biostudies-literatureLian LHHS | NIH (NIH)e2511483123https://www.ebi.ac.uk/biostudies/studies/S-EPMC12913010biostudies-literatureUnknown123(7)Granulocyte-macrophage colony-stimulating factor (GM-CSF) deficiency drives autoimmune pulmonary alveolar proteinosis (aPAP), a disease characterized by impaired macrophage-mediated clearance of pulmonary surfactants. Clinical data suggest that inhaled recombinant GM-CSF reduces symptoms in aPAP patients, providing a rationale for mRNA-based GM-CSF replacement therapies. However, these require effective mRNA delivery after nebulization. Here, we report the iterative in vivo design of a lipid nanoparticle, named nebulized lung delivery 2 (NLD2), that efficiently delivers mRNA after nebulization. NLD2 carrying GM-CSF mRNA transfected alveolar macrophages in vivo, leading to interleukin-10 pathway activation and subsequent surfactant lipoprotein clearance. In a preclinical disease model of aPProceedings of the National Academy of Sciences of the United States of AmericaLipid nanoparticle GM-CSF replacement for autoimmune pulmonary alveolar proteinosis.PMC12913010U19AI171421Gentry KJang BGuerrero-Ferreira RCParihar VCKim HZenhausern RCalkins RVanover DLian LDahlman JERadmand AHuayamares SGShakked ASantangelo PJSchrader Echeverri EfalseLipid nanoparticle GM-CSF replacement for autoimmune pulmonary alveolar proteinosis.Granulocyte-macrophage colony-stimulating factor (GM-CSF) deficiency drives autoimmune pulmonary alveolar proteinosis (aPAP), a disease characterized by impaired macrophage-mediated clearance of pulmonary surfactants. Clinical data suggest that inhaled recombinant GM-CSF reduces symptoms in aPAP patients, providing a rationale for mRNA-based GM-CSF replacement therapies. However, these require effective mRNA delivery after nebulization. Here, we report the iterative in vivo design of a lipid nanoparticle, named nebulized lung delivery 2 (NLD2), that efficiently delivers mRNA after nebulization. NLD2 carrying GM-CSF mRNA transfected alveolar macrophages in vivo, leading to interleukin-10 pathway activation and subsequent surfactant lipoprotein clearance. In a preclinical disease model of aP2026-01-01T00:00:00Z2026 Feb2026-07-16T06:55:30.134Z2026-07-09T13:10:37.395ZS-EPMC129130104167117610.1073/pnas.2511483123