Analysis of intractable factors in chronic airway infections: role of the autoimmunity induced by BPI-ANCA

Low-Avidity Autoantibodies against Bactericidal/Permeability-Increasing Protein Occur in Gram-Negative and Gram-Positive Bacteremia

Antibody autoreactivity against bactericidal/permeability-increasing protein (BPI) is strongly associated with Pseudomonas aeruginosa infection in cystic fibrosis (CF), non-CF bronchiectasis (BE), and chronic obstructive pulmonary disease (COPD). We examined the pathogen-specific nature of this autoreactivity by examining antibodies to BPI in bacteremia patients. Antibodies to BPI and bacterial antigens were measured in sera by ELISA from five patient cohorts (n = 214).

Antibody autoreactivity against bactericidal/permeability-increasing protein (BPI) is strongly associated with Pseudomonas aeruginosa infection in cystic fibrosis (CF), non-CF bronchiectasis (BE), and chronic obstructive pulmonary disease (COPD). We examined the pathogen-specific nature of this autoreactivity by examining antibodies to BPI in bacteremia patients. Antibodies to BPI and bacterial antigens were measured in sera by ELISA from five patient cohorts (n = 214). Antibody avidity was investigated. Bacteremic patient sera (n = 32) exhibited IgG antibody autoreactivity against BPI in 64.7% and 46.7% of patients with positive blood cultures for P. aeruginosa and Escherichia coli, respectively. Autoantibody titers correlated with IgG responses to bacterial extracts and lipopolysaccharide (LPS). A prospective cohort of bacteremic patient sera exhibited anti-BPI IgG responses in 23/154 (14.9%) patients with autoreactivity present at the time of positive blood cultures in patients with Gram-negative and Gram-positive bacteria, including 8/60 (13.3%) patients with Staphylococcus aureus. Chronic tissue infection with S. aureus was associated with BPI antibody autoreactivity in 2/15 patients (13.3%). Previously, we demonstrated that BPI autoreactivity in CF patient sera exhibits high avidity. Here, a similar pattern was seen in BE patient sera. In contrast, sera from patients with bacteremia exhibited low avidity. These data indicate that low-avidity IgG responses to BPI can arise acutely in response to bacteremia and that this association is not limited to P. aeruginosa. This is to be contrasted with chronic respiratory infection with P. aeruginosa, suggesting that either the chronicity or the site of infection selects for the generation of high-avidity responses, with biologic consequences for airway immunity.

Targeting IgG Autoantibodies for Improved Cytotoxicity of Bactericidal Permeability Increasing Protein in Cystic Fibrosis

In people with cystic fibrosis (PWCF), inflammation with concurrent infection occurs from a young age and significantly influences lung disease progression. Studies indicate that neutrophils are important effector cells in the pathogenesis of CF and in the development of anti-neutrophil cytoplasmic autoantibodies (ANCA). ANCA specific for bactericidal permeability increasing protein (BPI-ANCA) are detected in people with CF, and correlate with infection with Pseudomonas aeruginosa. The aim of this study was to determine the signaling mechanism leading to increased BPI release by CF neutrophils, while identifying IgG class BPI-ANCA in CF airways samples as the cause for impaired antimicrobial activity of BPI against P. aeruginosa. Plasma and/or bronchoalveolar lavage fluid (BAL) was collected from PWCF (n = 40), CF receiving ivacaftor therapy (n = 10), non-CF patient cohorts (n = 7) and healthy controls (n = 38). Plasma and BAL BPI and BPI-ANCA were measured by ELISA and GTP-bound Rac2 detected using an in vitro assay. The antibacterial effect of all treatments tested was determined by colony forming units enumeration. Levels of BPI are significantly increased in plasma (p = 0.007) and BALF (p < 0.0001) of PWCF. The signaling mechanism leading to increased degranulation and exocytosis of BPI by CF neutrophils (p = 0.02) involved enhancement of Rac2 GTP-loading (p = 0.03). The full-length BPI protein was detectable in all CF BAL samples and patients displayed ANCA with BPI specificity. IgG class autoantibodies were purified from CF BAL complexed to BPI (n=5), with IgG autoantibody cross-linking of antigen preventing BPI induced P. aeruginosa killing (p < 0.0001). Results indicate that the immune-mediated diminished antimicrobial defense, attributed to anti-BPI-IgG, necessitates the formation of a drug/immune complex intermediate that can maintain cytotoxic effects of BPI towards Gram-negative pathogens, with the potential to transform the current treatment of CF airways disease.

"NETtling" the host: Breaking of tolerance in chronic inflammation and chronic infection

How and why we break tolerance to self-proteins still remains a largely unanswered question. Neutrophils have been identified as a rich source of autoantigens in a wide array of autoimmune diseases that arise as a consequence of different environmental and genetic factors, e.g. rheumatoid arthritis (RA), lupus, vasculitis, cystic fibrosis (CF) etc. Specifically, neutrophil extracellular trap (NET) formation has been identified as a link between innate and adaptive immune responses in autoimmunity. Autoantigens including neutrophil granular proteins (targeted by anti-neutrophil cytoplasmic antibodies, ANCA) as well as post-translationally modified proteins, i.e. citrullinated and carbamylated proteins targeted by anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein antibodies (ACarPA), respectively, localize to the NETs. Moreover, NETs provide stimuli to dendritic cells that potentiate adaptive autoimmune responses. However, while NETs promote inflammation and appear to induce humoral autoreactivity across autoimmune diseases, the antigen specificity of autoantibodies found in these disorders is striking. These unique autoantigen signatures suggest that not all NETs are created equal and that the environment in which NETs arise shapes their disease-specific character. In this review article, we discuss the effects of different stimuli on the mechanism of NET formation as well as how they contribute to antigen specificity in the breaking of immune tolerance. Specifically, we compare and contrast the autoreactive nature of NETs in two settings of chronic airway inflammation: one triggered by smoking, a recognized environmental NET stimulus in RA patients, and one mediated by Pseudomonas aeruginosa, the most prevalent lung pathogen in CF patients. Finally, we draw attention to novel findings that, together with the specific environmental/chemical stimuli, should be taken into account when investigating how and why antigen specificity arises in the context of NET formation.

Pathogenesis of antimicrobial peptides LL-37 and CpG-ODN in ANCA associated vasculitis

OBJECTIVES

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) are a group of systemic autoimmune disorders characterized by necrotizing inflammation of small- to medium-sized blood vessels. The pathogenesis of patients with AAV are still in investigation. In this study, we explored the involvement of LL-37 and nucleic acids in AAV.

METHODS

15 patients with AAV diagnosed according to the Chapel Hill definition between October 2014 and July 2015 in the department of Nephrology of Huangdao, affiliated Hospital of Qingdao University were enrolled. 16 patients with chronic bronchitis (CB) were selected  as disease control group. 15 cases of healthy people from Medical Healthy Center were as healthy control group. Peripheral blood mononuclear cells (PBMCs) were collected from these groups and stimulated by LL-37and (or) two types of CpG-ODN for 7 days. The IFN-α and ANCA in vitro were measured by ELISA. The serum IFN-α, LL-37 and ANCA were measured also.

RESULTS

The serum level of IFN-α in AAV group was much higher than that in CB group (692.13 ± 407.28 vs 397.07 ± 211.62 pg/ml, p = 0.019), and that in healthy control group (692.13 ± 407.28 vs 251.54 ± 190.46 pg/ml, p < 0.001). The serum level of LL-37 in AAV group was much higher than that in CB group (101.18 ± 66.59 vs 40.23 ± 13.51 ng/ml, p < 0.001, and that in healthy control group (101.18 ± 66.59 vs 27.80 ± 16.86 ng/ml, p < 0.001). Also the level of IFN-α showed a significant positive relationship with ANCA in AAV group both in serum and in supernatant of cultured PBMCs stimulated by LL-37 and (or) CpG-ODN (r = 0.783, p = 0.001; r = 0.575, p = 0.064; r = 0.649, p = 0.031; r = 0.806, p = 0.003). In patients with AAV, the supernatant levels of IFN-α in cultured PBMCs stimulated by LL-37 and (or) CpG-ODN were higher than that without stimulating factor (p < 0.05). The supernatant level of IFN-α in cultured PBMC stimulated by LL-37 alone was lower than that stimulated by CpGA alone (699.57 ± 476.26 vs 2342.63 ± 2025.11 pg/ml, p = 0.001). But the supernatant level of IFN-α in cultured PBMCs stimulated by LL-37 alone was higher than in that stimulated by CpGB alone (699.57 ± 476.26 vs 153.35 ± 78.08 pg/ml, p < 0.001). The supernatant level of IFN-α in cultured PBMCs stimulated by both LL-37 and CpG-ODN was higher than that stimulated by LL-37 or CpG-ODN alone (2550.57 ± 2217.41 vs 699.57 ± 476.26 pg/ml, p = 0.003; 2550.57 ± 2217.41 vs 153.35 ± 78.08 pg/ml, p = 0.001; 2660.95 ± 391.31 vs 699.57 ± 476.26 pg/ml, p < 0.001; 2660.95 ± 391.31 vs 153.35 ± 78.08 pg/ml, p < 0.001). Either it is stimulated by LL-37 or CpG-ODN or both, the supernatant level of IFN-α in cultured PBMCs in AAV patients was the highest, that in healthy controls was the lowest. Either stimulated by LL-37 or CPG-ODN, or both, the levels of ANCA production in vitro in AAV groups were statistically significantly higher than those in CB group and healthy control group.

CONCLUSIONS

There were higher serum levels of LL-37 and IFN-α in patients with AAV. IFN-α could reach a higher level stimulated by LL-37 and nucleic acids both of which are related to infection. Patients with AAV have ANCA-producing B lymphocytes in the circulation even in remission stage. Infections could induce the relapse of AAV.

D-penicillamine-induced glomerulonephritis with crescent formation: Remission following drug discontinuation

We report a 71-year-old female who presented with rheumatoid arthritis complicated by proteinuria. She had been receiving D-penicillamine (D-Pc) for two years prior to presentation. A urinalysis showed proteinuria and hematuria which disappeared within 3 months after D-Pc was stopped. The renal histological findings showed focal proliferative glomerulonephritis with crescent formation. A total of 10 cases of D-Pc-induced glomerulonephritis with crescent formation without alveolar hemorrhage have previously been reported in the literature. To the best of our knowledge, this is the first case report in which the patient did not require any treatment.

The immune system vs. Pseudomonas aeruginosa biofilms

Ilya Metchnikoff and Paul Ehrlich were awarded the Nobel price in 1908. Since then, numerous studies have unraveled a multitude of mechanistically different immune responses to intruding microorganisms. However, in the vast majority of these studies, the underlying infectious agents have appeared in the planktonic state. Accordingly, much less is known about the immune responses to the presence of biofilm-based infections (which is probably also due to the relatively short period of time in which the immune response to biofilms has been studied). Nevertheless, more recent in vivo and in vitro studies have revealed both innate as well as adaptive immune responses to biofilms. On the other hand, measures launched by biofilm bacteria to achieve protection against the various immune responses have also been demonstrated. Whether particular immune responses to biofilm infections exist remains to be firmly established. However, because biofilm infections are often persistent (or chronic), an odd situation appears with the simultaneous activation of both arms of the host immune response, neither of which can eliminate the biofilm pathogen, but instead, in synergy, causes collateral tissue damage. Although the present review on the immune system vs. biofilm bacteria is focused on Pseudomonas aeruginosa (mainly because this is the most thoroughly studied), many of the same mechanisms are also seen with biofilm infections generated by other microorganisms.

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.

[A case of microscopic polyangiitis relapsed with diffuse alveolar hemorrhage and rapidly progressive glomerulonephritis]

The patient was a 63-year-old woman. She was admitted to our hospital with acute renal failure and multiple mononeuritis in 2002. She was diagnosed as microscopic polyangiitis based on positive for MPO-ANCA. Remission was induced by combination therapy with methylprednisolone pulse therapy and plasma exchange. Because condition of the disease was stable, prednisolone was discontinued from August 2006. Elevation of serum creatinine and microscopic hematuria was detected in November 2007. Fever and dyspnea occurred in January 24 2008. Elevation of CRP and serum creatinine was found, and infiltration in bilateral lung was noted on chest X-ray. She was admitted on the same day. After admission, she presented with hemosputum and exacerbation of dyspnea. Chest CT revealed diffuse consolidation and ground glass opacity, and MPO-ANCA converted to be positive. Diagnosis of diffuse alveolar hemorrhage and rapidly progressive glomerulonephritis with microscopic polyangiitis was made, and she was managed by artificial respirator and CHDF in ICU. Combination therapy with steroid pulse therapy and plasma exchange re-induced remission. Mizoribine was administrated as maintenance therapy with oral prednisolone.

CpG oligodeoxynucleotide stimulates production of anti-neutrophil cytoplasmic antibodies in ANCA associated vasculitis

BACKGROUND

Wegener's Granulomatosis and Microscopic Polyangiitis are life-threatening systemic necrotizing vasculitides of unknown aetiology. The appearance of circulating antibodies to neutrophil cytoplasmic antigens (ANCA) is strongly associated with the development of the disease. A link between infection and disease has long been suspected, and the appearance of ANCA antibodies has been reported following bacterial and viral infections. The depletion of circulating B cells with monoclonal antibody therapy can induce remission, and this observation suggests a pathogenic role for B cells in this disease. As bacterial DNA is known to induce B cell proliferation and antibody production via TLR-9 stimulation, we have explored the possibility that unmethylated CpG oligodeoxynucleotide, as found in bacterial and viral DNA, may play a role in stimulating circulating autoreactive B cells to produce ANCA in patients with vasculitis.

RESULTS

We have confirmed that unmethylated CpG oligonucleotide is a potent stimulator of antibody production by PBMC in vitro. The stimulation of PBMC with CpG oligonucleutides resulted in the production of similar amounts of IgG in both ANCA+ patients and normal controls. In spite of this, PR3 ANCA+ patients synthesised significantly higher amount of IgG ANCA than normal controls. In MPO ANCA+ patients, there was a tendency for patients to produce higher amount of ANCA than controls, however, the difference did not reach significance. Furthermore, we were able to detect circulating MPO-reactive B cells by ELISpot assay from the peripheral blood of 2 MPO+ ANCA vasculitis patients. Together, this indicates that circulating anti-neutrophil autoreactive B cells are present in ANCA+ vasculitis patients, and they are capable of producing antibodies in response to CpG stimulation. Of note, CpG also induced the production of the relevant autoantibodies in patients with other types of autoimmune diseases.

CONCLUSION

Circulating ANCA autoreactive B cells are present in patients with ANCA+ vasculitis. The production of ANCA from these cells in response to unmethylated CpG stimulation lead us to propose that stimulation of these cells by immunostimulatory DNA sequences such as CpG oligodeoxynucleotide during infection may provide a link between infection and ANCA associated vasculitis. This phenomenon may also apply to other antibody mediated autoimmune diseases.

Airway biofilms: implications for pathogenesis and therapy of respiratory tract infections

The differentiation of bacterial biofilms in the airway environment, the pathogenesis of airway biofilm, and possible therapeutic methods are discussed. Biofilm diseases that characteristically involve the respiratory system include cystic fibrosis (CF), diffuse panbronchiolitis (DPB), and bronchiectasia with Pseudomonas aeruginosa (P. aeruginosa) infection. There is evidence to suggest that almost all strains of P. aeruginosa have the genetic capacity to synthesize alginate, a main matrix of biofilms, when ecological conditions are unfavorable for their survival. The bacteria inside the mature biofilm show increased resistance to both antibacterials and phagocytic cells, express fewer virulence factors because of their stationary state of growth, and are less stimulatory to the mucosa because of the 'sandwich binding'. These factors facilitate both the colonization of bacteria and their extended survival even under unfavorable conditions. Since the biofilm limits colonization to a latent form, the clinical symptoms in this situation are unremarkable. However, the clinical progression of both CF and DPB proceeds in two characteristic directions. The first is an acute exacerbation caused by planktonic bacteria that have germinated from the biofilm. The second is a slow progression of disease that is induced by harmful immune reactions. The harmful reactions are mediated by alginate, which induces antigen antibody reactions around the airways, as well as formation of circulating immune complexes that are deposited on lung tissue. Furthermore, the highest titer of bacterial permeability increasing anti-neutrophil cytoplasmic autoantibodies (BPI-ANCA) is observed in association with highly impaired pulmonary function in patients with CF and DPB, as well as in patients with a lengthy period of colonization with P. aeruginosa. BPI-ANCA subsequently makes chronic airway infection even more intractable. The long-term use of 14- or 15-ring membered macrolides results in a favorable clinical outcome for patients with DPB and in some patients with CF. In the last 10 years, an increasing number of studies have reported secondary actions of macrolides that include effects on both airway and phagocytic cells, as well as an anti-biofilm activity. The 14- or 15-ring membered macrolides inhibit: (i) the alginate production from P. aeruginosa; (ii) the antibody reaction to alginate, which leads to a decrease in the immune complex formation; and (iii) the activation of the autoinducer 3-O-C12-homoserine lactone and subsequent expression of lasI and rhlI in quorum sensing systems in P. aeruginosa. These anti-biofilm actions of macrolides may represent their basic mechanisms of action on airway biofilm disease.

Microscopic polyangiitis associated with diffuse panbronchiolitis

There are several case reports of systemic vasculitis associated with chronic suppurative lung diseases. We describe a 46-year-old female, previously diagnosed as having diffuse panbronchiolitis (DPB), presenting with hemosputum and dyspnea. Her serum titer of MPO-ANCA was positive together with a high titer of BPI-ANCA. Chest X-ray and chest CT scan showed pulmonary hemorrhage, and the renal biopsy specimen revealed necrotizing, crescentic glomerulonephritis. She was diagnosed as having ANCA-associated vasculitis, and more specifically, microscopic polyangiitis accompanied by DPB. She was treated with methylprednisolone pulse therapy, followed by intravenous cyclophosphamide. This case suggested a possible association with chronic bacterial infection, which may play a role in the pathogenesis of ANCA-associated vasculitis.