A toxicology study of Csf2ra complementation and pulmonary macrophage transplantation therapy of hereditary PAP in mice.

Pulmonary macrophage transplantation (PMT) is a gene and cell transplantation approach in development as therapy for hereditary pulmonary alveolar proteinosis (hPAP), a surfactant accumulation disorder caused by mutations in CSF2RA/B (and murine homologs). We conducted a toxicology study of PMT of Csf2ra gene-corrected macrophages (mGM-Rα+Mϕs) or saline-control intervention in Csf2raKO or wild-type (WT) mice including single ascending dose and repeat ascending dose studies evaluating safety, tolerability, pharmacokinetics, and pharmacodynamics. Lentiviral-mediated Csf2ra cDNA transfer restored GM-CSF signaling in mGM-Rα+Mϕs. Following PMT, mGM-Rα+Mϕs engrafted, remained within the lungs, and did not undergo uncontrolled proliferation or result in bronchospasm, pulmonary function abnormalities, pulmonary or systemic inflammation, anti-transgene product antibodies, or pulmonary fibrosis. Aggressive male fighting caused a similarly low rate of serious adverse events in saline- and PMT-treated mice. Transient, minor pulmonary neutrophilia and exacerbation of pre-existing hPAP-related lymphocytosis were observed 14 days after PMT of the safety margin dose but not the target dose (5,000,000 or 500,000 mGM-Rα+Mϕs, respectively) and only in Csf2raKO mice but not in WT mice. PMT reduced lung disease severity in Csf2raKO mice. Results indicate PMT of mGM-Rα+Mϕs was safe, well tolerated, and therapeutically efficacious in Csf2raKO mice, and established a no adverse effect level and 10-fold safety margin.

A dried blood spot test for diagnosis of autoimmune pulmonary alveolar proteinosis.

Granulocyte/macrophage colony-stimulating factor autoantibodies (GMAbs) mediate the pathogenesis of autoimmune pulmonary alveolar proteinosis (autoimmune PAP) and their quantification in serum by enzyme-linked immunosorbent assay (ELISA) - the serum GMAb test - is the 'gold standard' for diagnosis of autoimmune PAP. Because GMAbs are high in autoimmune PAP and low or undetectable in healthy people, we hypothesized that the ELISA could be adapted for evaluation of blood obtained from the fingertip using a dried blood spot card (DBSC) for specimen collection. Here, we report development of such a method - the DBSC GMAb test - and evaluate its ability to measure GMAb concentration in blood and to diagnose autoimmune PAP. Fresh, heparinized whole blood was obtained from 60 autoimmune PAP patients and 19 healthy people and used to measure the GMAb concentration in blood (by the DBSC GMAb test). After optimization, the DBSC GMAb test was evaluated for accuracy, precision, reliability, sensitivity, specificity, and ruggedness. The coefficient of variation among repeated measurements was low with regard to well-to-well, plate-to-plate, day-to-day, and inter-operator variation, and results were unaffected by exposure of prepared DBSC specimens to a wide range of temperatures (from -80 °C to 65 °C), repeated freeze-thaw cycles, or storage for up to 2.5 months before testing. The limit of blank (LoB), limit of detection (LoD), and lower limit of quantification (LLoQ), were 0.01, 0.21, and 3.5 µg/ml of GMAb in the blood, respectively. Receiver operating curve characteristic analysis identified 2.7 µg/ml as the optimal GMAb concentration cutoff value to distinguish autoimmune PAP from healthy people. This cutoff value was less than the LLoQ and the ranges of GMAb results for autoimmune PAP patients and healthy people were widely separated (median (interquartile range): 22.6 (13.3-43.8) and 0.23 (0.20-0.30) µg/ml, respectively). Consequently, the LLoQ is recommended as the lower limit of the range indicating a positive test result (i.e., that autoimmune PAP is present); lower values indicate a negative test result (i.e., autoimmune PAP is not present). Among the 30 autoimmune PAP patients and 19 healthy people evaluated, the sensitivity and specificity of the DBSC GMAb test were both 100% for a diagnosis of autoimmune PAP. Results demonstrate the DBSC GMAb test reliably measures GMAbs in blood and performs well in the diagnosis of autoimmune PAP.

A murine model of hereditary pulmonary alveolar proteinosis caused by homozygous Csf2ra gene disruption.

Hereditary pulmonary alveolar proteinosis (hPAP) is a rare disorder caused by recessive mutations in GM-CSF receptor subunit α/ß genes (CSF2RA/CSF2RB, respectively) characterized by impaired GM-CSF-dependent surfactant clearance by alveolar macrophages (AMs) resulting in alveolar surfactant accumulation and hypoxemic respiratory failure. Because hPAP is caused by CSF2RA mutations in most patients, we created an animal model of hPAP caused by Csf2ra gene disruption (Csf2ra-/- mice) and evaluated the effects on AMs and lungs. Macrophages from Csf2ra-/- mice were unable to bind and clear GM-CSF, did not exhibit GM-CSF signaling, and had functional defects in phagocytosis, cholesterol clearance, and surfactant clearance. Csf2ra-/- mice developed a time-dependent, progressive lung disease similar to hPAP in children caused by CSF2RA mutations with respect to the clinical, physiological, histopathological, biochemical abnormalities, biomarkers of PAP lung disease, and clinical course. In contrast, Csf2ra+/- mice had functionally normal AMs and no lung disease. Pulmonary macrophage transplantation (PMT) without myeloablation resulted in long-term engraftment, restoration of GM-CSF responsiveness to AMs, and a safe and durable treatment effect that lasted for the duration of the experiment (6 mo). Results demonstrate that homozygous (but not heterozygous) Csf2ra gene ablation caused hPAP identical to hPAP in children with CSF2RA mutations, identified AMs as the cellular site of hPAP pathogenesis in Csf2ra-/- mice, and have implications for preclinical studies supporting the translation of PMT as therapy of hPAP in humans.

Role of GM-CSF in regulating metabolism and mitochondrial functions critical to macrophage proliferation.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) exerts pleiotropic effects on macrophages and is required for self-renewal but the mechanisms responsible are unknown. Using mouse models with disrupted GM-CSF signaling, we show GM-CSF is critical for mitochondrial turnover, functions, and integrity. GM-CSF signaling is essential for fatty acid ß-oxidation and markedly increased tricarboxylic acid cycle activity, oxidative phosphorylation, and ATP production. GM-CSF also regulated cytosolic pathways including glycolysis, pentose phosphate pathway, and amino acid synthesis. We conclude that GM-CSF regulates macrophages in part through a critical role in maintaining mitochondria, which are necessary for cellular metabolism as well as proliferation and self-renewal.

Increased Pulmonary GM-CSF Causes Alveolar Macrophage Accumulation. Mechanistic Implications for Desquamative Interstitial Pneumonitis.

Desquamative interstitial pneumonia (DIP) is a rare, smoking-related, diffuse parenchymal lung disease characterized by marked accumulation of alveolar macrophages (AMs) and emphysema, without extensive fibrosis or neutrophilic inflammation. Because smoking increases expression of pulmonary GM-CSF (granulocyte/macrophage-colony stimulating factor) and GM-CSF stimulates proliferation and activation of AMs, we hypothesized that chronic exposure of mice to increased pulmonary GM-CSF may recapitulate DIP. Wild-type (WT) mice were subjected to inhaled cigarette smoke exposure for 16 months, and AM numbers and pulmonary GM-CSF mRNA levels were measured. After demonstrating that smoke inhalation increased pulmonary GM-CSF in WT mice, transgenic mice overexpressing pulmonary GM-CSF (SPC-GM-CSF+/+) were used to determine the effects of chronic exposure to increased pulmonary GM-CSF (without smoke inhalation) on accumulation and activation of AMs, pulmonary matrix metalloproteinase (MMP) expression and activity, lung histopathology, development of polycythemia, and survival. In WT mice, smoke exposure markedly increased pulmonary GM-CSF and AM accumulation. In unexposed SPC-GM-CSF+/+ mice, AMs were spontaneously activated as shown by phosphorylation of STAT5 (signal inducer and activator of transcription 5) and accumulated progressively with involvement of 84% (interquartile range, 55-90%) of the lung parenchyma by 10 months of age. Histopathologic features also included scattered multinucleated giant cells, alveolar epithelial cell hyperplasia, and mild alveolar wall thickening. SPC-GM-CSF+/+ mice had increased pulmonary MMP-9 and MMP-12 levels, spontaneously developed emphysema and secondary polycythemia, and had increased mortality compared with WT mice. Results show cigarette smoke increased pulmonary GM-CSF and AM proliferation, and chronically increased pulmonary GM-CSF recapitulated the cardinal features of DIP, including AM accumulation, emphysema, secondary polycythemia, and increased mortality in mice. These observations suggest pulmonary GM-CSF may be involved in the pathogenesis of DIP.

Systemic Juvenile Idiopathic Arthritis-Associated Lung Disease: Characterization and Risk Factors.

OBJECTIVE: Systemic juvenile idiopathic arthritis (JIA) is associated with a recently recognized, albeit poorly defined and characterized, lung disease (LD). The objective of this study was to describe the clinical characteristics, risk factors, and histopathologic and immunologic features of this novel inflammatory LD associated with systemic JIA (designated SJIA-LD). METHODS: Clinical data collected since 2010 were abstracted from the medical records of patients with systemic JIA from the Cincinnati Children's Hospital Medical Center. Epidemiologic, cellular, biochemical, genomic, and transcriptional profiling analyses were performed. RESULTS: Eighteen patients with SJIA-LD were identified. Radiographic findings included diffuse ground-glass opacities, subpleural reticulation, interlobular septal thickening, and lymphadenopathy. Pathologic findings included patchy, but extensive, lymphoplasmacytic infiltrates and mixed features of pulmonary alveolar proteinosis (PAP) and endogenous lipoid pneumonia. Compared to systemic JIA patients without LD, those with SJIA-LD were younger at the diagnosis of systemic JIA (odds ratio [OR] 6.5, P = 0.007), more often had prior episodes of macrophage activation syndrome (MAS) (OR 14.5, P < 0.001), had a greater frequency of adverse reactions to biologic therapy (OR 13.6, P < 0.001), and had higher serum levels of interleukin-18 (IL-18) (median 27,612 pg/ml versus 5,413 pg/ml; P = 0.047). Patients with SJIA-LD lacked genetic, serologic, or functional evidence of granulocyte-macrophage colony-stimulating factor pathway dysfunction, a feature that is typical of familial or autoimmune PAP. Moreover, bronchoalveolar lavage (BAL) fluid from patients with SJIA-LD rarely demonstrated proteinaceous material and had less lipid-laden macrophages than that seen in patients with primary PAP (mean 10.5% in patients with SJIA-LD versus 66.1% in patients with primary PAP; P < 0.001). BAL fluid from patients with SJIA-LD contained elevated levels of IL-18 and the interferon-γ-induced chemokines CXCL9 and CXCL10. Transcriptional profiling of the lung tissue from patients with SJIA-LD identified up-regulated type II interferon and T cell activation networks. This signature was also present in SJIA-LD human lung tissue sections that lacked substantial histopathologic findings, suggesting that this activation signature may precede and drive the lung pathology in SJIA-LD. CONCLUSION: Pulmonary disease is increasingly detected in children with systemic JIA, particularly in association with MAS. This entity has distinct clinical and immunologic features and represents an uncharacterized inflammatory LD.

Long-Term Safety and Efficacy of Gene-Pulmonary Macrophage Transplantation Therapy of PAP in Csf2ra-/- Mice.

Hereditary pulmonary alveolar proteinosis (PAP) is a genetic lung disease characterized by surfactant accumulation and respiratory failure arising from disruption of GM-CSF signaling. While mutations in either CSF2RA or CSF2RB (encoding GM-CSF receptor α or ß chains, respectively) can cause PAP, α chain mutations are responsible in most patients. Pulmonary macrophage transplantation (PMT) is a promising new cell therapy in development; however, no studies have evaluated this approach for hereditary PAP (hPAP) caused by Csf2ra mutations. Here, we report on the preclinical safety, tolerability, and efficacy of lentiviral-vector (LV)-mediated Csf2ra expression in macrophages and PMT of gene-corrected macrophages (gene-PMT therapy) in Csf2ra gene-ablated (Csf2ra-/-) mice. Gene-PMT therapy resulted in a stable transgene integration and correction of GM-CSF signaling and functions in Csf2ra-/- macrophages in vitro and in vivo and resulted in engraftment and long-term persistence of gene-corrected macrophages in alveoli; restoration of pulmonary surfactant homeostasis; correction of PAP-specific cytologic, histologic, and biomarker abnormalities; and reduced inflammation associated with disease progression in untreated mice. No adverse consequences of gene-PMT therapy in Csf2ra-/- mice were observed. Results demonstrate that gene-PMT therapy of hPAP in Csf2ra-/- mice was highly efficacious, durable, safe, and well tolerated.

Pulmonary alveolar proteinosis: An autoimmune disease lacking an HLA association.

Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterized by the accumulation of pulmonary surfactant in alveolar macrophages and alveoli, resulting in respiratory impairment and an increased risk of opportunistic infections. Autoimmune PAP is an autoimmune lung disease that is caused by autoantibodies directed against granulocyte-macrophage colony-stimulating factor (GM-CSF). A shared feature among many autoimmune diseases is a distinct genetic association to HLA alleles. In the present study, we HLA-typed patients with autoimmune PAP to determine if this disease had any HLA association. We analyzed amino acid and allele associations for HLA-A, B, C, DRB1, DQB1, DPB1, DRB3, DRB4 and DRB5 in 41 autoimmune PAP patients compared to 1000 ethnic-matched controls and did not find any HLA association with autoimmune PAP. Collectively, these data may suggest the absence of a genetic association to the HLA in the development of autoimmune PAP.

Statin as a novel pharmacotherapy of pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a syndrome of reduced GM-CSF-dependent, macrophage-mediated surfactant clearance, dysfunctional foamy alveolar macrophages, alveolar surfactant accumulation, and hypoxemic respiratory failure for which the pathogenetic mechanism is unknown. Here, we examine the lipids accumulating in alveolar macrophages and surfactant to define the pathogenesis of PAP and evaluate a novel pharmacotherapeutic approach. In PAP patients, alveolar macrophages have a marked increase in cholesterol but only a minor increase in phospholipids, and pulmonary surfactant has an increase in the ratio of cholesterol to phospholipids. Oral statin therapy is associated with clinical, physiological, and radiological improvement in autoimmune PAP patients, and ex vivo statin treatment reduces cholesterol levels in explanted alveolar macrophages. In Csf2rb-/- mice, statin therapy reduces cholesterol accumulation in alveolar macrophages and ameliorates PAP, and ex vivo statin treatment increases cholesterol efflux from macrophages. These results support the feasibility of statin as a novel pathogenesis-based pharmacotherapy of PAP.

Prevalence and healthcare burden of pulmonary alveolar proteinosis.

Pulmonary alveolar proteinosis (PAP) is a rare syndrome of alveolar surfactant accumulation, resulting hypoxemic respiratory failure, and increased infection risk. Despite advances in our understanding of disease pathogenesis and the availability of improved diagnostics, the epidemiology and healthcare burden of PAP remain poorly defined. To determine the prevalence, and healthcare utilization and costs associated with PAP, we interrogated a large health insurance claims database containing comprehensive data for approximately 15 million patients in the United States. We also evaluated data from a referral-based diagnostic testing program collected over a 15-year period. The prevalence of PAP was determined to be 6.87 ± 0.33 per million in the general population, similar in males and females, and increased with age, however considering difficulties and delays in diagnosing this is likely a minimum estimate of true prevalence. PAP patients had significantly more comorbidities, health care utilization and associated costs compared to control patients precisely matched for age and gender. Between 2004 and 2018, 249 patients confirmed to have PAP were evaluated to identify the PAP-causing disease; 91.5% had autoimmune PAP, 3% had hereditary PAP caused by GM-CSF receptor mutations, 4% had secondary PAP, and 1.5% had congenital PAP. Considering the high diagnostic accuracy of serum GM-CSF autoantibody testing and predominance of autoimmune PAP, these results emphasize the importance of utilizing blood-based testing in PAP syndrome to identify the PAP-causing disease rather than invasive lung biopsies, resulting in earlier diagnosis, reduced morbidity and lower healthcare costs.

Pulmonary Transplantation of Human Induced Pluripotent Stem Cell-derived Macrophages Ameliorates Pulmonary Alveolar Proteinosis.

RATIONALE: Although the transplantation of induced pluripotent stem cell (iPSC)-derived cells harbors enormous potential for the treatment of pulmonary diseases, in vivo data demonstrating clear therapeutic benefits of human iPSC-derived cells in lung disease models are missing. OBJECTIVES: We have tested the therapeutic potential of iPSC-derived macrophages in a humanized disease model of hereditary pulmonary alveolar proteinosis (PAP). Hereditary PAP is caused by a genetic defect of the GM-CSF (granulocyte-macrophage colony-stimulating factor) receptor, which leads to disturbed macrophage differentiation and protein/surfactant degradation in the lungs, subsequently resulting in severe respiratory insufficiency. METHODS: Macrophages derived from human iPSCs underwent intrapulmonary transplantation into humanized PAP mice, and engraftment, in vivo differentiation, and therapeutic efficacy of the transplanted cells were analyzed. MEASUREMENTS AND MAIN RESULTS: On intratracheal application, iPSC-derived macrophages engrafted in the lungs of humanized PAP mice. After 2 months, transplanted cells displayed the typical morphology, surface markers, functionality, and transcription profile of primary human alveolar macrophages. Alveolar proteinosis was significantly reduced as demonstrated by diminished protein content and surfactant protein D levels, decreased turbidity of the BAL fluid, and reduced surfactant deposition in the lungs of transplanted mice. CONCLUSIONS: We here demonstrate for the first time that pulmonary transplantation of human iPSC-derived macrophages leads to pulmonary engraftment, their in situ differentiation to an alveolar macrophage phenotype, and a reduction of alveolar proteinosis in a humanized PAP model. To our knowledge, this finding presents the first proof-of-concept for the therapeutic potential of human iPSC-derived cells in a pulmonary disease and may have profound implications beyond the rare disease of PAP.

Impaired granulocyte-macrophage colony-stimulating factor bioactivity accelerates surgical recurrence in ileal Crohn's disease.

AIM: To examine the relationship between elevated granulocyte-macrophage colony-stimulating factor (GM-CSF) auto-antibodies (Ab) level and time to surgical recurrence after initial surgery for Crohn's disease (CD). METHODS: We reviewed 412 charts from a clinical database at tertiary academic hospital. Patients included in the study had ileal or ileocolonic CD and surgical resection of small bowel or ileocecal region for management of disease. Serum samples were analyzed for serological assays including GM-CSF cytokine, GM-CSF Ab, ASCA IgG and IgA, and genetic markers including SNPs rs2066843, rs2066844, rs2066845, rs2076756 and rs2066847 in NOD2, rs2241880 in ATG16L1, and rs13361189 in IRGM. Cox proportional-hazards models were used to assess the predictors of surgical recurrence. RESULTS: Ninety six percent of patients underwent initial ileocecal resection (ICR) or ileal resection (IR) and subsequently 40% of patients required a second ICR/IR for CD. GM-CSF Ab level was elevated at a median of 3.81 mcg/mL. Factors predicting faster time to a second surgery included elevated GM-CSF Ab [hazard ratio (HR) 3.52, 95%CI: 1.45-8.53, P = 0.005] and elevated GM-CSF cytokine (HR = 2.48, 95%CI: 1.31-4.70, P = 0.005). Factors predicting longer duration between first and second surgery included use of Immunomodulators (HR = 0.49, 95%CI: 0.31-0.77, P = 0.002), the interaction effect of low GM-CSF Ab levels and smoking (HR = 0.60, 95%CI: 0.45-0.81, P = 0.001) and the interaction effect of low GM-CSF cytokine levels and ATG16L1 (HR = 0.65, 95%CI: 0.49-0.88, P = 0.006). CONCLUSION: GM-CSF bioavailability plays a critical role in maintaining intestinal homeostasis. Decreased bioavailability coupled with the genetic risk markers and/or smoking results in aggressive CD behavior.

Familial Association of Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in Inflammatory Bowel Disease.

OBJECTIVES: Elevated granulocyte-macrophage colony-stimulating factor auto-antibodies (GM-CSF Ab) are associated with increased intestinal permeability and stricturing behavior in Crohn disease (CD). We tested for familial association of serum GM-CSF Ab level in CD and ulcerative colitis (UC) families. METHODS: Serum GM-CSF Ab concentration was determined in 230 pediatric CD probands and 404 of their unaffected parents and siblings, and 45 UC probands and 71 of their unaffected parents and siblings. A linear mixed effects model was used to test for familial association. The intra-class correlation coefficient (ICC) was used to determine the degree of association of the serum GM-CSF Ab level within families in comparison with the degree of association among families. RESULTS: The median (IQR) serum GM-CSF Ab concentration was higher in CD probands than in UC probands (1.5 [0.5,5.4] µg/mL vs 0.7 [0.3, 1.6] µg/mL, P = 0.0002). The frequency of elevated serum GM-CSF Ab concentration ≥1.6 µg/mL was increased in unaffected siblings of CD probands with elevated GM-CSF Ab, compared with unaffected siblings of CD probands without elevated GM-CSF Ab (33% vs 13%, respectively, P = 0.04). A similar result was observed within UC families. In families of CD patients, the mean (95th CI) ICC was equal to 0.153 (0.036, 0.275), P = 0.001, whereas in families of UC patients, the mean (95th CI) ICC was equal to 0.27 (0.24, 0.31), P = 0.047. CONCLUSIONS: These data confirmed familial association of serum GM-CSF Ab levels. This could be accounted for by either genetic or environmental factors shared within the family.

Targeting cholesterol homeostasis in lung diseases.

Macrophages are critical to organ structure and function in health and disease. To determine mechanisms by which granulocyte/macrophage-colony stimulating factor (GM-CSF) signaling normally maintains surfactant homeostasis and how its disruption causes pulmonary alveolar proteinosis (PAP), we evaluated lipid composition in alveolar macrophages and lung surfactant, macrophage-mediated surfactant clearance kinetics/dynamics, and cholesterol-targeted pharmacotherapy of PAP in vitro and in vivo. Without GM-CSF signaling, surfactant-exposed macrophages massively accumulated cholesterol ester-rich lipid-droplets and surfactant had an increased proportion of cholesterol. GM-CSF regulated cholesterol clearance in macrophages in constitutive, dose-dependent, and reversible fashion but did not affect phospholipid clearance. PPARγ-agonist therapy increased cholesterol clearance in macrophages and reduced disease severity in PAP mice. Results demonstrate that GM-CSF is required for cholesterol clearance in macrophages, identify reduced cholesterol clearance as the primary macrophage defect driving PAP pathogenesis, and support the feasibility of translating pioglitazone as a novel pharmacotherapy of PAP.

Pulmonary macrophage transplantation therapy.

Bone-marrow transplantation is an effective cell therapy but requires myeloablation, which increases infection risk and mortality. Recent lineage-tracing studies documenting that resident macrophage populations self-maintain independently of haematological progenitors prompted us to consider organ-targeted, cell-specific therapy. Here, using granulocyte-macrophage colony-stimulating factor (GM-CSF) receptor-ß-deficient (Csf2rb(-/-)) mice that develop a myeloid cell disorder identical to hereditary pulmonary alveolar proteinosis (hPAP) in children with CSF2RA or CSF2RB mutations, we show that pulmonary macrophage transplantation (PMT) of either wild-type or Csf2rb-gene-corrected macrophages without myeloablation was safe and well-tolerated and that one administration corrected the lung disease, secondary systemic manifestations and normalized disease-related biomarkers, and prevented disease-specific mortality. PMT-derived alveolar macrophages persisted for at least one year as did therapeutic effects. Our findings identify mechanisms regulating alveolar macrophage population size in health and disease, indicate that GM-CSF is required for phenotypic determination of alveolar macrophages, and support translation of PMT as the first specific therapy for children with hPAP.

Use of induced pluripotent stem cells to recapitulate pulmonary alveolar proteinosis pathogenesis.

RATIONALE: In patients with pulmonary alveolar proteinosis (PAP) syndrome, disruption of granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling is associated with pathogenic surfactant accumulation from impaired clearance in alveolar macrophages. OBJECTIVES: The aim of this study was to overcome these barriers by using monocyte-derived induced pluripotent stem (iPS) cells to recapitulate disease-specific and normal macrophages. METHODS: We created iPS cells from two children with hereditary PAP (hPAP) caused by recessive CSF2RA(R217X) mutations and three normal people, differentiated them into macrophages (hPAP-iPS-Mφs and NL-iPS-Mφs, respectively), and evaluated macrophage functions with and without gene-correction to restore GM-CSF signaling in hPAP-iPS-Mφs. MEASUREMENTS AND MAIN RESULTS: Both hPAP and normal iPS cells had human embryonic stem cell-like morphology, expressed pluripotency markers, formed teratomas in vivo, had a normal karyotype, retained and expressed mutant or normal CSF2RA genes, respectively, and could be differentiated into macrophages with the typical morphology and phenotypic markers. Compared with normal, hPAP-iPS-Mφs had impaired GM-CSF receptor signaling and reduced GM-CSF-dependent gene expression, GM-CSF- but not M-CSF-dependent cell proliferation, surfactant clearance, and proinflammatory cytokine secretion. Restoration of GM-CSF receptor signaling corrected the surfactant clearance abnormality in hPAP-iPS-Mφs. CONCLUSIONS: We used patient-specific iPS cells to accurately reproduce the molecular and cellular defects of alveolar macrophages that drive the pathogenesis of PAP in more than 90% of patients. These results demonstrate the critical role of GM-CSF signaling in surfactant homeostasis and PAP pathogenesis in humans and have therapeutic implications for hPAP.

Standardized serum GM-CSF autoantibody testing for the routine clinical diagnosis of autoimmune pulmonary alveolar proteinosis.

Autoantibodies against granulocyte/macrophage colony-stimulating factor (GMAbs) cause autoimmune pulmonary alveolar proteinosis (PAP) and measurement of the GMAb level in serum is now commonly used to identify this disease, albeit, in a clinical research setting. The present study was undertaken to optimize and standardize serum GMAb concentration testing using a GMAb enzyme-linked immunosorbent assay (GMAb ELISA) to prepare for its introduction into routine clinical use. The GMAb ELISA was evaluated using serum specimens from autoimmune PAP patients, healthy people, and GMAb-spiked serum from healthy people. After optimizing assay components and procedures, its accuracy, precision, reliability, sensitivity, specificity, and ruggedness were evaluated. The coefficient of variation in repeated measurements was acceptable (<15%) for well-to-well, plate-to-plate, day-to-day, and inter-operator variation, and was not affected by repeated freeze-thaw cycles of serum specimens or the reference standards, or by storage of serum samples at -80°C. The lower limit of quantification (LLOQ) of the PAP patient-derived polyclonal GMAb reference standard (PCRS) was 0.78ng/ml. Receiver operating characteristic curve analysis identified a serum GMAb level of 5µg/ml (based on PCRS) as the optimal cut off value for distinguishing autoimmune PAP serum from normal serum. A pharmaceutical-grade, monoclonal GMAb reference standard (MCRS) was developed as the basis of a new unit of measure for GMAb concentration: one International Unit (IU) of GMAb is equivalent to 1µg/ml of MCRS. The median [interquartile range] serum GMAb level was markedly higher in autoimmune PAP patients than in healthy people (21.54 [12.83-36.38] versus 0.08 [0.05-0.14] IU; n=56, 38; respectively; P<0.0001). Results demonstrate that serum GMAb measurement using the GMAb ELISA was accurate, precise, reliable, had an acceptable LLOQ, and could be accurately expressed in standardized units. These findings support the use of this GMAb ELISA for the routine clinical diagnosis of autoimmune PAP and introduce a new unit of measure to enable standardized reporting of serum GMAb data from different laboratories.

Granulocyte macrophage colony-stimulating factor auto-antibodies and disease relapse in inflammatory bowel disease.

OBJECTIVES: Along with others, we have reported that neutralization of granulocyte macrophage colony-stimulating factor (GM-CSF) increases intestinal permeability and bacterial translocation, and reduces neutrophil bacterial killing and anti-microbial seroreactivity. The objective was to investigate the utility of serum GM-CSF auto-antibody (Ab) as a marker for confirmation of stable remission and prediction of relapses in patients with inflammatory bowel disease (IBD). METHODS: We consecutively included 181 adults and children with Crohn's disease (CD, n=61) or ulcerative colitis (UC, n=120). Over a 3-year period, we collected 861 serum samples and 610 stool samples during regular follow-up visits. GM-CSF Abs and fecal S100 proteins were measured by an enzyme-linked immunoassay. RESULTS: Serum GM-CSF Ab levels correlated with disease activity, location, and extent. Time course analysis before and after relapse showed a clear increase of GM-CSF Ab concentrations up to 6 months before clinical relapse. At 1.7 µg/ml (CD) and 0.5 µg/ml (UC), the sensitivity and specificity of GM-CSF Ab for predicting relapse already 2-6 months earlier were 88% and 95% in CD and 62% and 68% in UC, respectively. A baseline GM-CSF Ab level of >1.7 µg/ml was significantly associated with relapse of CD within 18 months. CONCLUSIONS: As GM-CSF is required for myeloid cell antimicrobial functions and homeostatic responses to tissue injury, serum GM-CSF Ab levels might reflect the degree of bowel permeability and bacterial translocation. Therefore, GM-CSF Ab might identify IBD patients at risk of disease relapse at an early stage, which makes the test a potential tool for monitoring disease activity and optimizing therapy.

Increased prevalence of luminal narrowing and stricturing identified by enterography in pediatric Crohn's disease patients with elevated granulocyte-macrophage colony stimulating factor autoantibodies.

BACKGROUND: Crohn's disease (CD) patients with elevated granulocyte-macrophage colony-stimulating factor autoantibodies (GM-CSF Ab) are more likely to develop stricturing behavior requiring surgery. Computed tomography or magnetic resonance enterography (CTE or MRE) may detect luminal narrowing (LN) before stricture development. The objective of this study was to determine whether CD patients with elevated GM-CSF Ab (≥1.6 µg/mL) have a higher prevalence of LN and stricturing on CTE or MRE. METHODS: A single-center, cross-sectional study of 153 pediatric patients with CD and control subjects undergoing diagnostic CTE or MRE. Examinations were evaluated for disease activity using a novel scoring system and for the presence of LN, stricture, intra-abdominal abscess, or fistulae. Dichotomous outcomes were compared with respect to antibody status (high or low) using Fisher's exact test and logistic regression, whereas continuous outcomes were evaluated using unpaired t test. RESULTS: GM-CSF Ab were elevated in CD patients (n = 114) with a median (interquartile range) GM-CSF Ab level of 2.3 µg/mL (0.5-6.6 µg/mL) compared with 0.6 µg/mL (0.3-1.3 µg/mL) in healthy and disease control subjects (n = 39) (P = 0.001). Ileal disease location was more common in CD patients with high GM-CSF Ab (P < 0.001). LN increased from 39% in CD patients with low GM-CSF Ab to 71% in those with high levels (P = 0.004) and remained significantly associated with high GM-CSF Ab in a multivariate logistic model, which included age, gender, small bowel location, and duration of disease. Stricturing prevalence on CTE or MRE examination increased from 4% in CD patients with low GM-CSF Ab to 19% in those with high GM-CSF Ab (P = 0.03). CONCLUSIONS: Pediatric CD patients with high GM-CSF Ab levels have a higher prevalence of LN on CTE or MRE. Further study will be needed to determine whether medical therapy will reduce progression to stricturing behavior in these patients.

Assessment and management of pulmonary alveolar proteinosis in a reference center.

Pulmonary alveolar proteinosis (PAP) is a term defining an ultra-rare group of disorders characterised by a perturbation in surfactant homeostasis, resulting in its accumulation within airspaces and impaired gas transfer. In this report we provide data from a cohort of PAP patients (n=81) followed for more than two decades at the San Matteo University Hospital of Pavia, Italy. In agreement with other large series in PAP individuals, 90% of the study subjects were affected by autoimmune/idiopathic PAP, while the remaining subjects were divided as follow: congenital 1%, secondary 4% and PAP-like 5%. The disease affected males and females with a ratio of 2:1 and approximately one third of PAP patients were lifelong nonsmokers. Occupational exposure was reported in 35% of subjects in this series. With reference to the PAP clinical course, in 29 patients (7% with spontaneous remission) disease severity did not necessitate whole lung lavage (WLL) in the long-term follow up. On the other hand, 44 PAP patients underwent therapeutic WLL: in 31 subjects a single WLL was sufficient to provide long term, durable benefit, whereas 13 patients required multiple WLLs. The intra-patient mean interval between two consecutive WLLs was 15.7±13.6 months. When baseline data among never lavaged and PAP patients lavaged at least once were compared, the need for lavage was significantly associated with serum biomarkers (CEA, Cyfra, LDH), lung function parameters forced vital capacity (FVC), and lung diffusing capacity (Dlco). We conclude that patient cohorts with an ultra-rare disease, such as PAP, referred to a single reference center, can provide useful information on the natural history and clinical course of the disease.