High avidity cytokine autoantibodies in health and disease: pathogenesis and mechanisms

Selective production of IL-33-neutralizing autoantibody ameliorates asthma responses and severity

BACKGROUND

Natural anti-cytokine autoantibodies can regulate homeostasis of infectious and inflammatory diseases. The anti-cytokine autoantibody profile and relevance to the pathogenesis of asthma are unknown. We aim to identify key anti-cytokine autoantibodies in asthma patients, and reveal their immunological function and clinical significance.

METHODS

A Luciferase Immunoprecipitation System was used to screen serum autoantibodies against 11 key cytokines in patients with allergic asthma and healthy donors. The antigen-specificity, immunomodulatory functions and clinical significance of anti-cytokine autoantibodies were determined by ELISA, qPCR, neutralization assays and statistical analysis, respectively. Potential conditions for autoantibody induction were revealed by in vitro immunization.

RESULTS

Of 11 cytokines tested, only anti-IL-33 autoantibody was significantly increased in asthma, compare to healthy controls, and the proportion positive was higher in patients with mild-to-moderate than severe allergic asthma. In allergic asthma patients, the anti-IL-33 autoantibody level correlated negatively with serum concentration of pathogenic cytokines (e.g., IL-4, IL-13, IL-25 and IL-33), IgE, and blood eosinophil count, but positively with mid-expiratory flow FEF25-75%. The autoantibodies were predominantly IgG isotype, polyclonal and could neutralize IL-33-induced pathogenic responses in vitro and in vivo. The induction of the anti-IL-33 autoantibody in blood B-cells in vitro required peptide IL-33 antigen along with a stimulation cocktail of TLR9 agonist and cytokines IL-2, IL-4 or IL-21.

CONCLUSIONS

Serum natural anti-IL-33 autoantibodies are selectively induced in some asthma patients. They ameliorate key asthma inflammatory responses, and may improve lung function of allergic asthma.

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.

Clinical Significance of Uncommon, Non-Clinical, and Novel Autoantibodies

Autoantibodies are a common mark of autoimmune reaction and their identification in the patients' serum, cerebrospinal fluid, or tissues is generally believed to represent diagnostic or prognostic biomarkers of autoimmune diseases or autoinflammatory conditions. Traditionally, autoantibody testing is an important part of the clinical examination of suspected patients, and in the absence of reliable T cell tests, characterization of autoantibody responses might be suitable in finding causes of specific autoimmune responses, their strength, and sometimes commencement of autoimmune disease. Autoantibodies are also useful for prognostic stratification in clinically diverse groups of patients if checked repeatedly. Antibody discoveries are continuing, with important consequences for verifying autoimmune mechanisms, diagnostic feasibility, and clinical management. Adding newly identified autoantibody-autoantigen pairs to common clinical laboratory panels should help upgrade and harmonize the identification of systemic autoimmune rheumatic disorders and other autoimmune conditions. Herein, we aim to summarize our current knowledge of uncommon and novel autoantibodies in the context of discussing their validation, diagnostic practicability, and clinical relevance. The regular updates within the field are important and well justified.

Altered Levels of Natural Autoantibodies against Heat Shock Proteins in Pregnant Women with Hashimoto's Thyroiditis

The function of natural autoantibodies (nAAbs) in maintaining immunological tolerance has been comprehensively explained; however, their function in pregnant patients dealing with autoimmune diseases has not been thoroughly investigated. As Hashimoto's thyroiditis (HT) is the predominant organ-specific autoimmune condition of women of childbearing age, this study's objective was to evaluate IgM and IgG nAAbs targeting mitochondrial citrate synthase (CS) and heat shock proteins (Hsp60 and Hsp70) in women diagnosed with HT who were pregnant (HTP). Serum samples collected from HTP and healthy pregnant (HP) women in the first and third trimesters were tested using in-house-developed enzyme-linked immunosorbent assays (ELISAs). Our findings indicate the stability of nAAbs against CS and Hsps throughout the pregnancies of both healthy women and those with HT. However, during both trimesters, HTP patients displayed elevated levels of IgM isotype nAAbs against Hsp60 and Hsp70 compared to HP women, suggesting a regulatory role of IgM nAAbs during the pregnancies of patients with HT. Nonetheless, levels of IgG isotype nAAbs against Hsps were lower solely in the third trimester among HTP patients, resulting in a higher IgM/IgG ratio, which indicates their importance in alterations of the nAAb network during pregnancy in patients with HT.

Autoantibodies to Interferons in Infectious Diseases

Anti-cytokine autoantibodies and, in particular, anti-type I interferons are increasingly described in association with immunodeficient, autoimmune, and immune-dysregulated conditions. Their presence in otherwise healthy individuals may result in a phenotype characterized by a predisposition to infections with several agents. For instance, anti-type I interferon autoantibodies are implicated in Coronavirus Disease 19 (COVID-19) pathogenesis and found preferentially in patients with critical disease. However, autoantibodies were also described in the serum of patients with viral, bacterial, and fungal infections not associated with COVID-19. In this review, we provide an overview of anti-cytokine autoantibodies identified to date and their clinical associations; we also discuss whether they can act as enemies or friends, i.e., are capable of acting in a beneficial or harmful way, and if they may be linked to gender or immunosenescence. Understanding the mechanisms underlying the production of autoantibodies could improve the approach to treating some infections, focusing not only on pathogens, but also on the possibility of a low degree of autoimmunity in patients.

Autoantibodies of inflammatory cytokines as serum biomarkers in OSA patients

As many as 90% of patients with obstructive sleep apnea (OSA) may be undiagnosed. It is necessary to explore the potential value of autoantibodies against CRP, IL-6, IL-8 and TNF-α in the diagnosis of OSA. ELISA was performed to detect the level of autoantibodies against CRP, IL-6, IL-8 and TNF-α in sera from 264 OSA patients and 231 normal controls (NCs). The expression level of autoantibodies against CRP, IL-6 and IL-8 in OSA were significantly higher than that in NC while the level of anti-TNF-α was lower in OSA than that in NC. The per SD increment of anti-CRP, anti-IL-6 and anti-IL-8 autoantibodies were significantly associated with a 430%, 100% and 31% higher risk for OSA, respectively. The AUC of anti-CRP was 0.808 (95% CI: 0.771-0.845) when comparing OSA with NC, while the AUC increased to 0.876 (95% CI: 0.846-0.906) combining four autoantibodies. For discrimination of severe OSA versus NC and non-severe OSA versus NC, the AUC for four autoantibodies combination was 0.885 (95% CI: 0.851-0.918) and 0.876 (95% CI: 0.842-0.913). This study revealed the association between autoantibodies against inflammatory factors and OSA, and the combination of autoantibodies against CRP, IL-6, IL-8 and TNF-α may function as novel biomarker for monitoring the presence of OSA.

Immune responses in mildly versus critically ill COVID-19 patients

The current coronavirus pandemic (COVID-19), caused by SARS-CoV-2, has had devastating effects on the global health and economic system. The cellular and molecular mediators of both the innate and adaptive immune systems are critical in controlling SARS-CoV-2 infections. However, dysregulated inflammatory responses and imbalanced adaptive immunity may contribute to tissue destruction and pathogenesis of the disease. Important mechanisms in severe forms of COVID-19 include overproduction of inflammatory cytokines, impairment of type I IFN response, overactivation of neutrophils and macrophages, decreased frequencies of DC cells, NK cells and ILCs, complement activation, lymphopenia, Th1 and Treg hypoactivation, Th2 and Th17 hyperactivation, as well as decreased clonal diversity and dysregulated B lymphocyte function. Given the relationship between disease severity and an imbalanced immune system, scientists have been led to manipulate the immune system as a therapeutic approach. For example, anti-cytokine, cell, and IVIG therapies have received attention in the treatment of severe COVID-19. In this review, the role of immunity in the development and progression of COVID-19 is discussed, focusing on molecular and cellular aspects of the immune system in mild vs. severe forms of the disease. Moreover, some immune- based therapeutic approaches to COVID-19 are being investigated. Understanding key processes involved in the disease progression is critical in developing therapeutic agents and optimizing related strategies.

High-throughput identification of autoantibodies that target the human exoproteome

Autoantibodies that recognize extracellular proteins (the exoproteome) exert potent biological effects but are challenging to detect. Here, we developed rapid extracellular antigen profiling (REAP), a high-throughput technique for the comprehensive discovery of exoproteome-targeting autoantibodies. Patient samples are applied to a genetically barcoded yeast surface display library containing 2,688 human extracellular proteins. Antibody-coated yeast are isolated, and sequencing of barcodes is used to identify displayed antigens. To benchmark REAP's performance, we screened 77 patients with autoimmune polyglandular syndrome type 1 (APS-1). REAP sensitively and specifically detected both known and previously unidentified autoantibodies in APS-1. We further screened 106 patients with systemic lupus erythematosus (SLE) and identified numerous autoantibodies, several of which were associated with disease severity or specific clinical manifestations and exerted functional effects on cell signaling ex vivo. These findings demonstrate the utility of REAP to atlas the expansive landscape of exoproteome-targeting autoantibodies and their impacts on patient health outcomes.

The Role of GM-CSF Autoantibodies in Infection and Autoimmune Pulmonary Alveolar Proteinosis: A Concise Review

Autoantibodies to multiple cytokines have been identified and some, including antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF), have been associated with increased susceptibility to infection. High levels of GM-CSF autoantibodies that neutralize signaling cause autoimmune pulmonary alveolar proteinosis (aPAP), an ultrarare autoimmune disease characterized by accumulation of excess surfactant in the alveoli, leading to pulmonary insufficiency. Defective GM-CSF signaling leads to functional deficits in multiple cell types, including macrophages and neutrophils, with impaired phagocytosis and host immune responses against pulmonary and systemic infections. In this article, we review the role of GM-CSF in aPAP pathogenesis and pulmonary homeostasis along with the increased incidence of infections (particularly opportunistic infections). Therefore, recombinant human GM-CSF products may have potential for treatment of aPAP and possibly other infectious and pulmonary diseases due to its pleotropic immunomodulatory actions.

The signal pathways and treatment of cytokine storm in COVID-19

The Coronavirus Disease 2019 (COVID-19) pandemic has become a global crisis and is more devastating than any other previous infectious disease. It has affected a significant proportion of the global population both physically and mentally, and destroyed businesses and societies. Current evidence suggested that immunopathology may be responsible for COVID-19 pathogenesis, including lymphopenia, neutrophilia, dysregulation of monocytes and macrophages, reduced or delayed type I interferon (IFN-I) response, antibody-dependent enhancement, and especially, cytokine storm (CS). The CS is characterized by hyperproduction of an array of pro-inflammatory cytokines and is closely associated with poor prognosis. These excessively secreted pro-inflammatory cytokines initiate different inflammatory signaling pathways via their receptors on immune and tissue cells, resulting in complicated medical symptoms including fever, capillary leak syndrome, disseminated intravascular coagulation, acute respiratory distress syndrome, and multiorgan failure, ultimately leading to death in the most severe cases. Therefore, it is clinically important to understand the initiation and signaling pathways of CS to develop more effective treatment strategies for COVID-19. Herein, we discuss the latest developments in the immunopathological characteristics of COVID-19 and focus on CS including the current research status of the different cytokines involved. We also discuss the induction, function, downstream signaling, and existing and potential interventions for targeting these cytokines or related signal pathways. We believe that a comprehensive understanding of CS in COVID-19 will help to develop better strategies to effectively control immunopathology in this disease and other infectious and inflammatory diseases.

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.

Intravenous Immunoglobulin Attenuates Cecum Ligation and Puncture-Induced Acute Lung Injury by Inhibiting Apoptosis of Alveolar Epithelial Cells

PURPOSE

Intravenous immunoglobulin (IVIG) therapy has been used to treat sepsis, but its mechanisms of action remain unclear. Sepsis causes multiple organ failure, such as acute lung injury (ALI), which involves apoptosis of alveolar epithelial cells. In this study, we hypothesized that IVIG suppresses apoptosis in alveolar epithelial cells and evaluated mortality, cytokine levels, histological changes in the lung, and alveolar epithelial cell apoptosis after IVIG administration, in mice with experimentally induced sepsis.

METHODS

Mice received an injection of vehicle (saline) or immunoglobulin (100 mg/kg or 400 mg/kg) into the tail vein, after which they underwent cecal ligation and puncture. A sham-operated group was used as the normal control. Survival was assessed in all groups after 72 hours. Plasma levels of TNF-α and IL-6, histopathological changes and wet-to-dry ratio in lung, and alveolar epithelial cell apoptosis were evaluated in all groups at 4 hours after surgery.

RESULTS

In the vehicle group, histopathological injury of the lung was severe, and apoptosis of alveolar epithelial cells was significant. Survival and plasma cytokine levels were better in the IVIG treatment groups than in the vehicle group. IVIG 400 mg/kg suppressed apoptosis of alveolar epithelial cells and reduced ALI.

CONCLUSION

IVIG suppressed inflammatory cytokine levels and improved survival. Lung histopathology and alveolar epithelial cell apoptosis were improved by IVIG treatment, in a dose-dependent manner. Suppressing apoptosis in alveolar epithelial cells appears to be a mechanism by which IVIG improves survival.

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

High incidence of anti-cytokine autoantibodies in dogs with immune diseases suggests important immuno-regulatory functions

Autoantibodies against cytokines have been associated with immunodeficiency, susceptibility to infectious diseases, autoimmunity and inflammation in humans, but have not yet been investigated in the Veterinary field so far. The aim of the current study was to determine the presence of anti-cytokine autoantibodies in canines suffering from various conditions including recurrent infections, autoimmune diseases and cancer in comparison to healthy controls. This is the first report of the presence of autoantibodies against cytokines in dogs. A total of 101 serum samples (51 patients and 50 clinically healthy dogs) from the state of Mexico and surroundings were analysed using a multiplex bead-based flow cytometry assay. Results show significant levels of various anti-cytokine autoantibodies in diseased dogs but not in healthy controls. In addition we show distinct associations of various disease types to the specificity of anti-cytokine autoantibodies and to response complexities. Apart from the direct functional/causal implication of anti-cytokine auto-antibodies on disease processes, this findings point to the possibility to use anti-cytokine response patterns as diagnostic tools.

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.

Kawasaki disease shock syndrome: clinical characteristics and possible use of IL-6, IL-10 and IFN-γ as biomarkers for early recognition

BACKGROUND

As an acute febrile and inflammatory disease, Kawasaki disease (KD) could develop Kawasaki disease shock syndrome (KDSS) sometimes. However its pathogenesis was still not well known. This study was to learn more about the clinical features and evaluate the role of cytokines in the pathogenesis of KDSS.

METHODS

We collected clinical and laboratory data retrospectively for all patients with KDSS(KDSS, n = 27)who were hospitalized at our hospital from Jan 2014 to Oct 2017. For patient with KDSS, we randomly identified 43 patients with KD as control subjects (KD, n = 43). Clinical features, laboratory evaluations were collected. Cytokines IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ in serum were assayed using flow cytometric bead array.

RESULTS

The patients with KDSS were older age (43.41 ± 31.42 vs 28.81 ± 21.51 months, P < 0.05), longer duration of fever (10.63 ± 5.12 vs 6.98 ± 2.45 days, P < 0.05), higher WBC count, neutrophils, CRP, ESR, PCT and D-dimer, and lower hemoglobin and albumin, more severe hyponatremia and hypokalemia, more refractory to IVIG therapy, more coronary artery abnormalities (CAAs), aseptic meningitis, and longer duration of hospitalization than patients with KD (all P < 0.05). The levels of serum IL-6 [184.1 (27.7-2577.3) vs 54.1 (4-425) pg/ml], IL-10 [42.6 (5-236.7) vs 9.4 (3-94) pg/ml], TNF-α [2.6 (1.0-23.4) vs 2.1 (1-6) pg/ml] and IFN-γ [18.3 (4.5-94.4) vs 6.7 (2-56) pg/ml] in KDSS patients were significant higher than KD patients (all P < 0.05). ROC curves showed that 66.7 pg/ml of IL-6, 20.85 pg/ml of IL-10 and 8.35 pg/ml of IFN-γ had sensitivity and specificity for identifying KDSS as 85.2 and 62.8%; 66.7 and 83.7%; 74.1 and 74.4% respectively. No fatality was recorded in this series.

CONCLUSIONS

KDSS were characteristic as more cytokine production and prone to developing IVIG non-responsiveness and CAAs. KD patients with IL-6 above 66.7 pg/ml, IL-10 above 20.85 pg/ml, and IFN-γ above 8.35 pg/ml suggested higher risk for KDSS.

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.

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.

Transcriptional Analysis of Intravenous Immunoglobulin Resistance in Kawasaki Disease Using an Induced Pluripotent Stem Cell Disease Model

BACKGROUND

Approximately 10-20% of Kawasaki disease (KD) patients are resistant to intravenous immunoglobulin (IVIG) treatment. Further, these patients are at a particularly high risk of having coronary artery abnormalities. The mechanisms of IVIG resistance in KD have been analyzed using patient leukocytes, but not patient vascular endothelial cells (ECs). The present study clarifies the mechanisms of IVIG resistance in KD using an induced pluripotent stem cell (iPSC) disease model.Methods and Results:Dermal fibroblasts or peripheral blood mononuclear cells from 2 IVIG-resistant and 2 IVIG-responsive KD patients were reprogrammed by the episomal vector-mediated transduction of 6 reprogramming factors. KD patient-derived iPSCs were differentiated into ECs (iPSC-ECs). The gene expression profiles of iPSC-ECs generated from IVIG-resistant and IVIG-responsive KD patients were compared by RNA-sequencing analyses. We found that the expression ofCXCL12was significantly upregulated in iPSC-ECs from IVIG-resistant KD patients. Additionally, Gene Set Enrichment Analysis (GSEA) revealed that gene sets involved in interleukin (IL)-6 signaling were also upregulated.

CONCLUSIONS

The first iPSC-based model for KD is reported here. Our mechanistic analyses suggest thatCXCL12, which plays a role in leukocyte transmigration, is a key molecule candidate for IVIG resistance and KD severity. They also indicate that an upregulation of IL-6-related genes may be involved in this pathogenesis.

Pre-existing Antibody: Biotherapeutic Modality-Based Review

Pre-existing antibodies to biotherapeutic drugs have been detected in drug-naïve subjects for a variety of biotherapeutic modalities. Pre-existing antibodies are immunoglobulins that are either specific or cross-reacting with a protein or glycan epitopes on a biotherapeutic compound. Although the exact cause for pre-existing antibodies is often unknown, environmental exposures to non-human proteins, glycans, and structurally similar products are frequently proposed as factors. Clinical consequences of the pre-existing antibodies vary from an adverse effect on patient safety to no impact at all and remain highly dependent on the biotherapeutic drug modality and therapeutic indication. As such, pre-existing antibodies are viewed as an immunogenicity risk factor requiring a careful evaluation. Herein, the relationships between biotherapeutic modalities to the nature, prevalence, and clinical consequences of pre-existing antibodies are reviewed. Initial evidence for pre-existing antibody is often identified during anti-drug antibody (ADA) assay development. Other interfering factors known to cause false ADA positive signal, including circulating multimeric drug target, rheumatoid factors, and heterophilic antibodies, are discussed.

Plasma Anti-Glial Fibrillary Acidic Protein Autoantibody Levels during the Acute and Chronic Phases of Traumatic Brain Injury: A Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot Study

We described recently a subacute serum autoantibody response toward glial fibrillary acidic protein (GFAP) and its breakdown products 5-10 days after severe traumatic brain injury (TBI). Here, we expanded our anti-GFAP autoantibody (AutoAb[GFAP]) investigation to the multicenter observational study Transforming Research and Clinical Knowledge in TBI Pilot (TRACK-TBI Pilot) to cover the full spectrum of TBI (Glasgow Coma Scale 3-15) by using acute (<24 h) plasma samples from 196 patients with acute TBI admitted to three Level I trauma centers, and a second cohort of 21 participants with chronic TBI admitted to inpatient TBI rehabilitation. We find that acute patients self-reporting previous TBI with loss of consciousness (LOC) (n = 43) had higher day 1 AutoAb[GFAP] (mean ± standard error: 9.11 ± 1.42; n = 43) than healthy controls (2.90 ± 0.92; n = 16; p = 0.032) and acute patients reporting no previous TBI (2.97 ± 0.37; n = 106; p < 0.001), but not acute patients reporting previous TBI without LOC (8.01 ± 1.80; n = 47; p = 0.906). These data suggest that while exposure to TBI may trigger the AutoAb[GFAP] response, circulating antibodies are elevated specifically in acute TBI patients with a history of TBI. AutoAb[GFAP] levels for participants with chronic TBI (average post-TBI time 176 days or 6.21 months) were also significantly higher (15.08 ± 2.82; n = 21) than healthy controls (p < 0.001). These data suggest a persistent upregulation of the autoimmune response to specific brain antigen(s) in the subacute to chronic phase after TBI, as well as after repeated TBI insults. Hence, AutoAb[GFAP] may be a sensitive assay to study the dynamic interactions between post-injury brain and patient-specific autoimmune responses across acute and chronic settings after TBI.

Use of the VH6-1 gene segment to code for anti-interleukin-18 autoantibodies in multiple sclerosis

We investigated whether levels and repertoires of anti-interleukin-18 (IL-18) autoantibodies (auto-Abs) differ in multiple sclerosis (MS) patients and healthy donors (HDs). IL-18 concentration in MS patients' sera was higher than in HD, but the level of anti-IL-18 auto-Abs was lower in MS patients. Correlation patterns of IL-18/anti-IL-18 auto-Abs system differed in HD and MS patients, so we have compared segment composition of the anti-IL-18 single-chain variable fragments (scFvs) selected from MS and naïve phage display libraries. Considerable differences between anti-IL-18 auto-Abs of these libraries were found. MS panel contained auto-Abs displaying both signs of "fetal" and somatically hypermutated repertoires. Naïve panel mainly contained the naïve antibodies. These variations from the norm are possible results of abnormal regulation of the repertoire perhaps determined by remodeling of the molecular mechanisms involved in the V(D)J recombination and/or abnormal selection by antigen in MS pathogenesis.

2015 White Paper on recent issues in bioanalysis: focus on new technologies and biomarkers (Part 3 – LBA, biomarkers and immunogenicity)

The 2015 9th Workshop on Recent Issues in Bioanalysis (9th WRIB) took place in Miami, Florida with participation of 600 professionals from pharmaceutical and biopharmaceutical companies, biotechnology companies, contract research organizations and regulatory agencies worldwide. WRIB was once again a 5 day, week-long event – A Full Immersion Bioanalytical Week – specifically designed to facilitate sharing, reviewing, discussing and agreeing on approaches to address the most current issues of interest in bioanalysis. The topics covered included both small and large molecules, and involved LCMS, hybrid LBA/LCMS and LBA approaches, including the focus on biomarkers and immunogenicity. This 2015 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2015 edition of this comprehensive White Paper has been divided into three parts. Part 3 discusses the recommendations for large molecule bioanalysis using LBA, biomarkers and immunogenicity. Part 1 (small molecule bioanalysis using LCMS) and Part 2 (hybrid LBA/LCMS and regulatory inputs from major global health authorities) have been published in volume 7, issues 22 and 23 of Bioanalysis, respectively.

Broad-spectrum antibodies against self-antigens and cytokines in RAG deficiency

Patients with mutations of the recombination-activating genes (RAG) present with diverse clinical phenotypes, including severe combined immune deficiency (SCID), autoimmunity, and inflammation. However, the incidence and extent of immune dysregulation in RAG-dependent immunodeficiency have not been studied in detail. Here, we have demonstrated that patients with hypomorphic RAG mutations, especially those with delayed-onset combined immune deficiency and granulomatous/autoimmune manifestations (CID-G/AI), produce a broad spectrum of autoantibodies. Neutralizing anti-IFN-α or anti-IFN-ω antibodies were present at detectable levels in patients with CID-G/AI who had a history of severe viral infections. As this autoantibody profile is not observed in a wide range of other primary immunodeficiencies, we hypothesized that recurrent or chronic viral infections may precipitate or aggravate immune dysregulation in RAG-deficient hosts. We repeatedly challenged Rag1S723C/S723C mice, which serve as a model of leaky SCID, with agonists of the virus-recognizing receptors TLR3/MDA5, TLR7/-8, and TLR9 and found that this treatment elicits autoantibody production. Altogether, our data demonstrate that immune dysregulation is an integral aspect of RAG-associated immunodeficiency and indicate that environmental triggers may modulate the phenotypic expression of autoimmune manifestations.

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.

Emerging clinical phenotypes associated with anti-cytokine autoantibodies

Anti-cytokine autoantibodies (AAbs) are frequent and involve a very large panel of cytokines both in healthy subjects and in patients with various pathological conditions. In healthy individuals, anti-cytokine AAbs are described as a part of the natural AAb repertoire and are thought to contribute to the fine regulation of cytokine homeostasis. In some patients, neutralizing AAbs targeting cytokines required for the immune protection against specific microbes may induce acquired immunodeficiency leading to very specific infectious phenotypes. For instance, anti-IFNγ AAbs may induce disseminated non-tuberculous mycobacterial infections; anti-IL-17 AAbs are associated with the development of chronic mucosal candidiasis, and anti-IL-6 AAbs with severe staphylococcal or streptococcal infections. In patients with autoimmune diseases, AAbs directed against pathogenic cytokines are able to influence the course of the diseases. In lupus patients, neutralizing anti-IFNα and anti-TNFα AAbs are associated with a decreased bioactivity of the corresponding cytokine and a lower disease severity. Similarly, anti-IL-1α AAbs are associated with nondestructive forms of chronic polyarthritis. More surprisingly, neutralizing anti-BAFF AAbs are observed in the serum of lupus patients with elevated IFNα signature and higher disease activity. In this review, we summarize the current literature describing the different phenotypes and the main mechanisms associated with the occurrence of anti-cytokine AAbs.

Body fluid biomarkers in multiple sclerosis: how far we have come and how they could affect the clinic now and in the future

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system, which affects over 2.5 million people worldwide. Although MS has been extensively studied, many challenges still remain in regards to treatment, diagnosis and prognosis. Typically, prognosis and individual responses to treatment are evaluated by clinical tests such as the expanded disability status scale, MRI and presence of oligoclonal bands in the cerebrospinal fluid. However, none of these measures correlates strongly with treatment efficacy or disease progression across heterogeneous patient populations and subtypes of MS. Numerous studies over the past decades have attempted to identify sensitive and specific biomarkers for diagnosis, prognosis and treatment efficacy of MS. The objective of this article is to review and discuss the current literature on body fluid biomarkers in MS, including research on potential biomarker candidates in the areas of miRNA, mRNA, lipids and proteins.

2014 White Paper on recent issues in bioanalysis: a full immersion in bioanalysis (Part 3 – LBA and immunogenicity)

The 2014 8th Workshop on Recent Issues in Bioanalysis (8th WRIB), a 5-day full immersion in the evolving field of bioanalysis, took place in Universal City, California, USA. Close to 500 professionals from pharmaceutical and biopharmaceutical companies, contract research organizations and regulatory agencies worldwide convened to share, review, discuss and agree on approaches to address current issues of interest in bioanalysis. The topics covered included both small and large molecules, and involved LCMS, hybrid LBA/LCMS, LBA approaches and immunogenicity. From the prolific discussions held during the workshop, specific recommendations are presented in this 2014 White Paper. As with the previous years’ editions, this paper acts as a practical tool to help the bioanalytical community continue advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2014 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations for Large molecules bioanalysis using LBA and Immunogenicity. Part 1 (Small molecules bioanalysis using LCMS) and Part 2 (Hybrid LBA/LCMS, Electronic Laboratory Notebook and Regulatory Agencies' Input) were published in the Bioanalysis issues 6(22) and 6(23), respectively.

Detection of anti-cytokine antibodies and their clinical relevance

Cytokines regulate many aspects of cell growth and differentiation and play pivotal roles in the orchestration of immune defence against invading pathogens. Though 'self' proteins, they are potentially immunogenic and can give rise to anti-cytokine autoantibodies (aCA). The main foci of the article are a critical summary of the various methodologies applied for detecting and measuring aCA and a broad review of studies of the occurrence, characterization and clinical relevance of aCA in normal healthy individuals, patients with autoimmune diseases or microbial infections and aCA in patients whose disease is treated with recombinant cytokine products. The need for technical and methodological improvement of assays, including validation and standardization, together with approaches to harmonize calculation and reporting of results is also discussed.

Anti-granulocyte-macrophage colony-stimulating factor autoantibodies are a risk factor for central nervous system infection by Cryptococcus gattii in otherwise immunocompetent patients

Cryptococcosis is caused by either Cryptococcus neoformans or C. gattii. While cryptococcal meningoencephalitis is caused mostly by C. neoformans in immunocompromised patients, the risk factors remain unclear for patients with no known immune defect. Recently, anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies were detected in the plasma of seven “immunocompetent” cryptococcosis patients, and the cryptococcal strains from these patients were reported as C. neoformans (three strains), C. gattii (one strain), and Cryptococcus (three strains not identified to the species level). We identified all three strains that had not been identified to the species level as C. gattii. Notably, the three strains that were reported as C. neoformans but were unavailable for species confirmation originated from Sothern California and Thailand where C. gattii is endemic. Most clinical laboratories designate C. neoformans without distinguishing between the two species; hence, these three strains could have been C. gattii. Since C. gattii infects more immunocompetent patients than C. neoformans, we pursued the possibility that this antibody may be more prevalent in patients infected with C. gattii than in those infected with C. neoformans. We screened the plasma of 20 healthy controls and 30 “immunocompetent” patients with cryptococcal meningoencephalitis from China and Australia (multiple ethnicities). Anti-GM-CSF autoantibodies were detected only in the plasma of seven patients infected by C. gattii and one healthy volunteer and in none infected by C. neoformans. While plasma from these C. gattii patients completely prevented GM-CSF-induced p-STAT5 in normal human peripheral blood mononuclear cells (PBMCs), plasma from one healthy volunteer positive for anti-GM-CSF autoantibodies caused only partial blockage. Our results suggest that anti-GM-CSF autoantibodies may predispose otherwise immunocompetent individuals to meningoencephalitis caused by C. gattii but not necessarily to that caused by C. neoformans.

Cryptococcal meningoencephalitis is the most serious central nervous system (CNS) infection caused by Cryptococcus neoformans or C. gattii. Cryptococcus primarily infects immunocopromised patients but is also sporadically encountered in otherwise “immunocompetent” patients with no known risk. In a recent study, anti-GM-CSF autoantibodies were detected in the plasma of seven otherwise immunocompetent patients with cryptococcal meningoencephalitis. Four of seven (57%) cryptococcal isolates from these patients were identified as C. gattii, while three strains were unavailable for species confirmation. We collected plasma from 30 otherwise healthy patients with CNS cryptococcosis in China and Australia (multiethnic) and analyzed the samples for the presence of anti-GM-CSF autoantibodies. The results suggest that anti-GM-CSF autoantibodies are a risk factor for CNS infection by C. gattii but not C. neoformans. GM-CSF may have a specific role in host defense against C. gattii, thereby elevating the importance of determining the level of anti-GM-CSF autoantibodies which can impact clinical management.

Granulocyte macrophage colony-stimulating factor and the intestinal innate immune cell homeostasis in Crohn's disease

Current literature consolidates the view of Crohn's disease (CD) as a form of immunodeficiency highlighting dysregulation of intestinal innate immunity in the pathogenesis of CD. Intestinal macrophages derived from blood monocytes play a key role in sustaining the innate immune homeostasis in the intestine, suggesting that the monocyte/macrophage compartment might be an attractive therapeutic target for the management of CD. Granulocyte macrophage colony-stimulating factor (GM-CSF) is a hematopoietic growth factor that also promotes myeloid cell activation, proliferation, and differentiation. GM-CSF has a protective effect in human CD and mouse models of colitis. However, the role of GM-CSF in immune and inflammatory reactions in the intestine is not well defined. Beneficial effects exerted by GM-CSF during intestinal inflammation could relate to modulation of the mucosal barrier function in the intestine, including epithelial cell proliferation, survival, restitution, and immunomodulatory actions. The aim of this review is to summarize potential mechanistic roles of GM-CSF in intestinal innate immune cell homeostasis and to highlight its central role in maintenance of the intestinal immune barrier in the context of immunodeficiency in CD.

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

OBJECTIVES

Along with others, we have reported that neutralization of granulocyte macrophage colony-stimulating factor (GM-CSF) increases intestinal permeability and bacterial translocation, and reduces neutrophil bacterial killing and anti-microbial seroreactivity. The objective was to investigate the utility of serum GM-CSF auto-antibody (Ab) as a marker for confirmation of stable remission and prediction of relapses in patients with inflammatory bowel disease (IBD).

METHODS

We consecutively included 181 adults and children with Crohn's disease (CD, n=61) or ulcerative colitis (UC, n=120). Over a 3-year period, we collected 861 serum samples and 610 stool samples during regular follow-up visits. GM-CSF Abs and fecal S100 proteins were measured by an enzyme-linked immunoassay.

RESULTS

Serum GM-CSF Ab levels correlated with disease activity, location, and extent. Time course analysis before and after relapse showed a clear increase of GM-CSF Ab concentrations up to 6 months before clinical relapse. At 1.7 μg/ml (CD) and 0.5 μg/ml (UC), the sensitivity and specificity of GM-CSF Ab for predicting relapse already 2-6 months earlier were 88% and 95% in CD and 62% and 68% in UC, respectively. A baseline GM-CSF Ab level of >1.7 μg/ml was significantly associated with relapse of CD within 18 months.

CONCLUSIONS

As GM-CSF is required for myeloid cell antimicrobial functions and homeostatic responses to tissue injury, serum GM-CSF Ab levels might reflect the degree of bowel permeability and bacterial translocation. Therefore, GM-CSF Ab might identify IBD patients at risk of disease relapse at an early stage, which makes the test a potential tool for monitoring disease activity and optimizing therapy.

Paediatric Crohn disease patients with stricturing behaviour exhibit ileal granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibody production and reduced neutrophil bacterial killing and GM-CSF bioactivity

Granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies are associated with stricturing behaviour in Crohn disease (CD). We hypothesized that CD ileal lamina propria mononuclear cells (LPMC) would produce GM-CSF autoantibodies and peripheral blood (PB) samples would contain GM-CSF neutralizing capacity (NC). Paediatric CD and control PBMC and ileal biopsies or LPMC were isolated and cultured and GM-CSF, immunoglobulin (Ig)G and GM-CSF autoantibodies production were measured by enzyme-linked immunosorbent assay (ELISA). Basal and GM-CSF-primed neutrophil bacterial killing and signal transducer and activator of transcription 5 (STAT5) tyrosine phosphorylation (pSTAT5) were measured by flow cytometry. GM-CSF autoantibodies were enriched within total IgG for LPMC isolated from CD ileal strictures and proximal margins compared to control ileum. Neutrophil bacterial killing was reduced in CD patients compared to controls. Within CD, neutrophil GM-CSF-dependent STAT5 activation and bacterial killing were reduced as GM-CSF autoantibodies increased. GM-CSF stimulation of pSTAT5 did not vary between controls and CD patients in washed PB granulocytes in which serum was removed. However, GM-CSF stimulation of pSTAT5 was reduced in whole PB samples from CD patients. These data were used to calculate the GM-CSF NC. CD patients with GM-CSF NC greater than 25% exhibited a fourfold higher rate of stricturing behaviour and surgery. The likelihood ratio (95% confidence interval) for stricturing behaviour for patients with elevation in both GM-CSF autoantibodies and GM-CSF NC was equal to 5 (2, 11). GM-CSF autoantibodies are produced by LPMC isolated from CD ileal resection specimens and are associated with reduced neutrophil bacterial killing. CD peripheral blood contains GM-CSF NC, which is associated with increased rates of stricturing behaviour.

Levels of TNF, TNF autoantibodies and soluble TNF receptors in patients with bronchial asthma

OBJECTIVES

The aim of the study was to evaluate the potential contribution made by tumor necrosis factor (TNF) autoantibodies to the pathogenesis of bronchial asthma (BA).

METHODS

We used affinity chromatography methods and a magnetic separation procedure to purify human autoantibodies specific to TNF. The autoantibodies were used as a calibration material to determine the absolute content of autoantibodies to TNF using enzyme-linked immunosorbent assay (ELISA). TNF content and levels of soluble receptors to TNF were determined using the ELISA commercial test kits.

RESULTS

We demonstrated significant increases in the levels of TNF and soluble TNF receptors in the sera of patients with uncontrolled and controlled BA, as compared with healthy donors. Levels of autoantibodies of the IgG2 and IgG4 subclasses were significantly higher in sera from patients with uncontrolled BA than in healthy donors. Levels of IgG2 autoantibodies were significantly higher in sera from patients with uncontrolled BA than in patients with controlled BA.

CONCLUSIONS

BA is associated with changes in the levels of not only TNF and soluble receptors for TNF, but also autoantibodies to TNF. Given the magnitude of the changes in the levels of different subclasses of autoantibodies to TNF, we propose that these autoantibodies might contribute to the pathogenesis of BA.

Evaluation of pre-existing antibody presence as a risk factor for posttreatment anti-drug antibody induction: analysis of human clinical study data for multiple biotherapeutics

Biotherapeutic-reactive antibodies in treatment-naïve subjects (i.e., pre-existing antibodies) have been commonly detected during clinical immunogenicity assessments; however information on pre-existing antibody prevalence, physiological effects, and impact on posttreatment anti-drug antibody (ADA) induction remains limited. In this analysis, pre-existing antibody prevalence and impact on posttreatment ADA induction were determined using ADA data from 12 biotherapeutics analyzed in 32 clinical studies. Approximately half (58%) of the biotherapeutics were associated with some level of pre-existing antibodies and 67% of those were associated with posttreatment ADA induction. Across all studies, 5.6% of study subjects demonstrated presence of pre-existing antibodies, among which, 17% of the individual subjects had posttreatment increases in their ADA titers while 16% had decreased titers and 67% had no change in titers. However, in studies conducted in the rheumatoid arthritis (RA) population, 14.8% of RA patients were associated with pre-existing antibodies and 30% of those had posttreatment titer increases. The results suggest that in most study subjects, pre-existing antibodies pose a low risk for posttreatment ADA induction. That said, the high risk of induction implicated for RA patients, primarily observed in treatments evaluating novel antibody-based constructs, indicates that further understanding of the contribution of product and disease-specific factors is needed. Cross-industry efforts to collect and analyze a larger data set would enhance understanding of the prevalence, nature, and physiological consequences of pre-existing antibodies, better inform the immunogenicity risk profiles of products associated with these antibodies and lead to better fit-for-purpose immunogenicity management and mitigation strategies.

Anti-GM-CSF autoantibodies in patients with cryptococcal meningitis

Cryptococcal meningitis has been described in immunocompromised patients, as well as in those for whom no immune defect has been identified. GM-CSF regulates the function of phagocytes and pulmonary alveolar macrophages, critical elements in cryptococcal control. We performed clinical histories, immunological evaluation, and anticytokine autoantibody screening in four current patients with cryptococcal meningitis and identified and tested 103 archived plasma/cerebrospinal fluid samples from patients with cryptococcal meningitis. We assessed the ability of anti-GM-CSF autoantibody-containing plasmas to inhibit GM-CSF signaling. We recognized anti-GM-CSF autoantibodies in an otherwise healthy female with cryptococcal meningitis who later developed pulmonary alveolar proteinosis (PAP). Her diagnosis prompted screening of patients with cryptococcal meningitis for anticytokine autoantibodies. We identified seven HIV-negative patients with cryptococcal meningitis who tested positive for high-titer anti-GM-CSF autoantibodies. Two of the seven later developed evidence of PAP. Plasma from all patients prevented GM-CSF-induced STAT5 phosphorylation and MIP-1α production in normal PBMCs. This effect was limited to their IgG fraction. Anti-GM-CSF autoantibodies are associated with some cases of cryptococcal meningitis in otherwise immunocompetent patients. These cases need not have associated PAP.

Immunoregulation by naturally occurring and disease-associated autoantibodies : binding to cytokines and their role in regulation of T-cell responses

The role of naturally occurring autoantibodies (NAbs) in homeostasis and in disease manifestations is poorly understood. In the present chapter, we review how NAbs may interfere with the cytokine network and how NAbs, through formation of complement-activating immune complexes with soluble self-antigens, may promote the uptake and presentation of self-molecules by antigen-presenting cells. Both naturally occurring and disease-associated autoantibodies against a variety of cytokines have been reported, including NAbs against interleukin (IL)-1α, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, interferon (IFN)-α, IFN-β, IFN-γ, macrophage chemotactic protein-1 and IL-21. NAbs against a variety of other self-antigens have also been reported, and using thyroglobulin as an example we discuss how NAbs are capable of promoting uptake of immune complexes via complement receptors and Fc-receptors on antigen-presenting cells and thereby regulate T-cell activity. Knowledge of the influence of NAbs against cytokines on immune homeostasis is likely to have wide-ranging implications both in understanding pathogenesis and in treatment of many immunoinflammatory disorders, including a number of autoimmune and autoinflammatory diseases.

Beware of Antibodies to Dietary Proteins in “Antigen-specific” Immunoassays! Falsely Positive Anticytokine Antibody Tests Due to Reactivity with Bovine Serum Albumin in Rheumatoid Arthritis (The Swedish TIRA Project)

Objective.

To evaluate (1) to what extent sera from healthy subjects and patients with rheumatoid arthritis (RA) contain antibodies to bovine serum albumin (BSA); and (2) if anti-BSA antibodies interfere with results of enzyme-linked immunoassays (ELISA) containing BSA.

Methods.

The ELISA used was a previously developed in-house assay of autoantibodies to tumor necrosis factor (TNF). Anti-TNF and anti-BSA antibodies were analyzed by ELISA in 189 patients with early RA and 186 healthy blood donors. TNF preparations containing either BSA or human serum albumin (HSA) as carrier proteins were used as antigens in the anti-TNF assay. The presence and levels of antibodies were analyzed in relation to disease course and to the presence/absence of rheumatoid factor (RF).

Results.

In patients with RA, anti-TNF/BSA levels strongly correlated with anti-BSA levels (r = 0.81, p < 0.001), whereas anti-TNF/HSA did not (r = −0.09). Neither the presence nor the levels of anti-BSA in RA patients were associated with disease progression, and antibody levels were not significantly altered compared to controls (p = 0.11). IgG reactivity with TNF/HSA was neglible. In paired sera, preincubation with BSA abolished the anti-TNF/BSA reactivity. There were no indications of RF interference with anti-BSA or anti-TNF reactivity.

Conclusion.

Antibodies to BSA are common in patients with RA as well as in healthy individuals. Their presence does not seem to be associated with RA disease activity or disease course, but may severely interfere with ELISA containing BSA. The use of BSA as a “blocking agent” or carrier protein in immunoassays should therefore be avoided.