From infection to autoimmunity: a new model for induction of ANCA against the bactericidal/permeability increasing protein (BPI)

Bactericidal Permeability-Increasing Protein (BPI) Inhibits Mycobacterium tuberculosis Growth

Bactericidal permeability-increasing protein (BPI) is a multifunctional cationic protein produced by neutrophils, eosinophils, fibroblasts, and macrophages with antibacterial anti-inflammatory properties. In the context of Gram-negative infection, BPI kills bacteria, neutralizes the endotoxic activity of lipopolysaccharides (LPSs), and, thus, avoids immune hyperactivation. Interestingly, BPI increases in patients with Gram-positive meningitis, interacts with lipopeptides and lipoteichoic acids of Gram-positive bacteria, and significantly enhances the immune response in peripheral blood mononuclear cells. We evaluated the antimycobacterial and immunoregulatory properties of BPI in human macrophages infected with Mycobacterium tuberculosis. Our results showed that recombinant BPI entered macrophages, significantly reduced the intracellular growth of M. tuberculosis, and inhibited the production of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-α). Furthermore, BPI decreased bacterial growth directly in vitro. These data suggest that BPI has direct and indirect bactericidal effects inhibiting bacterial growth and potentiating the immune response in human macrophages and support that this new protein's broad-spectrum antibacterial activity has the potential for fighting tuberculosis.

Aptamer proteomics of serum exosomes from patients with Primary Raynaud's and patients with Raynaud's at risk of evolving into Systemic Sclerosis

BACKGROUND

A major unmet need for Systemic Sclerosis (SSc) clinical management is the lack of biomarkers for the early diagnosis of patients with Raynaud's Phenomenon at high risk of evolving into SSc.

OBJECTIVE

To identify proteins contained within serum exosomes employing an aptamer proteomic analysis that may serve to reveal patients with Raynaud's Phenomenon at risk of developing SSc.

METHODS

Exosomes were isolated from serum samples from patients with Primary Raynaud's Phenomenon and from patients with Raynaud's Phenomenon harbouring serum antinuclear antibodies (ANA) who may be at high risk of evolving into SSc. The expression of 1,305 proteins was quantified using SOMAscan aptamer proteomics, and associations of the differentially elevated or reduced proteins with the clinical subsets of Raynaud's Phenomenon were assessed.

RESULTS

Twenty one differentially elevated and one differentially reduced (absolute fold change >|1.3|) proteins were identified. Principal component analysis using these 22 most differentially expressed proteins resulted in excellent separation of the two Raynaud's Phenomenon clinical subsets. Remarkably, the most differentially elevated proteins are involved in enhanced inflammatory responses, immune cell activation and cell migration, and abnormal vascular functions.

CONCLUSION

Aptamer proteomic analysis of circulating exosomes identified differentially elevated or reduced proteins between Raynaud's Phenomenon at high risk of evolving into SSc and Primary Raynaud's Phenomenon patients. Some of these proteins are involved in relevant biological pathways that may play a role in SSc pathogenesis including enhanced inflammatory responses, immune cell activation, and endothelial cell and vascular abnormalities.

Predicting bacterial infection risk in patients with ANCA-associated vasculitis in southwest China: development of a new nomogram

OBJECTIVES

The aim of this study was to develop and assess a risk nomogram of bacterial infection in patients with ANCA-associated vasculitis (AAV) in southwest China.

METHOD

We established a prediction model based on a training dataset of 249 AAV patients. The least absolute shrinkage and selection operator (Lasso) was used to screen feature variables. Multivariate logistic regression analysis was used to build a prediction model for feature variables. Nomogram was used to predict the risk of bacterial infection in AAV patients. Receiver operating characteristic (ROC) curve was used to evaluate and verify the prediction accuracy of the model. Calibration and clinical useful range was assessed using calibration curve and decision curve analysis, respectively.

RESULTS

Bactericidal permeability enhancement protein of ANCAs (BPI-ANCAs), procalcitonin (PCT), and white blood cell (WBC) were the characteristic variables in this study. Nomogram showed that positive BPI-ANCAs and PCT had higher positive predictive value for bacterial infection in AAV patients. The area under curve (AUC) of the model was 0.703 (95% confidence interval: 0.640-0.766). In the validation model, the AUC was 0.745 (95% confidence interval: 0.617-0.872). Decision curve analysis showed that the nonadherence nomogram was clinically useful within the threshold probability range of 0.31-0.85.

CONCLUSIONS

Nomogram combined with BPI-ANCAs and PCT has the guiding significance for predicting bacterial infection risk in AAV. As an ANCA-specific autoantibody, BPI-ANCAs is helpful for clinicians to understand the role of specific autoantibodies in the pathogenesis of AAV. Key Points • BPI-ANCAs, PCT, and WBC could predict bacterial infection in AAV patients. • Nomogram showed that positive BPI-ANCAs had a high positive predictive value for bacterial infection in AAV patients.

Anti-neutrophil cytoplasmic antibodies (ANCA): Antigen interactions and downstream effects

Neutrophils are the most abundant leukocytes in circulation and are key "first responders" in the immune response to infectious and non-infectious stimuli. Unlike other immune cells, neutrophils can mount a robust response (including a change in surface markers and the production of extracellular traps and reactive oxygen species) just minutes after sensing a disturbance. It has been speculated that, in some individuals, the activation of neutrophils inadvertently leads to the generation of anti-neutrophil cytoplasmic autoantibodies (ANCA) against particular neutrophil proteins (antigens) such as myeloperoxidase (MPO) and proteinase 3 (PR3). In these individuals, continuous ANCA-antigen interactions are thought to drive persistent activation of neutrophils, chronic immune activation, and disease, most notably, small vessel vasculitis. There are significant gaps however in our understanding of the underlying mechanisms and even the pathogenicity of ANCA given that vasculitis can develop in the absence of ANCA, and that ANCA have been found in circulation in other conditions with no apparent contribution to disease. These gaps are particularly evident in the context of human studies. Herein, we review knowledge on neutrophil-derived ANCA antigens PR3 and MPO, ANCA generation, and ANCA-antigen interaction(s) that may promote immune activation and disease.

BPI-ANCA is expressed in the airways of cystic fibrosis patients and correlates to platelet numbers and Pseudomonas aeruginosa colonization

BACKGROUND

Autoantibodies to bactericidal/permeability-increasing protein (BPI), BPI-ANCA, are often present in serum of patients with cystic fibrosis (CF), and correlate to airway colonization with Pseudomonas aeruginosa. The aim of the study was to investigate if BPI-ANCA IgA is also present in the airways of CF patients, and if its presence correlates with neutrophil counts, platelets, and P. aeruginosa DNA in sputum.

METHODS

BPI-ANCA IgA was quantified in serum and sputum samples from adult CF patients (n = 45) by ELISA. Sputum neutrophil counts, platelets, and platelet-neutrophil complexes were assessed by flow cytometry, and P. aeruginosa DNA was analysed with RT-PCR.

RESULTS

Serum BPI-ANCA IgA was present in 44% of the study participants, and this group also had significantly enhanced BPI-ANCA levels in sputum compared to serum negative patients. Sputum levels of BPI-ANCA IgA correlated with P. aeruginosa DNA (r = 0.63, p = 0.0003) and platelet counts in sputum (r = 0.60, p = 0.0002).

CONCLUSIONS

BPI-ANCA is expressed in the airways of CF patients and correlates with P. aeruginosa load and platelet counts, suggesting a link to airway inflammation and mucosal immunity.

Prevalence of Bactericidal/Permeability-Increasing Protein Autoantibodies in Cystic Fibrosis Patients: Systematic Review and Meta-Analysis

Background: There have been varying reports on the prevalence of antineutrophil cytoplasmic antibodies with bactericidal/permeability-increasing protein (BPI-ANCA) specificity in cystic fibrosis (CF) patients. These autoantibodies are believed to develop in response to infection and colonization, especially with Pseudomonas aeruginosa. The aim of this review was to estimate the overall prevalence of BPI-ANCA in CF patients. Methods: We searched PubMed, Scopus, and Embase databases for studies reporting the prevalence of BPI-ANCA in CF patients. We also searched the Journal of Cystic Fibrosis and our institution's library for relevant studies on BPI-ANCA. We calculated the proportion with a 95% confidence interval (CI) to assess the prevalence of BPI-ANCA in the individual studies and then pooled the results using a random effects model. Publication bias was assessed using graphical and statistical methods. Finally, we assessed statistical heterogeneity using the I ² test. Results: Our search yielded 12 eligible studies published between 1996 and 2015. The prevalence of BPI-ANCA in patients with CF varied from 17.9% to 83% with a pooled prevalence of 49.45% (95% CI 35.53-63.42). No evidence of bias was found. However, there was evidence of statistically significant variation in the prevalence estimate due to heterogeneity (I ² = 93.4%, P < 0.01). Conclusions: Given the highly varying prevalence of BPI-ANCA in patients with CF, more well-designed prospective clinical studies are needed to determine its true prevalence and clinical relevance.

The Pathogenicity of BPI-ANCA in a Patient With Systemic Vasculitis

Objective: ANCA associated vasculitis (AAV) is characterized by systemic necrotizing vasculitis with the presence of ANCA. Although BPI-ANCA is one of the atypical ANCAs and is occasionally seen in patients with vasculitis, the pathogenicity of BPI-ANCA remains unclear. This study was performed to examine the pathogenic role of BPI-ANCA against neutrophils.

Methods: A 76-year-old Japanese man showed BPI-ANCA positive systemic vasculitis with a medical history of Pseudomonas aeruginosa infection. BPI-ANCA IgGs were eluted from the patient serum using an immunoadsorbent column. In vitro experiment, healthy donor neutrophils were treated with BPI-AAV IgGs, MPO-AAV IgGs, healthy control IgGs under TNFα stimulation. After 3 h incubation, neutrophil extracellular trap (NET) was assessed by immunofluorescent imaging. To determine the pathogenicity of BPI-ANCA, TNFα-primed neutrophils were incubated with monoclonal BPI-ANCA in the presence or absence of recombinant BPI.

Results: BPI-AAV IgGs-treated neutrophils showed NET formation with histone citrullination. Interestingly, the monoclonal BPI-ANCA did not induce NET, but the immune complexes (ICs) of recombinant BPI and BPI-ANCA induced TNFα-dependent NET formation with hypercitrullination. Furthermore, TNFα increased the expression of BPIs in neutrophils and the BPIs were translocated to cell surface.

Conclusion: BPI-ANCA could affect neutrophils leading to NET formation and may play a role in the development of systemic vasculitis as pathogenic autoantibody.

Clinical significance of BPI-ANCA detecting in COPD patients with Pseudomonas aeruginosa colonization

Background

Antineutrophil cytoplasmic autoantibodies against neutrophil granule bactericidal/permeability‐increasing protein (BPI‐ANCA) has been found in many inflammatory diseases, such as COPD, which can reduce the killing effect of BPI on Gram‐negative bacteria. This study was aimed to assess the clinical significance of BPI‐ANCA detecting in COPD patients with Pseudomonas aeruginosa (P aeruginosa) colonization.

Methods

A total of 216 COPD patients with lung P aeruginosa colonization, 244 patients with P aeruginosa infection from June 2015 to June 2018, and 100 healthy individuals were included. Serum BPI‐ANCA, tumor necrosis factor (TNF)‐α, and interleukin (IL)‐6 and IL‐1β levels were detected by ELISA, and the lung function of the patients was measured at stable clinical stages. Patients with COPD were grouped according to BPI‐ANCA detection and GOLD criteria, and serum TNF‐α, IL‐6, and IL‐1β levels and indices reflecting lung function were compared and analyzed between groups.

Results

Positive rate of BPI‐ANCA in COPD patients with P aeruginosa colonization was 48.15%; and compared with BPI‐ANCA(‐) group, FEV₁%pred and FEV₁/FVC(%) in BPI‐ANCA(+) patients were significantly decreased, while TNF‐α, IL‐6, and IL‐1β levels were elevated. There were 31.73% and 36.54% BPI‐ANCA(+) patients with severe and very severe airflow limitation, respectively, which was significantly higher than that in the BPI‐ANCA(‐) group. FEV₁%pred and FEV₁/FVC(%) were negatively correlated with TNF‐α, IL‐6, IL‐1β, and NEU%. C‐reactive protein (CRP) was negatively correlated with FEV₁%pred, yet not significantly correlated with FEV₁/FVC(%).

Conclusion

BPI‐ANCA positivity is associated with inflammatory status in COPD patients with pulmonary P aeruginosa colonization and can be used as a potential biomarker assessing disease severity.

Bronchiectasis is highly prevalent in anti-MPO ANCA-associated vasculitis and is associated with a distinct disease presentation

OBJECTIVES

To assess the prevalence of bronchiectasis in a Western cohort with ANCA-positive granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA) and its correlations with disease presentation and outcome.

METHODS

Retrospective study of ANCA-associated vasculitis (AAV) patients followed at Nantes University Hospital (2005-2015). Clinical, biological, and follow-up data were collected through chart review. Two experienced radiologists blinded to the clinical data interpreted chest high-resolution CTs according to the Feischner Society criteria.

RESULTS

Fifty-eight patients were included: 30 had MPA (51.7%) and 28 had GPA (48.3%). The median age at AAV diagnosis was 65.5 years. Anti-MPO-ANCA and anti-PR3-ANCA were present in 39 (67.2%) and 19 (32.8%) patients, respectively. Overall, bronchiectasis was found in 22 patients (37.9%), all of whom had anti-MPO ANCA. In multivariate analysis, bronchiectasis was independently associated with anti-MPO-ANCA, female gender and age at AAV diagnosis. Furthermore, anti-MPO ANCA patients with bronchiectasis had more frequent peripheral nerve involvement (54.5 vs. 17.6%, p = 0.019) and less frequent renal involvement than those without bronchiectasis (40.9% vs. 82.3%, p = 0.009). Disease course, survival and risk of severe pulmonary infection were similar in patients with and without bronchiectasis on chest CT.

CONCLUSIONS

This study shows that bronchiectasis is a highly prevalent pre-existing respiratory condition in Caucasian patients with anti-MPO AAV. This subset of patients exhibits a distinct presentation. Further studies are needed to confirm these findings and clarify the clinical implications of this association. Whether the respiratory tract could be the site of initiation of anti-MPO auto-immunity remains to be investigated.

Characteristics and prognosis of microscopic polyangiitis with bronchiectasis

BACKGROUND

Major pulmonary manifestations associated with microscopic polyangiitis (MPA) include diffuse alveolar hemorrhage (DAH) and interstitial pneumonia (IP).We previously showed bronchiectasis (BE) was one of the pulmonary complications of MPA. However, clinical features of BE patients with MPA are not fully understood. We investigated the characteristics and prognosis of BE patients with MPA.

METHODS

Forty-five MPA patients were retrospectively studied. The patients were divided into two groups: patients with BE and those without BE.

RESULTS

Thirty-one of 45 patients (69%) had pulmonary involvement including IP (23/45, 51%), BE (7/45, 16%), and DAH (5/45, 11%). There were no differences between the patients with BE versus those without with regard to clinical characteristics and initial treatments. However, the prognosis for patients with BE was better than those without BE during the first year after diagnosis, but it was worse between 1 and 5 years, which was statistically significant. Two BE patients died between 1 and 5 years as a result of pneumonia.

CONCLUSIONS

BE as a complication of MPA might be related to lower mortality in the acute phase and higher mortality in the chronic phase compared to other pulmonary manifestations. More attention to pulmonary infection is needed for patients with BE during the chronic phase.

The role for neutrophil extracellular traps in cystic fibrosis autoimmunity

While respiratory failure in cystic fibrosis (CF) frequently associates with chronic infection by Pseudomonas aeruginosa, no single factor predicts the extent of lung damage in CF. To elucidate other causes, we studied the autoantibody profile in CF and rheumatoid arthritis (RA) patients, given the similar association of airway inflammation and autoimmunity in RA. Even though we observed that bactericidal permeability-increasing protein (BPI), carbamylated proteins, and citrullinated proteins all localized to the neutrophil extracellular traps (NETs), which are implicated in the development of autoimmunity, our study demonstrates striking autoantibody specificity in CF. Particularly, CF patients developed anti-BPI autoantibodies but hardly any anti-citrullinated protein autoantibodies (ACPA). In contrast, ACPA-positive RA patients exhibited no reactivity with BPI. Interestingly, anti-carbamylated protein autoantibodies (ACarPA) were found in both cohorts but did not cross-react with BPI. Contrary to ACPA and ACarPA, anti-BPI autoantibodies recognized the BPI C-terminus in the absence of posttranslational modifications. In fact, we discovered that P. aeruginosa-mediated NET formation results in BPI cleavage by P. aeruginosa elastase, which suggests a novel mechanism in the development of autoimmunity to BPI. In accordance with this model, autoantibodies associated with presence of P. aeruginosa on sputum culture. Finally, our results provide a role for autoimmunity in CF disease severity, as autoantibody levels associate with diminished lung function.

Serum anti-lysozyme is associated with disease activity of Behçet's disease

OBJECTIVES

We investigated the association between autoantibodies against non-myeloperoxidase (MPO) neutrophil granule antigens and activity of Behçet's disease (BD).

METHODS

We consecutively enrolled 51 BD patients. We assessed clinical data and BD activity using patients' index scores from the Behçet's Disease Current Activity Form and we performed tests for antibodies against proteinase 3 (PR3), MPO, bactericidal permeability increasing protein (BPI), cathepsin G, elastase, lactoferrin and lysozyme.

RESULTS

The median patient index score was 2.0, and 56.9% of patients had active BD. In multivariate analysis of variables with significant correlations, only anti-lysozyme showed a significant correlation with BD activity (P = 0.002). In multivariate logistic regression analyses of variables, when patients were classified into groups according to the optimal cutoff levels of erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and anti-lysozyme (ESR > 42.5 mm/h, CRP > 1.35 mg/L and anti-lysozyme > 2.95 IU/mL), the variable with independent predictive value was anti-lysozyme (odds ratio 8.384, P = 0.015).

CONCLUSION

Anti-lysozyme was significantly correlated with disease activity score and it was the only independent value to predict active disease in patients with BD. Furthermore, patients having anti-lysozyme levels ≥ 2.95 IU/mL had a significantly higher risk of having active BD than those who did not.

Antimicrobial proteins in intestine and inflammatory bowel diseases

Mucosal surface of the intestinal tract is continuously exposed to a large number of microorganisms. To manage the substantial microbial exposure, epithelial surfaces produce a diverse arsenal of antimicrobial proteins (AMPs) that directly kill or inhibit the growth of microorganisms. Thus, AMPs are important components of innate immunity in the gut mucosa. They are frequently expressed in response to colonic inflammation and infection. Expression of many AMPs, including human β-defensin 2-4 and cathelicidin, is induced in response to invasion of pathogens or enteric microbiota into the mucosal barrier. In contrast, some AMPs, including human α-defensin 5-6 and human β-defensin 1, are constitutively expressed without microbial contact or invasion. In addition, specific AMPs are reported to be associated with inflammatory bowel disease (IBD) due to altered expression of AMPs or development of autoantibodies against AMPs. The advanced knowledge for AMPs expression in IBD can lead to its potential use as biomarkers for disease activity. Although the administration of exogenous AMPs as therapeutic strategies against IBD is still at an early stage of development, augmented induction of endogenous AMPs may be another interesting future research direction for the protective and therapeutic purposes. This review discusses new advances in our understanding of how intestinal AMPs protect against pathogens and contribute to pathophysiology of IBD.

Antimicrobial peptides and colitis

Antimicrobial peptides (AMPs) are important components of innate immunity. They are often expressed in response to colonic inflammation and infection. Over the last several years, the roles of several antimicrobial peptides have been explored. Gene expression of many AMPs (beta defensin HBD2-4 and cathelicidin) is induced in response to invasion of gut microbes into the mucosal barrier. Some AMPs are expressed in a constitutive manner (alpha defensin HD 5-6 and beta defensin HBD1), while others (defensin and bactericidal/ permeability increasing protein BPI) are particularly associated with Inflammatory Bowel Disease (IBD) due to altered defensin expression or development of autoantibodies against Bactericidal/permeability increasing protein (BPI). Various AMPs have different spectrum and strength of antimicrobial effects. Some may play important roles in modulating the colitis (cathelicidin) while others (lactoferrin, hepcidin) may represent biomarkers of disease activity. The use of AMPs for therapeutic purposes is still at an early stage of development. A few natural AMPs were shown to be able to modulate colitis when delivered intravenously or intracolonically (cathelicidin, elafin and SLPI) in mouse colitis models. New AMPs (synthetic or artificial non-human peptides) are being developed and may represent new therapeutic approaches against colitis. This review discusses the latest research developments in the AMP field with emphasis in innate immunity and pathophysiology of colitis.

Glomerular disease in patients with infectious processes developing antineutrophil cytoplasmic antibodies

To identify differences in treatment and outcome of various types of glomerulonephritis developing in the course of infections triggering antineutrophil cytoplasmic antibody (ANCA) formation, we analyzed published reports of 50 patients. Immunosuppressives were added to antibiotics in 22 of 23 patients with pauci-immune glomerulonephritis. Improvement was noted in 85% of 20 patients with information on outcomes. Death rate was 13%. Corticosteroids were added to antibiotics in about 50% of 19 patients with postinfectious glomerulonephritis. Improvement rate was 74%, and death rate was 26%. Two patients with mixed histological features were analyzed under both pauci-immune and post-infectious glomerulonephritis categories. In 9 patients with other renal histology, treatment consisted of antibiotics alone (7 patients), antibiotics plus immunosuppressives (1 patient), or immunosuppressives alone (1 patient). Improvement rate was 67%, permanent renal failure rate was 22%, and death rate was 11%. One patient with antiglomerular basement disease glomerulonephritis required maintenance hemodialysis. Glomerulonephritis developing in patients who became ANCA-positive during the course of an infection is associated with significant mortality. The histological type of the glomerulonephritis guides the choice of treatment. Pauci-immune glomerulonephritis is usually treated with addition of immunosuppressives to antibiotics.

Extensive endoscopic image-guided sinus surgery decreases BPI-ANCA in patients with cystic fibrosis

Antineutrophil cytoplasm autoantibodies (ANCA) directed against bactericidal/permeability-increasing protein (BPI) are common in patients with cystic fibrosis (CF), and serum levels are correlated with lung colonization by Pseudomonas aeruginosa and the severity of lung damage. The production of BPI-ANCA may be due to the costimulation of BPI when mounting an immune response against P. aeruginosa. The effect of surgery aiming to eradicate bacteria and infected tissue on BPI-ANCA levels is sparsely described. A cohort of patients with CF were included: 53 patients having extensive image-guided sinus surgery (EIGSS) with topical postoperative antibiotic treatment, 131 non-operated controls and 36 who had double lung transplantation (LTX). In all 219 patients, serum samples before and after surgery or at similar intervals were analysed for IgG and IgA BPI-ANCA. The EIGSS group showed a highly significant decrease in both IgA and IgG BPI-ANCA levels compared with their own preoperative values and control group values (P < 0.001-0.02). The LTX patients also showed a highly significant decrease in both IgA and IgG BPI-ANCA levels (P < 0.001). EIGSS and LTX decrease IgA and IgG BPI-ANCA levels in patients with CF, indicating that extensive removal of infected tissue influences the pathogenic process of autoantibody production. The results shown herein are in favour of applying EIGSS in selected patients with CF and for using BPI-ANCA as a surrogate marker for guiding further therapeutic interventions.

BPI-ANCA and long-term prognosis among 46 adult CF patients: a prospective 10-year follow-up study

Introduction. Anti-neutrophil cytoplasmic antibodies specific for bactericidal/permeability-increasing protein (BPI-ANCA) are frequent in CF patients and mainly develop in response to infection with Pseudomonas aeruginosa. It is not known to what extent BPI-ANCA correlates to prognosis. Objectives. To evaluate the prognostic value of IgA-BPI-ANCA, measured at the beginning of the study, for transplantation-free survival. Methods. A cohort of 46 adult, nontransplanted CF patients was generated, 1995–1998, and characterized using Leeds criteria, lung function, and IgA-BPI-ANCA levels measured by ELISA. The cohort was followed until December 2009, using the combined endpoint of death or lung transplantation. Results. Lung function and IgA-BPI-ANCA, but not Leeds criteria, were significantly associated with adverse outcome. No patient with normal lung function at baseline reached endpoint. Within 10 years 8/11 with high BPI-ANCA reached an endpoint compared to 3/17 ANCA-negative patients. A similar result was seen within the Leeds I group where 7 out of 9 BPI-ANCA-positive patients reached endpoint, compared to none of the 5 patients without BPI-ANCA. Conclusions. IgA-BPI-ANCA is associated with adverse outcome among Pseudomonas aeruginosa infected CF patients, suggesting that BPI-ANCA is a biomarker of an unfavourable host-pathogen interaction.

In silico analysis of HLA associations with drug-induced liver injury: use of a HLA-genotyped DNA archive from healthy volunteers

Background

Drug-induced liver injury (DILI) is one of the most common adverse reactions leading to product withdrawal post-marketing. Recently, genome-wide association studies have identified a number of human leukocyte antigen (HLA) alleles associated with DILI; however, the cellular and chemical mechanisms are not fully understood.

Methods

To study these mechanisms, we established an HLA-typed cell archive from 400 healthy volunteers. In addition, we utilized HLA genotype data from more than four million individuals from publicly accessible repositories such as the Allele Frequency Net Database, Major Histocompatibility Complex Database and Immune Epitope Database to study the HLA alleles associated with DILI. We utilized novel in silico strategies to examine HLA haplotype relationships among the alleles associated with DILI by using bioinformatics tools such as NetMHCpan, PyPop, GraphViz, PHYLIP and TreeView.

Results

We demonstrated that many of the alleles that have been associated with liver injury induced by structurally diverse drugs (flucloxacillin, co-amoxiclav, ximelagatran, lapatinib, lumiracoxib) reside on common HLA haplotypes, which were present in populations of diverse ethnicity.

Conclusions

Our bioinformatic analysis indicates that there may be a connection between the different HLA alleles associated with DILI caused by therapeutically and structurally different drugs, possibly through peptide binding of one of the HLA alleles that defines the causal haplotype. Further functional work, together with next-generation sequencing techniques, will be needed to define the causal alleles associated with DILI.

Symptomatic anti-neutrophil cytoplasmic antibody-positive disease complicating subacute bacterial endocarditis: to treat or not to treat?

A 54-year-old man was diagnosed with Streptococcus mutans endocarditis of the mitral valve. Serological tests disclosed the presence of multiple autoantibodies including c-ANCA, anti-PR3 and anti-MPO. While the fever subsided with antibiotics, mental status and renal function deteriorated rapidly. Kidney biopsy revealed pauci-immune glomerulonephritis and acute eosinophilic interstitial nephritis. The abnormal clinical features improved rapidly after addition of corticosteroids and cyclophosphamide to the antibiotics. Immunosuppressive agents may be required in a fraction of the patients with infective endocarditis who develop ANCA and ANCA-mediated renal disease. Histological identification of the type of renal disease is imperative for the choice of the treatment.

Deficient expression of bactericidal/permeability-increasing protein in immunocompromised hosts: translational potential of replacement therapy

BPI (bactericidal/permeability-increasing protein) is a 55 kDa anti-infective molecule expressed in neutrophil and eosinophil granules and on some epithelial cells. BPI's high affinity for the lipid A region of endotoxin targets its opsonizing, microbicidal and endotoxin-neutralizing activities towards Gram-negative bacteria. Several immunocompromised patient populations demonstrate BPI deficiency, including newborns, those with anti-neutrophil cytoplasmic antibodies (as in cystic fibrosis and HIV infection) and those exposed to radiochemotherapy. BPI may be replenished by administering agents that induce its expression or by administration of recombinant BPI congeners, potentially shielding BPI-deficient individuals against Gram-negative bacterial infection, endotoxemia and its toxic sequelae.

Anti-neutrophil cytoplasmic autoantibodies against bactericidal/permeability-increasing protein in patients with rheumatoid arthritis and their correlation with bronchial involvement

Anti-neutrophil cytoplasmic autoantibodies against bactericidal/permeability-increasing protein (BPI-ANCA) are known to be present in patients with cystic fibrosis, diffuse panbronchiolitis, and inflammatory bowel disease, especially in relation to chronic Gram-negative bacterial infection. To investigate the possible role of BPI-ANCA in rheumatoid arthritis (RA), we measured the serum titer of BPI-ANCA and examined clinical manifestations, including pulmonary complications, in patients with RA. Seventy-four RA patients were recruited to our study. The titer of BPI-ANCA was measured by enzyme-linked immunosorbent assay (ELISA). Pulmonary complications were evaluated using high-resolution computed tomography (HRCT), which revealed 26 patients with bronchial diseases (BD group), 25 with interstitial pneumonia (IP group), and 23 without any particular lung lesion (normal group). The correlations between the titer of BPI-ANCA and patients' clinical and laboratory findings were then analyzed. The numbers of tender joints, swollen joints, and the Disease Activity Score including 28 joint count were significantly higher in the BD group. The titer of BPI-ANCA was positively correlated with age, erythrocyte sedimentation rate (ESR), and bronchial involvement in all subjects. Stepwise multiple regression analysis of factors affecting the titer of BPI-ANCA selected ESR and bronchial involvement as independent variables. Our results show that BPI-ANCA was positively correlated with chronic inflammatory status in RA patients, and we is believe it is positively linked with bronchial diseases.

Mechanisms and markers of vascular damage in ANCA-associated vasculitis

Much progress has been made in understanding the pathogenesis of anti-neutrophil cytoplasmic antibodies (ANCA)-associated small-vessel vasculitis and interaction between ANCA and micro-vascular endothelial cells are centre stage. The interactions of these key players culminate in respiratory burst of the neutrophil with release of radicals and proteases and subsequent endothelial cell and tissue damage. During the last decade, markers have become available to assess the extent and/or acuity of vascular damage in a clinical setting. First, circulating endothelial cells (CEC) have emerged as reliable surrogate markers of endothelial damage in vasculitis. More recently, endothelial microparticles have been used and appear to reflect damage and activation of the cells. Data on endothelial progenitor cells in vasculitis are sparse but intriguing while a genuine progenitor cell deficiency remains controversial. The severely damaged phenotype of CEC in vasculitis led to the hypothesis that such circulating apoptotic and/or necrotic debris may itself be a mediator of disease and first data from experimental studies have added proof to this assumption. Such effects may well contribute to a pro-inflammatory environment in ANCA-associated small-vessel vasculitis and in vascular disease in general. Here, we review mechanisms and markers of endothelial damage and repair in ANCA-associated vasculitis and put these findings into perspective.

Infectious serologies and autoantibodies in Wegener's granulomatosis and other vasculitides: novel associations disclosed using the Rad BioPlex 2200

In this study we assess the presence of antibodies against infectious agents as well as for a variety of autoantibodies in an attempt to establish associations between various vasculitides and infections in order to shed light on the etiopathogenesis of these diseases and perhaps implicate a potential cure. Sera from patients with Wegener's granulomatosis (WG), polyarteritis nodosa, microscopic polyangiitis, Churg Strauss, and giant cell arteritis were compared to healthy control sera. Serum samples were assessed, using the Bio-Rad BioPlex 2200, for the presence of Toxoplama gondii, cytomegalovirus (CMV), Epstein-Barr virus (EBV), Treponema pallidum, and Saccharomyces cerevisiae. Hepatitis B virus (HBV), hepatitis C virus (HCV), and anti-Helicobacter pylori antibodies were assessed by ELISA. In addition, sera were tested for a panel of antibodies associated with thrombophilia as well as various autoantibodies. The prevalence of antibodies toward HCV and H. pylori was significantly higher among patients with WG. IgG antibodies toward T. gondii and IgM antibodies toward CMV were significantly more common among WG patients than among controls. WG patients exhibited more antibodies toward EBV viral capsid antigen IgG and EBV early antigen IgG compared to sera from healthy controls. In WG, positive associations were disclosed between CMV IgG antibodies and the presence of gastrointestinal manifestations and renal involvement, and there was a higher Birmingham vasculitis activity score in association with elevated titers of EBV viral capsid antigen IgG antibodies. Otorhinolaryngeal manifestations were more common in those with positive IgG antibodies for EBV early antigen. Our results unveil novel associations between WG and various infectious agents, including HCV, H. pylori, T. gondii, CMV, and EBV. In addition to putative roles in initiation and exacerbation of the vasculitic process, it seems that these infectious agents also modulate the clinical phenotype of the disease.

The role of infections in the immunopathogensis of systemic sclerosis--evidence from serological studies

Infections are believed to often play a role in the immunopathogenesis of autoimmune disorders; such is the case in systemic sclerosis (SSc). In order to evaluate the potential role infections may have on the pathogenesis of SSc, we assessed serological reactivity against various infectious agents in patients with SSc and compared them with healthy controls. Serological samples obtained from 80 patients with SSc were compared with 296 compatible healthy controls. Both groups were of European origin. All samples were tested for the presence of antibodies directed against hepatitis B virus, hepatitis C virus, toxoplasmosis, rubella, CMV, EBV, and Treponema pallidum. We applied Bio-Rad commercial and experimental kits to assess most antigens and ELISA assays to complete the panel. Patients with SSc had elevated IgM and IgG against Toxoplasma gondii and against CMV. Higher titers were also detected against the hepatitis B virus core protein (recombinant HBc antigen) using MONOLISA anti-HBc Plus commercial kit (Bio-Rad). A significantly higher rate of IgM antibodies against the capsid antigen of the EBV was detected in SSc patients compared with healthy controls, as well. These data demonstrate that antibodies against CMV, HBV, and toxoplasmosis were detected more often in patients with SSc. This association implies that infectious agents may have a role in disease pathogenesis and expression.

The clinical value of neutrophil extracellular traps

Neutrophil extracellular traps (NETs) have recently been discovered as a central part of antimicrobial innate immunity. In the meanwhile, evidence accumulated that NETs are also generated upon non-infectious stimuli in various clinical settings. In acute or chronic inflammatory disorders aberrantly enhanced NET formation and/or decreased NET degradation seems to correlate with disease outcome. This review summarizes current knowledge about the relation of NETs in a broad spectrum of clinical settings. Specifically, we focus on the importance of NETs as a predictive marker in severely ill patients and further, we speculate about the potential pathophysiology of NETs.

Autoantibodies against bactericidal/permeability-increasing protein (BPI) in children with acute pneumonia

Antineutrophil cytoplasmic antibodies directed against bactericidal/permeability-increasing protein (BPI), an inhibitor of a lipopolysaccharide of gram-negative bacteria, are a common feature of chronic neutrophilic inflammatory processes such as cystic fibrosis. We investigated whether serum and salivary anti-BPI autoantibodies also appear in the course of acute pneumonia in 24 otherwise healthy children. Nine (38%) and four (17%) patients had detectable serum anti-BPI immunoglobulin G (IgG) (> or =4 IU mL(-1)) and IgA (ratio> or =1.2), respectively, on the day of hospital admission (day 0). There was no increase in the rate of occurrence or the concentration of these antibodies in the convalescent sera obtained on day 30. The presence of anti-BPI IgG on admission did not correlate with inflammatory markers (peripheral white blood cell count, C-reactive protein) or temperature on admission. Also, salivary anti-BPI IgA, determined on days 0, 3-5 and 30, did not appear during the course of acute pneumonia. In summary, a substantial proportion of previously healthy children have pre-existing anti-BPI IgG autoantibodies. Acute neutrophilic infection, i.e. pneumonia, however, neither triggered the appearance of new antibodies nor boosted the concentrations of pre-existing ones. Thus, in typical acute pneumonia in children, autoantibodies directed against BPI may not have clinical significance.

Bactericidal/permeability-increasing protein (BPI) and BPI homologs at mucosal sites

At mucosal surfaces, we must co-exist with a high density of diverse microorganisms; therefore, protection against these occurs on multiple levels. Leukocyte- and epithelial derived-antimicrobial peptides and proteins (AMPs) comprise an essential component of immune defense. These molecules possess antibacterial, antifungal and signalling properties and probably contribute to defence and maintenance of homeostasis between the host and commensal microorganisms. Among these AMPs is bactericidal/permeability-increasing protein (BPI), an antimicrobial protein with potent endotoxin-neutralising activity, and several homologs. This review explores the roles of BPI and and its homologs at the mucosal interface. Congeners of BPI are under biopharmaceutical development as novel anti-infective agents, highlighting the potential therapeutic relevance of this protein family.

The effect of melanism and vitamin D synthesis on the incidence of autoimmune disease

Melanin has several physiological roles in maintaining health, but, notably, it affects the synthesis of vitamin D. Melanin is the primary determinant of the degree of skin pigmentation and protects the body from harmful ultraviolet radiation. Synthesis of 1,25-dihydroxyvitamin D(3) (1,25[OH](2)D(3)) in the skin, however, is dependent on ultraviolet B light. Highly pigmented skin, to the level found in people of African origin, abrogates almost all ultraviolet-induced 1,25(OH)(2)D(3) synthesis. Numerous animal models and clinical studies have underlined the essential role of vitamin D as a modulator of the different processes of the immune system. Evidence indicates that serum concentrations of 1,25(OH)(2)D(3) and the prevalence of autoimmune diseases in a certain population are associated with the latitude at which that population resides. This article explores the relationship between skin pigmentation, vitamin D and the prevalence of autoimmune disease.

Pathways to ANCA production: from differentiation of dendritic cells by proteinase 3 to B lymphocyte maturation in Wegener's granuloma

Wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome are idiopathic systemic vasculitides in which circulating anti-neutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3) or myeloperoxidase (MPO) are commonly found. Within the last 25 years, these antibodies were subject of intensive studies, and a growing body of evidence arose for a distinct role of ANCA in the pathogenesis of the ANCA-associated vasculitides (AAV). Yet, the evidence derived from clinical observations and in vitro studies remains circumstantial. The various animal models have provided substantial support for a pathogenic role of MPO-ANCA in vivo, but the debate if ANCA play a primary role in the pathogenesis of these diseases is still open. The aim of this review was to update current basic and clinical research on ANCA in the pathophysiology of AAV and to point out and discuss limitations and inconsistencies of the clinical and experimental evidence.

Autoantibodies in primary sclerosing cholangitis

The aetiology of primary sclerosing cholangitis (PSC) is not known and controversy exists as to whether PSC should be denominated an autoimmune disease. A large number of autoantibodies have been detected in PSC patients, but the specificity of these antibodies is generally low, and the frequencies vary largely between different studies. The presence of autoantibodies in PSC may be the result of a nonspecific dysregulation of the immune system, but the literature in PSC points to the possible presence of specific antibody targets in the biliary epithelium and in neutrophil granulocytes. The present review aims to give an overview of the studies of autoantibodies in PSC, with a particular emphasis on the prevalence, clinical relevance and possible pathogenetic importance of each individual marker.

[Progress in pathogenesis and therapy of vasculitis syndrome]

Since antineutrophil cytoplasmic autoantibody (ANCA) was found, the researches in the pathogenesis of vasculitis syndrome have been developing. Proinflammatory cytokines including tumor necrosis factor-alpha are induced by certain infections, by which ANCA that binds to granule components of cytoplasm adhesions to endothelial cells. These endothelial cells produce proteolytic enzymes and oxygen radicals, which leads to vasculitis. It might be contributed in the production of ANCA that bacterial organisms are mimicry to the peptide sequences of granule components. The multicentric randomized clinical trials undertaken by the European Vasculitis Study Group (EUVAS) optimized that cyclophosphamide-corticosteroid combination therapy was useful to ANCA-associated vasculitis. It is increasing evidences that biologics are useful to ANCA-associated vasculitis, although it is necessary to take care of severe adverse effects.

The curiously suspicious: infectious disease may ameliorate an ongoing autoimmune destruction in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease, which can arise from a combination of genetic and environmental factors. In the past, infections (Epstein Barr virus, parvovirus B-19) have been indicated to play a causative role in the development of autoimmune diseases, such as SLE. On the other hand, with the emergence of the "hygiene hypothesis" infections have also shown to play a protective role in autoimmune diseases. Two case studies are presented which provide clinical evidence of SLE patients with severe, long-term disease, despite immunosuppresive therapy. The course of both diseases changed remarkably after they experienced infections with multiple microbes (bacterial, viral and fungal). Surprisingly, their clinical and laboratory signs of SLE normalized and they are now symptom-free after 5 and 3year follow-ups. The second patient has even had a normal pregnancy, which was a trigger factor for disease flare in the past. The infections presumably changed the host immune systems and the mechanisms of their protective effects are most likely multifactorial. Our cases illustrate that infections could be beneficial in SLE patients and re-directing research toward novel innate-based SLE therapy should be explored.