Idiopathic pulmonary alveolar proteinosis (PAP) is a newly recognized autoimmune disorder characterized by neutralizing autoantibodies to granulocyte-macrophage colony stimulating factor (GMCSF) and severely dysregulated lung surfactant metabolism, the GM-CSh requirement in normal surfactant homeostasis is evidenced by studies of GM-CSF-deficient mice which develop a PAP-like syndrome reversible with exogenous GM-CSF. How GM-CSF maintains surfactant homeostasis is unknown. Human PAP alveolar macrophages (AM) can produce and respond to GM-CSF but have low expression of the nuclear transcription factor, peroxisome proliferator-activated receptor qamma (PPARgamma). GM-CSF upregulates PPARgamma, suggesting a GM-CSF-PPARgamma link in human PAP. Interestingly, PPARgamma deficiency is also linked to B cell hyperactivity and autoimmunity in experimental models. Other cytokine anomalies associated with B cell dysfunction occur in PAP. lnterleukm-10 (IL-10), a pleiotropic cytokine that stimulates antibody synthesis, is elevated in PAP lung and blood and blocks AM GM-CSF production. Activin A, a cytokine that may restrain B cell cycling, is upregulated by GM-CSF, and is also reduced in PAP. Thus, these data suggest that the presence of neutralizing auto-antibodies to GMCSF in PAP results in cytokine dysregulation, severely impaired surfactant catabolism and clinical disease. Depletion of B lymphocytes has shown promising clinical results in autoimmune disease. Rituximab, a chimeric murine-human monoclonal antibody directed against the B cell-specific membrane antigen CD20, selectively depletes B cells. Based upon our PAP data, it is hypothesized that reducing PAP B Cells in the context of a Rituximab clinical trial will diminish levels of anti- GM-CSF antibodies, and thus resolve pulmonary disease. Mechanism studies outlined in Aims 1-3 will be conducted on immune cells from lung and blood at baseline and post Rituximab therapy.
Aim 1 will investigate: (a) effects of IL-10, activin A, and PPARgamma on untreated PAP B cell proliferation and anti- GM-CSF synthesis; and (b) B cell levels and anti-GM-CSF liters.
Aim 2 will examine the role of PAP AM in localized B-cell regulation, specifically: (a) GM-CSF effect on expression of IL-10, activin A and follistatin, (activin A inhibitor); and (b) activin A effect on PPARgamma expression.
Aim 3 will examine PAP T cells for: (a) regulation of PAP B cell synthesis of anti-GM-CSF; and (b) regulatory phenotype (CD4/CD25, PPARgamma expression), cytokines (activin A, IL-2, IL-10), and proliferation. The long-term objective of this application is to delineate relationships among immune cells, cytokines and anti-GM-CSF autoantibody in PAP pathophysiology. The rituximab trial offers a unique opportunity to explore effects of B cell depletion on PAP pulmonary AM function and at the same time investigate new therapy that may improve the lung disease in PAP.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Special Emphasis Panel (ZRG1-ITHA (51))
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Rothermel, Annette L
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East Carolina University
Internal Medicine/Medicine
Schools of Medicine
United States
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Malur, Anagha; Kavuru, Mani S; Marshall, Irene et al. (2012) Rituximab therapy in pulmonary alveolar proteinosis improves alveolar macrophage lipid homeostasis. Respir Res 13:46
Kavuru, M S; Malur, A; Marshall, I et al. (2011) An open-label trial of rituximab therapy in pulmonary alveolar proteinosis. Eur Respir J 38:1361-7