaluating its role, recent data suggest that exogenous GM-CSF therapy (to treat GM-CSF deficiency) has potential in the treatment of autoimmune pulmonary alveolar proteinosis.…”

Pulmonary pharmacodynamics of an anti-GM-CSFRα antibody enables therapeutic dosing that limits exposure in the lung

“…[22][23][24][25] Additionally, transfer of auto-antibodies from patients with anti-GM-CSF-associated PAP to non-human primates led to the formation of foamy macrophages. 26 These results indicate that GM-CSF plays an important role in the terminal differentiation of alveolar macrophages in mice and humans.…”

Biochemical index and immunological function in the peripheral blood of patients with idiopathic pulmonary alveolar proteinosis

“…Additionally, idiopathic PAP occurs in all ethnic groups, in the third to fourth decades of life and is approximately twice as common in males. The presence of idiopathic PAP may be associated with high levels of neutralizing GM-CSF autoantibody (2,3). High levels of GM-CSF autoantibody are associated with idiopathic PAP, and these autoantibodies are assumed to be critical in the pathogenesis of idiopathic PAP, but are not present in secondary or congenital PAP, other lung diseases or in healthy donors (4).…”