Complement Targeted Therapy for Myasthenia Gravis

Premkumar Christadoss, M.D.

Department of Microbiology and ImmunologyUniversity of Texas Medical Branch

301 University Blvd.Galveston, Texas, USA

Erdem Tüzün, M.D.

Department of NeurologyIstanbul Faculty of Medicine, Istanbul University

Istanbul, Turkey

Complement system is involved inComplement system is involved in

Myasthenia Gravis AChR-Ab +MuSK-Ab + ?Seronegative ?

Experimental Autoimmune Myasthenia Gravis (EAMG)

Active ImmunizationPassive Transfer

Ocular EAMG model

1° immunization:1° immunization: 20 20g TAChR/CFA per mouse s.c.g TAChR/CFA per mouse s.c.

2° immunization:2° immunization: 20 20g TAChR/CFA per mouse s.c.g TAChR/CFA per mouse s.c.

28 days28 days

28 days28 days

EAMGEAMG

AChR SourceAChR Source

Experimental Autoimmune Myasthenia Gravis

Grade 0:Grade 0: NormalNormal

Grade 1:Grade 1: Muscle weakness following exerciseMuscle weakness following exercise

Grade 2:Grade 2: Grade 1 symptoms at restGrade 1 symptoms at rest

Grade 3:Grade 3: MoribundMoribund

Ocular muscles are rarely involved in this model

Immunopathogenesis of EAMGImmunopathogenesis of EAMG

AChR

NK?

APC

B cell

IL-2IFN-IL

IL-1, IL-12

T helper

AChR-specific memory T cell

Proliferation and DifferentiationIL-10, IFN-, TNF-, IL-6,

IL-12, IL-2, IL-18

AChR-specific memory B cells

C’ C’

AChR-Ab producing cells

Complement pathway activation

Damage to the neuromuscular junction

CD40L/CD40

Class II

Peptide(146-162)

CD4

TCR

B7CD 28

aTAChR in CFA-BTx TAChR in CFA-C3

CFA-BTx CFA-C3

Complement on NMJ

normal partial complete

Immunization with human-AChR -subunit induces ocular symptoms

Complement-antibody-clinical severity correlations

C3 levels correlate with clinical severity of AChR-Ab-positive generalized MG patients with no treatment

(Liu A, Muscle Nerve, 2009)

MG patients with high AChR-Ab levels have lower C3 and C4concentrations suggesting increased complement consumption

(Romi F, J Neuroimmunol, 2005)

Ser

um

im

mu

ne

com

ple

x (O

D)

Grip strength (gr)

TAChR-immunized B6 mice

Cli

nic

al

gra

des

Serum immune complex (OD)

TAChR-immunized RIIIS/J mice

C1 C4b C2a

C3 C5 MAC

CLASSICAL PATHWAY

MBL PATHWAY

ALTERNATIVE PATHWAY

(C5bC9)

C3b Bb C3bBb

MBLMASP1MASP2

COMPLEMENT PATHWAYS

Which pathway is involved in EAMG?

D

COMMON PATHWAY

Complement KO mice are resistant to EAMG

0

20

40

60

80

100

120

140

WT C3 KO C4 KO C5deficient

C6 KO C5aR KO MBL KO

EAM

G in

cide

nce

%

B6imm.

B6imm.

B6imm.

B6imm.

B6imm.

Lewis rats

Passive

C1qC1qrs C4C4b C2a

C3C3 C5C5 MAC

CLASSICAL PATHWAY

MBL PATHWAY

ALTERNATIVE PATHWAY

(C5bC6C6C7C8C9)

C3b Bb C3bBb

MBLMASP1MASP2

COMPLEMENT PATHWAYS

C5a

??

D

COMMON PATHWAY

Complement targeted therapy for EAMG

Lewis rats

Passive

Lewis rats

Passive

Lewis rats

Passive

Lewis rats

Passive

Wistar rats

Passive

0

20

40

60

80

100

Control sCR1 Crry-Ig anti-C5 C5-bindingprotein

anti-C6

EAMG

incid

ence

%

Anti-C5 complement monoclonal antibodies

Eculizumab paroxysmal nocturnal

hemoglobinuria

Pexelizumab coronary heart disease

! Risk for infections !

Can EAMG be treated by classical pathway inhibition?

C4+/+

C4+/-

C4-/-

Tuzun E. et al, 2003

EAMG incidence Anti-AChR IgG

C4+/+ C4-/-

C3

IgG

RED -BTx bindingGREEN C3, or IgG deposits

C4 KO mice display normal immune functions

Normal cytokine production Normal lymphocyte proliferation Normal germinal center in spleenNormal lymph node cell counts

Intact alternative pathway for host defense against microorganisms

Anti-C1q Prevents EAMG

200 μgDay -7

200 μgDay -4

100 μgDay 0

100 μg2 times a week – 5 weeks

Tuzun E. et al., 2006

NM

J d

epo

sits

Clin

ical

inci

den

ce %

pg

/ml

IL-6

B6 mice

AChR imm. AChR imm.

Anti-C1q Treatment Prevents EAMG (Tuzun E. et al., 2007)

Gri

p s

tren

gth

sC

linic

al g

rad

esEAMG mice treated with 10g anti-C1q 2 times a week-4 weeks

Anti-C1q enhances serum immune complex levels

Anti-C1q induces glomerular C3 and IgG deposits

Complement targeted therapy for EAMG

0

20

40

60

80

100

Control anti-C1q sCR1 Crry-Ig anti-C5 C5-bindingprotein

anti-C6

EAM

G in

cide

nce

%

B6imm.

Lewis rats

Passive

Lewis rats

Passive

Lewis rats

Passive

Lewis rats

Passive

Wistar rats

Passive

Other targets, double hit method?

Prevention – 0.01 mg IL-1ra

Reduced serum C3 levels

0.01 mg IL-1ra placebo

Prevention – 0.5 mg anti-IL-6

Reduced serum C1q levels

0.5 mg anti-IL-6 PBS

Reduced serum complement Reduced serum complement

levelslevels

CD59 KO

FcRIII KOReduced NMJ complement depositsReduced NMJ complement deposits

IFN- KO

IL-5 KO

ICOS KO

EAMG-resistant KO strainsEAMG-resistant KO strains

Non-AChR Ab mediated MG, alternative pathway

Leite et al., 2008 complement activating IgG1 in anti-MuSK+ and seronegative MG

Shiraishi et al., 2005 2 of 8 anti-MuSK+ patients display NMJ C3 deposits

1

1.5

2

2.5

1 1.5 2 2.5 3anti-MuSK Ab (nmol/l)

iC3

b (

OD

)

R=0.44p=0.03

FBb

**

*;p=0.045

THANKS!

UTMBUTMBPremkumar ChristadossSaini ShamsherHuan YangBenjamin ScottElzbieta GoluszkoJing Li

Istanbul UniversityIstanbul UniversityVuslat YılmazGüher Saruhan-DireskeneliFeza DeymeerPiraye OflazerYeşim Parman