Granulocyte/macrophage–colony-stimulating factor autoantibodies and myeloid cell immune functions in healthy subjects

Autoimmune pulmonary alveolar proteinosis developed during treatment for systemic sclerosis: a case report

BACKGROUND

Reports of autoimmune diseases coexisting with autoimmune pulmonary alveolar proteinosis (autoimmune PAP; APAP) are extremely rare. APAP coexisting with autoimmune diseases may often be misdiagnosed as connective tissue disease-associated interstitial lung disease (ILD). Here, we describe a rare case of a patient with systemic sclerosis who was diagnosed with APAP after the exacerbation of lung opacities during treatment with immunosuppressive agents.

CASE PRESENTATION

A 72-year-old woman was diagnosed with systemic sclerosis (SSc) at the age of 68, and initiated treatment with prednisolone (PSL). At the age of 70, she was diagnosed with ILD associated with SSc. Despite intravenous cyclophosphamide (IVCY), no improvement was observed. A significant elevation of Krebs von den Lungen-6 (KL-6) and a crazy-paving pattern on chest computed tomography (CT) are observed. Bronchoscopy showed milky white bronchoalveolar lavage fluid (BALF) and histology of periodic acid-Schiff (PAS) stain-positive eosinophilic granular material. Serum anti granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies were measured, and the result was positive, leading to the diagnosis of APAP.

CONCLUSION

In patients with interstitial lung shadows who do not improve with immunosuppressive treatment, PAP is one of the differential diagnoses that should be considered. All physicians should be aware that the appropriate diagnosis of PAP and the measurement of serum anti-GM-CSF antibodies will critically affect patient outcomes.

Pathogenesis-driven treatment of primary pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a syndrome that results from the accumulation of lipoproteinaceous material in the alveolar space. According to the underlying pathogenetic mechanisms, three different forms have been identified, namely primary, secondary and congenital. Primary PAP is caused by disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling due to the presence of neutralising autoantibodies (autoimmune PAP) or GM-CSF receptor genetic defects (hereditary PAP), which results in dysfunctional alveolar macrophages with reduced phagocytic clearance of particles, cholesterol and surfactant. The serum level of GM-CSF autoantibody is the only disease-specific biomarker of autoimmune PAP, although it does not correlate with disease severity. In PAP patients with normal serum GM-CSF autoantibody levels, elevated serum GM-CSF levels is highly suspicious for hereditary PAP. Several biomarkers have been correlated with disease severity, although they are not specific for PAP. These include lactate dehydrogenase, cytokeratin 19 fragment 21.1, carcinoembryonic antigen, neuron-specific enolase, surfactant proteins, Krebs von Lungen 6, chitinase-3-like protein 1 and monocyte chemotactic proteins. Finally, increased awareness of the disease mechanisms has led to the development of pathogenesis-based treatments, such as GM-CSF augmentation and cholesterol-targeting therapies.

Nocardia Infection in Patients With Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies: A Prospective Multicenter French Study

Background

Nocardiosis, a bacterial opportunistic infection caused by Nocardia spp, has recently been reported in patients with anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies, but insufficient data are available about disease presentation, outcomes, and occurrence of autoimmune pulmonary alveolar proteinosis (aPAP) in this population.

Methods

We performed a prospective, multicenter, nationwide study in France and included patients with a Nocardia infection who had anti-GM-CSF autoantibodies. We describe their clinical, microbiological, and radiological characteristics, and their outcome at 1 year of follow-up.

Results

Twenty patients (18 [90%] male) were included, with a median age of 69 (interquartile range, 44-75) years. The organs most frequently involved were the brain (14/20 [70%]) and the lung (12/20 [60%]). Half of the infections were disseminated (10/20 [50%]). Nocardia identification was predominantly made in abscess fluid (17/20 [85%]), among which 10 (59%) were brain abscesses. The 1-year all-cause mortality was 5% (1/20), and only 1 case of aPAP (1/20 [5%]) occurred during the follow-up period.

Conclusions

Nocardiosis with anti-GM-CSF autoantibodies is associated with a low mortality rate despite a high incidence of brain involvement. Although the occurrence of aPAP was infrequent during the 1-year follow-up period, long-term clinical data are needed to fully understand the potential relationship between nocardiosis, anti-GM-CSF autoantibodies, and aPAP.

The ouroboros of autoimmunity

Human autoimmunity against elements conferring protective immunity can be symbolized by the 'ouroboros', a snake eating its own tail. Underlying infection is autoimmunity against three immunological targets: neutrophils, complement and cytokines. Autoantibodies against neutrophils can cause peripheral neutropenia underlying mild pyogenic bacterial infections. The pathogenic contribution of autoantibodies against molecules of the complement system is often unclear, but autoantibodies specific for C3 convertase can enhance its activity, lowering complement levels and underlying severe bacterial infections. Autoantibodies neutralizing granulocyte-macrophage colony-stimulating factor impair alveolar macrophages, thereby underlying pulmonary proteinosis and airborne infections, type I interferon viral diseases, type II interferon intra-macrophagic infections, interleukin-6 pyogenic bacterial diseases and interleukin-17A/F mucocutaneous candidiasis. Each of these five cytokine autoantibodies underlies a specific range of infectious diseases, phenocopying infections that occur in patients with the corresponding inborn errors. In this Review, we analyze this ouroboros of immunity against immunity and posit that it should be considered as a factor in patients with unexplained infection.

Anti-cytokine autoantibodies: mechanistic insights and disease associations

Anti-cytokine autoantibodies (ACAAs) are increasingly recognized as modulating disease severity in infection, inflammation and autoimmunity. By reducing or augmenting cytokine signalling pathways or by altering the half-life of cytokines in the circulation, ACAAs can be either pathogenic or disease ameliorating. The origins of ACAAs remain unclear. Here, we focus on the most common ACAAs in the context of disease groups with similar characteristics. We review the emerging genetic and environmental factors that are thought to drive their production. We also describe how the profiling of ACAAs should be considered for the early diagnosis, active monitoring, treatment or sub-phenotyping of diseases. Finally, we discuss how understanding the biology of naturally occurring ACAAs can guide therapeutic strategies.

Anticytokine Autoantibodies in Infectious Diseases: A Practical Overview

Anticytokine autoantibodies (ACAAs) are a fascinating group of antibodies that have gained more and more attention in the field of autoimmunity and secondary immunodeficiencies over the years. Some of these antibodies are characterized by their ability to target and neutralize specific cytokines. ACAAs can play a role in the susceptibility to several infectious diseases, and their infectious manifestations depending on which specific immunological pathway is affected. In this review, we will give an outline per infection in which ACAAs might play a role and whether additional immunomodulatory treatment next to antimicrobial treatment can be considered. Finally, we describe the areas for future research on ACAAs.

Functional autoantibodies: Definition, mechanisms, origin and contributions to autoimmune and non-autoimmune disorders

A growing body of evidence underscores the relevance of functional autoantibodies in the development of various pathogenic conditions but also in the regulation of homeostasis. However, the definition of functional autoantibodies varies among studies and a comprehensive overview on this emerging topic is missing. Here, we do not only explain functional autoantibodies but also summarize the mechanisms underlying the effect of such autoantibodies including receptor activation or blockade, induction of receptor internalization, neutralization of ligands or other soluble extracellular antigens, and disruption of protein-protein interactions. In addition, in this review article we discuss potential triggers of production of functional autoantibodies, including infections, immune deficiency and tumor development. Finally, we describe the contribution of functional autoantibodies to autoimmune diseases including autoimmune thyroid diseases, myasthenia gravis, autoimmune pulmonary alveolar proteinosis, autoimmune autonomic ganglionopathy, pure red cell aplasia, autoimmune encephalitis, pemphigus, acquired thrombotic thrombocytopenic purpura, idiopathic dilated cardiomyopathy and systemic sclerosis, as well as non-autoimmune disorders such as allograft rejection, infectious diseases and asthma.

The world of rare interstitial lung diseases

The world of rare interstitial lung diseases (ILDs) is diverse and complex. Diagnosis and therapy usually pose challenges. This review describes a selection of rare and ultrarare ILDs including pulmonary alveolar proteinosis, pulmonary alveolar microlithiasis and pleuroparenchymal fibroelastosis. In addition, monogenic ILDs or ILDs in congenital syndromes and various multiple cystic lung diseases will be discussed. All these conditions are part of the scope of the European Reference Network on rare respiratory diseases (ERN-LUNG). Epidemiology, pathogenesis, diagnostics and treatment of each disease are presented.

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.

GM-CSF antibodies in artificial stone associated silicoproteinosis: A case report and literature review

Pulmonary alveolar proteinosis (PAP) is a rare lung disease where there is accumulation of surfactant in the alveoli. It can be classified based on the underlying aetiology into three categories: primary, secondary and congenital. Autoantibodies to granulocyte-macrophage colony-stimulating factor (GM-CSF-Ab) are a key diagnostic feature of autoimmune PAP. High intensity occupational exposure and inhalation of toxic particles such as silica can cause a form of secondary PAP called acute silicoproteinosis. We describe a 26-year-old stone benchtop fabricator with silicoproteinosis following daily exposure to high levels of silica who had elevated serum GM-CSF-Ab. We discuss the role of GM-CSF-Ab in cases of PAP with occupational inhalational exposure and the challenges in its interpretation.

Cryptococcus gattii Infection as the Major Clinical Manifestation in Patients with Autoantibodies Against Granulocyte-Macrophage Colony-Stimulating Factor

PURPOSE

Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are a predisposing factor for pulmonary alveolar proteinosis (PAP) and Cryptococcus gattii cryptococcosis. This study aimed to investigate clinical manifestations in anti-GM-CSF Ab-positive patients with C. gattii cryptococcosis and analyze the properties of anti-GM-CSF Abs derived from these patients and patients with PAP.

METHODS

Thirty-nine patients diagnosed with cryptococcosis (caused by C. neoformans or C. gattii) and 6 with PAP were enrolled in the present study. Clinical information was obtained from medical records. Blood samples were collected for analysis of autoantibody properties. We also explored the National Health Insurance Research Database (NHIRD) of Taiwan to investigate the epidemiology of cryptococcosis and PAP.

RESULTS

High titers of neutralizing anti-GM-CSF Abs were identified in 15 patients with cryptococcosis (15/39, 38.5%). Most anti-GM-CSF Ab-positive cryptococcosis cases had central nervous system (CNS) involvement (14/15, 93.3%). Eleven out of 14 (78.6%) anti-GM-CSF Ab-positive CNS cryptococcosis patients were confirmed to be infected with C. gattii, and PAP did not occur synchronously or metachronously in a single patient from our cohort. Exploration of an association between HLA and anti-GM-CSF Ab positivity or differential properties of autoantibodies from cryptococcosis patients and PAP yielded no significant results.

CONCLUSION

Anti-GM-CSF Abs can cause two diseases, C. gattii cryptococcosis and PAP, which seldom occur in the same subject. Current biological evidence regarding the properties of anti-GM-CSF Abs cannot provide clues regarding decisive mechanisms. Further analysis, including more extensive cohort studies and investigations into detailed properties, is mandatory to better understand the pathogenesis of anti-GM-CSF Abs.

[Anti-cytokine autoantibodies: Review of the literature]

Anti-cytokine antibodies (ACA) are an emerging cause of acquired immunodeficiency, especially in previously healthy adults. The most frequently reported are anti-IFN-γ responsible for disseminated non-tuberculous mycobacteria infections, and anti-GM-CSF mainly in mycobacteria, cryptococcosis and nocardiosis infections. The presence of anti-IFN-α in severe COVID-19 infections has recently been described. The search for and detection of these ACAs in an unusual infection situation makes it possible to set up specific therapies in addition to the anti-infective treatment. ACAs are also frequent in various autoimmune pathologies where, in addition to being indicators of the breakdown of immune tolerance, they can modulate the activity of the disease according to their cytokine target. In this review of the literature, we will focus on the epidemiology and the clinical impact of these ACAs in healthy subjects and in infectious or dysimmune diseases.

Autoimmune Pulmonary Alveolar Proteinosis

Autoimmune pulmonary alveolar proteinosis (PAP) is a rare disease characterized by myeloid cell dysfunction, abnormal pulmonary surfactant accumulation, and innate immune deficiency. It has a prevalence of 7-10 per million; occurs in individuals of all races, geographic regions, sex, and socioeconomic status; and accounts for 90% of all patients with PAP syndrome. The most common presentation is dyspnea of insidious onset with or without cough, production of scant white and frothy sputum, and diffuse radiographic infiltrates in a previously healthy adult, but it can also occur in children as young as 3 years. Digital clubbing, fever, and hemoptysis are not typical, and the latter two indicate that intercurrent infection may be present. Low prevalence and nonspecific clinical, radiological, and laboratory findings commonly lead to misdiagnosis as pneumonia and substantially delay an accurate diagnosis. The clinical course, although variable, usually includes progressive hypoxemic respiratory insufficiency and, in some patients, secondary infections, pulmonary fibrosis, respiratory failure, and death. Two decades of research have raised autoimmune PAP from obscurity to a paradigm of molecular pathogenesis-based diagnostic and therapeutic development. Pathogenesis is driven by GM-CSF (granulocyte/macrophage colony-stimulating factor) autoantibodies, which are present at high concentrations in blood and tissues and form the basis of an accurate, commercially available diagnostic blood test with sensitivity and specificity of 100%. Although whole-lung lavage remains the first-line therapy, inhaled GM-CSF is a promising pharmacotherapeutic approach demonstrated in well-controlled trials to be safe, well tolerated, and efficacious. Research has established GM-CSF as a pulmonary regulatory molecule critical to surfactant homeostasis, alveolar stability, lung function, and host defense.

A mini-whole lung lavage to treat autoimmune pulmonary alveolar proteinosis (PAP)

Background

PAP is an ultra-rare respiratory syndrome characterized by the accumulation of surfactant within the alveoli. Whole lung lavage (WLL) is the current standard of care of PAP, however it is not a standardized procedure and the total amount of fluid used to wash each lung is still debated. Considering ICU hospitalization associated risks, a “mini-WLL” with anticipated manual clapping and reduced total infusion volume and has been proposed in our center.

The aim of the study is to retrospectively analyze the efficacy of mini-WLL compared to standard WLL at the Pavia center.

Methods

13 autoimmune PAP patients eligible for WLL were included: 7 patients were admitted to mini-WLL (9 L total infusion volume for each lung) and 6 patients underwent standard WLL (14 L of infusion volume). Functional data (VC%, FVC%, TLC%, DLCO%) and alveolar-arterial gradient values (A-aO2) were collected at the baseline and 1, 3, 6, 12, 18 months after the procedure.

Results

A statistically significant improvement of VC% (p = 0.013, 95%CI 3.49–30.19), FVC% (p = 0.016, 95%CI 3.37–32.09), TLC% (p = 0.001, 95%CI 7.38–30.34) was observed in the mini-WLL group in comparison with the standard WLL group, while no significant difference in DLCO% and A-aO2 mean values were reported.

Conclusion

Mini-WLL has demonstrated higher efficacy in ameliorating lung volumes, suggesting that a lower infusion volume is sufficient to remove the surfactant accumulation and possibly allows a reduced mechanical insult of the bronchi walls and the alveoli. However, no statistically significant differences were found in terms of DLCO% and Aa-O2.

Revisiting the role of pulmonary surfactant in chronic inflammatory lung diseases and environmental exposure

Pulmonary surfactant is a crucial and dynamic lung structure whose primary functions are to reduce alveolar surface tension and facilitate breathing. Though disruptions in surfactant homeostasis are typically thought of in the context of respiratory distress and premature infants, many lung diseases have been noted to have significant surfactant abnormalities. Nevertheless, preclinical and clinical studies of pulmonary disease too often overlook the potential contribution of surfactant alterations - whether in quantity, quality or composition - to disease pathogenesis and symptoms. In inflammatory lung diseases, whether these changes are cause or consequence remains a subject of debate. This review will outline 1) the importance of pulmonary surfactant in the maintenance of respiratory health, 2) the diseases associated with primary surfactant dysregulation, 3) the surfactant abnormalities observed in inflammatory pulmonary diseases and, finally, 4) the available research on the interplay between surfactant homeostasis and smoking-associated lung disease. From these published studies, we posit that changes in surfactant integrity and composition contribute more considerably to chronic inflammatory pulmonary diseases and that more work is required to determine the mechanisms underlying these alterations and their potential treatability.

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 β-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.

Diagnostic yield and safety of bronchofiberscopy for pulmonary alveolar proteinosis

BACKGROUND

Pulmonary alveolar proteinosis (PAP) is a diffuse lung disease characterized by the abnormal accumulation of surfactant-like material within the alveolar spaces and distal bronchioles. If high-resolution computed tomography (HRCT) indicates the presence of PAP, a definitive diagnosis of PAP is established when consistent pathological findings are obtained. Herein, we retrospectively studied the yield and safety of bronchofiberscopy in the diagnosis of PAP.

METHODS

One hundred and fifty consecutive patients with PAP were prospectively registered in the PAP cohort database of the National Hospital Organization Kinki-Chuo Chest Medical Center between January 1991 and December 2018. We examined 86 patients who underwent bronchofiberscopy with bronchoalveolar lavage (BAL) and transbronchial lung forceps biopsy (TBLB).

RESULTS

The patients included 56 men and 30 women, with a median age of 57 years. All patients had autoimmune PAP, and the median level of anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies was 42.8 μg/mL. The diagnostic yield was 90.7% (78/86) with BAL and 81.4% (70/86) with TBLB. The combination of BAL and TBLB increased the yield to 98.8%. Age, disease severity score, and frequency of traction bronchiectasis on HRCT were significantly different between the TBLB-positive and TBLB-negative groups. No patient developed serious complications due to bronchofiberscopy; TBLB-related complications included pneumothorax (3.5%) and minimal bleeding (7.0%).

CONCLUSIONS

Bronchofiberscopy, in combination with BAL and TBLB, is an effective and safe method for the diagnosis of PAP, with a yield of 98.8%.

B cell-activating factors in autoimmune pulmonary alveolar proteinosis

Background

Autoimmune pulmonary alveolar proteinosis (APAP) results from the suppression of granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling by a neutralizing autoantibody against GM-CSF. B cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are involved in immunoglobulin G production and are overproduced in various autoimmune disorders. We hypothesized that BAFF and/or APRIL levels would be elevated in serum and bronchoalveolar lavage fluid (BALF) and serum and BALF levels of BAFF and APRIL respond to the treatments (whole lung lavage (WLL) or inhalation of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF)) in patients with APAP.

Subjects and methods

BAFF and APRIL levels in serum and BALF from 110 patients with APAP were measured at baseline and during and after treatment, using an enzyme-linked immunosorbent assay kit. We enrolled 34 healthy volunteers as serum cytokine controls, and 13 disease controls for BALF. Associations of BAFF and APRIL levels with clinical measures were assessed to clarify their clinical roles.

Results

In patients with APAP, serum BAFF and APRIL levels were significantly increased relative to healthy volunteers (p < 0.0001 and p < 0.05, respectively), and BALF BAFF and APRIL levels were significantly increased versus disease controls (p < 0.0001 and p < 0.01, respectively). Serum BAFF levels (but not APRIL levels) were significantly correlated with Krebs von den Lungen-6 (KL-6), surfactant protein (SP)-D, SP-A, and lactate dehydrogenase (p < 0.0001). There was no significant correlation between serum BAFF or APRIL levels and anti-GM-CSF autoantibody. BAFF and APRIL were negatively correlated with single-breath diffusion capacity for carbon monoxide (DLco) (p = 0.004) and forced vital capacity (p = 0.04), respectively. BAFF (but not APRIL) in BALF was negatively correlated with vital capacity (p = 0.04) and DLco (p = 0.006). There were significant correlations between disease severity and BAFF levels in serum (p = 0.04) and BALF (p = 0.007). Serum levels of anti-GM-CSF autoantibody, BAFF, and APRIL were not significantly affected by WLL or inhalation of recombinant human GM-CSF.

Conclusions

BAFF and APRIL levels of sera and BALF in APAP were significantly increased compared with healthy volunteer and disease control, and the BAFF and APRIL pathway might have important specific roles in pathogenesis of APAP. Our data suggest a new perspective of future treatment for APAP.

Genetic determinants of risk in autoimmune pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a devastating lung disease caused by abnormal surfactant homeostasis, with a prevalence of 6-7 cases per million population worldwide. While mutations causing hereditary PAP have been reported, the genetic basis contributing to autoimmune PAP (aPAP) has not been thoroughly investigated. Here, we conducted a genome-wide association study of aPAP in 198 patients and 395 control participants of Japanese ancestry. The common genetic variant, rs138024423 at 6p21, in the major-histocompatibility-complex (MHC) region was significantly associated with disease risk (Odds ratio [OR] = 5.2; P = 2.4 × 10-12). HLA fine-mapping revealed that the common HLA class II allele, HLA-DRB1*08:03, strongly drove this signal (OR = 4.8; P = 4.8 × 10-12), followed by an additional independent risk allele at HLA-DPβ1 amino acid position 8 (OR = 0.28; P = 3.4 × 10-7). HLA-DRB1*08:03 was also associated with an increased level of anti-GM-CSF antibody, a key driver of the disease (β = 0.32; P = 0.035). Our study demonstrated a heritable component of aPAP, suggesting an underlying genetic predisposition toward an abnormal antibody production.

Usefulness of the IgA and IgG Responses to Macrophage Migration Inhibitory Factor for the Diagnosis of Tuberculosis

Serological tests offer the potential in order to improve the diagnosis of tuberculosis (TB). Macrophage migration inhibitory factor (MIF) plays a protective role in infection control in TB; however, to date, no studies on antibody responses to MIF have been reported. We measured immunoglobulin (Ig)A and IgG responses to MIF in individuals with either active tuberculosis (ATB; n = 65), latent tuberculosis (LTBI; n = 53), or in non-infected individuals (NI; n = 62). The QuantiFERON-TB Gold In-Tube (QFT-GIT) assay was used in order to screen for LTBI. The level of IgA against MIF was significantly lower in LTBI and ATB patients than in NI individuals, was significantly related to LTBI and ATB diagnosis, and it could discriminate between LTBI and ATB. In contrast, the level of IgG against MIF was significantly lower in LTBI patients than in NI individuals and was significantly related to LTBI diagnosis. Anti-MIF IgG levels were significantly lower in AFB-negative TB, minimal TB, and new ATB patients, than in the NI group. IgA and IgG levels against MIF both showed significant negative correlations with IFN-γ levels, as assessed using the QFT-GIT test. Although none of the antibodies could achieve high diagnostic predictive power individually, our results suggest the possibility of using IgA antibody responses to MIF in the diagnosis of LTBI and ATB.

Clinical significance of serum anti-granulocyte-macrophage colony-stimulating factor autoantibodies in patients with sarcoidosis and hypersensitivity pneumonitis

Background

Anti-granulocyte–macrophage colony-stimulating factor autoantibody (GMAb) has been recognized as a diagnostic biomarker for autoimmune pulmonary alveolar proteinosis (aPAP). The aims of this study were to know the incidence of increased level of serum GMAb in granulomatous lung diseases (sarcoidosis and hypersensitivity pneumonitis [HP]) and to clarify the role of GMAb. Consecutive individuals diagnosed with sarcoidosis (n = 92) and HP (n = 45) at National Hospital Organization Kinki-Chuo Chest Medical Center were retrospectively analyzed. We measured serum GMAb levels at the diagnosis. Cut-off values of GMAb discriminating aPAP (n = 110) from healthy controls (n = 31) were determined by receiver operating characteristic (ROC) curve analysis. We compared the clinical features of sarcoidosis and HP patients with GMAb levels above the cut-off value (“Elevated-GMAb”) with those of patients whose GMAb levels below the cut-off value (“Low-GMAb”). Radiological and pathological findings in elevated-GMAb patients were re-evaluated to elucidate the role of GMAb in granulomatous lung diseases.

Results

Analysis of ROC indicated a sensitivity and specificity of 100% at GMAb level of 3.33 μg/mL for discriminating aPAP from healthy controls (area under curve = 1.000, p < 0.0001). The percentages of elevated-GMAb sarcoidosis and HP patients were 5.4% (n = 5) and 11.1% (n = 5), respectively. The number of comorbid sarcoidosis and HP patients with aPAP was two and one, respectively. Elevated-GMAb sarcoidosis patients presented with significantly higher serum levels of Krebs von den Lungen (KL)-6, surfactant protein-D (SP-D), lactate dehydrogenase, and the requirement of systemic corticosteroid therapy. Elevated-GMAb HP patients demonstrated older age, higher serum KL-6, SP-D, carcinoembryonic antigen, and cytokeratin fragment 21-1 levels, and a higher percentage of lymphocytes in bronchoalveolar lavage than low-GMAb patients. A subset of patients presented with radiological and pathological findings characteristic of aPAP.

Conclusions

We demonstrated the percentage of elevated-GMAb sarcoidosis and HP patients who presented with several features suggestive of aPAP. Elevated-GMAb sarcoidosis and HP patients without definitive aPAP diagnosis may have subclinical or early-stage aPAP and may not necessarily indicate false positives. Upon diagnosis of sarcoidosis or HP, measurement of GMAb may be useful in detecting possible comorbidity of subclinical or early-onset aPAP.

Alveolar proteinosis due to toxic inhalation at workplace

We report a clinical case of a 39-year old male, without any known previous medical condition but with occupational exposure to paints and dust cement, who presented an autoimmune pulmonary alveolar proteinosis (PAP) triggered by exposure to toxic inhalation at his workplace. PAP is a rare lung disease characterized by intra-alveolar abnormal accumulation of surfactant. The presence of a crazy-paving pattern in high-resolution computed tomography scan brings the suspicion of PAP although histopathology results of bronchoalveolar lavage are always required for its final diagnosis. The autoimmune form of PAP due to toxic inhalation, such as the one here described, is rare and it is usually difficult to establish a causal relationship.

GM-CSF in inflammation

GM-CSF is a potential therapeutic target in inflammation and autoimmunity. This study reviews the literature on the biology of GM-CSF, in particular that describing the research leading to clinical trials targeting GM-CSF and its receptor in numerous inflammatory/autoimmune conditions, such as rheumatoid arthritis.

Granulocyte–macrophage colony-stimulating factor (GM-CSF) has many more functions than its original in vitro identification as an inducer of granulocyte and macrophage development from progenitor cells. Key features of GM-CSF biology need to be defined better, such as the responding and producing cell types, its links with other mediators, its prosurvival versus activation/differentiation functions, and when it is relevant in pathology. Significant preclinical data have emerged from GM-CSF deletion/depletion approaches indicating that GM-CSF is a potential target in many inflammatory/autoimmune conditions. Clinical trials targeting GM-CSF or its receptor have shown encouraging efficacy and safety profiles, particularly in rheumatoid arthritis. This review provides an update on the above topics and current issues/questions surrounding GM-CSF biology.

Pulmonary alveolar proteinosis

PAP is an ultra-rare disease in which surfactant components, that impair gas exchange, accumulate in the alveolae. There are three types of PAP. The most frequent form, primary PAP, includes autoimmune PAP which accounts for over 90% of all PAP, defined by the presence of circulating anti-GM-CSF antibodies. Secondary PAP is mainly due to haematological disease, infections or inhaling toxic substances, while genetic PAP affects almost exclusively children. PAP is suspected if investigation for ILD reveals a crazy-paving pattern on chest CT scan, and is confirmed by a milky looking BAL that gives a positive PAS reaction indicating extracellular proteinaceous material. PAP is now rarely confirmed by surgical lung biopsy. WLL is still the first-line treatment, with an inhaled GM-CSF as second-line treatment. Inhalation has been found to be better than subcutaneous injections. Other treatments, such as rituximab or plasmapheresis, seem to be less efficient or ineffective. The main complications of PAP are due to infections by standard pathogens (Streptococcus, Haemophilus and Enterobacteria) or opportunistic pathogens such as mycobacteria, Nocardia, Actinomyces, Aspergillus or Cryptococcus. The clinical course of PAP is unpredictable and spontaneous improvement can occur. The 5-year actuarial survival rate is 95%.

Proteogenomic analysis of granulocyte macrophage colony- stimulating factor autoantibodies in the blood of a patient with autoimmune pulmonary alveolar proteinosis

Recently, attempts to reveal the structures of autoantibodies comprehensively using improved proteogenomics technology, have become popular. This technology identifies peptides in highly purified antibodies by using an Orbitrap device to compare spectra from liquid chromatography-tandem mass spectrometry against a cDNA database obtained through next-generation sequencing. In this study, we first analyzed granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies in a patient with autoimmune pulmonary alveolar proteinosis, using the trapped ion mobility spectrometry coupled with quadrupole time-of-flight (TIMS-TOF) instrument. The TIMS-TOF instrument identified peptides that partially matched sequences in up to 156 out of 162 cDNA clones. Complementarity-determining region 3 (CDR3) was fully and partially detected in nine and 132 clones, respectively. Moreover, we confirmed one unique framework region 4 (FR4) and at least three unique across CDR3 to FR4 peptides via de novo peptide sequencing. This new technology may thus permit the comprehensive identification of autoantibody structure.

Natural Autoantibodies in Chronic Pulmonary Diseases

In autoantibody-mediated autoimmune diseases, pathogenic autoantibodies generated by a failure of central or peripheral tolerance, have different effects mediated by a variety of mechanisms. Interestingly, even non-autoimmune chronic diseases have a set of disease-specific natural autoantibodies that are maintained for a long time. Because most of these natural autoantibodies target intracellular proteins or long non-coding RNAs, they are speculated to be non-pathological and have some important as yet unrecognized physiological functions such as debris clearance. Recently, we revealed a set of disease-specific natural autoantibodies of chronic pulmonary diseases with unknown etiology by protein arrays that enable detection of specific autoantibodies against >8000 targets. Surprisingly, some of the targeted antigens of disease-specific autoantibodies were subsequently reported by other laboratories as strongly associated with the disease, suggesting that these antigens reflect the pathology of each disease. Furthermore, some of these autoantibodies that target extracellular antigens might modify the original course of each disease. Here, we review the disease-specific natural autoantibodies of chronic pulmonary diseases, including chronic fibrosing idiopathic interstitial pneumonias, sarcoidosis, and autoimmune pulmonary alveolar proteinosis, and discuss their utility and effects.

Validation of a new serum granulocyte-macrophage colony-stimulating factor autoantibody testing kit

Very recently, a modest but significant efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF) inhalation therapy for the treatment of mild to moderate autoimmune pulmonary alveolar proteinosis (aPAP) has been reported. As the ability to measure the level of GM-CSF autoantibody (GMAb) in the serum is required to decide the indication for this therapy, we developed a high-performance GMAb testing kit for clinical use. As the kit succeeded in reducing nonspecific IgG binding to the ELISA plate, the predictive performance shown in the training study to discriminate aPAP patients from healthy subjects was perfect, providing a cut-off value of 1.65 U·mL^-1 in 78 patients with aPAP and 90 healthy subjects in an operator-blinded manner using logistic regression analysis. As in the validation study, serum samples from another 213 patients with aPAP were also blinded and evaluated in an operator-blinded manner against external 207 samples from patients with other types of PAP and patients exhibiting various ground-glass opacities on chest high-resolution computed tomography that require discrimination from PAP. The logistic regression analysis of these validation data sets revealed values of 97.6% and 100% for specificity and sensitivity, respectively. Thus, this new GMAb testing kit is reliable for the diagnosis of aPAP and differential diagnosis of other lung diseases.

High Levels of Anti-GM-CSF Antibodies in Deep Infiltrating Endometriosis

Endometriosis is a chronic hormono-dependent inflammatory gynecological disease. Endometriosis can be subdivided into three forms: superficial peritoneal implants, endometrioma, and deep infiltrating endometriosis (DIE). Inflammation is a typical feature of endometriosis with overproduction of prostaglandins, chemokines, and cytokines, like granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF is a hematopoietic growth factor and immune modulator which belongs to the group of cytokines that actively participate in inflammatory reactions. GM-CSF autoantibodies (Ab) are described in inflammatory diseases such as Crohn disease and ulcerative colitis where high concentrations of anti-GM-CSF Ab are correlated with severity, complications, and relapses. We have evaluated the presence of anti-GM-CSF Ab in the serum of 106 patients with endometriosis and 92 controls using a home-made enzyme-linked immunosorbent assay (ELISA) and correlated the results with the form and severity of the disease. We found that anti-GM-CSF Ab level is significantly increased in the sera of patients with endometriosis compared to controls and is associated with the severity of the disease especially in patients with deep endometriosis (p < 0.0001) with the highest number of lesions (p = 0.0034), including digestive involvement (p = 0.0041). We also found a correlation between these levels of anti-GM-CSF Ab and the number of lesions in DIE patients (r = 0.913). In this way, searching anti-GM-CSF Ab in endometriosis patient sera could be of value for patient follow-up and put further insight into the role of inflammation and of GM-CSF in endometriosis pathogenesis.

Clinical Significance of Interferon-γ Neutralizing Autoantibodies Against Disseminated Nontuberculous Mycobacterial Disease

Background

Interferon-γ neutralizing autoantibodies (nIFNγ-autoAbs) are reported in patients with disseminated nontuberculous mycobacteria (NTM) infection and may function by increasing the infection risk. Notwithstanding, the prevalence of nIFNγ-autoAbs as well as the clinical presentation, diagnosis, and natural history of disseminated NTM infection in these patients is poorly understood.

Methods

In this retrospective observational study, data and sera for 331 Japanese subjects with mycobacterial infection were collected and analyzed. IFNγ-autoAb titers in sera were quantified using an enzyme-linked immunosorbent assay; neutralizing capacity was evaluated via flow cytometry.

Results

Disseminated NTM was identified in 50 human immunodeficiency virus-uninfected patients. Of these, 30 of 37 (81%) immunocompetent patients had an increased nIFNγ-autoAb titer whereas only 1 of 13 (7.7%) immunodeficient patients had an increased nIFNγ-autoAb titer (P < .0001, χ2 test). Presenting symptoms were nonspecific and NTM infection was not included in the differential diagnosis in most cases. All patients with disseminated NTM and an increased serum nIFNγ-autoAb level received prolonged antimicrobial therapy. In 6 cases when antibiotic treatment was discontinued, NTM infection recurred and required resumption of antibiotic therapy for infection control. The mortality rate was 3.2% in disseminated NTM patients with nIFNγ-autoAbs and 21% in those without.

Conclusions

nIFNγ-autoAbs were present in most patients with disseminated NTM infection without a diagnosis of clinical immunodeficiency. Diagnosis of disseminated NTM requires a high degree of suspicion and can be improved by measuring serum nIFNγ-autoAb titer. Long-term antibiotic therapy helps prevent recrudescent NTM infection.

An updated review on phenocopies of primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) refer to a heterogenous group of disorders characterized clinically by increased susceptibility to infections, autoimmunity and increased risk of malignancies.

These group of disorders present with clinical manifestations similar to PIDs with known genetic defects but have either no genetic defect or have a somatic mutation and thus have been labelled as “Phenocopies of PIDs”. These diseases have been further subdivided into those associated with somatic mutations and those associated with presence of auto-antibodies against various cytokines.

In this review, we provide an update on clinical manifestations, diagnosis and management of these diseases.

Memory B cell pool of autoimmune pulmonary alveolar proteinosis patients contains higher frequency of GM-CSF autoreactive B cells than healthy subjects

The IgG-type neutralizing GM-CSF autoantibody (GMAb) is known to be the causative agent for autoimmune pulmonary alveolar proteinosis (APAP). Previous studies report that serum levels of IgG-GMAb are approximately 50-fold higher in APAP patients than in healthy subjects (HS). Serum levels of IgM-GMAb are also higher in APAP patients than in HS, but this has been assumed to be an etiological bystander. However, the mechanism for the excessive production of IgG-GMAb in APAP remains unclear. To investigate this, we detected putative GMAb-producing B cells (PGMPB) by inoculated B cells from the peripheral blood of APAP patients, HS, and umbilical cord blood mononuclear cells (UCBMNs) with Epstein-Barr virus. Both ELISA and ELISPOT assays showed that IgM-type GMAb was consistently and frequently present in all three groups, whereas IgG-type GMAb was high only in APAP patients, in whom it was exclusively produced in memory B cells and not in naive B cells. Since PGMPB in UCBMNs produced IgM-GMAb, but not IgG-GMAb, to the same extent as in HS and APAP patients, most IgM-GMAb reacted with GM-CSF in a non-specific manner. The memory B cell pool of APAP patients contain higher frequency of PGMPB than that of healthy subjects.

Pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a syndrome characterized by the accumulation of alveolar surfactant and dysfunction of alveolar macrophages. PAP results in progressive dyspnoea of insidious onset, hypoxaemic respiratory failure, secondary infections and pulmonary fibrosis. PAP can be classified into different types on the basis of the pathogenetic mechanism: primary PAP is characterized by the disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF) signalling and can be autoimmune (caused by elevated levels of GM-CSF autoantibodies) or hereditary (due to mutations in CSF2RA or CSF2RB, encoding GM-CSF receptor subunits); secondary PAP results from various underlying conditions; and congenital PAP is caused by mutations in genes involved in surfactant production. In most patients, pathogenesis is driven by reduced GM-CSF-dependent cholesterol clearance in alveolar macrophages, which impairs alveolar surfactant clearance. PAP has a prevalence of at least 7 cases per million individuals in large population studies and affects men, women and children of all ages, ethnicities and geographical locations irrespective of socioeconomic status, although it is more-prevalent in smokers. Autoimmune PAP accounts for >90% of all cases. Management aims at improving symptoms and quality of life; whole-lung lavage effectively removes excessive surfactant. Novel pathogenesis-based therapies are in development, targeting GM-CSF signalling, immune modulation and cholesterol homeostasis.

Genetic and Transcriptomic Variation Linked to Neutrophil Granulocyte-Macrophage Colony-Stimulating Factor Signaling in Pediatric Crohn's Disease

BACKGROUND

Granulocyte-macrophage colony-stimulating factor auto-antibodies (GMAbs) suppress neutrophil-extrinsic GM-CSF signaling and increase risk for stricturing behavior in Crohn's disease (CD). We aimed to define clinical, genomic, and functional associations with neutrophil-intrinsic GM-CSF signaling.

METHODS

Missense mutations in CSF2RA, CSF2RB, JAK2, STAT5A, and STAT5B were identified using whole-exome sequencing in 543 pediatric inflammatory bowel disease (IBD) patients. Neutrophil-intrinsic GM-CSF signaling was defined using the GM-CSF-induced STAT5 stimulation index (GMSI) in 180 pediatric IBD patients and 26 non-IBD controls. Reduced GM-CSF signaling (GMSI-Lo) was defined as the 20th percentile within the control group. Variation in neutrophil phospho-protein abundance, bacterial killing, and the global pattern of gene expression with the GMSI was determined.

RESULTS

We validated 18 potentially damaging missense mutations in CSF2RA and CSF2RB. CSF2RA A17G carriage increased from 10% in those with intact neutrophil GMSI to 32% in those with low GMSI (P = 0.02). The frequency of reduced Staphylococcus aureus killing increased from 17% in those with intact neutrophil GMSI to 35% in GMSI-Lo neutrophils (P = 0.043). Crohn's disease neutrophils with low GMSI exhibited specific alterations in phospho-protein networks and genes regulating cytokine production, wound healing, and cell survival and proliferation. Stricturing behavior increased from 7% in patients with both low GMAb and intact GMSI to 64% in patients with both elevated GMAb and low GMSI (P < 0.0001).

CONCLUSIONS

Low/normal neutrophil-intrinsic GM-CSF signaling is associated with CSF2RA missense mutations, alterations in gene expression networks, and higher rates of disease complications in pediatric CD.

Pulmonary Alveolar Proteinosis with Ulcerative Colitis

A 65-year-old Japanese man was referred to our hospital for the further assessment of cough and dyspnea. He had a history of ulcerative colitis for which he was receiving treatment. Chest computed tomography showed a crazy-paving pattern. His bronchoalveolar lavage fluid had a milky appearance, and a transbronchial lung biopsy specimen revealed acellular periodic acid-Schiff stain-positive bodies. The serum anti-granulocyte macrophage-colony stimulating factor (GM-CSF) antibody titer was elevated. The diagnosis was autoimmune pulmonary alveolar proteinosis (PAP). There are few reports of autoimmune PAP in patients with ulcerative colitis. Some reports suggest that PAP and inflammatory bowel disease might have a common pathogenesis involving the anti-GM-CSF antibody.

Assay system development to measure the concentration of sargramostim with high specificity in patients with autoimmune pulmonary alveolar proteinosis after single-dose inhalation

During a clinical trial of a Saccharomyces cerviciae-derived recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF), sargramostim, in patients with autoimmune pulmonary alveolar proteinosis (aPAP), we conducted a pharmacokinetic study of single-dose sargramostim inhalation. Several problems were encountered whereby sargramostim formed an immune-complex with GM-CSF autoantibodies (GMAbs) immediately after entering the body; thus, we could not measure the concentration of sargramostim using a commercial high sensitivity enzyme-linked immunosorbent assay (ELISA). Moreover, the ELISA could not discriminate inhaled sargramostim from intrinsic GM-CSF. To solve these problems, we developed a novel ELISA system with a capture antibody that is specific for sargramostim and a detection antibody capable of binding with GM-CSF. This system quantified the serum sargramostim concentration, but not E. coli-, CHO-, or HEK293T-derived human recombinant GM-CSF. Using this system, serum pharmacokinetics were estimated in five patients after inhalation of 250 μg sargramostim, with a mean Cmax of 9.7 ± 2.85 pg/ml at a Tmax of 2 ± 1.22 h.

Elevated Serum Anti-GM-CSF Antibodies before the Onset of Autoimmune Pulmonary Alveolar Proteinosis in a Patient with Sarcoidosis and Systemic Sclerosis

Pulmonary alveolar proteinosis (PAP) is characterized by the accumulation of periodic acid-schiff stain-positive lipoproteinaceous materials in the alveolar space due to impaired surfactant clearance by alveolar macrophage. Autoimmune PAP is the most common form of PAP, but rarely accompanies collagen disease or sarcoidosis. We report here a rare case of autoimmune PAP preceded by systemic sclerosis and sarcoidosis. A 64-year-old woman was admitted to our hospital for blurred vision, muscle weakness of extremities, Raynaud's phenomenon, and exertional dyspnea. We diagnosed her as having systemic sclerosis complicated with sarcoidosis. Chest computed tomography (CT) and transbronchial lung biopsy showed the findings of pulmonary fibrosis without PAP. We treated her with corticosteroid and intravenous cyclophosphamide therapy, followed by tacrolimus therapy. Thereafter, her symptoms improved except for exertional dyspnea, and she began to complain of productive cough thirteen months after corticosteroid and immunosuppressant therapy. On the second admission, a chest CT scan detected the emergence of crazy-paving pattern in bilateral upper lobes. Bronchoalveolar lavage (BAL) fluid with milky appearance and a lung biopsy specimen revealed acellular periodic acid-schiff stain-positive bodies. The serum titer of anti-granulocyte macrophage colony stimulating factor (GM-CSF) antibodies was elevated on first admission and remained high on second admission. We thus diagnosed her as having autoimmune PAP. Reducing the dose of immunosuppressive agents and repeating the segmental BAL resulted in the improvement of her symptoms and radiological findings. Immunosuppressant therapy may trigger the onset of autoimmune PAP in a subset of patients with systemic sclerosis and/or sarcoidosis.

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.

Clinical significance of serum anti-GM-CSF autoantibody levels in autoimmune pulmonary alveolar proteinosis

AIM

Precise clinical significance of antigranulocyte-macrophage colony stimulating factor (GM-CSF) autoantibody levels in autoimmune pulmonary alveolar proteinosis (aPAP) has not been well studied.

METHODS

We obtained sera from 50 healthy controls, 46 aPAP patients, 50 with sarcoidosis, 52 with idiopathic interstitial pneumonia and 75 with pneumoconiosis. The clinical course of aPAP patients was assessed by scoring computed tomography images in 19 patients.

RESULTS

The cut-off level of anti-GM-CSF IgG for discrimination between aPAP and other diffuse lung diseases was 2.8 μg/ml with 100% sensitivity and 98% specificity. Antibody levels at baseline were significantly lower in the improved group than in the unimproved group (p = 0.008).

CONCLUSION

Our results indicate the existence of threshold levels of serum anti-GM-CSF IgG for the development and persistence of aPAP.

Distinct Functions of Autoantibodies Against Interferon in Systemic Lupus Erythematosus: A Comprehensive Analysis of Anticytokine Autoantibodies in Common Rheumatic Diseases

OBJECTIVE

Anticytokine autoantibodies occur across a range of hematologic, pulmonary, and infectious diseases. However, systematic investigation of their presence and significance in autoimmune diseases is lacking. This study was undertaken to examine the distinct functions of anticytokine autoantibodies in patients with systemic lupus erythematosus (SLE) compared to patients with other rheumatic diseases and healthy controls.

METHODS

Serum samples from patients with SLE (n = 199), patients with primary Sjögren's syndrome (SS) (n = 150), patients with rheumatoid arthritis (RA) (n = 149), and healthy controls (n = 200) were screened for 24 anticytokine autoantibodies using a multiplex bead-based assay. To evaluate the biologic activity of anticytokine autoantibodies, their ability to block cytokine-induced signal transduction or protein expression was measured. RNA sequencing was performed on whole blood in a subset of healthy controls and patients with SLE.

RESULTS

Patients with SLE and those with SS had a striking excess of autoantibodies against interferons and the interferon-responsive chemokine interferon-inducible protein 10 (IP-10). Only autoantibodies against type I interferon, interleukin-12 (IL-12), and IL-22 exhibited neutralizing activity. In SLE, the presence of anti-interferon-γ autoantibodies was correlated with more severe disease activity, higher levels of anti-double-stranded DNA antibodies, and elevated expression of interferon-α/β-inducible genes. Conversely, in SLE patients with blocking anti-interferon-α autoantibodies, the type I interferon gene expression signature was normalized. Anti-type III interferon autoantibodies (λ2, λ3) and anti-IP-10 autoantibodies were newly recognized in SLE patient serum, and autoantibodies against macrophage-colony stimulating factor, IL-4, IL-7, IL-17, and IL-22, none of which have been previously identified in rheumatic conditions, were discovered.

CONCLUSION

Anticytokine autoantibodies are associated with distinct patterns of disease in SLE, SS, and RA. Anti-interferon autoantibodies are overrepresented in patients with SLE and those with SS, and fall into distinct functional classes, with only a subset of anti-type I interferon antibodies exhibiting neutralizing activity. Anti-interferon-γ autoantibodies are correlated with increased disease activity and interferon-related gene expression, suggesting that such autoantibodies may contribute to the pathogenesis of SLE.

Production of pure fractions of immunoglobulin G subclass autoantibodies against tumor necrosis factor

Autoantibodies directed against cytokines are important effector molecules regulating the biological activity of cytokines. There is experimental evidence indicating that autoantibodies belonging to different immunoglobulin G (IgG) subclasses may have different functional activity. The purpose of this work was to develop a protocol for the purification of fractions of IgG subclass antibodies directed against tumor necrosis factor (TNF). We developed a series of steps, including gel filtration, positive and negative affinity chromatography, and ultrafiltration, to achieve this goal. Our protocol purified IgG subclass autoantibodies directed against TNF from a human immunoglobulin preparation. The isolation of these anti-TNF autoantibodies will enable evaluation of the effect of TNF-specific antibodies on TNF biological activity. Our newly developed technique for purifying subclasses of anti-TNF autoantibodies may be important for both basic research on the functional activity of these autoantibodies and for clinical immunology.

A newly identified novel variant in the CSF2RA gene in a child with pulmonary alveolar proteinosis: a case report

BACKGROUND

The congenital form of pulmonary alveolar proteinosis due to colony stimulating factor 2 receptor alpha gene mutations is a rare disease with only a few cases reported worldwide. In this study we report a new case of pulmonary alveolar proteinosis with a novel variant in colony stimulating factor 2 receptor alpha gene.

CASE PRESENTATION

A 5-year-old Saudi boy presented with a history of progressive dyspnea over 6 months; he was diagnosed as having pulmonary alveolar proteinosis. A molecular study revealed a novel variation in colony stimulating factor 2 receptor alpha gene. His clinical condition showed significant improvement after whole lung lavage.

CONCLUSIONS

This case has the typical presentation of congenital pulmonary alveolar proteinosis due to colony stimulating factor 2 receptor alpha defect with a novel variant in this gene likely to be pathogenic.

GM-CSF as a therapeutic target in autoimmune diseases

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been known as a hematopoietic growth factor and immune modulator. Recent studies revealed that GM-CSF also had pro-inflammatory functions and contributed to the pathogenicity of Th17 cells in the development of Th17-mediated autoimmune diseases. GM-CSF inhibition in some animal models of autoimmune diseases showed significant beneficial effects. Therefore, several agents targeting GM-CSF are being developed and are expected to be a useful strategy for the treatment of autoimmune diseases. Particularly, in clinical trials for rheumatoid arthritis (RA) patients, GM-CSF inhibition showed rapid and significant efficacy with no serious side effects. This article summarizes recent findings of GM-CSF and information of clinical trials targeting GM-CSF in autoimmune diseases.

Autoantibody-Mediated Pulmonary Alveolar Proteinosis in Rasgrp1-Deficient Mice

Pulmonary alveolar proteinosis (PAP) is a rare lung syndrome caused by the accumulation of surfactants in the alveoli. The most prevalent clinical form of PAP is autoimmune PAP (aPAP) whereby IgG autoantibodies neutralize GM-CSF. GM-CSF is a pleiotropic cytokine that promotes the differentiation, survival, and activation of alveolar macrophages, the cells responsible for surfactant degradation. IgG-mediated neutralization of GM-CSF thereby inhibits alveolar macrophage homeostasis and function, leading to surfactant accumulation and innate immunodeficiency. Importantly, there are no rodent models for this disease; therefore, underlying immune mechanisms regulating GM-CSF-specific IgG in aPAP are not well understood. In this article, we identify that autoimmune-prone Rasgrp1-deficient mice develop aPAP: 1) Rasgrp1-deficient mice exhibit reduced pulmonary compliance and lung histopathology characteristic of PAP; 2) alveolar macrophages from Rasgrp1-deficient mice are enlarged and exhibit reduced surfactant degradation; 3) the concentration of GM-CSF-specific IgG is elevated in both serum and bronchoalveolar lavage fluid from Rasgrp1-deficient mice; 4) GM-CSF-specific IgG is capable of neutralizing GM-CSF bioactivity; and 5) Rasgrp1-deficient mice also lacking CD275/ICOSL, a molecule necessary for conventional T cell-dependent Ab production, have reduced GM-CSF-specific autoantibody and do not develop PAP. Collectively, these studies reveal that Rasgrp1-deficient mice, to our knowledge, represent the first rodent model for aPAP.

Phase 2, randomised placebo-controlled trial to evaluate the efficacy and safety of an anti-GM-CSF antibody (KB003) in patients with inadequately controlled asthma

OBJECTIVES

We wished to evaluate the effects of an antigranulocyte-macrophage colony-stimulating factor monoclonal antibody (KB003) on forced expiratory volume in 1 s (FEV1), asthma control and asthma exacerbations in adult asthmatics inadequately controlled by long-acting bronchodilators and inhaled/oral corticosteroids.

SETTINGS

47 ambulatory asthma care centres globally.

PRIMARY OUTCOME MEASURES

Change in FEV1 at week 24.

PARTICIPANTS

311 were screened, 160 were randomised and 129 completed the study.

INTERVENTIONS

7 intravenous infusions of either 400 mg KB003 or placebo at baseline and weeks 2, 4, 8, 12, 16 and 20.

PRIMARY AND SECONDARY OUTCOME MEASURES

FEV1 at week 24, asthma control, exacerbation rates and safety in all participants as well as prespecified subgroups.

MAIN RESULTS

In the KB003 treated group, FEV1 at week 24 improved to 118 mL compared with 54 mL in the placebo group (p=0.224). However, FEV1 improved to 253 vs 26 mL at week 24 (p=0.02) in eosinophilic asthmatics (defined as >300 peripheral blood eosinophils/mL at baseline) and comparable improvements were seen at weeks 20 (p=0.034) and 24 (p=0.077) in patients with FEV1 reversibility ≥ 20% at baseline and at weeks 4 (p=0.029), 16 (p=0.018) and 20 (p=0.006) in patients with prebronchodilator FEV1 ≤ 50% predicted at baseline. There were no effects on asthma control or exacerbation rates. The most frequent adverse events in the KB003 group were rhinosinusitis and headache. There was no significant difference in antidrug antibody response between placebo and treated groups. There were no excess infections or changes in biomarkers known to be associated with the development of pulmonary alveolar proteinosis.

CONCLUSIONS

Higher doses and/or further asthma phenotyping may be required in future studies with KB003.

TRIAL REGISTRATION NUMBER

NCT01603277; Results.

Targeting GM-CSF in inflammatory diseases

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a growth factor first identified as an inducer of differentiation and proliferation of granulocytes and macrophages derived from haematopoietic progenitor cells. Later studies have shown that GM-CSF is involved in a wide range of biological processes in both innate and adaptive immunity, with its production being tightly linked to the response to danger signals. Given that the functions of GM-CSF span multiple tissues and biological processes, this cytokine has shown potential as a new and important therapeutic target in several autoimmune and inflammatory disorders - particularly in rheumatoid arthritis. Indeed, GM-CSF was one of the first cytokines detected in human synovial fluid from inflamed joints. Therapies that target GM-CSF or its receptor have been tested in preclinical studies with promising results, further supporting the potential of targeting the GM-CSF pathway. In this Review, we discuss our expanding view of the biology of GM-CSF, outline what has been learnt about GM-CSF from studies of animal models and human diseases, and summarize the results of early phase clinical trials evaluating GM-CSF antagonism in inflammatory disorders.

GATA2 deficiency in children and adults with severe pulmonary alveolar proteinosis and hematologic disorders

BACKGROUND

The majority of cases with severe pulmonary alveolar proteinosis (PAP) are caused by auto-antibodies against GM-CSF. A multitude of genetic and exogenous causes are responsible for few other cases. Goal of this study was to determine the prevalence of GATA2 deficiency in children and adults with PAP and hematologic disorders.

METHODS

Of 21 patients with GM-CSF-autoantibody negative PAP, 13 had no other organ involvement and 8 had some form of hematologic disorder. The latter were sequenced for GATA2.

RESULTS

Age at start of PAP ranged from 0.3 to 64 years, 4 patients were children. In half of the subjects GATA2-sequence variations were found, two of which were considered disease causing. Those two patients had the typical phenotype of GATA2 deficiency, one of whom additionally showed a previously undescribed feature - a cholesterol pneumonia. Hematologic disorders included chronic myeloic leukemia, juvenile myelo-monocytic leukemia, lymphoblastic leukemia, sideroblastic anemia and two cases of myelodysplastic syndrome (MDS). A 4 year old child with MDS and DiGeorge Syndrome Type 2 was rescued with repetitive whole lung lavages and her PAP was cured with heterologous stem cell transplant.

CONCLUSIONS

In children and adults with severe GM-CSF negative PAP a close cooperation between pneumologists and hemato-oncologists is needed to diagnose the underlying diseases, some of which are caused by mutations of transcription factor GATA2. Treatment with whole lung lavages as well as stem cell transplant may be successful.

Neutralization and clearance of GM-CSF by autoantibodies in pulmonary alveolar proteinosis

Pulmonary alveolar proteinosis (PAP) is a severe autoimmune disease caused by autoantibodies that neutralize GM-CSF resulting in impaired function of alveolar macrophages. In this study, we characterize 21 GM-CSF autoantibodies from PAP patients and find that somatic mutations critically determine their specificity for the self-antigen. Individual antibodies only partially neutralize GM-CSF activity using an in vitro bioassay, depending on the experimental conditions, while, when injected in mice together with human GM-CSF, they lead to the accumulation of a large pool of circulating GM-CSF that remains partially bioavailable. In contrast, a combination of three non-cross-competing antibodies completely neutralizes GM-CSF activity in vitro by sequestering the cytokine in high-molecular-weight complexes, and in vivo promotes the rapid degradation of GM-CSF-containing immune complexes in an Fc-dependent manner. Taken together, these findings provide a plausible explanation for the severe phenotype of PAP patients and for the safety of treatments based on single anti-GM-CSF monoclonal antibodies.

Autoimmune pulmonary alveolar proteinosis is caused by autoantibodies to GM-CSF. Here the authors show that the individual autoantibodies only partially neutralize GM-CSF and that antibodies to at least three different epitopes are required to block GM-CSF bioavailability.

Cytokines: The Good, the Bad, and the Deadly

Over the past 30 years, the world of pharmaceutical toxicology has seen an explosion in the area of cytokines. An overview of the many aspects of cytokine safety evaluation currently in progress and evolving strategies for evaluating these important entities was presented at this symposium. Cytokines play a broad role to help the immune system respond to diseases, and drugs which modulate their effect have led to some amazing therapies. Cytokines may be "good" when stimulating the immune system to fight a foreign pathogen or attack tumors. Other "good" cytokine effects include reduction of an immune response, for example interferon β reduction of neuron inflammation in patients with multiple sclerosis. They may be "bad" when their expression causes inflammatory diseases, such as the role of tumor necrosis factor α in rheumatoid arthritis or asthma and Crohn's disease. Therapeutic modulation of cytokine expression can help the "good" cytokines to generate or quench the immune system and block the "bad" cytokines to prevent damaging inflammatory events. However, care must be exercised, as some antibody therapeutics can cause "ugly" cytokine release which can be deadly. Well-designed toxicology studies should incorporate careful assessment of cytokine modulation that will allow effective therapies to treat unmet needs. This symposium discussed lessons learned in cytokine toxicology using case studies and suggested future directions.