Analysis of the MILES cohort reveals determinants of disease progression and treatment response in lymphangioleiomyomatosis

INTRODUCTION

The Multicenter International Lymphangioleiomyomatosis (LAM) Efficacy of Sirolimus (MILES) trial revealed that sirolimus stabilised lung function in patients with moderately severe LAM. The purpose of this study was to further examine the MILES cohort for the effects of racial, demographic, clinical and physiological patient characteristics on disease progression and treatment response in LAM.

METHODS

MILES subjects were stratified on the basis of menopausal status (pre-menopausal/post-menopausal), race (Asian/Caucasian), bronchodilator responsiveness (present/absent), initial forced expiratory volume in 1 s (FEV₁; 51-70% versus ≤50% predicted) and tuberous sclerosis complex (TSC) association (yes/no). A linear mixed effects model was used to compare slope differences, and nonparametric tests were used to compare medians and proportions between treatment groups in each stratum.

RESULTS

In the MILES placebo group, pre-menopausal patients declined 5-fold faster than post-menopausal patients (mean±se FEV₁ slope -17±3 versus -3±3 mL·month^-1; p=0.003). Upon treatment with sirolimus, both the pre-menopausal (-17±3 versus -1±2 mL·month^-1; p<0.0001) and post-menopausal patients (-3±3 versus 6±3 mL·month^-1; p=0.04) exhibited a beneficial response in mean±se FEV₁ slope compared with the placebo group. Race, LAM subtype, bronchodilator responsiveness or baseline FEV₁ did not impact the rate of disease progression in the placebo group or treatment response in the sirolimus group. Menopausal status and race had differential effects on the adverse event profile of sirolimus. Baseline serum vascular endothelial growth factor (VEGF)-D >600 pg·mL^-1 identified subgroups of patients who were more likely to decline on placebo and respond to treatment with sirolimus.

CONCLUSIONS

In LAM patients, treatment with sirolimus is beneficial regardless of menopausal status, race, bronchodilator responsiveness, baseline FEV₁ or TSC association. Serum VEGF-D and menopausal status can help inform therapeutic decisions.

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.

IFN-β Improves Sepsis-related Alveolar Macrophage Dysfunction and Postseptic Acute Respiratory Distress Syndrome-related Mortality

IFN-β is reported to improve survival in patients with acute respiratory distress syndrome (ARDS), possibly by preventing sepsis-induced immunosuppression, but its therapeutic nature in ARDS pathogenesis is poorly understood. We investigated the therapeutic effects of IFN-β for postseptic ARDS to better understand its pathogenesis in mice. Postseptic ARDS was reproduced in mice by cecal ligation and puncture to induce sepsis, followed 4 days later by intratracheal instillation of Pseudomonas aeruginosa to cause pneumonia with or without subcutaneous administration of IFN-β 1 day earlier. Sepsis induced prolonged increases in alveolar TNF-α and IL-10 concentrations and innate immune reprogramming; specifically, it reduced alveolar macrophage (AM) phagocytosis and KC (CXCL1) secretion. Ex vivo AM exposure to TNF-α or IL-10 duplicated cytokine release impairment. Compared with sepsis or pneumonia alone, pneumonia after sepsis was associated with blunted alveolar KC responses and reduced neutrophil recruitment into alveoli despite increased neutrophil burden in lungs (i.e., "incomplete alveolar neutrophil recruitment"), reduced bacterial clearance, increased lung injury, and markedly increased mortality. Importantly, IFN-β reversed the TNF-α/IL-10-mediated impairment of AM cytokine secretion in vitro, restored alveolar innate immune responsiveness in vivo, improved alveolar neutrophil recruitment and bacterial clearance, and consequently reduced the odds ratio for 7-day mortality by 85% (odds ratio, 0.15; 95% confidence interval, 0.03-0.82; P = 0.045). This mouse model of sequential sepsis → pneumonia infection revealed incomplete alveolar neutrophil recruitment as a novel pathogenic mechanism for postseptic ARDS, and systemic IFN-β improved survival by restoring the impaired function of AMs, mainly by recruiting neutrophils to alveoli.

Epidemiology of Rare Lung Diseases: The Challenges and Opportunities to Improve Research and Knowledge

Rare lung diseases encompass a broad spectrum of conditions and affect an estimated 1.2-2.5 million people in North America and 1.5-3 million people in Europe. While individual rare lung diseases affect less than 1 in 2000 individuals, collectively they have a significant impact upon the population at large. Hence it is vital to understand firstly the epidemiology and subsequently the pathogenesis and clinical course of these disorders. Through a greater understanding of these aspects of disease, progress can be made in reducing symptoms, containing healthcare costs and utilizing resources efficiently. Furthermore, a greater understanding of the pathobiology of rare lung diseases can inform both the pathogenesis and management of more common pulmonary disorders.In this chapter we review how epidemiological approaches and the utilization of patient registries has improved the knowledge and management of rare lung diseases. We further focus on the epidemiology of several of the more widely known rare pulmonary disorders, including idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF) and alpha-1 antitrypsin deficiency (AATD). To conclude we describe how patient advocacy groups and foundations have driven advances in research and management of ultra-rare lung diseases, namely, the major strides made in the management and understanding of lymphangioleiomyomatosis (LAM) and pulmonary alveolar proteinosis (PAP).We conclude that the models used to study some of the rarest of diseases may be successfully adopted by other rare and common disease communities, leading to improved care and the possibility of novel therapeutic options.

Function and Safety of Lentivirus-Mediated Gene Transfer for CSF2RA-Deficiency

Hereditary pulmonary alveolar proteinosis (hPAP) is a rare disorder of pulmonary surfactant accumulation and hypoxemic respiratory failure caused by mutations in CSF2RA (encoding the granulocyte/macrophage colony-stimulating factor [GM-CSF] receptor α-chain [CD116]), which results in reduced GM-CSF-dependent pulmonary surfactant clearance by alveolar macrophages. While no pharmacologic therapy currently exists for hPAP, it was recently demonstrated that endotracheal instillation of wild-type or gene-corrected mononuclear phagocytes (pulmonary macrophage transplantation [PMT]) results in a significant and durable therapeutic efficacy in a validated murine model of hPAP. To facilitate the translation of PMT therapy to human hPAP patients, a self-inactivating (SIN) lentiviral vector was generated expressing a codon-optimized human CSF2RA-cDNA driven from an EF1α short promoter (Lv.EFS.CSF2RAcoop), and a series of nonclinical efficacy and safety studies were performed in cultured macrophage cell lines and primary human cells. Studies in cytokine-dependent Ba/F3 cells demonstrated efficient transduction, vector-derived CD116 expression proportional to vector copy number, and GM-CSF-dependent cell survival and proliferation. Using a novel cell line constructed to express a normal GM-CSF receptor β subunit and a dysfunctional α subunit (due to a function-altering CSF2RAG196R mutation) that reflects the macrophage disease phenotype of hPAP patients, it was demonstrated that Lv.EFS.CSF2RAcoop transduction restored GM-CSF receptor function. Further, Lv.EFS.CSF2RAcoop transduction of healthy primary CD34+ cells did not adversely affect cell proliferation or affect the cell differentiation program. Results demonstrate Lv.EFS.CSF2RAcoop reconstituted GM-CSF receptor α expression, restoring GM-CSF signaling in hPAP macrophages, and had no adverse effects in the intended target cells, thus supporting testing of PMT therapy of hPAP in humans.

An Official American Thoracic Society Workshop Report: Translational Research in Rare Respiratory Diseases

Rare respiratory diseases (RRDs) are a heterogeneous group of disorders that collectively represent a significant health care burden. In recent years, strong advocacy and policy initiatives have led to advances in the implementation of research and clinical care for rare diseases. The development of specialized centers and research networks has facilitated support for affected individuals as well as emerging programs in basic, translational, and clinical research. In selected RRDs, subsequent gains in knowledge have informed the development of targeted therapies and effective diagnostic tests, but many gaps persist. There was therefore a desire to identify the elements contributing to an effective translational research program in RRDs. To this end, a workshop was convened in October 2015 with a focus on the implementation of effective transnational research networks and collaborations aimed at developing novel diagnostic and therapeutic tools. Key elements included an emphasis on molecular pathogenesis, the continuing engagement of patient advocacy groups and policy makers, the effective use of preclinical models in the translational research pipeline, and the detailed phenotyping of patient cohorts. During the course of the workshop, current logistical and knowledge gaps were identified, and new solutions or opportunities were highlighted.

Prediction of complicated disease course for children newly diagnosed with Crohn's disease: a multicentre inception cohort study

BACKGROUND

Stricturing and penetrating complications account for substantial morbidity and health-care costs in paediatric and adult onset Crohn's disease. Validated models to predict risk for complications are not available, and the effect of treatment on risk is unknown.

METHODS

We did a prospective inception cohort study of paediatric patients with newly diagnosed Crohn's disease at 28 sites in the USA and Canada. Genotypes, antimicrobial serologies, ileal gene expression, and ileal, rectal, and faecal microbiota were assessed. A competing-risk model for disease complications was derived and validated in independent groups. Propensity-score matching tested the effect of anti-tumour necrosis factor α (TNFα) therapy exposure within 90 days of diagnosis on complication risk.

FINDINGS

Between Nov 1, 2008, and June 30, 2012, we enrolled 913 patients, 78 (9%) of whom experienced Crohn's disease complications. The validated competing-risk model included age, race, disease location, and antimicrobial serologies and provided a sensitivity of 66% (95% CI 51-82) and specificity of 63% (55-71), with a negative predictive value of 95% (94-97). Patients who received early anti-TNFα therapy were less likely to have penetrating complications (hazard ratio [HR] 0·30, 95% CI 0·10-0·89; p=0·0296) but not stricturing complication (1·13, 0·51-2·51; 0·76) than were those who did not receive early anti-TNFα therapy. Ruminococcus was implicated in stricturing complications and Veillonella in penetrating complications. Ileal genes controlling extracellular matrix production were upregulated at diagnosis, and this gene signature was associated with stricturing in the risk model (HR 1·70, 95% CI 1·12-2·57; p=0·0120). When this gene signature was included, the model's specificity improved to 71%.

INTERPRETATION

Our findings support the usefulness of risk stratification of paediatric patients with Crohn's disease at diagnosis, and selection of anti-TNFα therapy.

FUNDING

Crohn's and Colitis Foundation of America, Cincinnati Children's Hospital Research Foundation Digestive Health Center.

Epidermal growth factor receptor signalling regulates granulocyte-macrophage colony-stimulating factor production by airway epithelial cells and established allergic airway disease

BACKGROUND

Airway epithelial cells (AEC) are increasingly recognized as a major signalling centre in the pathogenesis of allergic asthma. A previous study demonstrated that epithelial growth factor receptor (EGFR) signalling in AEC regulated key features of allergic airway disease. However, it is unclear what mediators are regulated by EGFR signalling in AEC, although the production of the pro-inflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) is EGFR dependent in keratinocytes.

OBJECTIVES

To determine whether EGFR signalling regulates GM-CSF production by human AEC downstream of the clinically relevant mediators house dust mite (HDM) and interleukin (IL)-17A and in a mouse model of established allergic asthma.

METHODS

EGFR inhibitors were used to determine whether EGFR signalling regulates GM-CSF production by cultured human AEC in response to HDM and IL-17A. The roles of EGFR ligands, p38 mitogen-activated protein kinase (MAPK) and tumour necrosis factor-alpha (TNF-α) converting enzyme (TACE) were also assessed. To determine whether EGFR regulates GM-CSF as well as key asthma characteristics in vivo, mice were chronically exposed to HDM to establish allergic airway disease and then treated with the EGFR inhibitor Erlotinib.

RESULTS

EGFR inhibition reduced HDM and IL-17A induced GM-CSF production in a dose-dependent manner in cultured human AEC. GM-CSF production also required amphiregulin, p38 MAPK signalling and protease/TACE activity. In mice with established allergic airway disease, EGFR inhibition reduced levels of GM-CSF and TNF-α, as well as airway hyperreactivity, cellular inflammation, smooth muscle thickening and goblet cell metaplasia without changes in IgE and Th1, Th2 and Th17 cytokines.

CONCLUSIONS AND CLINICAL RELEVANCE

Results link HDM, IL-17A, amphiregulin, EGFR and GM-CSF in a mechanistic pathway in AEC and demonstrate that EGFR regulates GM-CSF production and the severity of established disease in a clinically relevant asthma model. These results identify the EGFR→GM-CSF axis as a target for therapeutic development.

Whole lung lavage therapy for pulmonary alveolar proteinosis: a global survey of current practices and procedures

BACKGROUND

Whole lung lavage (WLL) is the current standard of care treatment for patients affected by pulmonary alveolar proteinosis (PAP). However, WLL is not standardized and international consensus documents are lacking. Our aim was to obtain a factual portrayal of WLL as currently practiced with respect to the procedure, indications for its use, evaluation of therapeutic benefit and complication rate.

METHODS

A clinical practice survey was conducted globally by means of a questionnaire and included 27 centers performing WLL in pediatric and/or adult PAP patients.

RESULTS

We collected completed questionnaires from 20 centres in 14 countries, practicing WLL in adults and 10 centers in 6 countries, practicing WLL in pediatric patients. WLL is almost universally performed under general anesthesia, with a double-lumen endobronchial tube in two consecutive sessions, with an interval of 1-2 weeks between sessions in approximately 50 % of centres. The use of saline warmed to 37 °C, drainage of lung lavage fluid by gravity and indications for WLL therapy in PAP were homogenous across centres. There was great variation in the choice of the first lung to be lavaged: 50 % of centres based the choice on imaging, whereas 50 % always started with the left lung. The choice of position was also widely discordant; the supine position was chosen by 50 % of centres. Other aspects varied significantly among centres including contraindications, methods and timing of follow up, use of chest percussion, timing of extubation following WLL and lung isolation and lavage methods for small children. The amount of fluid used to perform the WLL is a critical aspect. Whilst a general consensus exists on the single aliquot of fluid for lavage (around 800 ml of warm saline, in adults) great variability exists in the total volume instilled per lung, ranging from 5 to 40 liters, with an average of 15.4 liters/lung.

CONCLUSIONS

This international survey found that WLL is safe and effective as therapy for PAP. However these results also indicate that standardization of the procedure is required; the present survey represents the a first step toward building such a document.

Murine iPSC-Derived Macrophages as a Tool for Disease Modeling of Hereditary Pulmonary Alveolar Proteinosis due to Csf2rb Deficiency

Induced pluripotent stem cells (iPSCs) represent an innovative source for the standardized in vitro generation of macrophages (Mφ). We here describe a robust and efficient protocol to obtain mature and functional Mφ from healthy as well as disease-specific murine iPSCs. With regard to morphology, surface phenotype, and function, our iPSC-derived Mφ (iPSC-Mφ) closely resemble their counterparts generated in vitro from bone marrow cells. Moreover, when we investigated the feasibility of our differentiation system to serve as a model for rare congenital diseases associated with Mφ malfunction, we were able to faithfully recapitulate the pathognomonic defects in GM-CSF signaling and Mφ function present in hereditary pulmonary alveolar proteinosis (herPAP). Thus, our studies may help to overcome the limitations placed on research into certain rare disease entities by the lack of an adequate supply of disease-specific primary cells, and may aid the development of novel therapeutic approaches for herPAP patients.

Respirable indium exposures, plasma indium, and respiratory health among indium-tin oxide (ITO) workers

BACKGROUND

Workers manufacturing indium-tin oxide (ITO) are at risk of elevated indium concentration in blood and indium lung disease, but relationships between respirable indium exposures and biomarkers of exposure and disease are unknown.

METHODS

For 87 (93%) current ITO workers, we determined correlations between respirable and plasma indium and evaluated associations between exposures and health outcomes.

RESULTS

Current respirable indium exposure ranged from 0.4 to 108 μg/m(3) and cumulative respirable indium exposure from 0.4 to 923 μg-yr/m(3) . Plasma indium better correlated with cumulative (rs  = 0.77) than current exposure (rs  = 0.54) overall and with tenure ≥1.9 years. Higher cumulative respirable indium exposures were associated with more dyspnea, lower spirometric parameters, and higher serum biomarkers of lung disease (KL-6 and SP-D), with significant effects starting at 22 μg-yr/m(3) , reached by 46% of participants.

CONCLUSIONS

Plasma indium concentration reflected cumulative respirable indium exposure, which was associated with clinical, functional, and serum biomarkers of lung disease. Am. J. Ind. Med. 59:522-531, 2016. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Pulmonary Alveolar Proteinosis Syndrome

Pulmonary alveolar proteinosis (PAP) is a rare syndrome characterized by the accumulation of surfactant in alveoli and terminal airways resulting in respiratory failure. PAP comprises part of a spectrum of disorders of surfactant homeostasis (clearance and production). The surfactant production disorders are caused by mutations in genes required for normal surfactant production. The PAP syndrome is identified based on history, radiologic, and bronchoalveolar lavage and/or histopathologic findings. The diagnosis of PAP-causing diseases in secondary PAP requires further studies. Whole-lung lavage is the current standard therapy and promising new pharmacologic therapies are in development.

Recombinant Adeno-Associated Virus Vector Genomes Take the Form of Long-Lived, Transcriptionally Competent Episomes in Human Muscle

Gene augmentation therapy as a strategy to treat alpha-1 antitrypsin (AAT) deficiency has reached phase 2 clinical testing in humans. Sustained serum levels of AAT have been observed beyond one year after intramuscular administration of a recombinant adeno-associated virus (rAAV) vector expressing the AAT gene. In this study, sequential muscle biopsies obtained at 3 and 12 months after vector injection were examined for the presence of rAAV vector genomes. Each biopsy sample contained readily detectable vector DNA, the majority of which existed as double-stranded supercoiled and open circular episomes. Episomes persisted through 12 months, although at slightly lower levels than observed at 3 months. There was a clear dose response when comparing the low- and mid-vector-dose groups to the high-dose group. The highest absolute copy numbers were found in a high-dose subject, and serum AAT levels at 12 months confirmed that the high-dose group also had the highest sustained serum AAT levels. Sequence analysis revealed that the vast majority of episomes contained double-D inverted terminal repeats ranging from fully intact to severely deleted. Molecular clones of vector genomes derived directly from the biopsies were transcriptionally active, potentially identifying them as the source of serum AAT in the trial subjects.

A standardized blood test for the routine clinical diagnosis of impaired GM-CSF signaling using flow cytometry

Impaired signaling by granulocyte/macrophage-colony stimulating factor (GM-CSF) drives the pathogenesis of two diseases (autoimmune and hereditary pulmonary alveolar proteinosis (PAP)) representing over ninety percent of patients who develop PAP syndrome but not a broad spectrum of diseases that cause PAP by other mechanisms. We previously exploited the ability of GM-CSF to rapidly increase cell-surface CD11b levels on neutrophils (CD11bSurface) to establish the CD11b stimulation index (CD11b-SI), a test enabling the clinical research diagnosis of impaired GM-CSF signaling based on measuring CD11bSurface by flow cytometry using fresh, heparinized blood. (CD11b-SI is defined as GM-CSF-stimulated- CD11bSurface minus unstimulated CD11bSurface divided by un-stimulated CD11bSurface multiplied by 100.) Notwithstanding important and unique diagnostic utility, the test is sensitive to experimental conditions that can affect test performance. The present study was undertaken to optimize and standardize CD11b-SI test for detecting impaired GM-CSF signaling in heparinized human blood specimens from PAP patients. Results demonstrated the test was sensitive to choice of anticoagulant, pretesting incubation on ice, a delay between phlebotomy and test performance of more than one hour, and the concentration GM-CSF used to stimulate blood. The standardized CD11b-SI test reliably distinguished blood specimens from autoimmune PAP patients with impaired GM-CSF signaling from those of health people with normal signaling. Intra-subject differences were smaller than inter-subject differences in repeated measures. Receiver operating characteristic curve analysis identified a CD11b-SI test result of 112 as the optimal cut off threshold for diagnosis of impaired GM-CSF signaling in autoimmune PAP for which the sensitivity and specificity were both 100%. These results support the use of this standardized CD11b-SI for routine clinical identification of impaired GM-CSF signaling in patients with autoimmune PAP. The CD11b-SI may also have utility in clinical trials of novel therapeutic strategies targeting reduction in GM-CSF bioactivity now under evaluation for multiple common autoimmune and inflammatory disorders.

Pulmonary macrophage transplantation therapy

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

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

RATIONALE

In patients with pulmonary alveolar proteinosis (PAP) syndrome, disruption of granulocyte/macrophage colony-stimulating factor (GM-CSF) signaling is associated with pathogenic surfactant accumulation from impaired clearance in alveolar macrophages.

OBJECTIVES

The aim of this study was to overcome these barriers by using monocyte-derived induced pluripotent stem (iPS) cells to recapitulate disease-specific and normal macrophages.

METHODS

We created iPS cells from two children with hereditary PAP (hPAP) caused by recessive CSF2RA(R217X) mutations and three normal people, differentiated them into macrophages (hPAP-iPS-Mφs and NL-iPS-Mφs, respectively), and evaluated macrophage functions with and without gene-correction to restore GM-CSF signaling in hPAP-iPS-Mφs.

MEASUREMENTS AND MAIN RESULTS

Both hPAP and normal iPS cells had human embryonic stem cell-like morphology, expressed pluripotency markers, formed teratomas in vivo, had a normal karyotype, retained and expressed mutant or normal CSF2RA genes, respectively, and could be differentiated into macrophages with the typical morphology and phenotypic markers. Compared with normal, hPAP-iPS-Mφs had impaired GM-CSF receptor signaling and reduced GM-CSF-dependent gene expression, GM-CSF- but not M-CSF-dependent cell proliferation, surfactant clearance, and proinflammatory cytokine secretion. Restoration of GM-CSF receptor signaling corrected the surfactant clearance abnormality in hPAP-iPS-Mφs.

CONCLUSIONS

We used patient-specific iPS cells to accurately reproduce the molecular and cellular defects of alveolar macrophages that drive the pathogenesis of PAP in more than 90% of patients. These results demonstrate the critical role of GM-CSF signaling in surfactant homeostasis and PAP pathogenesis in humans and have therapeutic implications for hPAP.

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

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

Human Treg responses allow sustained recombinant adeno-associated virus-mediated transgene expression

Recombinant adeno-associated virus (rAAV) vectors have shown promise for the treatment of several diseases; however, immune-mediated elimination of transduced cells has been suggested to limit and account for a loss of efficacy. To determine whether rAAV vector expression can persist long term, we administered rAAV vectors expressing normal, M-type α-1 antitrypsin (M-AAT) to AAT-deficient subjects at various doses by multiple i.m. injections. M-specific AAT expression was observed in all subjects in a dose-dependent manner and was sustained for more than 1 year in the absence of immune suppression. Muscle biopsies at 1 year had sustained AAT expression and a reduction of inflammatory cells compared with 3 month biopsies. Deep sequencing of the TCR Vβ region from muscle biopsies demonstrated a limited number of T cell clones that emerged at 3 months after vector administration and persisted for 1 year. In situ immunophenotyping revealed a substantial Treg population in muscle biopsy samples containing AAT-expressing myofibers. Approximately 10% of all T cells in muscle were natural Tregs, which were activated in response to AAV capsid. These results suggest that i.m. delivery of rAAV type 1-AAT (rAAV1-AAT) induces a T regulatory response that allows ongoing transgene expression and indicates that immunomodulatory treatments may not be necessary for rAAV-mediated gene therapy.