C3 glomerulopathy and monoclonal gammopathy: Role of monoclonal Ig - PowerPoint PPT Presentation

C3 glomerulopathy and monoclonal gammopathy: Role of monoclonal Ig on complement dysregulation 4th meeting of IKMG Dr Sophie Chauvet Department of Nephrology, European Hospital Georges Pompidou, APHP, Paris INSERM 1138, Research Team « Complement and Disease », Paris (Dr Frémeaux-Bacchi) In collaboration with Pr Frank Bridoux, Poitiers

No Conflict of Interest

Complement system Alternative pathway Classical pathway Lectin pathway hydrolysis Immun Complexes mannoses MBL C3(H 2 O) C1q C3 C3 convertase Alternative C3 convertase C3bBb C4bC2a C3a C3b C5 convertase C3b, iC3b C3a, C5a C5b9 C5b C6 C7 C8 C9 Chemotaxis Opsonisation Activation and Lysis

Complement alternative pathway is physiologically activated and amplified on activating surface Spontaneous Hydrolyse hydrolysis C3 spontanée C3H2O C3a B D C3b B C3 C3H2O Auto C5a amplifica-on C5 conv C3 conv B Bb B b B Mg ++ D C3b b C3b 3 C C3b MAC Activating surface

Complement alternative pathway regulation in fluid phase and on host cell surface Hydrolyse C3 spontanée Inactivating cleavage of C3b in iC3b (cofactor activity) C3 convertase FH C3H2O dissociation B D C3b B FH C3 C3H2O Auto amplifica-on FH, FI C3 convertase C5 convertase CD46, CR1 B Bb B Mg ++ Bb D C3b C3b C3b C3b MAC FH inhibition of C3convertase Non activating surface formation

Overactivation of the AP and kidney diseases Atypical HUS C3 glomerulopathy = acute Thrombotic Microangiopathy Chronic kidney disease with acute renal failure <0.2/Million/an <0.6/Millions/an Target of complement attack= Target of complement attack= endothelial cell mesangial cell C5a C5a Bb Bb Bb Bb C3b C3b C3b C3b F.Fakhouri et al, Lancet 2017 Smith et al, Nat Rev Nephrol 2019

Complement abnormalities are distinct in aHUS and C3G Complement abnormalities aHUS C3G Genetic variant 60-70% 20% Loss of function of regulators (FH, FI, CD46) 75% 90% Gain of function of C3 convertase (C3, FB) 25% 10% Acquired abnormalities 10% 50-80% Gain of function of convertase - 40-65% (C3/C5 NeF, anti-C3b or anti-FB antibodies) Loss of function of FH (Anti-FH antibody) 10% 15% Frémeaux-Bacchi et al, CJASN 2013 ↓ C3 level (30%) ↓C3 level (40-60%) Dragon Durey MA et al, Nat Rev Nephrol 2016 Marinozzi MC et al, KI 2017 ↑sC5b-9 (65%) Blanc et al. J Immunol 2016

MIg and C3G/aHUS occurence: Epidemiological data Atypical HUS C3 glomerulopathy 146 TMA between 2000 and 2016 36 patients with C3G associated with MIg: 20 patients with MIg 65% of patients aged over 50 21% of patients aged over 50 Ravindran et al. Kidney Int 2018 Ravindran et al. Kidney Int 2017 22 patients with MIg and aHUS 60 patients with C3G associated with MIg 29% of patients with aHUS age over 50 65% of patients aged over 50 Dr Frémeaux Bacchi, aHUS french registry, unpubished data Chauvet et al. Blood 2017

C3G and MIg-C3G have distinct complement profiles complement biomarkers are distinct Target of anti-complement Abs are distinct Variations in complement genes are less frequent Chauvet et al. Frontiers Immunol 2018

PIGNMID and monoclonal lambda LC with anti-FH antibody activity (Jokiranta et al. J Immunol 1999) Part 1: MIg=auto antibody? Working hypothesis Target= C3bBb, C3b, FB, FH, FI, CR1….? Hydrolyse C3 spontanée C3H2O B D C3b B C3 C3H2O Auto amplifica-on B Bb B Mg ++ D C3b C3b C3b

Comparision of HC and LC isotype specificy Anti complement protein Ab pt MIg spécificity Heavy chain Light chain G40 IgA k Anti FI a k G38 IgG2 k Anti FH g 2 k G51 IgA k Anti FH a k G7 IgG1 l Anti FH g 3 k and l G22 IgG4 k Anti FH g 2 k and l G8 IgG4 l Anti CR1 k and l g 1 G13 IgG1 k Anti CR1 g 1 k and l G15 IgG1 l Anti CR1 k and l g 1, g 4 G35 IgG3k Anti CR1 g 1 k and l G46 IgG2 k Anti CR1 g 1 k and l G56 IgG1 k Anti FI g 2 k and l G20 IgG2 l Anti FH/CR1 g 1 anti FH and g 1 anti FH k and l g 2 anti FH and g 1 anti k and l G32 IgG4 l anti FH/anti CR1 CR1

MIg acts as a anti complement protein Ab in 3/13 tested samples Anti complement protein Ab pt MIg spécificity Heavy chain Light chain G40 IgA k Anti FI a k G38 IgG2 k Anti FH g 2 k G51 IgA k Anti FH a k G7 IgG1 l Anti FH g 3 k and l G22 IgG4 k Anti FH g 2 k and l G8 IgG4 l Anti CR1 k and l g 1 G13 IgG1 k Anti CR1 g 1 k and l G15 IgG1 l Anti CR1 k and l g 1, g 4 G35 IgG3k Anti CR1 g 1 k and l G46 IgG2 k Anti CR1 g 1 k and l G56 IgG1 k Anti FI g 2 k and l G20 IgG2 l Anti FH/CR1 g 1 anti FH and g 1 anti FH k and l g 2 anti FH and g 1 anti k and l G32 IgG4 l anti FH/anti CR1 CR1

Isotype specificity of Abs and MIg are different in 75% of tested samples Anti complement protein Ab pt MIg spécificity Heavy chain Light chain G40 IgA k Anti FI a k G38 IgG2 k Anti FH g 2 k G51 IgA k Anti FH a k G7 IgG1 l Anti FH g 3 k and l G22 IgG4 k Anti FH g 2 k and l G8 IgG4 l Anti CR1 k and l g 1 G13 IgG1 k Anti CR1 g 1 k and l G15 IgG1 l Anti CR1 k and l g 1, g 4 G35 IgG3k Anti CR1 g 1 k and l G46 IgG2 k Anti CR1 g 1 k and l G56 IgG1 k Anti FI g 2 k and l G20 IgG2 l Anti FH/CR1 g 1 anti FH and g 1 anti FH k and l g 2 anti FH and g 1 anti k and l G32 IgG4 l anti FH/anti CR1 CR1

Part 2 Pecularities of MIg: -Abnormalities of glycosilation Working hypothesis -mutation in VD and CD -capacity to form macromolecular complexes Monoclonal Ig C3b C3b B Bb C3b C3b D Modification of complement protein binding sites on Ig that could enhance AP activation. Cogné M et al. Blood 1992

Total purified Ig are able to enhance C3 convertase activity C3+B+D G12 IgG-HD In fluid phase +purified IgG FB (ng) 50 25 12.5 0 50 25 12.5 0 α 45min (37°C) α ’ β C3+FB+FD' Study of C3 cleavage in C3b On immobilized Ig (WB) IgG'of'pa/ents'with' normal'and'low'C3'level' Purified IgG 12/33 patients Ig « activators in fluid phase » 13/34 patients Ig « activators as platform » ** NS NS 1.5 ** * 1.5 NS ** *** 1.0 1.0 α '/beta ratio α '/beta ratio m+2SD m+2SD 0.5 0.5 0.0 0.0 Ig-HD MIg-C3GN MIg w/o KD C3NeF Ig-HD MIg-C3GN MIg w/o KD

The capacity of Ig to enhance C3 convertase activity but not anti- complement antibodies activity drive complement biomarkers n=11 n=29

Role of the monoclonal Ig in C3 convertase overactivation Purification of monoclonal component by chromatography Polyclonal Ig Monoclonal Ig Different elution fractions G20 3 Ig monoclonale Polyclonal(Ig( Monoclonal(Ig( Ig polyclonales α ' /beta ratio 0(((((25((((((50( 0(((((25((((((50( 2 FB#(ng)# α" α" 1 α � " 0 G12 G20 G40 G56 β" β" C3-Activating IgG Non C3-activating IgG

Impact of hematological response on C3 convertase activity in vitro and complement biomarkers C3 level significantly increased in patients who Capacity of total Ig to enhance C3 reached hematological response convertase is decresad * 2.0 G5 1.5 α '/beta ratio G37 G53 1.0 0.5 0.0 at diagnosis after HR

Impact of Hematological response on renal outcomes Chauvet et al. Blood 2017

Mechanisms of TMA in the setting of MIg are heterogeneous TMA and MIg POEMS Post infectious HUS cryoglobulinemia Drugs* * Proteasome inhibitors Undetermined? ADAMTS13 deficiency Bone marrow Tx Complement overactivation? Secondary HUS TTP aHUS Other.. Is MIg the main cause, a second hit or an aggravating factor in TMA??

Causes of TMA in the setting of MIg are heterogeneous 146 patients with TMA 20 patients with MIg What is the role of the MIg? What is the mechanism of endothelial damage? Ravindran et al. Kidney Int 2017

HUS and MIg: a complement mediated disease? IgA - 45 years -purpura and severe distal angiopathy -anemia, thrombocytopenia and acute renal failure Diagnosis of Atypical HUS in the setting of Monoclonal IgA kappa No genetic variant in complement genes but positive for anti-FH IgA Rigothier et al. AJKD 2015

Role of the monoclonal IgA on complement activation on cell surface activated HUVEC 80 C3 60 Count 40 20 0 0 1 2 3 4 10 10 10 10 10 C3 deposition Increase of complement activation on endothelial in presence of patient sera. Rigothier et al. AJKD 2015

C3 Glomerulopathy and atypical HUS associated with MIg Summary MIg-C3G MIg-aHUS ✓ ✓ Epidemiological association 13 times more frequent 5-6 times more frequent ✓ ✓ Clinical arguments More severe disease More severe disease ✓ ✘ Therapeutic arguments Improvement with HR ✓ ✓ Complement mediated disease ✓ ✘ Role of the MIg in complement AP overactivation To determin

Acknowledgments Research team in Cordelier Research Center French registry of C3G/aHUS Dr Véronique Frémeaux-Bacchi Dr Marie-Agnès Dragon Durey Dr Lubka Roumenina Manon Martins Paula Vieira-Martins Pauline Bordereau Dr Marie Daugan Tania Robe Rybkine Pr Bridoux, Pr Touchard , CHU Poitiers, France Pr Aucouturier, Immunologie Saint Antoine