RENAL VASCULITIS(AAV)
Dr Rajesh Jhorawat
Nephrology, SMS
Land mark steps..
In 1808, Willan- distinguished purpura caused by infections from non-infectious purpura
Henoch and his teacher, Schönlein, described a broad spectrum of signs and symptoms that were associated with purpura, and with small vessel vasculitis
In 1866, Kussmaul and Maier described “periarteritis nodosa” later changed to “polyarteritis nodosa”
In 1936, Friedrich Wegener, a German pathologist, described three patients with necrotizing granuloma
In 1954, Goodman and Churg wrote a detailed description of “Wegener´s granulomatosis” (WG)
In 1970s, Fauci and Wolff introduced treatment with cyclophosphamide and corticosteroids for WG
In 1985, DeRemee published a report on the benefits of using cotrimoxazole (trimethoprim/ sulfamethoxazole) in WG
In 1985, Van der Woude et al who reported autoantibodies(ANCA) sensitive and specific for the WG
Vasculitis
INFLAMMATION OF BLOOD VESSEL
CLASSIFICATION OF VASCULITIS
1990- American College of Rheumatology (ACR) Classification Criteria
1994- Chapel Hill Consensus Conference (CHCC)
European Medicines Agency developed a stepwise lgorithm for vasculitis in 2007
CHCC definitions were revised in 2012
• ANCA testing not included
• PAN and MPA put togather
•Size of blood vessel (tissue Bx)•PAN and MPA seperated•ANCA suggested•AAV- WG, CSS, MPA
•ACR•Lanham crietria for CSS•ANCA•CHCC defination
Large vessels are the aorta and its major branches and theanalogous veins.
Medium vessels are the main visceral arteries and veins and their initial branches
Small vessels are intraparenchymal arteries,arterioles, capillaries, venules, and veins
ANCA-associated Vasculitis (AAV) Antineutrophil cytoplasm antibody (ANCA)–
associated vasculitis (AAV) is a group of multisystem diseases
Characterized by a pauci-immune small-vessel vasculitis with presence of circulating autoantibodies
Annual incidence of 20 per million Outcomes are often poor with a mortality of
25% at 5 years. Renal involvement is frequently seen and is
strongly associated with outcomes
ANCA-associated Vasculitis (AAV)
But newer insights for classification have emerged from large cohort and genetic studies esp. with two recent studies
Mahr et al Lyons et al.
ANCA and other antibodies
Antineutrophil cytoplasmic autoantibodies (ANCA) are a group of antibodies that react with cytoplasmic antigens in human neutrophils
These antibodies originally reported in 1964 and the first report linking these antibodies to disease was in 1982(Davies et al)
About 90% of patients with small-vessel vasculitis or pauci-immune NCGN have ANCA
The major autoantigens of ANCA are MPO and PR3.
MPO-ANCA is the predominant serotype in MPA patients, whereas PR3-ANCA is usually found in GPA.
True dual positivity is rare and raises suspicion of a drug-induced vasculitis.
Methods of Detection
IIF(screening)
ELISA(specificity)
Indirect Fluorescent Assay (IFA) In the immunofluorescent test for ANCA, several
patterns of cellular staining may be seen Two major patterns of staining have been
described and well characterized when ethanol-fixed neutrophils are used in the immunofluorescent ANCA test1. Cytoplasmic pattern called C-ANCA, are usually
directed against a serine protease, Proteinase 3 (PR3)
2. Perinuclear pattern called P-ANCA, are usually due to antibodies directed against myeloperoxidase (MPO)
C-ANCA P-ANCA
FIXATIVE PR3 MPO
ETHANOL CYTOPLASMIC PERINUCLEAR
FORMALIN CYTOPLAMIC CYTOPLASMIC
•Selected cohorts studied•Disease extent and activity at the time of serum sampling•Criteria used for setting the diagnoses•Way positive cutoff values for the assays used have been set
ANCA TESTING- CLINICAL USE DIAGNOSIS, PROGNOSIS, AND FOLLOW-UP
Most experts on vasculitis agree that the level of PR3-ANCA and MPO-ANCA is higher in active and/or extensive phase of the disease
PR3-ANCA and MPO-ANCA have some influence on the development of clinical features. Renal and respiratory involvement in PR3-ANCA Renal limited involvement is more often in MPO-
ANCA Patients positive for PR3-ANCA suffered more
frequent relapses than those positive for MPO-ANCA.
AAV- other Autoantibodies
These different autoantibodies are likely to reflect mechanisms operating in the inflammatory events and may even be part of an
orchestrated attackon the endothelium and basement membrane
Directed to small vessel ECs
Idiopathic AAV and in drug-induced vasculitis
Increase level is observed in relapse
Induce adhesion molecule expression and increased cytokine secretion
Don’t cross react and fluctuate independently with ANCA
Autoantibodies to the a3-domain of type IV collagen
Observed co-occurrance with ANCAs (esp. with anti-MPO)
co-occurrence with ANCAs influence outcome
Anti–endothelial cell antibodies (AECA)
Antibodies to Glomerular Basement Membrane( Anti-GBM)
Rare Anti–b2-glycoprotein 1,
anticardiolipin, or the lupus anticoagulant
With ACA more extensive and more severe disease
In Drug-induced vasculitis, antiphospholipid antibodies of the IgM class
Antiphospholipid Autoantibodies
Pathology
Basic leasion- segmental fibrinoid necrosis, often accompanied by leukocyte infiltration and leukocytoclasia (leukocyte fragmentation)
Patients with pauci-immune small-vessel vasculitis also may have renal arteritis, most often affecting interlobular arteries and medullary angiitis affecting the vasa recta
The medullary angiitis may be severe enough to cause papillary necrosis
Clinical Manifestations(AAV)
Treatment
Without therapy, ANCA vasculitis with GN is associated with very poor outcomes
Treatment with corticosteroids and cyclophosphamide has dramatically improved the short- and long-term outcomes of ANCA vasculitis associated with systemic disease.
Treatment with immunosuppressive therapy is therefore considered indicated in all cases of ANCA vasculitis and GN
Induction trials in AAV
Treatment
Rare possible exception relates to patients with severe kidney-limited disease, in the absence of extrarenal manifestations of small-vessel vasculitis
OR Patients with severe pauci-immune
NCGN requiring dialysis,
TreatmentBenefit/Risk
of Tx
Evidence- study-1
Study 2
Maintenance Therapy
Transplantation in AAV
Future option in AAV
THANK YOU
An increased prevalence of thromboembolic disease occurs in AAV, and autoantibodies have now been described to plasminogen and tissue plasminogen activator in the sera of one quarter of PR3-ANCA-positive AAV patients.
The presence of antiplasminogen antibodies correlated with venous thrombosis and with the severity of renal vasculitis
GENETICS AND THE ENVIRONMENT
Evidence for a genetic contribution in AAV has been increasing with familial associations and study of candidate genes, especiallyHLA DPB1*0401in European GPA patients.
Associations with HLA-DP, SERPINA1, and PRTN3 were identified for GPA. SERPINA1 encodes for a-1 antitrypsin and PRTN3 encodes for PR3.
An association with HLA-DQ was identified for MPA.
Interestingly, the genetics were more strongly associated with ANCA specificity (MPO-/PR3-ANCA) than clinical diagnosis (MPA/GPA).
Associations with environmental factors, such as air pollutants, infections, and drugs, have also been associated.
Silica is a well-known air pollutant contributing to many autoimmune diseases including AAV.
Peptides from Staphylococcus aureus have strong homology with peptides from complementary PR3, and Staphylococcus aureus infection has been associated with initiation and relapse of GPA
The anti-hLAMP-2 antibody also has 100% homology to FimH in Gram-negative bacteria.
In 2011, a Japanese group revealed that MPO-ANCA– activated glomerular endothelial cells directly in a murine model. They identified a new target antigen of MPO-ANCA, moesin, on the glomerular endothelium.
Moesin has partial amino-acid sequence homology with an epitope of MPO-ANCA
They found a high prevalence of anti-moesin antibodies in MPA patients
Cocaine use has caused several vasculitis syndromes including AAV, recently associated with contamination of cocaine by levamisole.
Propylthiouracil (PTU) is the most frequent cause of drug-induced AAV (especially MPA) The finding of multiple autoantibodies is more common in drug-induced than primary AAV, suggesting a dysregulation of self-tolerance.
HISTOPATHOLOGY
AAV often affects the kidneys and is the most common cause of rapidly progressive glomerulonephritis.
Renal involvement is an important predictor of increased mortality risk and morbidity in AAV, and renal biopsy aids in both diagnosis and prognosis.
An outcome-based classification of ANCA-associated glomerulonephritis histology has been developed to formalize the predictive value of the renal biopsy.
A validation study with 100 renal biopsies from AAV patients revealed that the classification was an independent predictor for estimated GFR after 1 year and 5 years.
Although the ‘Focal’ class showed good preservation of renal function and the ‘Crescentic’ class a good chance for renal recovery, the ‘Mixed’ and ‘Sclerotic’ classes had, respectively, intermediate and high risks of progression to end-stage renal disease.
T-cell tubulitis was an independent predictor for estimated GFR after 12 months and tubular atrophy was an independent predictor for estimated GFR after 12 months and 24 months.
Another recent topic in histopathology is the involvement of the complement system, especially the alternative pathway.
Xinget al.,detected components of the alternative pathway, factor B, factor P, C3d, and membrane-attack complex, in glomeruli and small blood vessels in kidney biopsy specimens from AAV patients
Treatment
The current treatment for AAV has been optimized by randomized controlled trials performed over the last 20 years
It is not curative but aims to control disease activity in a 3- to 6-month induction phase of high-dose glucocorticoid and daily oral or intravenous-pulsed cyclophosphamide that is effective in 80–90%.
Despite maintenance therapy of low-dose glucocorticoid and azathioprine or methotrexate, at least 10% of patients relapse each year
Induction trials
A rationale for B cell–targeted therapy in AAV has emerged from the presence of B cells at sites of inflammation, correlation of B-cell activation with disease activity in GPA, the efficacy of cyclophosphamide, which is a relatively B cell–specific immunosuppressant, and the contribution of ANCA to the pathogenesis.
Several case series and small prospective studies highlighted the efficacy of the anti-CD20 B cell–depleting monoclonal antibody, rituximab in refractory AAV.
Subsequently, two randomized trials evaluated rituximab for remission induction in new and relapsing patients.
Both the RAVE and RITUXVAS trials found similar remission rates for newly diagnosed patients between rituximab- and cyclophosphamide-based regimens when combined with high-dose glucocorticoid.
The RAVE trial also demonstrated superiority of rituximab for the subgroup treated for relapsing disease. However, no differences in safety were observed between the treatment groups, suggesting that glucocorticoid rather than cyclophosphamide is the major treatment-related cause of toxicity in AAV.
Rituximab is now indicated for relapsing AAV and newly diagnosed AAV when cyclophosphamide avoidance is desirable.
The pathogenicity of ANCA has contributed to a therapeutic rationale for plasma exchange in AAV
A metaanalysis of plasma exchange trials suggests a beneficial effect on the risk for end-stage renal disease but no effect on mortality
Current practice recommends plasma exchangefor those with severe renal disease or alveolar hemorrhage, although the evidence base in the latter indication is weak.
The PEXIVAS trial is examining the effect of plasma exchange on patients with a GFR below 50 ml/min or with severe alveolar hemorrhage
Maintenance therapy
Following control of features of vasculitis activity, the maintenance therapy aims to prevent vasculitis returning.
The WEGENT trial aimed to demonstrate the superiority of methotrexate over azathioprine, but adverse event rates were similar and relapse rates at 36 months were 50 and 47%, respectively.
The IMPROVE trial found mycophenolate mofetil was less effective compared with azathioprine for prevention of relapse, 55% vs. 38% after 39 months, with similar adverse event rates.
Maintenance Trials
Consequently, azathioprine or methotrexate, with or without low-dose glucocorticoid, is the preferred maintenance agents.
Recently, Smith et al. published a retrospective study, which revealed that a 2-year fixed interval routine rituximab therapy reduced relapse rate in relapsing AAV patients treated with rituximab.
This subject will be further studied in the
ongoing RITAZAREM trial
EGPA
EGPA has been excluded from most AAV trials. Recently, a French group examined the response to
glucocorticoids in nonsevere EGPA and glucocorticoids, as well as cyclophosphamide in severe EGPA.
Relapse rates in nonsevere EGPA are high if treated with glucocorticoids alone and studies of combinations with other immunosuppressants are needed.
Similarly, only anecdotal data exist for the role of rituximab in EGPA.
Two, small, open-label studies of an antiinterleukin-5 antibody, mepolizumab, have reported goodeffects in EGPA
OUTCOME
Long-term outcome studies by the European Vasculitis Society cohort with 535 AAV patients with a median of 5.2-year follow-up reported cumulative survival rates at 1 and 5 years of 88 and 78%, respectively.
Frequent causes of death within the first year were infection (48%) and active vasculitis (19%), and those after 1 year were cardiovascular disease (26%), malignancy (22%), and infection (20%).
In the same cohort, 38% of 535 patients experienced a relapse, and the relapse was more common in PR3-ANCA-positive patients.
As to malignancy, only the risk of nonmelanoma skin cancer was increased in this cohort
The low increases in cancer risk compared with previous studies might reflect short follow-up or lower exposure to cyclophosphamide in current protocols.
The French Vasculitis Study Group also showed similar results in their study for urotoxic adverse events .The risk of bladder cancer in AAV was low in an intravenous-pulsed cyclophosphamide group and a group diagnosed after 1998.
Longer follow-up is necessary because of the late development of malignancy.
Newer Therapeutic Agents
The proteasome inhibitor Bortezomib has demonstrated a stronger effect on autoantibody production than cyclophosphamide in experimental models.
The immunosuppressive agent gusperimus proved efficacy in controlling disease activity in two nonrandomized trials of refractory or relapsing GPA.
The anti-CD52 pan lymphocyte–depleting antibody, alemtuzumab, has led to sustained treatment-free remissions in AAV, but it is strongly immunosuppressive and is associated with severe adverse events in the elderly and those with renal failure.
CONCLUSIONS
The classification of vasculitis has been further revised and new genetic associations are likely to drive more changes in how vasculitis is subgrouped.
The discovery of newer autoantibodies raises the potential for newer biomarkers of clinical utility, as well as inspiring pathogenetic studies.
Rituximab is now firmly established in the treatment of ANCA vasculitis, and further innovations permitting reduced immunosuppressive and glucocorticoid exposure are in development.
Much of the recent progress has developed from the creation of international collaborative networks permitting consensus approaches and large-scale clinical studies.