Anti-idiotypic activity against anti-myeloperoxidase antibodies in pooled human immunoglobulin

Intravenous immunoglobulin therapy in antineutrophil cytoplasmic antibody-associated vasculitis

INTRODUCTION

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) includes three heterogeneous and difficult to treat clinical entities. Intravenous immunoglobulins (IVIG) may constitute a good therapeutic option, although data hitherto are scarce. The aim of this study was to assess the effectiveness and safety of IVIG in AAV in a real-world setting.

METHODS

Single center observational study of patients with AAV with at least one cycle of IVIG since January of 2000 to December of 2020. AAV diagnosis was based on a compatible clinical presentation and positive ANCA serology and/or compatible histology. Disease activity was assessed by the Birmingham Vasculitis Activity Score (BVAS). The effectiveness was evaluated by clinical and laboratory parameters (CRP, ESR) and its glucocorticoid-sparing effect. These variables were measured at one, six, twelve and twenty-four months of IVIG treatment. The doses of IVIG were 2g/kg in the following cycles of administration: 1 g/kg/day in 2 days (n=12); 0.5 g/kg/day in 4 days (n=11); 0.4 g/kg/day in 5 days (n=5). The clinical improvement was classified according to BVAS categories in remission, partial response and no response.

RESULTS

Twenty-eight patients (15 granulomatosis-polyangiitis, 10 microscopic polyangiitis and 3 eosinophilic granulomatosis with polyangiitis) were included. Reasons for using IVIG were relapse/refractory disease (n=25), active or suspected infection (n=3), and both (n=5). We observed a rapid and maintained BVAS score improvement, increasing from 34.6% at 1 month to 56.5% at 2 years of follow-up (p=0.12), and a reduction of glucocorticoids dose. Therapy was well tolerated and adverse events mild and scarce.

CONCLUSION

IVIG represents an effective and relative safe therapeutic alternative in relapsing/refractory AAV or in presence of a concomitant active infection.

Intravenous Immunoglobulin as an Immunomodulating Agent in Antineutrophil Cytoplasmic Antibody-Associated Vasculitides: A French Nationwide Study of Ninety-Two Patients

OBJECTIVE

Intravenous immunoglobulin (IVIG) represents a therapeutic alternative in antineutrophil cytoplasmic antibody-associated vasculitides (AAV), but its efficacy has been evaluated in only 2 small prospective trials. The aim of this study was to evaluate the efficacy and safety of IVIG in patients with AAV.

METHODS

We conducted a nationwide retrospective study of patients who received IVIG as immunomodulatory therapy for AAV.

RESULTS

A total of 92 patients (mean age 51 years) presenting with either granulomatosis with polyangiitis (Wegener's) (68%), eosinophilic granulomatosis with polyangiitis (Churg-Strauss) (22%), or microscopic polyangiitis (10%) received at least 1 course of IVIG. Antineutrophil cytoplasmic antibodies were present in 72% during the flare that required IVIG, as determined by immunofluorescence assay. IVIG was initiated because of relapsing disease in 83% of cases. IVIG was given for a median of 6 months (range 1-156 months) and in combination with corticosteroids in 21% of the patients or with other immunosuppressive agents in 77%. Efficacy of IVIG was assessed in the entire population and in a subset of 34 patients with unmodified background therapy. Remission rates at 6 months were 56% in the entire population and 58% in the unmodified background therapy group. Refractory disease and treatment failure at 6 months were observed in 7% and 18% in the whole population and 3% and 21% in the unmodified background therapy group, respectively. Adverse events (AEs) occurred in 33%, including serious AEs in 12% and AEs leading to discontinuation of IVIG in 7%.

CONCLUSION

This large study shows the clinical benefit of IVIG as adjunctive therapy, with an acceptable tolerance profile, and thus supports its use in AAV patients with refractory or relapsing disease.

Anti-idiotype antibodies in immune regulation of anca associated vasculitis

BACKGROUND

Anti-idiotype antibodies (anti-ids) have a potential role in the immunomodulation of various autoimmune disorders. The immunoregulatory role of anti-idiotypic antibodies in ANCA-associated vasculitis needs to be studied. This study was conducted in clinically and histopathologically diagnosed ANCA-associated vasculitis (AAV) patients.

METHODS

Anti-ids were tested in 100 AAV patients of which 80 had anti-MPO and 20 had anti-PR3 antibodies at various stages of disease over a period of 2-3 years. The disease activity was estimated by the Birmingham vasculitis activity score (BVAS). The affinity-purified ANCA F(ab')2 fragments were prepared using three each of anti-MPO and anti-PR3 high titer sera and were used as idiotype coats for anti-idiotype antibody detection by ELISA. Positivity was confirmed by fluid phase inhibition ELISA.

RESULTS

Patients who went into remission showed 53.8% anti-ids to anti-MPO and 52.9% to anti-PR3 with low BVAS values (0-8), whereas in patients with active disease, only 12.5% had anti-ids to anti-MPO and 10% had anti-ids to anti-PR3 with comparatively high BVAS (18-32), while five cases who had relapse (BVAS 18-20) did not have anti-ids to anti-MPO or anti-PR3. An inverse correlation was noted between ANCA and anti-ids (r = -0.901).

CONCLUSIONS

High prevalence of anti-ids in remission cases and low prevalence in active cases with absence of anti-ids in relapse cases as well as an inverse correlation of ANCA and anti-ids indicate its beneficial effect on the disease process, thus suggesting the dynamic role of anti-idiotype networks in the immunoregulation of AAV.

Comparison of characteristics of natural autoantibodies against myeloperoxidase and anti-myeloperoxidase autoantibodies from patients with microscopic polyangiitis

OBJECTIVE

Natural autoantibodies (NAAs) against MPO exist in normal human plasma. In the current study, the immune characteristics of MPO-NAA and MPO-ANCA were examined and compared with the aim to investigate the pathogenesis of MPO-ANCA.

METHODS

MPO-NAAs were affinity purified from normal plasma of five healthy blood donors and one batch of IVIG. MPO-ANCAs were purified from plasma of 10 patients with MPA. Antigen specificity of the antibodies was tested by western blot analysis. The titre, the avidity, the Immunoglobulin G (IgG) subclasses and the effect of the antibodies towards the binding between ceruloplasmin and MPO were tested using ELISAs. The MPO-NAA-induced production of reactive oxygen species was assessed using oxidation of dihydrorhodamine (DHR) to rhodamine.

RESULTS

MPO-NAA recognized epitope(s) in the heavy chains of MPO with conformation-dependent structure, the same as MPO-ANCA. The median titre of MPO-NAA was lower than that of MPO-ANCA (1 : 40 vs 1 : 4800, P < 0.001). The median avidity of MPO-NAA was lower than that of MPO-ANCA (2.2 × 10(7) vs 8.7 × 10(7)/M, P = 0.014). The IgG subclasses of MPO-NAA were mainly restricted to IgG1 (100%) and lack of IgG3. The inhibition effect on the binding between ceruloplasmin and MPO was lower for MPO-NAA than MPO-ANCA (P = 0.046). The MPO-NAA-induced respiratory burst of neutrophils was significantly weaker than that of MPO-ANCA (P = 0.036).

CONCLUSION

The lower titre, lower avidity and lack of IgG3 subclass compared with MPO-ANCA may contribute to the non-pathogenic co-existence of MPO-NAA with MPO in serum.

Natural autoantibodies to myeloperoxidase, proteinase 3, and the glomerular basement membrane are present in normal individuals

Anti-neutrophil cytoplasmic antibodies (ANCAs) have a pathogenic role in ANCA-associated vasculitis. The origin of ANCAs and anti-glomerular basement membrane (GBM) antibodies, however, is unknown. In this study, we determined whether natural autoantibodies against myeloperoxidase (MPO), proteinase 3 (PR3), and GBM were present in each of 10 healthy Chinese and Swedish individuals, negative for all three antigens by routine ELISA. Antibodies were purified from isolated IgG by antigen-specific affinity columns. Natural anti-GBM autoantibodies gave a linear staining pattern along the GBM of human renal sections. On ethanol-fixed granulocytes, both natural anti-MPO and anti-PR3 autoantibodies gave cytoplasmic staining. The titers of natural anti-MPO/PR3 autoantibodies were significantly lower than those from patients with vasculitis. In competition ELISA, the binding of natural anti-MPO autoantibodies could be inhibited by MPO, but not by PR3 or noncollagenous domains from type IV collagen. The same specificity results were found for natural anti-PR3 and anti-GBM autoantibodies. Overall, individuals of the Chinese origin had more natural autoantibodies than did those of the Swedish origin, but no other differences were found. Hence, our study shows that healthy individuals have masked circulating, noncross-reactive, antigen-specific natural autoantibodies against MPO, PR3, and GBM in their serum and IgG fractions. Further studies are needed to determine their role if any in the etiology of ANCA-associated vasculitis and anti-GBM disease.

Improvements in Treatment Strategies for Patients With Antineutrophil Cytoplasmic Antibody-associated Rapidly Progressive Glomerulonephritis

The course of rapidly progressive glomerulonephritis (RPGN) caused by antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is often life-threatening, especially in the elderly when pulmonary involvement and/or severely impaired renal function are present. Corticosteroids and cyclophosphamide are the first-line treatment, but ironically infection, not vascular events such as hemorrhage, caused by the vasculitis itself, is the most common cause of death of RPGN patients. Several new treatment strategies, such as leukocytapheresis (LCAP) and intravenous immunoglobulin (IVIg), have become available during the past decade and these treatments have made it possible to treat high-risk RPGN patients without inducing serious immunosuppressive states. In the present paper we review recent clinical trials of LCAP and IVIg therapy in patients with pauci-immune/ANCA-associated RPGN, and show improved clinical outcomes after using these new treatment strategies in our institution.

Use of immunofluorescence and confocal laser scanning microscopy in identifying rare cases of anti-neutrophil cytoplasmic antibodies (ANCA) showing dual specificities to myeloperoxidase and proteinase3

Anti-neutrophil cytoplasmic antibodies (ANCA) are the immunodiagnostic markers for idiopathic necrotizing crescentic glomerulonephritis affecting mainly medium to small sized blood vessels. The diagnosis of ANCA associated vasculitis (AAV) is mainly based on clinical and histopathological characteristics along with the serological evidence. Immunofluorescence microscopy (IIF) is considered as the "gold standard" for ANCA detection, and ANCA showing two major patterns ie, cytoplasmic (c-ANCA) and perinuclear (p-ANCA) react with different antigenic targets of neutrophils like Proteinase3 (PR3) and Myeloperoxidase (MPO). A third unusual and rare immunofluorescence pattern called as "X- ANCA" or atypical ANCA is also sometimes seen. The difficulty in identification of ANCA immunofluorescence patterns is mainly seen due to the rare dual patterns seen in the same sera and also the additional nuclear immunofluorescence seen due to presence of anti-nuclear antibodies. ANCA testing by immunofluorescence and Confocal Laser scanning microscopy, as well as by specific ELISAs for detection of anti-PR3 and anti-MPO antibodies have helped in improving the diagnosis. Patients having dual specificities to MPO and PR3 in a patient is a rare finding. Among 425 clinically and histopathologically proven cases of AAV, eight patients (1.9%) had dual specificities, of which five patients showed mixed immunofluorescence pattern and 3 patients showed X-ANCA pattern which was confirmed by both immunofluorescence and Confocal Laser scanning microscopy and the dual specificities to MPO and PR3 were detected by individual ELISAs.

Antineutrophil cytoplasm antibody-induced neutrophil nitric oxide production is nitric oxide synthase independent

BACKGROUND

Antineutrophil cytoplasm antibodies (ANCAs) are implicated in the pathogenesis of systemic vasculitis. We asked whether ANCA could induce nitric oxide (NO) release from human neutrophils and, if so, whether this NO production was dependent on NO synthase (NOS) activity.

METHODS

Neutrophil NO production was measured using a chemiluminescence assay, and NOS activity was determined by the conversion of [(14)C] L-arginine to [(14)C] L-citrulline and NOS mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Human neutrophils isolated from healthy donors were incubated at 37 degrees C with human ANCA, normal human IgG, murine monoclonal myeloperoxidase ANCA, murine proteinase-3 ANCA, or their respective isotypic controls for 6 to 12 hours in RPMI. Both human and monoclonal ANCA led to a dose-dependent increase of NO compared with control IgG. Neutrophils, either freshly isolated or incubated for seven hours with murine monoclonal myeloperoxidase ANCA, proteinase-3 ANCA, or a mixture of interleukin-1 beta, tumor necrosis factor-alpha, interferon-gamma plus lipopolysaccharide showed no NOS activity with low conversion rates of [(14)C] L-arginine to [(14)C] L-citrulline, which could not be inhibited by N(G)-monomethyl-L-arginine (NOS inhibitor). To detect NOS mRNA expression, RT-PCR was performed using oligonucleotide primers derived from mRNA sequences of either human constitutive endothelial NOS (eNOS), constitutive neuroneal NOS (nNOS), or human hepatocyte inducible NOS (iNOS). There was no expression of either eNOS, nNOS, or iNOS in untreated, human and murine monoclonal ANCA-treated, or cytokine-treated neutrophils.

CONCLUSION

These data suggest that human neutrophils produce NO in response to ANCA but in a NOS-independent way. NO can be generated from a nonenzymatic interaction between hydrogen peroxide and arginine. We postulate that this is the predominant pathway of NO synthesis in neutrophils, since ANCAs are capable of inducing reactive oxygen species production from neutrophils.

Anti-idiotypic antibodies prevent the serologic detection of antiribosomal P autoantibodies in healthy adults

A subset of SLE patients has serologically detectable autoantibodies to the ribosomal P proteins (anti-P). We reported the discovery of covert anti-P antibodies and their masking IgG-inhibitory antibodies in the sera of healthy adults. The aim of this study was to determine if these IgG-inhibitory antibodies are anti-idiotypic antibodies (anti-Ids). IgG and IgG-depleted fractions of plasma from two healthy adults were assayed for inhibition of anti-P F(ab')2 binding to the ribosomal P proteins in immunoblot. Anti-P antibody activity was completely inhibited by plasma IgG, whereas there was no inhibition by IgG-depleted plasma. IgG-inhibitory antibodies recognized a cross-reactive epitope among anti-P from different SLE patients. Plasma IgG from one healthy adult was depleted of pepsin agglutinators and generic anti-F(ab')2 antibodies by adsorption with an affinity column prepared with normal IgG F(ab')2. Unretained IgG bound exclusively to anti-P F(ab')2 in ELISA. Using four affinity columns, we isolated IgG anti-Ids to anti-P antibodies from four healthy adults. These purified anti-Ids bound to anti-P F(ab')2 from a healthy adult and SLE patients. They did not bind to F(ab')2 fragments prepared from normal IgG or anti-dsDNA. Ribosomal antigens blocked this anti-Id-Id interaction. Purified anti-Ids inhibited the binding of anti-P F(ab')2 from patients to ribosomal P proteins. SLE patients without overt anti-P antibodies also possessed IgG anti-Ids to anti-P antibodies. We conclude that IgG-inhibitory antibodies are anti-Ids to anti-P antibodies, and are directed to public idiotopes on anti-P antibodies. These anti-Ids may be part of an Id network that regulates anti-P antibody expression, and perhaps pathogenicity.

Incidence and disease associations of a proteinase 3-antineutrophil cytoplasmic antibody idiotype (5/7 Id) whose antiidiotype inhibits proteinase 3-antineutrophil cytoplasmic antibody antigen binding activity

OBJECTIVE

To evaluate the potential of a monoclonal proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA) antiidiotype autoantibody (5/7 anti-Id) as a candidate for specific immunotherapy in Wegener's granulomatosis (WG), and to estimate the immunodiagnostic value of the corresponding idiotype (5/7 Id).

METHODS

We analyzed the incidence of 5/7 Id in patients with ANCA-associated vasculitides (WG, microscopic polyangiitis, Churg-Strauss syndrome), in disease controls (systemic lupus erythematosus patients), and in healthy donors. We then investigated the presence of 5/7 Id in relation to disease stage, clinical activity, and organ manifestations in 86 patients with WG. Finally, we investigated the ability of the 5/7 anti-Id reagent to inhibit the binding of PR3-ANCA to corresponding antigen in 19 WG patients.

RESULTS

The incidence of 5/7 Id was significantly more frequent in WG patients (43 of 86; 50%). We did not find a significant correlation between the prevalence of idiotype expression and disease activity or organ manifestations. Further, we demonstrated in vitro suppression of PR3-ANCA antigen binding activity by 5/7 anti-Id in 11 of 19 WG patients who were positive for 5/7 Id.

CONCLUSION

This study shows that 5/7 Id is a common idiotype with a significantly increased incidence in WG and that 5/7 anti-Id inhibits PR3-ANCA antigen binding activity. Based on these observations, we conclude that 5/7 anti-Id is a promising tool for the development of a specific immunotherapy for WG.

Classification, pathogenesis, and treatment of systemic vasculitis

Patients with systemic vasculitis (SV), especially Wegener's granulomatosis and microscopic polyangiitis, regularly present with renal involvement. Although considered a rare disease, either the incidence of SV is increasing or it is being increasingly recognized. Accurate classification systems are required to allow comparison of data from different groups investigating and treating these patients. Systemic vasculitis is known to be an autoimmune disease, but the mechanisms of pathogenesis have not been established, despite many studies on this topic in recent years. Most of this work has been done in vitro, although development of animal models is underway. Patient and renal survival have improved with aggressive immunosuppressive treatment, but morbidity is high and controversies remain in establishing the most effective regimens with minimum adverse effects. In this review we discuss the classification of SV, review the current knowledge of pathogenic mechanisms, and consider the relative merits of different treatment protocols.

Immunity in the connective tissue diseases. The humoral side of the coin

Clinicians who care for patients with various connective tissue diseases frequently employ measurements of autoantibodies such as rheumatoid factors (RFs), anti-Sm antibodies, or anti-neutrophil cytoplasmic antibodies (cANCA) as a method to follow patients. Although the primary specificity of RFs appears to be directed against the Fc portion (C gamma 3 and C gamma 2 domains) of IgG, epitope mapping studies have now also demonstrated that many RFs also react with linear regions on beta 2-microglobulin and Class I HLA molecules. Cross reacting regions of IgG, beta 2m, and HLA Class I frequently show immunodominant tyrosines, trytophanes, valines, leucines, glutamic acids, aspartic acids, and threonines. Immunodominant linear epitopes on Sm antigen may be limited to regions expressing the PPPGMRPP or PPPGIRGP motifs. A number of linear regions of Proteinase 3 reacting with IgG antibodies in the sera of patients with Wegener's granulomatosis have now been identified. However, affinity purified rabbit antibodies to two of these major PR3 antigenic sties (ATVQLPQ and RVGAHDP) linked to Sepharose to form affinity columns, absorbed equal amounts of a mixture of many serum proteins from both Wegener's patients and normal controls. Continued study of this interface between autoantibody production, disease, and normal immune modulation is necessary.

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.

Mechanisms of endothelial cell injury in vasculitis

The aetiology of the primary systemic vasculitides remains obscure. Recent years have seen significant advances in our understanding of inflammation and in particular the role of and interaction between the vascular endothelium, mediators and immune effector cells. This has helped to further elucidate those specific processes relevant to vasculitis which result in endothelial cell damage. In Wegener's granulomatosis and microscopic polyarteritis the evidence favours an autoimmune inflammatory response characterised by specific mediators in which the endothelium is both target and active participant. Current treatment of these disorders with combinations of corticosteroids and cytotoxics is highly effective in inducing remission. However, long-term use of this therapy is potentially toxic and there remains also a significant risk of relapse. It is hoped that increased understanding of the pathogenesis of systemic vasculitis will enable more specific, less toxic and more effective therapies to be defined. Jayne et al. have suggested a beneficial effect of intravenous pooled normal human immunoglobulin (IVIG) in patients with ANCA-positive vasculitis. In vitro studies have shown that IVIG contains antiidiotypic antibodies to ANCA and AECA, capable of inhibiting the binding of these autoantibodies to their autoantigens. In vivo, IVIG may also provide the immunoregulatory elements needed for the idiotype network and control of the autoimmune repertoire. Mathieson et al. successfully used monoclonal antibodies to T cells (Campath-H directed against CDw52) in a patient with ANCA-negative dermal lymphocytic vasculitis. Monoclonal antibodies to CAMs have been used in human renal transplant rejection and reduced the inflammation and proteinuria in animal models of anti-glomerular basement membrane disease. In vasculitis, the therapeutic use of specific anti-CAM antibodies may result from further definition of the role of CAMs. Increased understanding of the pathogenesis of systemic vasculitis is likely to provide the basis for the use of more specific immunotherapies in the future.