Daina Selga

Rats and mice immunised with chimeric human/mouse proteinase 3 produce autoantibodies to mouse Pr3 and rat granulocytes

Aim: In this study, we employed chimeric human/mouse Proteinase 3 (PR3) proteins as tools to induce an autoantibody response to PR3 in rats and mice. Method: Rats and mice were immunised with recombinant human PR3 (HPR3), recombinant murine PR3 (mPR3), single chimeric human/mouse PR3 (HHm, HmH, mHH, mmH, mHm, Hmm) or pools of chimeric proteins. Antibodies to mPR3 and HPR3 were measured by ELISA. Antibodies to rat PR3 were determined by indirect immunofluorescence (IIF) on rat white blood cells. Urinalysis was performed by dipstick analysis. Kidney and lung tissue was obtained for pathological examination. Results: In mice, immunisation with the chimeric human/mouse PR3 Hmm led to an autoantibody response to mPR3. Rats immunised with the chimeric human/mouse PR3 Hmm, HmH and mmH, or a pool of the chimeric human/mouse PR3 proteins, produced antibodies selectively binding to rat granulocytes as detected by IIF. No gross pathological abnormalities could be detected in kidney or lungs of mice or rats immunised with chimeric human/mouse PR3. Conclusion: Immunisation with chimeric human/mouse proteins induces autoantibodies to PR3 in rats and mice. Chimeric proteins can be instrumental in developing experimental models for autoimmune diseases.

High Proteinase 3-Anti-Neutrophil Cytoplasmic Antibody (ANCA) Level Measured by the Capture Enzyme-Linked Immunosorbent Assay Method Is Associated with Decreased Patient Survival in ANCA-Associated Vasculitis with Renal Involvement

Wegener granulomatosis (WG) and microscopic polyangiitis (MP), diseases associated with antineutrophil cytoplasmic antibodies (ANCA), had an extremely poor prognosis before the introduction of cyclophosphamide and corticosteroids for their treatment. However, there is still reduced patient survival, and some studies have documented severe side effects of the immunosuppressants used. This 10-yr follow-up study assessed 117 consecutive patients with WG or MP with biopsy-confirmed renal involvement. The cumulative relative patient survival was lower: 0.664 for women and 0.648 for men. The causes of death (n = 64) were in most cases registered as associated with the vasculitic disease. Analysis of possible predictive factors for patient survival by multiple Cox regression analysis revealed that a very high level of proteinase 3 (PR3)-ANCA measured by the capture ELISA method, a diagnosis of MP, and older age were factors predicting poorer patient survival. High levels of B-thrombocytes at time of diagnosis were associated with a better prognosis. For patients surviving the first year, remission-sustaining therapy with azathioprine for longer than 12 mo was associated with improved patient survival. Thirty-nine patients developed end-stage renal failure. Elevated serum creatinine at time of diagnosis and a very high level of PR3-ANCA by capture ELISA were factors predicting a higher risk for renal failure during follow-up. The epitope on PR3 assessed by capture ELISA needs to be further analyzed and explored: it seemed to implicate poorer patient and renal survival in WG or MP with renal involvement.

The challenge of managing patients with polyarteritis nodosa.

Purpose of reviewIn this short review we focus on the problems faced by clinicians caused by the changing definitions of polyarteritis nodosa. Recent findingsThe term polyarteritis nodosa has been used for more than 100 years as a diagnostic term for patients with systemic vasculitis; however, specific vasculitides have been singled out like branches being chopped off a tree. Now, so little is left of the trunk of that tree that it is questionable to what extent we can trust older literature with respect to clinical features, natural history and response to treatment. Many authors of case reports, as well as authors of reviews and book chapters, claim they adhere to the Chapel Hill Consensus Conference definition of polyarteritis nodosa, yet still cite almost exclusively studies using older definitions without highlighting this dilemma. In the past year, two proposals affecting classification have been published: one stating that cutaneous polyarteritis nodosa and hepatitis-associated polyarteritis nodosa are diseases distinct from classical polyarteritis nodosa, and one providing an algorithm to separate microscopic polyangiitis from classical polyarteritis nodosa. SummaryThere is hope that a wide acceptance of the new classification principles will lead to a more uniform way to diagnose classical polyarteritis nodosa, which will facilitate clinical studies and eventually improve management.

Epitope mapping of anti-PR3 antibodies using chimeric human/mouse PR3 recombinant proteins

Autoantibodies against proteinase 3 (PR3) and myeloperoxidase (MPO) (ANCA = anti‐neutrophil cytoplasmic antibodies) are used as diagnostic tools for patients with small vessel vasculitis. ANCA are detected by different assays, but the correlation between the results of these assays is generally poor. The overall aim of the study was to provide a framework for the future development of new assays with an increased diagnostic yield. In order to express discrete epitopes of human PR3 (hPR3), the nonantigenic molecules murine PR3 (mPR3) and human leucocyte elastase (HLE) were used as a framework. We constructed recombinant chimeric vectors and were able to produce 6 hPR3/mPR3 proteins and 3 hPR3/HLE proteins. Anti‐PR3 monoclonal antibodies differed in their binding pattern to the chimeras, but no distinct binding region could be identified for any monoclonal antibody. The recombinant hPR3/mPR3 were also tested in ELISA with sera from patients with Wegeners granulomatosis with renal involvement. The results show that patients have antibodies to different constructs, indicating that the patients vary in their antibody repertoire from the beginning of the disease, and that patients may have antibodies from a broad range of clones early in the course of the disease. Recombinant hPR3/mPR3 chimeric proteins have a potential to be used as antigens in future ANCA assays.

Outcome and Treatment of Elderly Patients with ANCA-Associated Vasculitis

BACKGROUND AND OBJECTIVES ANCA-associated vasculitis is commonly found in elderly patients, but there are few data concerning outcome and treatment in the highest age groups. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Consecutive patients (N=151) presenting between 1997 and 2009 were retrospectively included from local registries in six centers in Sweden, the United Kingdom, and the Czech Republic if diagnosed with microscopic polyangiitis or granulomatosis with polyangiitis at age ≥75 years during the study period. Patients were followed until 2 years from diagnosis or death. Data on survival and renal function were analyzed with respect to age, sex, ANCA specificity, renal function, C-reactive protein, comorbidities, and Birmingham Vasculitis Activity Score at diagnosis as well as treatment during the first month. RESULTS Median follow-up was 730 days (interquartile range, 244-730). Overall 1-year survival was 71.5% and 2-year survival was 64.6%. Older age, higher creatinine, and lower Birmingham Vasculitis Activity Score were associated with higher mortality in multivariable analysis. Patients who were not treated with standard immunosuppressive therapy had significantly worse survival. Renal survival was 74.8% at 1 year. No new cases of ESRD occurred during the second year. High creatinine at diagnosis was the only significant predictor of renal survival in multivariable analysis. CONCLUSIONS ANCA-associated vasculitis is a disease with substantial mortality and morbidity among elderly patients. This study showed a better prognosis for those who received immunosuppressive treatment and those who were diagnosed before having developed advanced renal insufficiency.

Phagocytosis of apoptotic cells by macrophages in anti-neutrophil cytoplasmic antibody-associated systemic vasculitis

Anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis (AAV) is a group of autoimmune diseases, including granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). It is not known why ANCA develop, but it has been shown that they participate in pathogenesis by activating polymorphonuclear neutrophils (PMNs). In this study we hypothesize that dysregulation of phagocytosis in AAV leads to the accumulation of apoptotic neutrophils seen in association with blood vessels in AAV. These cells progress into secondary necrosis, contributing to tissue damage and autoantibody formation. Peripheral blood cells were counted, and phagocytosis was investigated using monocyte‐derived macrophages (MØ) and PMNs from healthy blood donors (HBD), AAV patients and systemic lupus erythematosus (SLE) patients. Furthermore, the effect of serum was assessed. Phagocytosis was measured using flow cytometry. The results showed no deviation in monocyte subpopulations for AAV patients compared to HBDs, although there was a decrease in lymphocyte and pDC (plasmacytoid dendritic cell) populations (4·2 × 106 cells/l versus 10·4 × 106 cells/l, P < 0·001). The number of neutrophils was increased (6·0 × 109 cells/l versus 3·8 × 109 cells/l, P < 0·001). There were no differences found in the ability of MØs to engulf apoptotic cells, nor when comparing apoptotic PMNs to become engulfed. However, serum from AAV donors tended to decrease the phagocytosis ability of MØs (36%) compared to serum from HBDs (43%). In conclusion, there is no intrinsic dysfunction in the MØs or in the PMNs that have an effect on phagocytic activity, but ANCA may play a role by decreasing phagocytic ability.

Epitope shift of proteinase-3 anti-neutrophil cytoplasmic antibodies in patients with small vessel vasculitis.

Anti‐neutrophil cytoplasmic antibodies against proteinase 3 (PR3‐ANCA) are used as diagnostic tools for patients with small vessel vasculitis (AASV). We have produced chimeric mouse/human PR3 molecules and investigate changes in reactivity over time and the possible relationship between epitope specificity and clinical course. Thirty‐eight PR3‐ANCA‐positive patients diagnosed between 1990 and 2003 were followed until December 2005. Plasma was collected at each out‐patient visit and older samples were retrieved retrospectively. Patients reacted with multiple epitopes at the time of diagnosis. At subsequent relapses 12 patients shifted reactivity, in 11 cases from epitopes located in the C‐terminal towards epitopes in the N‐terminal. Patients with reactivity against N‐terminal parts of PR3 at diagnosis had a significantly lower relapse rate, 30% compared to 78% in the group with predominantly C‐terminal reactivity (P = 0·04). The reactivity pattern did not correlate to outcome measured as death, end‐stage renal disease or vasculitis activity index score (VDI) at 5 years. Further research is necessary to conclude if this is a general phenomenon.

Impaired phagocytosis and reactive oxygen species production in phagocytes is associated with systemic vasculitis

BackgroundAnti-neutrophil cytoplasmic antibodies associated vasculitides (AAV) is a group of autoimmune diseases, characterized by small vessel inflammation. Phagocytes such as neutrophils and monocytes are the main effector cells found around the inflamed vessel wall. Therefore, we wanted to investigate aspects of function and activation of these cells in patients with AAV.MethodsFlow cytometry was used to evaluate: the expression of activation markers (CD11c, CD62L, CD177 and C5aR); the number of recently released neutrophils from bone marrow, defined as CD10-D16low cells in peripheral blood; and the capacity of peripheral blood monocytes and polymorphonuclear leukocytes (PMN) to produce reactive oxygen species and to phagocytose opsonized bacteria.ResultsAAV patients (n = 104) showed an increase of CD10-CD16low neutrophils and total PMN in peripheral blood, suggesting a combination of increased bone marrow release and prolonged survival. An increased percentage of AAV PMN expressed CD177 but no other signs of activation were seen. A decreased production of reactive oxygen species was observed in AAV phagocytes, which was associated with disease activity. Moreover, granulocytes from patients with microscopic polyangiitis showed lower oxidative burst capacity compared to patients with granulomatosis with polyangiitis or eosinophilic granulomatosis with polyangiitis. In addition, decreased phagocytosis capacity was seen in PMN and monocytes.ConclusionOur results indicate that phagocytes from AAV patients have impaired function, are easily mobilized from bone marrow but are not particularly activated. The association between low reactive oxygen species formation in PMN and disease severity is consistent with findings in other autoimmune diseases and might be considered as a risk factor.