Efficacy and safety of Creon 24,000 in subjects with exocrine pancreatic insufficiency due to cystic fibrosis

BACKGROUND

Pancreatic enzyme replacement therapy is critical for adequate nutrition in cystic fibrosis (CF) patients with exocrine pancreatic insufficiency (EPI).

METHODS

This was a double-blind, randomised, placebo-controlled, two-period crossover study assessing efficacy and safety of Creon 24,000-unit capsules in CF subjects > or =12 years with EPI. Patients were randomised to one of two 5-day sequences, Creon/placebo or placebo/Creon (target dose, 4000 lipase units/g fat). Primary outcome was the coefficient of fat absorption (CFA); secondary outcomes were coefficient of nitrogen absorption (CNA), symptoms, and safety.

RESULTS

Thirty-two subjects were randomised. Mean CFA and CNA were significantly greater with Creon than placebo (CFA, 88.6% vs. 49.6%; CNA, 85.1% vs. 49.9%; p<0.001 for both). Symptoms were improved and fewer treatment-emergent adverse events were reported with Creon than placebo. One patient discontinued for weight loss unrelated to study drug.

CONCLUSIONS

This study demonstrated Creon was effective in treating EPI due to CF and was safe and well tolerated.

Pulmonary alveolar proteinosis, a primary immunodeficiency of impaired GM-CSF stimulation of macrophages

Pulmonary alveolar proteinosis (PAP) is a rare syndrome characterized by accumulation of pulmonary surfactant, respiratory insufficiency, and increased infections. It occurs in various clinical settings that disrupt surfactant catabolism in alveolar macrophages, including a relatively more common autoimmune disease caused by GM-CSF autoantibodies and a rare congenital disease caused by CSF2RA mutations. Recent results demonstrate that GM-CSF is crucial for alveolar macrophage terminal differentiation and immune functions, pulmonary surfactant homeostasis, and lung host defense. GM-CSF is also required to determine the basal functional capacity of circulating neutrophils, including adhesion, phagocytosis, and microbial killing. PAP research has illuminated the crucial role of GM-CSF in innate immunity and led to novel therapy for PAP and the potential use of anti-GM-CSF therapy in other common disorders.

Plasmapheresis for treatment of pulmonary alveolar proteinosis

Whole lung lavage (WLL) is currently the standard therapy for pulmonary alveolar proteinosis (PAP). Nevertheless, some PAP patients respond poorly to WLL or require it frequently. The present paper reports a patient with autoimmune PAP with persistent disease despite three WLL treatments over 10 months. Plasmapheresis with ten 1.5-L plasma exchanges was performed, which lowered the serum granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibody level from 250 microg mL(-1) to 156 microg mL(-1) but did not improve respiratory impairment. Further WLL therapy was required and transiently effective. Serum GM-CSF autoantibody levels declined progressively, reaching a value of 56 microg mL(-1) 80 weeks after completion of plasmapheresis. However, this decrease was not accompanied by clinical improvement and the patient required additional WLL therapy. The results confirm that minor reductions in serum granulocyte-macrophage colony-stimulating factor autoantibody levels from plasmapheresis are not reflected in clinical improvement in the severity of lung disease in pulmonary alveolar proteinosis.

Quantitative analysis of longitudinal response to aerosolized granulocyte-macrophage colony-stimulating factor in two adolescents with autoimmune pulmonary alveolar proteinosis

BACKGROUND

Autoimmune pulmonary alveolar proteinosis (APAP) is characterized by autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF) in blood and tissues, resulting in alveolar surfactant protein accumulation. Patients with APAP present with ground-glass opacities (GGOs) and interlobular septal thickening on thin-slice chest CT scans. Aerosolized GM-CSF therapy (aeroGM-SCF) has qualitatively improved the clinical condition of patients with APAP. This report details quantitative chest CT responses to aeroGM-CSF.

METHODS

Two adolescent patients (aged 16 and 19 years) with APAP were treated with aeroGM-CSF. Clinical parameters, including pulmonary function tests and chest CT scans, were obtained before and after aeroGM-CSF therapy. To evaluate the effect of the therapy, serial chest CT scans were analyzed using a novel approach permitting quantitative assessment of improvement in GGOs, lung weight, and gas volume.

RESULTS

In association with GM-CSF treatment, nutritional status and pulmonary function improved. Quantitative analysis of the CT scans demonstrated reduction in GGOs and lung weight, concomitant with an increase in airspace volume and lung inflation. The findings were consistent with a qualitative reduction in GGOs on chest CT imaging.

CONCLUSIONS

Quantitative analysis of CT holds promise as a sensitive diagnostic tool permitting longitudinal and objective analysis of the therapeutic response to aeroGM-CSF in patients with APAP.

Granulocyte-macrophage colony-stimulating factor autoantibodies in murine ileitis and progressive ileal Crohn's disease

BACKGROUND & AIMS

Genetic variations that affect innate immunity increase risk of ileal Crohn's disease (CD). However, the penetrance of susceptibility genes, including NOD2, is low, suggesting additional risk factors. Neutralizing autoantibodies (Ab) against granulocyte-macrophage colony-stimulating factor (GM-CSF Ab) reduce neutrophil antimicrobial function in patients with primary alveolar proteinosis (PAP). We investigated whether GM-CSF Ab regulates neutrophil function in CD.

METHODS

Serum samples from 354 adult and pediatric patients with inflammatory bowel disease (IBD) were analyzed for GM-CSF Ab and IBD markers. Levels of GM-CSF Ab were compared with patients' CD features and neutrophil function. Intestinal barrier function and nonsteroidal anti-inflammatory drug (NSAID)-induced injury were assessed in GM-CSF-null and NOD2-null mice.

RESULTS

Median GM-CSF Ab levels increased from 0.4 microg/mL in control serum to 2.4 microg/mL in pediatric CD and 11.7 microg/mL in adult CD serum and were associated with ileal involvement (P<.001). Ileal location, duration of disease, and increased GM-CSF Ab levels were associated with stricturing/penetrating behavior (odds ratio, 2.2; P=.018). The positive and negative predictive values of GM-CSF Ab for stricturing/penetrating behavior were comparable with that of other IBD serum markers. CD patients with increased GM-CSF Ab had reduced neutrophil phagocytic capacity and increased accumulation of pSTAT3+ neutrophils in the affected ileum. GM-CSF-null mice and NOD2-null mice in which GM-CSF was neutralized had defects in mucosal barrier function and developed a transmural ileitis following NSAID exposure.

CONCLUSIONS

GM-CSF regulates ileal homeostasis in CD and in mouse models. CD patients with increases in serum GM-CSF Ab might benefit from GM-CSF administration.

Familial pulmonary alveolar proteinosis caused by mutations in CSF2RA

Primary pulmonary alveolar proteinosis (PAP) is a rare syndrome characterized by accumulation of surfactant in the lungs that is presumed to be mediated by disruption of granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling based on studies in genetically modified mice. The effects of GM-CSF are mediated by heterologous receptors composed of GM-CSF binding (GM-CSF-Rα) and nonbinding affinity-enhancing (GM-CSF-Rβ) subunits. We describe PAP, failure to thrive, and increased GM-CSF levels in two sisters aged 6 and 8 yr with abnormalities of both GM-CSF-Rα–encoding alleles (CSF2RA). One was a 1.6-Mb deletion in the pseudoautosomal region of one maternal X chromosome encompassing CSF2RA. The other, a point mutation in the paternal X chromosome allele encoding a G174R substitution, altered an N-linked glycosylation site within the cytokine binding domain and glycosylation of GM-CSF-Rα, severely reducing GM-CSF binding, receptor signaling, and GM-CSF–dependent functions in primary myeloid cells. Transfection of cloned cDNAs faithfully reproduced the signaling defect at physiological GM-CSF concentrations. Interestingly, at high GM-CSF concentrations similar to those observed in the index patient, signaling was partially rescued, thereby providing a molecular explanation for the slow progression of disease in these children. These results establish that GM-CSF signaling is critical for surfactant homeostasis in humans and demonstrate that mutations in CSF2RA cause familial PAP.

Characteristics of a large cohort of patients with autoimmune pulmonary alveolar proteinosis in Japan

RATIONALE

Acquired pulmonary alveolar proteinosis (PAP) is a syndrome characterized by pulmonary surfactant accumulation occurring in association with granulocyte/macrophage colony-stimulating factor autoantibodies (autoimmune PAP) or as a consequence of another disease (secondary PAP). Because PAP is rare, prior reports were based on limited patient numbers or a synthesis of historical data.

OBJECTIVES

To describe the epidemiologic, clinical, physiologic, and laboratory features of autoimmune PAP in a large, contemporaneous cohort of patients with PAP.

METHODS

Over 6 years, 248 patients with PAP were enrolled in a Japanese national registry, including 223 with autoimmune PAP.

MEASUREMENTS AND MAIN RESULTS

Autoimmune PAP represented 89.9% of cases and had a minimum incidence and prevalence of 0.49 and 6.2 per million, respectively. The male to female ratio was 2.1:1, and the median age at diagnosis was 51 years. A history of smoking occurred in 56%, and dust exposure occurred in 23%; instances of familial onset did not occur. Dyspnea was the most common presenting symptom, occurring in 54.3%. Importantly, 31.8% of patients were asymptomatic and were identified by health screening. Intercurrent illnesses, including infections, were infrequent. A disease severity score reflecting the presence of symptoms and degree of hypoxemia correlated well with carbon monoxide diffusing capacity and serum biomarkers, less well with pulmonary function, and not with granulocyte/macrophage colony-stimulating factor autoantibody levels or duration of disease.

CONCLUSIONS

Autoimmune PAP had an incidence and prevalence higher than previously reported and was not strongly linked to smoking, occupational exposure, or other illnesses. The disease severity score and biomarkers provide novel and potentially useful outcome measures in PAP.

Diffuse lung disease in young children: application of a novel classification scheme

RATIONALE

Considerable confusion exists regarding nomenclature, classification, and management of pediatric diffuse lung diseases due to the relative rarity and differences in the spectrum of disease between adults and young children.

OBJECTIVES

A multidisciplinary working group was formed to: (1) apply consensus terminology and diagnostic criteria for disorders presenting with diffuse lung disease in infancy; and (2) describe the distribution of disease entities, clinical features, and outcome in young children who currently undergo lung biopsy in North America.

METHODS

Eleven centers provided pathologic material, clinical data, and imaging from all children less than 2 years of age who underwent lung biopsy for diffuse lung disease from 1999 to 2004.

MEASUREMENTS AND MAIN RESULTS

Multidisciplinary review categorized 88% of 187 cases. Disorders more prevalent in infancy, including primary developmental and lung growth abnormalities, neuroendocrine cell hyperplasia of infancy, and surfactant-dysfunction disorders, constituted the majority of cases (60%). Lung growth disorders were often unsuspected clinically and under-recognized histologically. Cases with known surfactant mutations had characteristic pathologic features. Age at biopsy and clinical presentation varied among categories. Pulmonary hypertension, presence of a primary developmental abnormality, or ABCA3 mutation was associated with high mortality, while no deaths occurred in cases of pulmonary interstitial glycogenosis, or neuroendocrine cell hyperplasia of infancy.

CONCLUSIONS

This retrospective cohort study identifies a diverse spectrum of lung disorders, largely unique to young children. Application of a classification scheme grouped clinically distinct patients with variable age of biopsy and mortality. Standardized terminology and classification will enhance accurate description and diagnosis of these disorders.

Molecular pathogenesis of alpha-1-antitrypsin deficiency-associated liver disease: a meeting review

In recent years, we have witnessed several important paradigm shifts in understanding the molecular basis of liver disease in alpha-1-antitrypsin (AT) deficiency. These shifts have become possible as a result of a number of advances in research on the cell biology of aggregation-prone mutant proteins and in research on the pathobiological mechanisms of liver disease in general. Late-breaking research in these areas was the subject of an AASLD/Alpha-1 Foundation Single Topic Conference in Atlanta, Georgia, on January 26 to 28, 2006. The conference was titled "Alpha-1-Antitrypsin Deficiency and Other Liver Diseases Caused by Aggregated Proteins." Investigators from all over the world, representing a broad array of scientific disciplines and perspectives, discussed the pathobiology of AT deficiency, mechanisms of cell injury in diseases associated with aggregation-prone proteins, pathways by which cells respond to protein aggregation and mislocalization, and mechanisms of liver injury in general and in diseases related to AT deficiency. A session of the meeting was devoted to novel therapeutic strategies being developed for AT deficiency as well as to strategies either in development or already being applied to the class of diseases associated with mutant proteins.

Anti-cytokine autoantibodies are ubiquitous in healthy individuals

Anti-cytokine autoantibodies in healthy individuals have been widely reported but the occurrence is variable and inconstant. We hypothesized that cytokine-binding in vivo may explain their variable and infrequent detection. Therefore, we focused on the detection of the cytokine-autoantibody complexes and found that anti-cytokine autoantibody to IL-2, IL-8, tumor necrosis factor-alpha, vascular endothelial growth factor and granulocyte-colony stimulating factor were present in all 15 individuals evaluated, while those to IL-3, osteopontin and macrophage-colony stimulating factor were not detected in anyone. Autoantibodies against IL-4, IL-6, IL-10, and interferon-gamma were variously detected. Thus, we discovered that anti-cytokine autoantibodies to multiple cytokines are ubiquitous in healthy individuals.

PU.1 redirects adenovirus to lysosomes in alveolar macrophages, uncoupling internalization from infection

Adenovirus is endocytosed and efficiently destroyed by human and murine alveolar macrophages (AMs) and rapidly cleared from the lungs of wild-type but not GM-CSF(-/-) mice. We hypothesized that GM-CSF may regulate adenovirus clearance in AMs via the transcription factor PU.1 by redirecting virion trafficking from the nucleus to lysosomes. This hypothesis was tested in murine AM cell lines with altered GM-CSF and/or PU.1 expression including MH-S (GM-CSF(+/+)PU.1(Pos)), mAM (GM-CSF(-/-)/PU.1(Neg)), and mAM(PU.1+) (GM-CSF(-/-)/PU.1(Pos); PU.1-transduced mAM cells) and A549 (an epithelial-like cell line) using a human adenovirus expressing a beta-galactosidase reporter. In PU.1(Neg) mAM and A549 cells, adenovirus efficiently escaped from endosomes, translocated to the nucleus, and expressed the viral reporter in most cells. In marked contrast, in PU.1(Pos) mAM(PU.1+) and MH-S cells, adenovirus failed to escape from endosomes, colocalized exclusively with endosome/lysosome markers (Rab5, Rab7, and Lamp1), and rarely expressed the reporter. Retroviral expression of PU.1 in A549 cells blocked endosomal escape, nuclear translocation and reporter expression. Inhibition of endosome acidification also blocked escape, nuclear translocation, and reporter expression in PU.1(Neg) cells. The effect of PU.1 on viral trafficking and transduction could not be explained by an effect on endosome acidification or on differences in viral load. PU.1 reduced expression of integrin beta(5), a host factor important for endosomal escape of adenovirus, suggesting that PU.1 redirects adenoviral trafficking by modulating integrin signaling. These results demonstrate that PU.1 uncouples infection from internalization in AMs, providing a mechanism for AMs to avoid infection by adenovirus during clearance.

GM-CSF autoantibodies and neutrophil dysfunction in pulmonary alveolar proteinosis

BACKGROUND

Increased mortality from infection in patients with pulmonary alveolar proteinosis occurs in association with high levels of autoantibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF). We tested the hypothesis that neutrophil functions are impaired in patients with pulmonary alveolar proteinosis and that GM-CSF autoantibodies cause the dysfunction.

METHODS

We studied 12 subjects with pulmonary alveolar proteinosis, 61 healthy control subjects, and 12 control subjects with either cystic fibrosis or end-stage liver disease. We also studied GM-CSF-/- mice and wild-type mice. We evaluated basal neutrophil functions, neutrophil functions after priming by GM-CSF to augment antimicrobial functions, and the effects of highly purified GM-CSF autoantibodies on neutrophil functions in vitro and in vivo.

RESULTS

Neutrophils from subjects with pulmonary alveolar proteinosis had normal ultrastructure and differentiation markers but impaired basal functions and antimicrobial functions after GM-CSF priming. GM-CSF-/- mice also had reduced basal neutrophil functions, but functions after GM-CSF priming were unimpaired. The neutrophil dysfunction characteristic of pulmonary alveolar proteinosis was reproduced in a dose-dependent fashion in blood specimens from healthy control subjects after incubation with affinity-purified GM-CSF autoantibodies isolated from patients with pulmonary alveolar proteinosis. The injection of mouse GM-CSF antibodies into wild-type mice also caused neutrophil dysfunction.

CONCLUSIONS

The antimicrobial functions of neutrophils are impaired in patients with pulmonary alveolar proteinosis, owing to the presence of GM-CSF autoantibodies. The effects of these autoantibodies show that GM-CSF is an essential regulator of neutrophil functions.

GM-CSF regulates a PU.1-dependent transcriptional program determining the pulmonary response to LPS

Alveolar macrophages (AMs) normally respond to lipopolysaccharide (LPS) by activating Toll-like receptor (TLR)-4 signaling, a mechanism critical to lung host defense against gram-negative bacteria such as Pseudomonas aeruginosa. Because granulocyte macrophage colony-stimulating factor (GM-CSF)-deficient (GM(-/-)) mice are hyporesponsive to LPS, we evaluated the role of GM-CSF in TLR-4 signaling in AMs. Pulmonary TNF-alpha levels and neutrophil recruitment 4 h after intratracheal administration of Pseudomonas LPS were reduced in GM(-/-) compared with wild-type (GM(+/+)) mice. Secretion of TNF-alpha by AMs exposed to LPS ex vivo was also reduced in GM(-/-) mice and restored in mice expressing GM-CSF specifically in the lungs (SPC-GM(+/+)/GM(-/-) mice). LPS-dependent NF-kappaB promoter activity, TNF-alpha secretion, and neutrophil chemokine release were reduced in AM cell lines derived from GM(-/-) mice (mAM) compared with GM(+/+) (MH-S). Retroviral expression of PU.1 in mAM cells, which normally lack PU.1, rescued all of these AM defects. To determine whether GM-CSF, via PU.1, regulated expression of TLR-4 pathway components, mRNA and protein levels for key components were evaluated in MH-S cells (GM(+/+), PU.1(Positive)), mAM cells (GM(-/-), PU.1(Negative)), and mAMPU.1+ cells (GM(-/-), PU.1(Positive)). Cluster of differentiation antigen-14, radioprotective 105, IL-1 receptor-associated kinase (IRAK)-M mRNA, and protein were dependent upon GM-CSF and restored by expression of PU.1. In contrast, expression of other TLR-4 pathway components (myeloid differentiation-2, TLR-4, IRAK-1, IRAK-2, Toll/IL-1 receptor domain containing adapter protein/MyD88 adaptor-like, myeloid differentiation primary-response protein 88, IRAK-4, TNF receptor-associated factor-6, NF-kappaB, inhibitor of NF-kappaB kinase) were not GM-CSF or PU.1-dependent. These results show that GM-CSF, via PU.1, enables AM responses to P. aeruginosa LPS by regulating expression of a specific subset of components of the TLR-4 signaling pathway.

Genetic disorders influencing lung formation and function at birth

Adaptation to air breathing at birth is dependent on formation and function of the lung. Lung morphogenesis is a complex process dependent on precise temporal-spatial control of cell proliferation, differentiation and behavior mediated by autocrine-paracrine signaling that instructs transcriptional processes during organogenesis. Mutations in genes causing severe, and often lethal, lung malformations include those in the sonic hedgehog, fibroblast growth factor and thyroid transcription factor-1 pathways. Mutations in genes regulating surfactant homeostasis, necessary for reduction of surface tension in the alveoli, cause lethal respiratory distress at birth or interstitial lung disease in childhood. Inherited disorders of the surfactant system that affect neonatal respiratory adaptation at birth include hereditary surfactant protein B deficiency, mutations in surfactant protein C and the ABCA3 transporter.

Disruption of granulocyte macrophage-colony stimulating factor production in the lungs severely affects the ability of mice to control Mycobacterium tuberculosis infection

Mice lacking expression of granulocyte macrophage-colony stimulating factor (GM-CSF KO) are unable to contain Mycobacterium tuberculosis (M. tuberculosis) growth and succumb to infection by 35 days following pulmonary challenge. GM-CSF KO mice do not express normal levels of the inflammatory cytokine tumor necrosis factor alpha (TNF-alpha) nor the chemokines, regulated on activation, normal T expressed and secreted (RANTES), macrophage-inflammatory protein-1beta (MIP-1beta), MIP-1alpha, and lymphotactin, which are required for recruitment of lymphocytes and expression of a T helper cell type 1 (TH1) response within the lungs. In contrast, transgenic mice overexpressing GM-CSF in the lungs but with a lack of GM-CSF in other organs (GM+) are able to recruit lymphocytes and to express a TH1 response with production of TNF-alpha and interferon-gamma in the lungs. However, GM+ mice succumb to infection between 60 and 90 days post-challenge, as they are unable to develop a normal granulomatous response. Although GM+ mice are able to express the chemokine RANTES, they lack the ability to express other inflammatory chemokines such as lymphotactin and MIP-1beta. We conclude that GM-CSF is essential to the recruitment of lymphocytes and expression of a TH1 response in the lung, to the generation of a normal mononuclear granuloma, and most importantly, to the containment of M. tuberculosis bacterial growth.

PU.1 regulation of human alveolar macrophage differentiation requires granulocyte-macrophage colony-stimulating factor

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is critically implicated in lung homeostasis in the GM-CSF knockout mouse model. These animals develop an isolated lung lesion reminiscent of pulmonary alveolar proteinosis (PAP) seen in humans. The development of the adult form of human alveolar proteinosis is not due to the absence of a GM-CSF gene or receptor defect but to the development of an anti-GM-CSF autoimmunity. The role of GM-CSF in the development of PAP is unknown. Studies in the GM-CSF knockout mouse have shown that lack of PU.1 protein expression in alveolar macrophages is correlated with decreased maturation, differentiation, and surfactant catabolism. This study investigates PU.1 expression in vitro and in vivo in human PAP alveolar macrophages as well as the regulation of PU.1 by GM-CSF. We show for the first time that PU.1 mRNA expression in PAP bronchoalveolar lavage cells is deficient compared with healthy controls. PU.1-dependent terminal differentiation markers CD32 (FCgammaII), mannose receptor, and macrophage colony-stimulating factor receptor (M-CSFR) are decreased in PAP alveolar macrophages. In vitro studies demonstrate that exogenous GMCSF treatment upregulated PU.1 and M-CSFR gene expression in PAP alveolar macrophages. Finally, in vivo studies showed that PAP patients treated with GM-CSF therapy have higher levels of PU.1 and M-CSFR expression in alveolar macrophages compared with healthy control and PAP patients before GM-CSF therapy. These observations suggest that PU.1 is critical in the terminal differentiation of human alveolar macrophages.

High-affinity autoantibodies specifically eliminate granulocyte-macrophage colony-stimulating factor activity in the lungs of patients with idiopathic pulmonary alveolar proteinosis

Deficiency of granulocyte-macrophage colony-stimulating factor (GM-CSF) in mice results in pulmonary alveolar proteinosis (PAP) from impaired surfactant catabolism by alveolar macrophages (AMs). Recently, we have shown that neutralizing anti-GM-CSF autoantibodies develop specifically in patients with idiopathic pulmonary alveolar proteinosis (iPAP). Analogous to murine PAP models, it is plausible that the autoantibodies reduce GM-CSF activity, resulting in AM dysfunction and surfactant accumulation. To examine this hypothesis, we estimated the neutralizing activity of the autoantibodies in the lungs of patients and characterized their biologic properties. GM-CSF bioactivity was completely abrogated in the bronchoalveolar lavage fluid (BALF) of patients with iPAP but not in healthy subjects. Autoantibodies were present in the alveoli in high concentrations and colocalized with GM-CSF. They recognized human GM-CSF with high avidity (K(AV) = 20.0 +/- 7.5 pM) and high specificity, reacting with its superstructure and neutralizing GM-CSF activity to a level 4000 to 58 000 times the levels of GM-CSF normally present in the lung. Although target epitopes varied among patients, GM-CSF amino acids 78 to 94 were consistently recognized. Thus, autoantibodies bind GM-CSF with high specificity and high affinity, exist abundantly in the lung, and effectively block GM-CSF binding to its receptor, inhibiting AM differentiation and function. Our data strengthen the evidence associating anti-GM-CSF autoantibodies with the pathogenesis of this disease.

Endocytic internalization of adenovirus, nonspecific phagocytosis, and cytoskeletal organization are coordinately regulated in alveolar macrophages by GM-CSF and PU.1

GM-CSF gene-targeted (GM(-/-)) mice have impaired pulmonary clearance of bacterial and fungal pathogens by alveolar macrophages (AMs). Because AMs also clear adenovirus from the lung, the role of GM-CSF in endocytic internalization of adenovirus by AMs was evaluated. Pulmonary clearance of adenovirus was severely impaired in GM(-/-) mice compared to wild-type (GM(+/+)) mice as determined by Southern analysis of viral DNA. Internalization of adenovirus by AMs was deficient in GM(-/-) mice in vivo and in vitro as determined by uptake of fluorescently labeled adenovirus or by PCR quantification of adenoviral DNA internalized within AMs. An AM cell line previously established from GM(-/-) mice (mAM) had impaired internalization of adenovirus and transferrin-coated 100-nm latex beads compared to MH-S, a GM(+/+) AM cell line. Phagocytosis of 4- micro m latex beads was also impaired in mAM cells as determined by confocal and fluorescence microscopy. Retroviral vector-mediated reconstitution of PU.1 expression in cultured GM(-/-) AMs restored phagocytosis of 4- micro m beads, endocytosis of adenovirus, and transferrin-coated 100-nm beads (independent of integrin alpha(V) and transferrin receptors, respectively), and restored normal cytoskeletal organization, filamentous actin distribution, and stimulated formation of filopodia. Interestingly, mRNA for the phosphoinositide 3 kinase p110gamma isoform, important in macrophage phagocytic function, was absent in GM(-/-) AMs and was restored by PU.1 expression. These data show that GM-CSF, via PU.1, regulates endocytosis of small ( approximately 100 nm) pathogens/inert particles and phagocytosis of very large inert particles and suggests regulation of cytoskeletal organization by GM-CSF/PU.1 as the molecular basis of this control.

GM-CSF, via PU.1, regulates alveolar macrophage Fcgamma R-mediated phagocytosis and the IL-18/IFN-gamma -mediated molecular connection between innate and adaptive immunity in the lung

Severely impaired pulmonary microbial clearance was observed in granulocyte-macrophage colony-stimulating factor (GM-CSF)-deficient mice. To determine mechanisms by which GM-CSF mediates lung host defense, FcgammaR-mediated phagocytosis (opsonophagocytosis) by alveolar macrophages (AMs) was assessed in GM-CSF-sufficient (GM(+/+)) and -deficient (GM(-/-)) mice and in GM(-/-) mice expressing GM-CSF only in the lungs from a surfactant protein C (SPC) promoter (SPC-GM(+/+)/GM(-/-)). Opsonophagocytosis by GM(-/-) AMs was severely impaired and was restored by pulmonary GM-CSF expression in vivo or by PU.1 expression in vitro. Defective opsonophagocytosis by GM(-/-) AMs was associated with decreased FcgammaR expression. Because interferon-gamma (IFN-gamma) augments macrophage FcgammaR levels, the role of GM-CSF/PU.1 in the regulation of AM FcgammaR expression by IFN-gamma was assessed during adenoviral lung infection. Adenoviral infection stimulated IFN-gamma production and augmented FcgammaR levels on AMs in GM-CSF-expressing but not GM(-/-) mice. However, IFN-gamma exposure ex vivo stimulated FcgammaR expression on GM(-/-) AMs. Because interleukin-18 (IL-18) and IL-12 stimulate IFN-gamma production during adenoviral infection, their role in GM-CSF/PU.1 regulation of IFN-gamma-augmented FcgammaR expression on AMs was assessed. Adenoviral infection stimulated IL-18 and IL-12 production in GM-CSF-expressing mice, but both were markedly reduced or absent in GM(-/-) mice. IL-18 expression by GM(-/-) AMs was severely impaired and was restored by pulmonary GM-CSF expression in vivo or by PU.1 expression in vitro. Pulmonary administration of IL-18 in GM(-/-) mice stimulated IFN-gamma production and restored FcgammaR expression on AMs. These results show that GM-CSF, via PU.1, regulates constitutive AM FcgammaR expression and opsonophagocytosis and is required for the IFN-gamma-dependent regulation of AM FcgammaR expression, enabling AMs to release IL-18/IL-12 during lung infection.