Physiopathology of IgA Nephropathy

Center for Research on Inflammation - Inserm U1149

Paris Diderot Medical School & Bichat Hospital,

Inflamex Laboratory of Excellence

Renato C. Monteiro

ACTUALITÉS NEPHROLOGIQUES JEAN HAMBURGER, PARIS 2018

IgA Nephropathy (IgA-N)

Berger’s disease

• IgA-N is the most prevalent GN

• One of the first cause of ESRD

• Hematuria & proteinuria

• Absence of specific treatment

IgA1 complexes in the mesangium

Absence of symptoms

Haematuria very common

Deposits usually restricted to mesangium

Deposits usually pIgA1 Variable systemic involvement - HSP

Variable glomerular injury

Transplant recurrence

Features IgA nephropathy

IgA nephropathy

Is IgAN a single ‘disease’ ?

STEP 1 STEP 2

IgA deposit alone

Disease No disease?

IgA deposit + altered function

Data from autopsies

5-15% of general pop

Renal Biopsies

General population

IgA deposits 4-16%

IgAN ESRD

Hit 1: why?

Hit 2: why?

Hit 3: why?

Is IgAN a multi-hit disease?

< 0.5%

SUSCEPTIBILITY TO IgA NEPHROPATHY

Production of

‘pathogenic’ IgA

& complexes

Abnormal

Mucosal handling

of Ag?

‘Inflammatory

phenotype’

IgAN

Genetic influences

What leads to IgA1 deposits alone

without renal alterations?

What are the hits needed for disease

development?

J-chain

Polymeric IgA1 Secretory IgA

IgA1 IgA2

Secretory IgA

Polymeric IgA1

Kidney eluates from patient biopsies revealed abnormal IgA containing immune complexes

Negative charge of IgA1

From « Charge and size of mesangial IgA in IgA Nephropathy »

Monteiro, .., Berger, Lesavre. Kidney Int 1985

pIgA complexes

Galactose deficient IgA1 (Gd IgA1)

From Robert et al Trends Mol Med 2015

Suzuki J et al. J Am Soc Nephrol 2011

Gharavi A et al. Nat Genet 2011

Oxidative stress

(AOPP)

4-hit pathogenesis model of IgA Nephropathy

Why does Gd-pIgA1 deposit in the kidney ?

Is IgAN an IgA-immune complex disease?

Possible mechanisms of mesangial deposition

Gd-IgA1

Complex

formation

IgG-IgA1 IgA1

as antigen

IgA1-IgA1 self-

aggregation

Mesangial

Deposition

Soluble CD89

Complex

formation

B Cell antibody production IgA

Role of the CD89 receptor in IgAN

Mediators •TNF •IL-6 •IL-1

•Dual role in immunoregulation Inhibition vs activation

Cell effector functions •Clearance •Phagocytosis

Macrophages, PMN, Eosinophils Dendritic cells, Platelets, Kupffer cells

FcαRI (CD89)

leukocyte

IgA

sCD89

IgA-N

Launay et al J Exp Med 2000

Berthelot et al J Exp Med 2012

(Monteiro and Van De Winkel. Ann Rev Immunol, 2003)

Co IgAN MC RA AC

4

2

Units

Increased levels of Soluble CD89/IgA in IgA-N

Launay et al J Exp Med 2000

Units

Co Pat

IgGIgA

0

2

4

6

8

Pat

Soluble CD89 /IgA complexes in PEG precipitates:

Sandwich Elisa: A3 anti-FcαRI + Anti-IgA or IgG Ab

Soluble CD89 /IgA complexes: a marker for disease progression?

Vuong et al Kidney Int 2010

Sandwich Elisa: A3 anti-FcαRI + Anti-IgA Ab

Deposited in the

mesangium?

Human

Hinge

region

Fab

Fc

O-glycans

N-glycans

CD89 binding site

IgA1 IgA2

Two IgAs

Mouse

One IgA

IgA Fc receptor :

CD89

No CD89 homolog

THE CHALLENGE OF ANIMAL STUDIES IN IgA NEPHROPATHY

90% monomers in blood

IgA1 is highly glycosylated

80% polymers

Poorly glycosylated

Expression of human CD89 induces mouse IgA

deposits in mice

CD11b promotor FcRI EGF

Stop codon

Construct

83

96

73

Lines Non-Tg

Lt Tg

FcRI

CD11b Hematuria - +

Launay et al J Exp Med 2000

CD89Tg mice (human CD89)

IgA1KI mice (human IgA1)

x

IgA1KI-CD89Tg

Duchez et al. 2010 Launay et al. 2000

human

mouse

Berthelot et al. J Exp Med. 2012

IgA1KI-

CD89Tg

Wt

CD89 induces mesangial IgA1 deposition and renal dysfunction

10

20

30

Seru

m C

reati

nin

e (

mm

ol/l)

* 40 *

2

4

6

0 Pro

tein

/ C

reati

nin

e (

g/m

mo

l)

Hem

atu

ria (

x 1

0,0

00 R

BC

/ml)

**

10

0

20

30

40

50

IgA1 Knock-In/CD89 Tg:

an humanized mouse model for IgAN

Units

Co

Tg

0

5

10

IgAN is transferable by the serum

Serum FcRI Tg

IgAN

IgAN

Adoptive transfer

Rag2-/-

Rag2-/-

Hematuria +

Serum adsorbed by

anti-FcRI mAbs

Rag2-/-

No disease

Launay et al J Exp Med 2000; Berthelot et al 2012

Predictive power of circulating soluble CD89-IgA complexes:

the case of recurrent IgA nephropathy

Berthelot et al. Kidney Int 2015

R NR Ctr

% I

gA

-sC

D8

9 c

om

ple

xe

s

0

50

100

***

**

***

% I

gA

-sC

D8

9 c

om

ple

xe

s

PreTx M12-Tx R M6-post

Steroid pulse

** *

*

0

40

80

60

20

20 100 40 60 80

Specificity (%)

Se

ns

itiv

ity (

%)

0

20

100

40

60

80

AUC =0.76 [0.63 -

0.88] p=0.001

IgA-sCD89

complexes

Recurrence No

Recurrence

Anti-CD89 polyclonal Ab

From Robert et al Trends Mol Med 2015

IgA-CD89 complexes are nephrotoxics

FcRI/CD89 is shed from

blood monocytes

Receptor

interaction on

Mesangial cells

protease ?

?

Mechanims for mesangial IgA1 deposition:

• Mesangial IgA1 receptors ?

Absence of classical IgA receptors

(CD89, pIgR, ASGPR, Fcα/μR)

Fp: podocyte,

Mc: mesangial cell,

En: endothelial cell,

Ep: epithelial cell,

CL: capillary,

Bm: basement membrane

The CD71 (Transferrin Receptor) is a mesangial IgA1 receptor

Genes: Chromosome 3

Protein: TfR1

Expression: All mature cells but at low density

+++Red cell precursors

+++Mesangial cells from IgAN pat

+++Enterocytes from Coeliac pat

Ligands: Low density: Transferrin

High density : pIgA1

Physiological

Functions: Transferrin: Iron uptake

IgA1: erythropoeisis

Pathology: IgAN and Coeliac disease

Increased affinity for GDIgA1 from Lawrence et al Science 1999

Moura et al. J Exp Med, 2001, JASN 2004

Matysiak-Budnik et al J Exp Med 2008

Coullon et al Nat Med 2011

Upregulation of transferrin receptor

(CD71) in the mesangium of patients with IgAN and HSP

Normal

IgAN HSP

Haddad et al J Am Soc Nephrol 2003

1 : 0.5 µg/ml, 2 : 5 µg/ml, 3 : 50 µg/ml,

4 : 250 µg/ml,5 : 500 µg/ml, I : ionomycine

0.0 5.0x105

1.0x106

0.0

0.2

0.4

0.6

0.8

(F/F

0)-

1

t (ms)

1 2 3

4

pIgA1

0.0 5.0x105

1.0x106

0

1

2

3

4

(F/F

0)-

1

t (ms)

1 3 4 5 2 i

Fe-Tf

Differential signal by TfR ligands

Tamouza et al Kidney Int 2012

pIgA1 induces signal tranduction on mesangial cells

W: Wortmannin

R: Rapamycin Tamouza et al Kidney Int 2012

Phosphorylated Erk is associated with severe IgAN

Tamouza et al Kidney Int 2012

Phosphorylated ERK staining correlates with proteinuria

and blood pressure

Tamouza et al Kidney Int 2012

Fluorescence Intensity (log)

Cell

Nu

mb

er

desialylated &

degalactosylated

desialylated

Non treated

desialylated &

degalactosylated

+ sTfR1 IgG

Degalactosylation of IgA1 enhances binding to transferrin receptor

Moura et al J Am Soc Nephrol 2004

controls IgAN

Me

dia

n F

luo

resc

en

ce

In

ten

sit

y

p<0.001

0

2

4

6

8

10

12

Myeloma IgA1 Patient IgA

IgA1GD-soluble CD89 (with or w/o anti-IgA1 Ab ?)

Enhanced

TfR expression Proliferation IgA1 deposits

on mesangial TfR

TfR = transferrin receptor

Proposed role of IgA receptors in IgAN

An explanation for IgAN recurrence after transplantation ?

Cytokines

Chemokines

Mesangiopathy

Fibrosis Inflammation

pERK activation

What is the origin of the Gd-IgA1?

Is IgAN an enteric (mucosal) disease?

Kidneys

IgA-N

Skin

HSP

Dermatitis

Intestin

Celiac disease

Crohn

IgA

Other similarities between IgAN and celiac disease

IgA anti-gliadin Abs in both diseases (Coppo et al, J Am Soc Nephrol, 1992)

Overexpression of TfR in enterocytes of celiac patients (Matiziak et al J Exp Med 2008)

4% of IgAN patients develop CD (vs 1% in gen. population)

Decreased proteinuria in IgAN treated with gluten-free diet (Coppo et al, Clin Nephrol 1990)

Elevated intestinal permeability (Kovacs et al. Am J Nephrol, 1996)

Symptoms of mucosal atrophy (Fornasiery et al. Br Med J, 1987)

Protective effect of local action corticosteroids (Budesonide)

(Fellström et al. Lancet, 2017)

Altered intestinal functions

(from Fesus and Piacentini, Trends in Biochemical Sciences, 2002)

Hypothesis: TG2 mediates mesangial IgA1 deposits through TfR1

TG2 is overexpressed in IgAN (Ikee et al, 2007, Berthelot 2012)

Transglutaminase 2 (TG2): an enzyme linked to celiac disease

Human

TG2

IgAN patient Control

Mesangial TG2 overexpression in IgAN patients was confirmed

IgA1KI-CD89Tg IgA1KI WT

Mesangial TG2 overexpression in IgA1-CD89 Tg mice

Mouse

TG2

IgA1KI-CD89Tg

IgA1KI-CD89Tg-TGase2-/-

Decreased IgA1 deposits and hematuria

In IgA1KI-CD89Tg-TG2-/- mice

**

10

0

20

30

40

50

He

ma

turi

a (

x 1

0,0

00

RB

C/m

l)

TG2-/- IgA1KI-CD89Tg x

IgA1KI-CD89Tg-TG2-/-

Anti-human IgA Ab

Berthelot et al, J Exp Med, 2012

Working model for IgAN pathogenesis

Robert et al Trends Mol Med 2015

TG2 : an amplifier of IgA1-IC deposits

Gliadin interacts with soluble CD89

sCD89 binds to gliadin in a dose dependent way

OD

at 405nm

- Albumin Gliadin

CD89s-biot (µg/ml)

OD

at 405nm

0.8

0.6

0.4

0.2

0.0

1.5

1.0

0.5

0.0 0 1 2.5 5 7.5 10

Papista et al Kidney Int 2015

α1KI-CD89Tg α1KI 0

3

2

1

**

IgA

1 A

GA

/

IgA

concentr

ation x

10

-3

IgA anti-gliadin Abs

in α1KI-CD89Tg mice

Does gluten play a role in IgAN?

10

00

0 R

BC

/ m

l

60

40

20

0

** *

*

** ***

Mar

ked

/ G

lom

eru

lar

are

a

0.1

0.3

0

0.2

*** ***

***

*

** ***

Treatment with Gluten-free diet

≥ 3 generations 9 weeks 6 weeks 2 weeks α1KI-CD89Tg

IgA

Standard gluten diet

α1KI-CD89Tg: standard

gluten diet

Sacrifice

9 weeks

0 wk 3 wk 6 wk 10 wk 12 wk

Gluten-free diet

6 weeks Treatment 2 weeks

Gluten-free diet

Gluten-free diet

Early treatment by gluten-free diet prevents IgAN

HEMATURIA

New trials with gluten-free diet in IgAN: in patients

with good renal function and antibodies to gliadin!

From Aaron & Monteiro J Clin & Cell Immunol in press

GDIgA1-IgG

TG2

TfR1

(CD71)

GDIgA1-sCD89 GDIgA1-gliadin

Hit 2: Aberrant IgA1

Hit 3 : IgA1-CIC formation

GDIgA1

Hit 4 : Mesangial IgA1-CIC-CD71 in situ complex formation

Hit 1: Genetic susceptibility

GDIgA1-CIC

20,612 individuals of European and East Asian ancestry.

Six new genome-wide significant associations, four in ITGAM-

ITGAX, VAV3 and CARD9 and two new independent signals at

HLA-DQB1 and DEFA.

Most loci associated with risk of inflammatory bowel disease

(IBD), maintenance of the intestinal epithelial barrier or

response to mucosal pathogens.

Genetic risk correlates strongly with variation in local

pathogens, suggesting a possible role for host–intestinal

pathogen interactions in shaping the genetics of IgAN.

Kiryluk, et al . Nature Genetics 2014

Genome-wide association study (GWAS) of IgAN

GUT – KIDNEY AXIS

Question: Role of microbiota dysbiosis in IgAN?

Rationale: 1. Altered microbiota (De Angelis et al PloS One 2014), but studied in other CKD

2. Intestinal immunity gene linkage in IgAN patients (by GWAS Kiryluk et al. Nat Genet 2014)

3. Benefits of Budesonide, a corticosteroid with local intestinal action (Fellstrom et al Lancet 2017)

CD89-

Hypothesis:

Microbiota dysbiosis

induces dimeric Gd-IgA1

Intestinal dysbiosis in Italien IgAN patients (vs controls)

De Angelis et al PLoS One 2014

J Immunol. 2014 Jul 1;193(1):317-26.

PLoS One. 2014 Sep 29;9(9):e108723.

Streptococcus and IgAN

But no evidence for commensals

Putative role of genetic factors, food, intestinal microbiota and MALT in the pathogenesis of IgAN

ITGAM

ITGAX,

VAV3,

CARD9

HLADQ

B1 and

DEFA

Adapted from Levy et al Nat Rev Immunol 2017

Gluten,

other food &

evironmental

factors

Induction of

nephrotoxic

Gd IgA1 &

Abs Formation

of sCD89-

IgA1

complexes

IgA1

depo

sits

Circulation

Acknowledgments

Christina Papista

Laureline Berthelot

Gabriella Lauriero

Jonathan Chemouny

James Gleeson

Sanae Ben Mkaddem

Martin Flamant

Eric Daugas

François Vrtovsnik

CRI - INSERM U1149

COLLABORATORS

France

Michel Cogné

Limoges

Thomas Robert

Fatouma Touré

Philippe Rieu

Reims

Thank you for your attention !

“T” structure of IgA1

Binding site

to Fc receptor

in Cα2-Cα3

Hinge region:

Heavily

O-glycosilated

6% of Mr

Long hinge region

Jean Berger et al

Dépôts intercapillaires d’IgA-IgG.

J Urol Nephrol (Paris). Sept 1968; 74:694-5.

Berger’s disease or IgA nephropathy

1968 1972-3

Habib & Levy: Berger’s disease

Neglected disease French food & environnement?

1975

Severe disease

Recurrence

after Tx

Main contributions of Prof. Jean Berger

Description

by J. Berger

in Paris Description

by other groups:

- Netherlands (Maintz and coll)

- USA (West & Burkholder)

- UK (Davies and coll)

- Australia (Woodroffe & Clarkson)

- Japan (Ueda and coll)

1985

Elution’studies

Negative Charge

Polymeric IgA

Immune complexes