The Pathogenic Role of Anti-Granulocyte-Macrophage Colony-Stimulating Factor Autoantibodies in the Nocardiosis with the Central Nervous System Involvement.

PURPOSE: Anti-granulocyte-macrophage colony-stimulating factor autoantibodies (anti-GM-CSF Abs) are implicated in the pathogenesis of Cryptococcus gattii (C. gattii) infection and pulmonary alveolar proteinosis (PAP). Their presence has also been noted in nocardiosis cases, particularly those with disseminated disease. This study delineates a case series characterizing clinical features and specificity of anti-GM-CSF Abs in nocardiosis patients. METHODS: In this study, eight patients were recruited to determine the presence or absence of anti-GM-CSF Abs. In addition to the detailed description of the clinical course, we thoroughly investigated the autoantibodies regarding the characteristics, isotypes, subclasses, titers, and neutralizing capacities by utilizing the plasma samples from patients. RESULTS: Of eight patients, five tested positive for anti-GM-CSF Abs, all with central nervous system (CNS) involvement; patients negative for these antibodies did not develop CNS nocardiosis. Distinct from previously documented cases, none of our patients with anti-GM-CSF Abs exhibited PAP symptoms. The titer and neutralizing activity of anti-GM-CSF Abs in our cohort did not significantly deviate from those found in C. gattii cryptococcosis and PAP patients. Uniquely, one individual (Patient 3) showed a minimal titer and neutralizing action of anti-GM-CSF Abs, with no relation to disease severity. Moreover, IgM autoantibodies were notably present in all CNS nocardiosis cases investigated. CONCLUSION: The presence of anti-GM-CSF Abs suggests an intrinsic immunodeficiency predisposing individuals toward CNS nocardiosis. The presence of anti-GM-CSF Abs helps to elucidate vulnerability to CNS nocardiosis, even with low titer of autoantibodies. Consequently, systematic screening for anti-GM-CSF Abs should be considered a crucial diagnostic step for nocardiosis patients.

Infections in autoimmune pulmonary alveolar proteinosis: a large retrospective cohort.

BACKGROUND: Autoimmune pulmonary alveolar proteinosis (aPAP) is a rare disease, predisposing to an increased risk of infection. A complete picture of these infections is lacking. RESEARCH QUESTION: Describe the characteristics and clinical outcomes of patients diagnosed with aPAP, and to identify risk factors associated with opportunistic infections. METHODS: We conducted a retrospective cohort including all patients diagnosed with aPAP between 2008 and 2018 in France and Belgium. Data were collected using a standardised questionnaire including demographics, comorbidities, imaging features, outcomes and microbiological data. RESULTS: We included 104 patients, 2/3 were men and median age at diagnosis was 45 years. With a median follow-up of 3.4 years (IQR 1.7-6.6 years), 60 patients (58%), developed at least one infection, including 23 (22%) with opportunistic infections. Nocardia spp was the main pathogen identified (n=10). Thirty-five (34%) patients were hospitalised due to infection. In univariate analysis, male gender was associated with opportunistic infections (p=0.04, OR=3.88; 95% CI (1.02 to 22.06)). Anti-granulocyte macrophage colony-stimulating factor antibody titre at diagnosis was significantly higher among patients who developed nocardiosis (1058 (316-1591) vs 580 (200-1190), p=0.01). Nine patients had died (9%), but only one death was related to infection. INTERPRETATION: Patients with aPAP often presented with opportunistic infections, especially nocardiosis, which highlights the importance of systematic search for slow-growing bacteria in bronchoalveolar lavage or whole lung lavage.

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.

Prevalence and healthcare burden of pulmonary alveolar proteinosis.

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

Pulmonary 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.

Development of pulmonary alveolar proteinosis following exposure to dust after the Great East Japan Earthquake.

We report a unique case of pulmonary alveolar proteinosis that developed 3 weeks after the Great East Japan Earthquake and the subsequent tsunami. The patient had inhaled dust repeatedly while visiting her devastated neighborhood without wearing a protective mask. Five weeks after the earthquake, lung samples taken from the patient showed foreign particle deposition; however, her serum was negative for GM-CSF autoantibody. The patient's clinical symptoms resolved following whole lung lavage. We conclude that inhalation of fine dust particles after natural disasters may cause the onset of pulmonary alveolar proteinosis.

Light chain (κ/λ) ratio of GM-CSF autoantibodies is associated with disease severity in autoimmune pulmonary alveolar proteinosis.

Previous studies demonstrated that antigranulocyte colony-stimulating factor autoantibody (GMAb) was consistently present in patients with autoimmune pulmonary alveolar proteinosis (aPAP), and, thus, represented candidature as a reliable diagnostic marker. However, our large cohort study suggested that the concentration of this antibody was not correlated with disease severity in patients. We found that the κ/λ ratio of GMAb was significantly correlated with the degree of hypoxemia. The proportion of λ-type GMAb per total λ-type IgG was significantly higher in severely affected patients than those in mildly affected patients, but the proportion of κ-type was unchanged. The κ/λ ratio was significantly correlated with both KL-6 and SP-D, which have been previously reported as disease severity markers. Thus, the light chain isotype usage of GMAb may not only be associated with the severity of aPAP, but may also represent a useful disease severity marker.