Complement alternative pathway determines disease susceptibility and severity in antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis

Abstract

Activation of the alternative pathway (AP) of complement is involved in the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV), although the underlying molecular mechanisms are unclear. To gain insight into the role of the AP, common gene variants in CFH/CFHR1-5, CFB, C3 and MCP, and longitudinal determinations of plasma C3, C4, FH, FHR-1, FHR-2, FHR-5, FB, properdin and sC5b-9 levels were analyzed in a Spanish AAV cohort consisting of 102 patients; 54 with active AAV (active cohort) and 48 in remission not receiving immunosuppressants or dialysis therapy (remission cohort). The validation cohort consisted of 100 patients with ANCA-associated glomerulonephritis. Here, we demonstrated that common genetic variants in complement components of the AP are associated with disease susceptibility (CFB32Q/W) or severity of kidney damage in AAV (CFH-H1, CFH1H2 and ΔCFHR3/1). Plasma levels of complement components were significantly different between active and remission cohorts. In longitudinal observations, a high degree of AP activation at diagnosis was associated with worse disease outcome, while high basal FHR-1 levels and lower FH/FHR-1 ratios determined severe forms of kidney associated AAV. These genetic and plasmatic findings were confirmed in the validation cohort. Additionally, autoantibodies against FH and C3 convertase were identified in one and five active patients, respectively. Thus, our study identified key genetic and plasma components of the AP that determine disease susceptibility, prognosis, and severity in AAV. Our data also suggests that balance between FH and FHR-1 is critical and supports FHR-1 as a novel AP-specific therapeutic target in AAV. Activation of the alternative pathway (AP) of complement is involved in the pathogenesis of antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV), although the underlying molecular mechanisms are unclear. To gain insight into the role of the AP, common gene variants in CFH/CFHR1-5, CFB, C3 and MCP, and longitudinal determinations of plasma C3, C4, FH, FHR-1, FHR-2, FHR-5, FB, properdin and sC5b-9 levels were analyzed in a Spanish AAV cohort consisting of 102 patients; 54 with active AAV (active cohort) and 48 in remission not receiving immunosuppressants or dialysis therapy (remission cohort). The validation cohort consisted of 100 patients with ANCA-associated glomerulonephritis. Here, we demonstrated that common genetic variants in complement components of the AP are associated with disease susceptibility (CFB32Q/W) or severity of kidney damage in AAV (CFH-H1, CFH1H2 and ΔCFHR3/1). Plasma levels of complement components were significantly different between active and remission cohorts. In longitudinal observations, a high degree of AP activation at diagnosis was associated with worse disease outcome, while high basal FHR-1 levels and lower FH/FHR-1 ratios determined severe forms of kidney associated AAV. These genetic and plasmatic findings were confirmed in the validation cohort. Additionally, autoantibodies against FH and C3 convertase were identified in one and five active patients, respectively. Thus, our study identified key genetic and plasma components of the AP that determine disease susceptibility, prognosis, and severity in AAV. Our data also suggests that balance between FH and FHR-1 is critical and supports FHR-1 as a novel AP-specific therapeutic target in AAV. Lay SummaryThe activation of the complement alternative pathway (AP) has been involved in the pathogenesis of antineutrophil cytoplasmic antibody–associated vasculitis (AAV), although the underlying molecular mechanisms are unclear. Here, we have identified common genetic variants in complement genes of the AP that are associated with protection to develop AAV (CFB32Q/W) or that are associated with increased severity of the disease (deletion of CFHR1 and CFHR3, and CFH-H1). Consistent with these findings, circulating complement levels in active disease were altered compared with control and remission samples, and some of them have a prognostic value. Our data also suggest a crucial role of the balance between factor H (FH) and FH-related protein 1 in AAV. This study could explain the heterogeneity in prognosis and response to treatment observed in AAV. The activation of the complement alternative pathway (AP) has been involved in the pathogenesis of antineutrophil cytoplasmic antibody–associated vasculitis (AAV), although the underlying molecular mechanisms are unclear. Here, we have identified common genetic variants in complement genes of the AP that are associated with protection to develop AAV (CFB32Q/W) or that are associated with increased severity of the disease (deletion of CFHR1 and CFHR3, and CFH-H1). Consistent with these findings, circulating complement levels in active disease were altered compared with control and remission samples, and some of them have a prognostic value. Our data also suggest a crucial role of the balance between factor H (FH) and FH-related protein 1 in AAV. This study could explain the heterogeneity in prognosis and response to treatment observed in AAV. Antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV) is a systemic autoimmune disease that is characterized by necrotizing inflammation of predominantly small blood vessels and the presence of circulating ANCAs directed against myeloperoxidase or proteinase 3. The main histologic feature in the kidneys of patients with AAV is “pauci-immune” necrotizing crescentic glomerulonephritis with absent or scarce Ig and complement deposits.1Jennette J.C. Falk R.J. Hu P. Xiao H. Pathogenesis of antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitis.Annu Rev Pathol. 2013; 8: 139-160Crossref PubMed Scopus (200) Google Scholar,2Falk R.J. Jennette J.C. ANCA small-vessel vasculitis.J Am Soc Nephrol. 1997; 8: 314-322Crossref PubMed Google Scholar The complement system was not, therefore, initially thought to be associated with the development of AAV. Convincing evidence from animal models and clinical observations indicates, however, that activation of the complement system, the alternative pathway (AP) in particular, is pivotal for the development of AAV.3Gou S.J. Yuan J. Chen M. et al.Circulating complement activation in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis.Kidney Int. 2012; 83: 129-137Abstract Full Text Full Text PDF PubMed Scopus (206) Google Scholar, 4Villacorta J. Diaz-Crespo F. Acevedo M. et al.Glomerular C3d as a novel prognostic marker for renal vasculitis.Hum Pathol. 2016; 56: 31-39Crossref PubMed Scopus (28) Google Scholar, 5Xiao H. Schreiber A. Heeringa P. et al.Alternative complement pathway in the pathogenesis of disease mediated by anti-neutrophil cytoplasmic autoantibodies.Am J Pathol. 2007; 170: 52-64Abstract Full Text Full Text PDF PubMed Scopus (448) Google Scholar C5a is a potent anaphylatoxin and chemoattractant, crucial in disease pathogenesis,5Xiao H. Schreiber A. Heeringa P. et al.Alternative complement pathway in the pathogenesis of disease mediated by anti-neutrophil cytoplasmic autoantibodies.Am J Pathol. 2007; 170: 52-64Abstract Full Text Full Text PDF PubMed Scopus (448) Google Scholar and blockade of C5a or C5a receptor (CD88) ameliorates anti-myeloperoxidase necrotizing and crescentic glomerulonephritis in mice.6Xiao H. Dairaghi D.J. Powers J.P. et al.C5a receptor (CD88) blockade protects against MPO-ANCA GN.J Am Soc Nephrol. 2014; 25: 225-231Crossref PubMed Scopus (243) Google Scholar Recently, a phase 3 clinical trial (ADVOCATE, NCT02994927) has shown that C5a receptor inhibition with avacopan, a small antagonist, was effective in replacing high-dose glucocorticoids in patients with AAV treated with rituximab or cyclophosphamide during induction treatment.7Jayne D.R.W. Merkel P.A. Schall T.J. et al.Avacopan for the treatment of ANCA-associated vasculitis.N Engl J Med. 2021; 384: 599-609Crossref PubMed Scopus (362) Google Scholar The complement system is a major component of the innate immunity. On its activation through any of its 3 activation pathways (classical, lectin, or alternative), the complement system displays various effector functions, including induction of inflammation and cell damage. Unlike the classical and lectin pathways that need a stimulus to be triggered, the AP is always in “ready to fire” status; therefore, regulatory mechanisms are crucial to prevent uncontrolled complement activation. Factor H (FH) is the main regulator of the AP, both in fluid phase and on cellular surfaces. In certain circumstances, the regulatory activity of FH can be counteracted by FH-related proteins (FHRs; FHR1–5), other members of the FH protein family.8Lucientes-Continente L. Marquez-Tirado B. Goicoechea de Jorge E. The factor H protein family: the switchers of the complement alternative pathway.Immunol Rev. 2023; 313: 25-45Crossref PubMed Scopus (13) Google Scholar Unlike FH, the FHRs lack the complement regulatory domains of FH but share with FH similarities within the surface recognition domains. In contrast to FH, which inactivates surface-bound C3b and prevents further C3b generation and deposition (negative regulation), surface-bound FHRs promote complement activation through the AP.9Csincsi A.I. Kopp A. Zoldi M. et al.Factor H-related protein 5 interacts with pentraxin 3 and the extracellular matrix and modulates complement activation.J Immunol. 2015; 194: 4963-4973Crossref PubMed Scopus Google Scholar, A.I. et to protein and complement activation.J Immunol. PubMed Scopus Google Scholar, de Jorge E. et of complement factor H-related proteins modulates complement activation in A. 2013; PubMed Scopus Google Scholar, M. M. Factor H-related protein complement by as a for the of alternative pathway C3 convertase its with C3b 2012; Full Text Full Text PDF PubMed Scopus Google Scholar the balance between FH and the FHRs determine the of AP as we for and C3 or in the protein levels of FH or FHRs to the development of M. A. B. et al.Factor H-related proteins determine Immunol. 2015; Full Text Full Text PDF PubMed Scopus Google Scholar the of complement in AAV pathogenesis is the molecular mechanisms to of the AP are unclear. Here, we have characterized the circulating levels of various complement components and genetic of common complement gene variants in and we to disease susceptibility, and prognosis in a Spanish cohort of AAV. of patients with diagnosis of AAV with kidney to and validation from 5 Spanish from and were in the The cohort consisted of 102 patients, and was of 54 patients with a diagnosis of active AAV (active cohort) and 48 patients were in remission and not receiving immunosuppressants or dialysis therapy (remission cohort). The validation cohort was of 100 patients with ANCA-associated glomerulonephritis. The validation cohort was to the genetic we plasma from the genetic control of from the Spanish of and patients with C3 were from the active cohort were for were at and 3 Plasma and were treatment was and at clinical In the remission clinical data were and plasma and were the was in Plasma of patients of the validation cohort were at the of and were to the plasma complement determinations observed in the cohort. vasculitis was by the presence of associated with small-vessel in the of R.J. Jennette J.C. ANCA small-vessel vasculitis.J Am Soc Nephrol. 1997; 8: 314-322Crossref PubMed Google Scholar was at disease with vasculitis were disease activity was the P.A. R.J. et in systemic necrotizing Google Scholar were were to active vasculitis and in the or was the et to Med. PubMed Scopus Google Scholar was by or associated with of as as of disease was as the presence of active in by to active vasculitis remission was The study was by the of the and patients were as and or and the were as or were in of between were the or on the data were to between FH, C3, factor and to the of the complement components in the was was The between of complement genetic variants were by or ratios and were were the could not be and the was for the 5 different was and was were with and genetic of plasma and complement of of and in are in the the 102 patients with a diagnosis of AAV and renal were in the study of 54 patients were with active disease (active cohort) and 48 patients were in remission (remission cohort). the patients with active 5 AAV. 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E. et at the and variants in and with systemic and J 2021; Full Text Full Text PDF PubMed Scopus Google Scholar complement gene variants or plasma complement levels at diagnosis with kidney disease To patients from the AAV active cohort were into 3 and on of the levels at disease of a marker of that with the kidney activity in patients with J. L. Goicoechea E. et as a of disease activity and in antineutrophil antibody-associated J. 2021; PubMed Scopus Google Scholar clinical are in to patients with forms and to the severe our be with as to were for these both genetic variants and plasma levels of some components were significantly associated with kidney disease is significantly associated with increased renal and are associated with forms of kidney disease Consistent with these genetic observations, plasma FHR-1 levels are significantly lower in patients with the levels and the FH/FHR-1 is and and In FH, and C3 levels are significantly in with the that is complement activation in the severe forms of the disease In with these observations, FHR-1 levels and the FH/FHR-1 were also significantly different between patients with a severe renal histologic and patients with a severe and to the F. et of ANCA-associated Am Soc Nephrol. PubMed Scopus Google F. J. Acevedo M. et of kidney in renal a cohort Pathol. 2016; PubMed Scopus (28) Google Scholar and of complement gene variants in patients with AAV to antineutrophil cytoplasmic antibody–associated of the to The was data in a levels of complement components at diagnosis to plasmatic of was for the FH/FHR-1 the was complement C4, complement complement FB, factor FH, factor factor are as levels are by to and data of was for the FH/FHR-1 the was in a antineutrophil cytoplasmic antibody–associated of the to The was data C3, complement C4, complement complement FB, factor FH, factor factor are as levels are by to and data that our patients renal we sC5b-9 could be as marker of renal a of sC5b-9 in active AAV was observed compared with high levels of sC5b-9 were associated with both severe histologic and high levels of was between plasma and sC5b-9 between plasma sC5b-9 and renal histologic and not that sC5b-9 is a marker of complement activation and renal damage plasma sC5b-9 study was with the active patients from the cohort. of patients clinical patients not clinical patients and 5 patients were during the patients and to the of the clinical of was observed at diagnosis the and between patients remission and the that the kidney at diagnosis was worse in patients not remission the genetic of complement gene variants were not significantly different between patients remission or not of active cohort patients with AAV remission or remission at complement levels FH, FHR-1, FH/FHR-1 FHR-2, FHR-5, FB, C3, C4, antineutrophil cytoplasmic antibody–associated C3, complement C4, complement complement FB, factor FH, factor factor are as or data in a antineutrophil cytoplasmic antibody–associated C3, complement C4, complement complement FB, factor FH, factor factor are as or data levels of complement components were in AAV during the of the patients not remission significantly lower levels of FH, FB, and properdin at diagnosis compared with remission 5 and that a degree of AP activation at disease with a worse disease the longitudinal of plasma complement components during the of In patients C3 levels increased the FHR-1 and sC5b-9 In the remission was not renal treatment was plasma were FHR-1 levels increased in the the were longitudinal plasma complement C3, and factor protein levels in patients study was in the patients with active antineutrophil cytoplasmic antibody–associated vasculitis C3, and FHR-1 levels at the of diagnosis and were in patients C3, and FHR-1 levels at the of diagnosis and 3 were in patients not were determined the or the not is evidence that the activation of complement AP is involved in the pathogenesis of AAV. In the we a of the AP components in a Spanish AAV and we on disease susceptibility, and for the to our that genetic variants in complement components of the AP with protection to develop AAV (CFB32Q/W) and with severe forms of the disease (CFH-H1, and ΔCFHR3/1). we activation of the alternative and complement pathways in during active AAV. also evidence that a degree of AP activation at diagnosis with worse disease outcome, plasma FHR-1 levels and lower FH/FHR-1 with kidney disease autoantibodies against FH and the C3 convertase were although the of these in AAV pathogenesis is a the role of the complement system in AAV was as is not observed and the histologic renal are J.C. Falk R.J. Hu P. Xiao H. Pathogenesis of antineutrophil cytoplasmic autoantibody-associated small-vessel vasculitis.Annu Rev Pathol. 2013; 8: 139-160Crossref PubMed Scopus (200) Google Scholar,2Falk R.J. Jennette J.C. ANCA small-vessel vasculitis.J Am Soc Nephrol. 1997; 8: 314-322Crossref PubMed Google Scholar In the however, demonstrated that the levels of complement are significantly in active AAV compared with remission or control samples, that complement is during the active phase of the S.J. Yuan J. Chen M. et al.Circulating complement activation in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis.Kidney Int. 2012; 83: 129-137Abstract Full Text Full Text PDF PubMed Scopus (206) Google A. et alternative complement pathway in ANCA-associated further evidence and a Immunol. PubMed Scopus Google Scholar In our we also evidence of complement as the levels of C3, FH, FB, and sC5b-9 were significantly altered in with active disease compared with in we a between the levels of components of the C3 convertase FB, and and FH, which the activation of the AP during active AAV. the of sC5b-9 was significantly in active compared with remission samples, the activation of the pathway during the active phase of the In other in which the AP is has been shown that the regulatory of FH be by certain FH-related proteins and that the balance between these proteins the of complement activation and disease de Jorge E. et of complement factor H-related proteins modulates complement activation in A. 2013; PubMed Scopus Google M. A. B. et al.Factor H-related proteins determine Immunol. 2015; Full Text Full Text PDF PubMed Scopus Google de Jorge E. A. et al.Factor H by gene with Am Soc Nephrol. PubMed Scopus Google Scholar, F. Goicoechea de Jorge E. et the of factor H and the Immunol. 2021; PubMed Scopus Google Scholar, A. E. Goicoechea de Jorge E. et factor H-related protein 1 and factor H variants complement in Int. Full Text Full Text PDF PubMed Scopus Google Scholar, A. H. et CFHR1 and complement 2013; PubMed Scopus Google Scholar, H. et al.Circulating complement factor H-related proteins 1 and 5 with disease activity in Int. Full Text Full Text PDF PubMed Scopus Google Scholar the has been associated with protection to and and to C3 that the of FHR-1 complement by A. E. Goicoechea de Jorge E. et factor H-related protein 1 and factor H variants complement in Int. Full Text Full Text PDF PubMed Scopus Google H. et common with of CFHR1 and CFHR3, is associated with lower of PubMed Scopus Google B. J. A. et al.Factor H-related protein 1 disease susceptibility and prognosis in C3 Am Soc Nephrol. PubMed Scopus Google Scholar FHR-1, and levels have been associated with increased disease susceptibility and worse prognosis in various A. E. Goicoechea de Jorge E. et factor H-related protein 1 and factor H variants complement in Int. Full Text Full Text PDF PubMed Scopus Google H. et al.Circulating complement factor H-related proteins 1 and 5 with disease activity in Int. Full Text Full Text PDF PubMed Scopus Google B. J. A. et al.Factor H-related protein 1 disease susceptibility and prognosis in C3 Am Soc Nephrol. PubMed Scopus Google Scholar, L. F. et circulating levels of factor H-related protein are associated with PubMed Scopus Google Scholar, A. et complement factor H-related levels are associated with the Immunol. 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The of complement in AAV pathogenesis complement components therapeutic In avacopan, C5a receptor antagonist, is for the treatment of AAV and has been to be to the D.R.W. Merkel P.A. Schall T.J. et al.Avacopan for the treatment of ANCA-associated vasculitis.N Engl J Med. 2021; 384: 599-609Crossref PubMed Scopus (362) Google Scholar Our data also that the inhibition of components of the AP, as and FHR-1, be a therapeutic target in AAV. This is the of that target AP as or by J 2023; Google Scholar receiving from and and from has from for receiving and on a with and receiving from and and receiving from the other data are in the can be on to the of the the trial at the patients in the and of The also to de and the for Spanish for the of autoantibodies against the C3 is by de the and the of and are by the and and are by the de and the and respectively. This study has been also by de by the for and

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