Antineutrophil cytoplasmic antibodies, cystic fibrosis, and infection

Cystic fibrosis autoantibody signatures associate with Staphylococcus aureus lung infection or cystic fibrosis-related diabetes

Introduction

While cystic fibrosis (CF) lung disease is characterized by persistent inflammation and infections and chronic inflammatory diseases are often accompanied by autoimmunity, autoimmune reactivity in CF has not been studied in depth.

Methods

In this work we undertook an unbiased approach to explore the systemic autoantibody repertoire in CF using autoantibody microarrays.

Results and discussion

Our results show higher levels of several new autoantibodies in the blood of people with CF (PwCF) compared to control subjects. Some of these are IgA autoantibodies targeting neutrophil components or autoantigens linked to neutrophil-mediated tissue damage in CF. We also found that people with CF with higher systemic IgM autoantibody levels have lower prevalence of S. aureus infection. On the other hand, IgM autoantibody levels in S. aureus-infected PwCF correlate with lung disease severity. Diabetic PwCF have significantly higher levels of IgA autoantibodies in their circulation compared to nondiabetic PwCF and several of their IgM autoantibodies associate with worse lung disease. In contrast, in nondiabetic PwCF blood levels of IgA autoantibodies correlate with lung disease. We have also identified other autoantibodies in CF that associate with P. aeruginosa airway infection. In summary, we have identified several new autoantibodies and associations of autoantibody signatures with specific clinical features in CF.

IgM ANCA in healthy individuals and in patients with ANCA-associated vasculitis

Low levels of IgM auto-antibodies have been reported in health and disease. IgM anti-neutrophil cytoplasmic antibodies (ANCA) have been reported in patients with ANCA-associated vasculitis (AAV). We sought to investigate if healthy individuals may have IgM ANCA in their sera. The first aim of the study was to determine whether IgM ANCA was present in healthy individuals and in patients with ANCA-associated vasculitis. The second aim was to determine what happens to IgM ANCA levels over time. The third aim was to determine whether bacterial infections affected IgM ANCA levels in non-AAV patients. Sera from healthy individuals and patients with AAV were tested for IgM ANCA by immunofluorescence on fixed neutrophils, immunoprecipitation, Western blot and ELISA. Peripheral blood mononuclear cells were isolated and tested by ELISpot for circulating IgM ANCA B cells. To determine whether infection affected IgM ANCA levels, we studied non-AAV patients with bacterial endocarditis or Staphylococcus aureus bacteraemia and measured IgM ANCA levels over time. IgM ANCA is detectable in both healthy individuals and patients with AAV and the titres decreased with increasing age. Circulating IgM ANCA B cells were identified by ELISpot. In the presence of infection, we could not find a significant change in IgM ANCA levels. We report the presence of low-level specific IgM ANCA in the sera of healthy individuals and in patients with ANCA-associated vasculitis. Bacterial infection did not affect the level of IgM ANCA in this small study.

Peripheral nerve dysfunction in patients with cystic fibrosis

The objective of this study is to investigate the frequency, magnitude, and nature of peripheral nerve dysfunction in patients with cystic fibrosis (CF). Consecutive CF patients above the age of 3 years were recruited from the pediatric gastroenterology clinic. Twenty-five patients, 14 boys and 11 girls, were included, with mean age of 10.7 +/- 5.6 years. Nerve conduction studies were performed on the peroneal and median motor nerves, and median, ulnar and sural sensory nerves on one side. Fourteen patients (56%), 9 boys and 5 girls, had abnormal findings. All abnormalities were in the sensory nerves. Ulnar sensory nerve was abnormal in 48% of patients, sural sensory nerve in 44% of patients, and median sensory nerve in 28% of patients. Amplitudes were affected in all abnormal studies, associated with prolonged latencies in 20% of sural responses, 8% of ulnar responses, and 4% of median responses. Ten patients (40%) fulfilled the minimum case definition criterion for electrodiagnostic confirmation of distal polyneuropathy. Concordant abnormalities in three nerves were found in five patients (20%). The presence of neuropathy was not related to sex, age, type of CF symptoms, body mass index, or disease duration. In conclusion, CF is associated with peripheral nerve dysfunction, which is mostly sensory with an axonal trend. Care takers of patients with CF should be aware of the potential peripheral neurologic problems associated with the disease, especially with the improving survival of these patients.

Musculoskeletal manifestations in cystic fibrosis

Although bone and joint manifestations are common in children with cystic fibrosis (CF), they have received little attention in adults. As compared to healthy individuals, bone mineral density is low, even with calcium intakes greater than 1500 mg/d. Nevertheless, calcium and phosphate levels in blood and urine are often normal, and vitamin D levels vary. Short stature with a low body mass index and central hypogonadism are the rule in these patients. Fractures and kyphosis are often reported. CF arthropathy occurs in 2-8.5% of patients. Arthritis develops, and there may be skin eruptions. Non-steroidal antiinflammatory drug therapy is effective. Hypertrophic osteoarthropathy associated with respiratory failure is present in 2-7% of patients. Rheumatoid arthritis, spondyloarthropathies, sarcoidosis, and amyloidosis have been reported in association with CF. Knee pain due to patellofemoral syndrome, quinolone-induced arthropathy, and mechanical back pain have been described. Rheumatoid factor titers are higher than in healthy controls, particularly in patients with episodic arthritis. No data are available on antiperinuclear factor or antikeratin antibody titers. Tests for antinuclear antibody are usually negative. Circulating immune complex levels and antibodies to heat shock proteins may be elevated. Antineutrophil cytoplasmic antibody of the bactericidal/permeability-increasing protein (BPI) or azurocidin (AZ) type has been reported, often in high titers (up to 40%).

Test characteristics of immunofluorescence and ELISA tests in 856 consecutive patients with possible ANCA-associated conditions

OBJECTIVE

To examine the test characteristics of immunofluorescence (IF) and enzyme-linked immunosorbent assays (ELISA) in a consecutive series of patients under evaluation for anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

METHODS

Using stored sera, we performed a cross-sectional study on 856 consecutive patients tested prospectively for ANCA by IF, Based on guidelines from the 1994 Chapel Hill Consensus Conference (CHCC), we determined each patient's underlying diagnosis by a medical records review without regard to their ANCA status (the CHCC guidelines do not require ANCA as a prerequisite for diagnosis). We grouped patients with forms of vasculitis commonly associated with ANCA into one of 4 types of AAV: Wegener's granulomatosis (n = 45), microscopic polyangiitis (n = 12), Churg-Strauss syndrome (n = 4), and pauci-immune glomerulonephritis (n = 8). We also classified patients without clinical evidence of AAV (92% of all patients tested) into 5 predefined categories of disease (including "other") and an additional category for no identifiable disease. In a blinded fashion, we then performed ELISAs on the stored serum for antibodies to proteinase-3 (PR3) and myeloperoxidase (MPO) and calculated the test characteristics for both ANCA assay techniques.

RESULTS

Sixty-nine of the 856 patients (8.1%) had clinical diagnoses of AAV based on CHCC guidelines. The positive predictive value (PPV) of ELISA for AAV was superior to that of IF, 83% versus 45%. For patients with both positive IF tests and positive ELISA tests, the PPV increased to 88%. Both IF and ELISA had high negative predictive values (97% and 96%, respectively). Positive ELISA tests were associated with higher likelihood ratios (LR) than IF (54.2 [95% CI = 26.3, 111.5] versus 9.4 [95% CI = 6.9, 12.7]). The LR of both a positive IF and a positive ELISA was 82.1 (95% CI = 33.3, 202.5).

CONCLUSIONS

Compared with IF, an ELISA test fo ANCA was associated with a substantially higher PPV and LR for AAV. This fact, combined with the greater sensitivity of IF, suggests that an effective testing strategy is to perform ELISA tests only on samples that are positive for ANCA by IF.

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis. Wegener's granulomatosis, microscopic polyangiitis, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis (NCGN) are strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against either proteinase 3 (anti-PR3) or myeloperoxidase (anti-MPO). This has led some investigators to prefer combining these diseases under the common heading of ANCA-associated vasculitides. However, it is increasingly recognized that there are characteristic differences between patients with anti-PR3 and those with anti-MPO-associated vasculitis. This review focuses on the clinical, histopathologic, and possibly pathophysiologic differences between anti-PR3- and anti-MPO-associated vasculitis. Although there is considerable overlap, the anti-PR3- and anti-MPO-associated vasculitides are each characterized by particular clinical and histopathological findings. Extrarenal organ manifestations and respiratory tract granulomas occur more frequently in patients with anti-PR3 than in those with anti-MPO. Anti-PR3-positive patients with NCGN generally have a more dramatic deterioration of their renal function compared with anti-MPO-positive patients. The term "ANCA-associated vasculitis" is considered as a useful concept in the presence of systemic vasculitis. Likewise, in the presence of vasculitis, the terms "anti-PR3-associated vasculitis" and "anti-MPO-associated vasculitis" are useful concepts.

Subacute bacterial endocarditis with positive cytoplasmic antineutrophil cytoplasmic antibodies and anti-proteinase 3 antibodies

OBJECTIVE

To report a potentially important limitation of antineutrophil cytoplasmic antibody (ANCA) testing: positive results in patients with subacute bacterial endocarditis (SBE).

METHODS

We describe 3 patients with SBE who presented with features mimicking ANCA-associated vasculitis (AAV) and positive findings on tests for cytoplasmic ANCA (cANCA) by indirect immunofluorescence and for anti-proteinase 3 (anti-PR3)antibodies by antigen-specific enzyme-linked immunosorbent assay (ELISA). We also reviewed the published literature describing infectious diseases with (misinterpreted) positive ANCA results through a Medline search of English-language articles published between 1966 and January 1999. These previously reported cases were reinterpreted using an ANCA scoring system that combines the findings of immunofluorescence and antigen-specific ELISA testing.

RESULTS

We are now aware of a total of 7 cases of SBE with positive cANCA and anti-PR3 antibodies. We are not aware of any cases of SBE associated with antimyeloperoxidase/perinuclear ANCA. Clinical manifestations mimicking AAV included glomerulonephritis, purpura, epistaxis, or sinus symptoms in 6 of the patients. Streptococcal species were identified in 5 patients, and cardiac valvular abnormalities were demonstrated in 6. All patients except 1, who died of a complication of SBE, recovered with antibiotic therapy.

CONCLUSION

Findings of tests for anti-PR3/ cANCA antibodies may be positive in patients with SBE. When encountering ANCA positivity in patients suspected of having systemic vasculitis, physicians should take appropriate steps to rule out infectious diseases, including SBE, before committing the patient to long-term, aggressive immunosuppressive therapy.

Anti-phagocyte antibodies and infection

Autoantibodies specific to the cytoplasmic components of neutrophils and monocytes are associated with vasculitis and other idiopathic inflammatory disorders. In this study, using enzyme-linked immunosorbent assay (ELISA) and immunofluorescence assays, sera from patients with acute and chronic infection were examined for the presence of anti-neutrophil and anti-monocyte antibodies: cystic fibrosis (n = 23), acute appendicitis (n = 22), tuberculosis (n = 26), acute gastroenteritis (n = 38), bronchiectasis (n = 9) and chronic granulomatous disease (n = 6). Sera from patients with Wegener's granulomatosis (n = 14), rheumatoid factor positive (n = 15) and healthy volunteers (n = 20) were used as positive and negative controls. In patients with chronic infection, using an ELISA assay, antibodies reactive with neutrophil or monocyte components (% reacting with monocyte components in parenthesis) were found in: 70% (39%) of patients with cystic fibrosis, 4% (38%) of patients with tuberculosis, 0% (33%) of patients with bronchiectasis and 0% (17%) of patients with chronic granulomatous disease. When these sera were examined using an immunofluorescence assay, all of the positive samples were found to react with the cytoplasmic component of neutrophils or monocytes. In patients with acute infection no antibodies (either IgG or IgM) were detected against neutrophils or monocytes. These findings imply that antibodies directed against neutrophil cytoplasmic components are predominantly associated with chronic pyogenic infection and antibodies specific to monocyte cytoplasmic components are predominantly associated with chronic granulomatous infection. This mirrors the findings in idiopathic inflammatory disease where anti-monocyte antibodies are associated with granulomatous disorders such as sarcoidosis, and anti-neutrophil antibodies are associated with neutrophilic disorders such as ulcerative colitis. These results suggest that chronic stimulation of phagocytes by infectious agents may result in the generation of a humoral response against phagocyte cytoplasmic components. This furthers our understanding of humoral immune responses against phagocytic cell components during infection.

Microscopic polyarteritis following a suppurative wound infection

Bacterial and viral infections may be associated with the onset of a number of autoimmune diseases and relapses of these conditions. We describe a patient in whom there was a close temporal relationship between a suppurative wound infection and the onset of microscopic polyarteritis. The clinical features of this disease responded to treatment with high dose prednisolone and cyclophosphamide. The patient had several further infective episodes while being treated, but there were no disease exacerbations or relapses related to these. Anti-neutrophil cytoplasmic antibodies (ANCA) were never demonstrated in this patient. Thus while it is likely that the infection precipitated the onset of the systemic vasculitic illness, this occurred independently of ANCA.

Detection of anti-neutrophil cytoplasmic antibodies after acute Plasmodium falciparum malaria

Four of 30 patients with Plasmodium falciparum infection in Bangkok, Thailand, were positive for anti-neutrophil cytoplasmic antibodies by indirect immunofluorescence 1 month after antimalarial therapy. No myeloperoxidase, proteinase 3, lactoferrin, or elastase reactivity was found. Since no evidence of vasculitis was seen in these patients, anti-neutrophil cytoplasmic antibody production in malaria-infected susceptible patients probably represents a secondary response, indicating neutrophil activation.

An audit of ANCA in routine clinical practice

We have reviewed the medical records of 301/327 consecutive patients in whom anti-neutrophil cytoplasmic antibodies (ANCA) were detected by the Regional Immunology Laboratory in Northern Ireland between January 1988 and October 1991 (45 months). We have collected data for each patient regarding age, sex, smoking habit, area of residence, and details of any other autoantibody activity. Clinical diagnosis was established, with the number of organ systems involved and the evidence for that involvement (symptomatic, biochemical, radiological, and histological). Diagnoses were divided into four groups according to their recognised vasculitic features and these were related to the pattern of immunofluorescence and maximum ANCA titre detected. The most frequent diagnosis was rheumatoid arthritis (18.2% of patients) and the connective tissue disorders as a whole accounted for 27.9% of patients. ANCA were also detected in a wide range of clinical conditions which are not associated with vasculitis and these patients were an important source of 'false-positives'. The positive predictive value (PPV) of ANCA of all patterns and titres for vasculitic conditions was 27%, however, the detection of a classical ANCA pattern at high titre (> or = 1:640) was associated with an increased PPV of 75%. The coexistence of an antinuclear antibody (ANA) reduces the PPV of both classical and perinuclear ANCA, although perinuclear ANCA with antimyeloperoxidase specificity had an improved PPV. We conclude that ANCA testing should not be used as the only screening investigation for vasculitis but should be included in a rational investigative scheme. The interpretation of a positive ANCA result must take into account the presence of other autoantibodies and the full range of non-vasculitic conditions when the clinical situation is not typical of vasculitis.

Immunization with anti-neutrophil cytoplasmic antibody (ANCA) induces the production of mouse ANCA and perivascular lymphocyte infiltration

Wegener's granulomatosis (WG) is a granulomatous necrotizing vasculitis associated with the presence of ANCA, predominantly directed against proteinase 3 (PR3). The titres of ANCA correlate with disease activity and titre increases may precede disease exacerbations. Previously, we have shown that it is possible to induce autoimmune disease (systemic lupus erythematosus (SLE) and anti-phospholipid syndrome) in naive mice following active immunization with human autoantibodies, namely anti-DNA and anti-cardiolipin, respectively. The mice developed first anti-autoantibodies and, after about 4 months anti-anti-autoantibodies (Ab3), simulating auto-antibodies (Ab1) in their binding activities, and their presence was associated with the development of disease manifestations, characteristic of the human disease. So far, there is no good animal model for WG. In the current study we have immunized mice with human ANCA with the aim of inducing experimental WG. In two separate studies 30 mice were immunized in their footpads with autoantigen-purified IgG fraction (ANCA) from the sera of two patients with untreated WG, emulsified in Freund's complete adjuvant, followed 3 weeks later by ANCA injection in PBS. In the first experiment mice immunized with ANCA developed sterile microabscesses in the lungs after 8 months, and died after 8-15 months. In the second experiment, mice immunized with ANCA developed after 4 months mouse ANCA, with specificity both to PR3 and to myeloperoxidase, as well as anti-endothelial autoantibodies (AECA), as shown by radioimmunoprecipitation. Pathologically, the immunized mice developed proteinuria but not haematuria, and histological sections of the lungs demonstrated mononuclear perivascular infiltration, while diffuse granular deposition of immunoglobulins was noted in the kidneys. Our results point to a pathogenic role of ANCA in WG, and confirm the importance of the idiotypic network in the etiopathogenesis of autoimmune conditions.

Tropical rheumatology. Immunological aspects

The presence of auto-antibodies in infectious diseases continues to puzzle and provoke. It is hoped that sequencing studies in particular will yield further clues as to the role and mechanism of production of autoantibodies in infectious diseases. This, in turn, may also provide further insights into the role of auto-antibodies in auto-immune diseases. From a practical clinical viewpoint, the search for improved auto-antibody tests and new diagnostic markers with improved sensitivity and specificity must continue in the tropics. Until this is achieved, the results of auto-antibody tests in persons living in the tropics, persons from the tropics or patients with tropical infections, must be interpreted with caution.

Chronic suppurative lung disease with associated vasculitis

We report a patient with chronic bronchiectasis who developed systemic vasculitis. The patient was initially treated with immunosuppression; however, the addition of antibiotic therapy improved control of her vasculitis and the need for immunosuppression was reduced. Chronic bronchial suppuration may have an aetiological role in the pathogenesis of this condition.

Anti-neutrophil cytoplasm antibodies (ANCA) in rheumatoid arthritis: relationship to HLA-DR phenotypes, rheumatoid factor, anti-nuclear antibodies and disease severity

To investigate a possible relationship between the presence of anti-neutrophil cytoplasm antibodies (ANCA), rheumatoid factors (RF), anti-nuclear antibodies (ANA), disease severity and HLA-DR phenotypes, 46 consecutive ANCA+ and 48 ANCA-, clinically well-documented RA patients were studied for RF, ANA and HLA-DR phenotypes. The 46 ANCA+ patients showed predominantly an atypical perinuclear staining pattern (89%). ANCA positivity was associated with higher RF titres (P < 0.005) and advanced functional Steinbrocker grades III/IV (P < 0.015). ANCA+ patients were also more often positive for ANA than ANCA- patients (P < 0.008). There was no correlation between ANCA positivity and certain HLA-DR phenotypes although the frequency of DR4+ (67% vs 52%) and, in particular, of DR4+ blanks (phenotypically homozygous) was increased in ANCA+ as compared to ANCA- patients (20% vs 8%). DR4-DR1-RA patients were twice as frequent in the ANCA- than in the ANCA+ group (22.9% vs 8.7%). Correspondingly, the DR4+DR1- phenotype was increased among ANCA+ RA patients. Regarding functional Steinbrocker grades, the DR4+ phenotypes were slightly but not significantly increased in grades III and IV whereas ANCA positivity was significantly associated with severe functional Steinbrocker grades III/IV (66% ANCA+ vs 39% ANCA-, P < 0.015). ANCA positivity identified a population of RA patients with a long-standing and severe clinical course of the disease. There was no correlation between ANCA positivity and certain HLA-DR phenotypes.

Uveitis and anti-neutrophil cytoplasmic antibodies

Serum samples of 485 uveitis patients were screened for the presence of anti-neutrophil cytoplasmic antibodies using a standardized immunofluorescence test (IIF) on neutrophil granulocytes. Seventeen of these sera contained cytoplasmic (C)-ANCA antibodies, while two of the sera contained perinuclear (P)-ANCA antibodies (both antinuclear antibody (ANA)-positive, one anti-myeloperoxidase (MPO)-positive). None of the C-ANCA-positive sera reacted with proteinase-3 in ELISA using a highly purified proteinase-3 preparation. Four C-ANCA and one P-ANCA-positive serum reacted with MPO. The majority of the sera did react with azurophilic granules in ELISA. The implication of these results is that in patients with uveitis a positive C-ANCA test is not diagnostic for Wegener's granulomatosis, but is most probably caused by the presence of autoantibodies against as yet unknown constituents of azurophilic granules.

Autoantibodies in malaria, tuberculosis and hepatitis B in a west African population

Following reports of associations between autoantibodies and living in the tropics, we have studied the seroprevalence and nature of anti-nuclear antibodies, anti-cardiolipin antibodies, antibodies to extractable nuclear antigens and anti-neutrophilic cytoplasmic antibodies in 351 West Africans with malaria, tuberculosis or hepatitis B, or in good health. Amongst healthy West Africans we found a seroprevalence of 7% for anti-nuclear antibodies with several staining patterns, and of 30.3% for anti-cardiolipin antibodies. Among patients with tuberculosis and malaria there was twice that frequency of anti-nuclear antibodies (predominantly speckled in pattern), and anti-neutrophil cytoplasmic antibodies (predominantly IgM) were demonstrated in a few cases. A possible association between IgG anti-cardiolipin antibodies and tuberculosis was observed (P < 0.05), but antibodies to double-stranded DNA were not elevated and no antibodies to extractable nuclear antigens were found in any of the patients or healthy individuals studied. Our findings suggest the need for caution in the interpretation of autoantibody tests in subjects from or living in the tropics, as well as in patients with tropical infections.

Anti-neutrophil cytoplasmic antibodies (ANCA) and infection

As ANCA are occasionally noted in patients with infectious disorders independently of any vasculitis process, we examined serum from patients with acute infection (n = 22) and septic shock (n = 57). Only two patients with acute infection were ANCA positive as determined by indirect immunofluorescence and western blot analysis. The clinical recovery of both patients was associated with negative immunofluorescence and western blot tests.

ANCA and associated diseases: immunodiagnostic and pathogenetic aspects

The past decade has seen an explosion of data on the new group of autoantibodies known collectively as ANCA (anti-neutrophil cytoplasmic antibodies). ANCA are specific for granule proteins of granulocytes and monocytes and induce distinct fluorescence patterns, e.g. the cytoplasmic (classic) cANCA and the perinuclear pANCA. cANCA is induced by antibodies directed against Proteinase 3 (PR3; PR3-ANCA) in about 90% of all ANCA-positive sera, and pANCA is induced by antibodies against myeloperoxidase (MPO; MPO-ANCA) in about 40%. A further staining pattern, which does not have a clear cut association with a distinct granule protein, is sometimes seen in chronic inflammatory bowel diseases. PR3-ANCA are serological markers for Wegener's granulomatosis (WG) and MPO-ANCA are associated with certain subtypes of primary vasculitides. Evidence exists that both the autoantigen and ANCA participate in the pathogenesis of at least the group of 'ANCA-associated vasculitides'.

Fundamental and clinical aspects of anti neutrophil cytoplasmic antibodies (ANCA)

Anti-neutrophil cytoplasmic antibodies (ANCA) are associated with different forms of both primary and secondary vasculitis and glomerulonephritis. These antibodies are directed against different enzymes located in granulocyte granules. In this review ANCA-related antigens and solid phase assays for ANCA detection will be discussed. Furthermore, we will address the clinical relevance of ANCA and will deliberate on their possible pathogenic implications.

New horizons in renal vasculitis

After a long period during which few new data on the vasculitides emerged, the past decade has seen a real explosion of data on the subject. This began with basic clinical descriptions and the delineation of long term outcome as survival improved to a major extent under the influence of improved treatment regimes. In parallel, better understanding of the immunopathology has emerged. Of particular interest have been descriptions of autoantibody systems in vasculitis which seem to be specific to vasculitis and therefore diagnostically useful: the antineutrophil cytoplasmic antibodies (ANCA). Whether or not these are pathogenetically significant as well as useful remains a matter for debate. In parallel, anti endothelial cell antibodies have been described, but their role (if any), in pathogenesis remains equally obscure. There are some suggestions that vasculitis is becoming more common, but increased awareness and the availability of ANCA have undoubtedly increased awareness of the subject.