ANCA and infection

Streptococcal viridans subacute bacterial endocarditis associated with antineutrophil cytoplasmic autoantibodies (ANCA)

We report an illustrative case of a 60-year-old man with Streptococcus viridans subacute bacterial endocarditis (SBE) and positive antineutrophil cytoplasmic autoantibodies (c-ANCA). C-ANCA positivity has been associated with a variety of rheumatic and infectious disease areas, but has been rarely associated with SBE. The patient had mitral valve prolapse with mitral regurgitation, and S viridans SBE developed after a dental procedure. Laboratory abnormalities included anemia, elevated erythrocyte sedimentation rate, positive rheumatoid factor, positive anticardiolipin antibody, positive lupus anticoagulant, and highly elevated c-ANCA level. We believe this is only the ninth reported case of S viridans SBE with a positive c-ANCA, and the third with mitral valve prolapse and vegetations.

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.

Wegener's granulomatosis

Clinical manifestations of Wegener's granulomatosis are nonspecific and indistinguishable from a variety of neoplastic, infectious, and inflammatory diseases. Ophthalmic disease is the presenting feature in nearly one sixth of patients with Wegener's granulomatosis and will ultimately develop in a majority. The discovery of antineutrophil cytoplasmic antibodies, particularly antiproteinase-3, has changed the clinical approach to evaluating patients suspected of having Wegener's granulomatosis. These antibodies are distinguished from other related autoantibodies because they produce a coarse granular pattern of cytoplasmic staining on indirect immunofluorescence with ethanol-fixed neutrophils. Treatment of Wegener's granulomatosis with oral cyclophosphamide and corticosteroids has decreased morbidity and improved survival, but side effects from long-term immunosuppressive therapy are common and sometimes serious. The effectiveness of trimethoprim-sulfamethoxazole in decreasing the number and severity of recurrences of Wegener's granulomatosis is being investigated. It remains to be determined if wide use of trimethoprim-sulfamethoxazole in limited Wegener's granulomatosis could further improve the quality of life for some patients.

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.

Wegener's granulomatosis overlapped with Takayasu arteritis

A 27-year-old woman presented with destructive scleritis of the left eye with subcutaneous haemorrhage and swelling of the lower eyelid. She had experienced recurrent nasal bleeding for the last six years, and chronic sinusitis resulting in the destruction of the nasal septum and left maxillary sinus. Nasal mucosal biopsies demonstrated granuloma formation with no evidence of vasculitis. The level of serum cytoplasmic anti-neutrophil cytoplasm antibody (c-ANCA) was significantly increased. Furthermore, multiple sites of complete occlusions were detected in the left subclavian and common carotid arteries by subtraction angiography and MRI. We describe a case of Wegener's granulomatosis overlapped with Takayasu arteritis, which, to our knowledge, has not been previously reported.

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.

Multireactive pattern of serum autoantibodies in asymptomatic individuals with immunoglobulin A deficiency

Selective immunoglobulin A (IgA) deficiency (sIgAD) is associated with certain autoimmune states. Increased production of autoantibodies and eventual development of overt autoimmune disease are related in part to genetic and environmental factors as well as to the immune deficiency. We surveyed serum specimens from 60 healthy subjects with sIgAD for the presence of 21 different autoantibodies by enzyme-linked immunosorbent assays. The frequencies of 16 autoantibodies were higher in sIgAD patients than in normal healthy controls. Autoantibodies to Jo-1 (28%), cardiolipin (21%), phosphatidylserine (20%), Sm (15%), asialo-GM1 (21%), sulfatide (32%), sulfoglucuronyl paragloboside (11%), and collagen type I (10%) were detected at high frequencies in comparison to those of normal healthy controls. Many of the serum samples were multireactive (i.e., exhibited binding to more than two autoantigens). Forty percent (24 of 60) of sIgAD serum samples reacted against six or more autoantigens; 10% (6 of 60) of sIgAD serum samples were not reactive with any of the 21 autoantigens. Three percent (7 of 209) of consecutive serum samples submitted for autoimmune antibody analysis that were positive for autoantibodies were from patients with IgA deficiency. Our finding of an increased frequency of autoantibodies in sIgAD patients supports the notion of polyclonal stimulation by repeated environmental stimuli as an etiologic mechanism. Alternatively, the increased frequency may be caused by a dysregulation of the immune response in such individuals. The mere detection of autoantibodies cannot predict whether a subject with sIgAD will develop an autoimmune disease or determine which specific disease will emerge.

Antineutrophil cytoplasmic autoantibodies, autoantigens, and systemic vasculitis

Antineutrophil cytoplasmic antibodies (ANCA) encompass a heterogeneous group of autoantibodies targeting antigens in neutrophils (PMN), monocytes, and endothelial cells. ANCA are routinely detected by the indirect immunofluorescence technique (IFT) and at least three different patterns of fluorescence can be distinguished which have been assigned the acronyms cANCA, pANCA and aANCA. cANCA is mostly induced by proteinase 3 (PR3) antibodies (PR3-ANCA), and pANCA by myeloperoxidase (MPO) antibodies (MPO-ANCA), while aANCA has unidentified subspecificity. Over the past decade, ANCA have been the subject of extensive investigation. They have proved to be of significant value both as diagnostic tools and for follow-up in several forms of systemic vasculitis (e.g. Wegener's granulomatosis, WG; microscopic polyarteritis, MPA; Churg-Strauss syndrome, CSS) which are now termed 'ANCA-associated vasculitides'. Furthermore, it is suspected that the presence of ANCA is an important factor in the pathogenesis of these disease groups. Data regarding the detection of ANCA and their diagnostic value and role in the pathogenesis of vasculitic disorders will be discussed in this review. Growing evidence points to a pathophysiological and diagnostic relevance of the distribution of the ANCA target antigens PR3 and MPO (presence in the circulation, on cell membranes, and in tissue extracellularly). An autoimmune process has been implicated in the pathogenesis of ANCA-associated vasculitis, but it is uncertain which mechanism underlies the induction of the ANCA-related immunoresponse. In this paper mechanisms such as antigenic cross-reactivity between human PMN proteins and extrinsic antigens by molecular mimicry, idiotypic immunoglobulin regulation, and T-cell reactivity to PR3 and MPO will be discussed.

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.

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.

Alpha-enolase: a novel cytosolic autoantigen in ANCA positive vasculitis

Anti-neutrophil cytoplasmic antibodies (ANCA) in sera from patients with clinically proven vasculitis have been described as reacting with proteins present in the granules of human neutrophils. We have studied sera from 59 ANCA positive patients to further characterize the antibody response. In addition to the antigens previously identified in the vasculitic syndromes (myeloperoxidase and serine proteinase 3) the majority of these sera contained antibodies that reacted with a cytosolic extract of neutrophils on Western blots. Nearly 40% of these sera had antibodies directed against a cytosolic protein(s) of molecular mass 48 kD. This protein was purified from neutrophil cytosol by ammonium sulphate fractionation, anion exchange and reverse phase chromatography. Amino acid sequence analysis of a proteolytic fragment of this protein identified it as alpha enolase. The anti-enolase antibodies only recognized the alpha isoform and were present in sera giving either a pANCA or cANCA staining pattern by indirect immunofluorescence. Antibodies to alpha enolase were also found in sera from patients with systemic lupus erythematosus, particularly those with renal disease. We conclude that the antibody response in ANCA positive vasculitis is not restricted to neutrophil granule proteins.

Correlation of antineutrophil cytoplasmic antibodies with the extrarenal histopathology of Wegener's (pathergic) granulomatosis and related forms of vasculitis

We studied the histologic findings from extrarenal biopsies (especially of the lung or upper respiratory tract) or autopsies of 68 patients who were tested for serum antineutrophil cytoplasmic antibodies (ANCAs). We used antigen-specific assays to detect antibodies against proteinase 3 (PR3) and myeloperoxidase (MPO), the two types of ANCAs of proven diagnostic value for the spectrum of diseases that includes Wegener's (pathergic) granulomatosis, microscopic polyarteritis (microscopic polyangiitis), Churg-Strauss syndrome, idiopathic necrotizing and crescentic glomerulonephritis, and their variants. Twenty-eight patients had antibodies to PR3 and 16 had antibodies to MPO; no patient had antibodies to both. All 44 patients with ANCAs had histologic evidence of this spectrum of diseases. Thirteen patients without histologic evidence of this spectrum of diseases had negative tests for ANCAs. There were no pathologic features that reliably identified patients with one or the other type of ANCA. Eighteen of 31 patients with lesions of Wegener's granulomatosis had antibodies to PR3, seven had antibodies to MPO, and six had neither. Three of four patients with necrotizing arteries without granulomas had anti-MPO antibodies, but similar lesions were seen, together with extravascular granulomas, in three patients with anti-PR3 antibodies. Of 16 patients with alveolar hemorrhage, nine had anti-PR3 and five had anti-MPO antibodies. Two patients diagnosed clinically as having Churg-Strauss syndrome had anti-MPO antibodies. In 16 of the 25 patients with ANCAs and a histologic diagnosis of Wegener's granulomatosis the diagnosis was made on the basis of extravascular granulomatous lesions alone, which argues against the requirement for vasculitis. Of six patients with negative tests for ANCAs and histologically diagnosed Wegener's granulomatosis, none had evidence of renal involvement. We conclude that in the appropriate clinical setting the presence of anti-PR3 or anti-MPO antibodies provides reliable evidence of the above spectrum of diseases, but that subclassification (to the extent this is possible) depends on the presence of distinctive clinical or pathologic features. In patients with negative tests for ANCAs, interpretation of clinical and histologic findings remains the only definitive method of diagnosis.

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'.

ANCA in systemic vasculitides, collagen vascular diseases, rheumatic disorders and inflammatory bowel diseases

It was the aim of this study to reevaluate the diagnostic significance and clinical implication of ANCA after testing sera from 13,606 patients for the presence of ANCA. Our data confirm the high specificity (97%) and sensitivity (80%) of cANCA for Wegener's granulomatosis. pANCA were found in renal vasculitides (60%), collagen vascular diseases (SLE 20%, Sjögren's syndrome 26%, polymyositis 16%) and rheumatic disorders (Felty's syndrome 50%, rheumatoid arthritis 20%). A third fluorescence pattern in sera of patients with inflammatory bowel disease (ulcerative colitis 28/72, Crohn's disease 6/84), here called xANCA, was seen. Target antigens of granule proteins from PMN and monocytes (proteinase 3, myeloperoxidase, elastase, cathepsin G, lactoferrin, lysozyme) were identified.

Elevated serum levels of soluble interleukin-2 receptor in patients with Wegener's granulomatosis. Association with disease activity

OBJECTIVE

To investigate whether soluble interleukin-2 receptor (sIL-2R), a marker of T cell activation, could be a useful marker of disease activity in Wegener's granulomatosis (WG).

METHODS

Soluble IL-2R levels were determined by enzyme-linked immunosorbent assay. WG disease activity in 102 patients was assessed according to clinical features and levels of classic antineutrophil cytoplasmic antibody (c-ANCA) and C-reactive protein (CRP).

RESULTS

Soluble IL-2R levels were higher in patients with generalized and active disease than in those with limited and inactive disease. In 25 patients with complete clinical remission, sIL-2R levels were significantly elevated, although levels of CRP and c-ANCA were normal. Eight of these 25 patients had disease relapses within 6 months. Levels of sIL-2R were significantly higher in patients who had relapses than in those who did not. Patients with clinically active WG but low c-ANCA or CRP levels had elevated levels of sIL-2R.

CONCLUSION

Levels of sIL-2R correlate with disease activity in patients with WG, and may indicate imminent relapse.