Complement Regulatory Proteins on the Cornea and in the Aqueous Humor

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• Nalini S. Bora, Ph.D.
• Bernice Y. Jones Professor of Ophthalmology
• Vice Chair for Research
• Director of Research
• Department of Ophthalmology, Jones Eye Institute
• Professor of Microbiology and Immunology
• University of Arkansas for Medical Sciences
• Little Rock, AR

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Finding a Cure for Ocular Diseases

• Autoimmune Uveitis
• Keratitis
• Glaucoma
• Diabetic Retinopathy
• Age-related Macular Degeneration
• Uveal Melanoma

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• Complement
• and
• Ocular Diseases

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Classical pathway
Alternative Pathway
Lectin Pathway
MBL
MASP-1 MASP-2
CFB
C1
C1INH
C4
CFHCFI
C4, C2
DAF ,MCP CR1, Crry
C4bp
C3 Convertase
C4b2a
C3 Convertase
C5 Convertase (C4b2a3b, C3bBb3b)
CD59
S Protein Clusterin
MAC
Cell Lysis
Bora et al., Seminars in Immunopathol, 2008
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Traditional Functions of Complement

• Lysis of foreign particles (cell, bacteria and
  viruses)
• Clearance of potentially damaging particles from
  circulation
• - Immune complexes
• - Apoptotic cells (Autoimmunity by
  exposing neo-
• antigens)
• Generation of biologically active molecules
• - Mediate opsonization,
• - Promote and perpetuate immune and
  inflammatory
• reactions

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Non-Traditional Functions of Complement

• Antigen specific immune responses
• - Antigen processing and presentation
• - T cell proliferation and differentiation
• - B cell activation
• - Induction of tolerance (T regulatory
• cells)

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Sohn and Bora et al. (Nature Medicine, Vol.  9,
206 212, 2003)
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Complement Regulatory Proteins
Lectin
Classical
Alternative
C4bp
DAF MCPCR1Crry
C1INH
Factor H Factor I
C3b
S Protein Clusterin
CD59
Membrane Attack Complex (C5b-9)
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• Complement
• in
• Ocular Protection

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CRegs are Differentially Expressed in Normal
Human Eye
IOVS, 1993 343579-3584
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• Expression levels of MCP, DAF and CD59 are
  several fold higher on corneal and uveal cells
  than most blood cells.
• Our studies of biosynthetic labelling with in
  vitro cultured human ciliary epithelium cells
  (ODMC1-2) and 35S-methionine suggest that these
  cells synthesize MCP, DAF and CD59 protein.
• Thus, CRegs present in the eye are not passively
  deposited.

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CRegs are Differentially Expressed in Normal
Human Eye
IOVS, 1993 343579-3584
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Soluble CRegs are Present in Normal Human Aqueous
Humor
(IOVS, 200041 4195-4202)
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Functionally Active Complement System is Present
in Normal Eye
IOVS, 2000413492-3502
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Effect of CVF on Complement Hemolytic Activity
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Cobra Venom Factor (CVF)
CVF Factor B C3bBb (factor H
and I resistant) (C3b)

Unrestricted AP activation
Complement
depletion
C3
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Complement System is Continuously Activated in
the Normal Eye
C3 Split Products
MAC
IOVS, 2000413492-3502
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CRegs are Present in the Normal Eye
IOVS, 2000413492-3502
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Intraocular CRegs are Functionally Active
IOVS, 2000413492-3502
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• Complement
• and
• Age-related Macular Degeneration
  

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Age-related Macular Degeneration

• AMD is the leading cause of legal blindness in
  individuals over age 55.
• According to WHO and NEI approximately 2 million
  people in USA alone have some form of AMD.
• AMD is a significant public health concern
  worldwide.

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• Non-exudative (dry-type)
• 90 of AMD cases
• Small yellowish deposits called drusen start to
  accumulate beneath the macula
• It does not usually cause total loss of central
  vision
• It can often progress to the more severe wet
  form.
• Exudative (wet-type)
• 10 of AMD cases
• 90 of severe central vision loss
• Choroidal neo-vascularization (CNV) cause wet AMD
• Leads to sudden loss of central vision

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Choroidal Neovascularization (CNV)

• Major cause of severe vision loss in AMD is
  pathological neovascularization under the retina
  producing a lesion called choroidal
  neovascularization.
• CNV is a complex pathogenic process in which new
  blood vessels are generated from pre-existing
  choroidal vessels.
• Common symptom of wet AMD.

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Current Management/Treatment

• Antioxidant supplements reduce the damage
  caused by oxidative stress in the macula.
• Lifestyle and dietary modifications
• - Quit smoking
• - Decrease fat intake
• - Maintain healthy weight
• - Increase intake of green leafy vegetables,
  
• whole grains, fish, nuts

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Current Management/Treatment

• Injection of antiangiogenic agents directly into
  the vitreous
• - Macugen - mRNA aptamer and VEGF antagonist.
• - Lucentis (Genentech) - a humanized mAb
  fragment that
• inhibits VEGF, administered monthly.
• - Avastin (Genentech) - mAb to VEGF used as
  anticancer
• agent

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Current Management/Treatment

• Photodynamic therapy (PDT) light sensitive dye
  (Visudyne, Novartis) injected intravenously
  concentrates in new vessels, activated by laser
  beam (689 nm) focused over the macula, causes
  localized choroidal neovascular thrombosis.
• Argon laser photocoagulation used rarely since
  it can create large retinal scars with permanent
  loss of vision.
• Vireoretinal surgery surgical extraction of
  neovascular complex

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Current Management/Treatment

• Disadvantages
• - Repeated injections or treatments
• - Cost intensive
• - Eye infection
• - Retinal detachment
• - Ocular hemorrhage
• - Increased intra-ocular pressure
• - Eye pain

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Murine model of Laser-induced CNV
Animals C57BL/6 mice (6-8 wk
old) Animal model of CNV Rupture Bruchs
membrane with laser photocoagulation using
Krypton red laser (50 µm spot size 0.05s
duration 260 mW).
(http//www.engin.brown.edu/courses/en122/images/U
tahRetina.jpg)
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Macula is an oval spot near the center of the
retina. Diameter 5 mm, contains ganglion
cells Fovea is in the center of Macula,
contains largest concentration of cone
cells. Responsible for central high resolution
vision allowing a person to see fine details.
(http//www.engin.brown.edu/courses/en122/images/U
tahRetina.jpg)
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Krypton LASER
DAY1
DAY3
DAY5
DAY7
Green New vessels Red Elastin stain
(Exposed Bruchs membrane)
LSCM
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Laser Induced Choroidal Neovascularization (CNV)

• Animals perfused with PBS containing FITC-dextran
  (molecular mass 2x106) and sacrificed.
• RPE-choroid-scleral flat mounts prepared.
• Incidence and the size of CNV determined by
  confocal microscopy.
• The CNV complex size graded by morphometric
  analysis of the images obtained from confocal
  microscopy using Image Pro 5.0 software.

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Risk Factors for Wet AMD
Advanced age
Genetic Caucasians Gender
Genetic Polymorphism
(CFH Y402H)
Environmental Smoking, Chronic alcohol
consumption
AMD
Oxidative stress
Inflammation Complement System
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Lectin Pathway
Classical Pathway
Alternative Pathway
Immune complexes C1 C2 C4
Carbohydrates MBL MASP1 MASP2 C2 C4
C3b Factor B Factor D
C3 Convertase
X
CFH
X
C3
MCP, DAF, Crry
X
C3b
C5 Convertase
C5
C5b
CD59
X
C6 C7 C8 C9
X
MAC (C5b-9)
Cell Activation, Proliferation, Migration and
Death
Current Immunology Reviews, 2010
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Complement and C3 are Required for the
Development of Laser-induced CNV
J of Immunology, 174 491-497, 2005
Complement Depleted
Complement Sufficient
C3 -/- Mice
WT Control
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C5 is Required for the Development of
Laser-induced CNV
Bora et al., J of Immunology, 1771872-1878, 2006
Wild-Type
C5 -/-
Reconstituted C5 -/-
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Induction of Growth Factors Requires the Presence
of C and MAC
(Bora et al., J of Immunology, 174 491-497,
2005)
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Induction of Growth Factors Requires the Presence
of C and MAC
(Bora et al., J of Immunology, 174 491-497,
2005)
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Classical and/or Lectin Pathways are Not
Essential for the Development
of Laser-induced CNV
WT Control
C4 -/- mice

• J of Immunology, 1771872-1878, 2006
  

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Classical Pathway is Not Essential for the
Development of
Laser-induced CNV
Control siRNA
C1q siRNA (50 mg)
PBS
J of Immunology, 1771872-1878, 2006

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Factor B-Dependent Alternative Pathway is
Essential for the
Development of Laser-Induced CNV
Factor B siRNA (50 mg)
Control siRNA
PBS
Bora et al., J of Immunology, 1771872-1878, 2006

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Factor H and Factor B during Laser-induced CNV
Protein
mRNA
J of Immunology, 1771872-1878, 2006
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Activation of Alternative Pathway Leads to
Increased MAC Deposition
During Laser-Induced CNV
Bora et al., J of Immunology, 1771872-1878, 2006

Control siRNA
Factor B siRNA
Day 3
Day 3
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A
C
CD59a
CD59a
19 kDa
204 bp
42 kDa
?-actin
?-actin
746 bp
N 1 3 5 7
N 1 3 5
7
Day Post-Laser
Day Post-Laser
B
D
CD59 (both mRNA and protein) was down-regulated
during laser-induced CNV.
J of Immunology, 1781783-1790, 2007
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Laser
Complement Activation
C5b
C6
C7
C9
rsCD59
C8
In absence of MAC formation the release of growth
factors- VEGF, ?-FGF and TGF- ? is reduced. This
leads to inhibition of CNV
No C9 Polymerization
C9 Polymerization
Increased MAC formation leads to the release of
growth factors - VEGF, ?-FGF and TGF- ? that
results in the development of CNV
X
Cell Membrane
Extracellular Doman
GPI Anchor
Cytoplasm
MAC
Membrane-bound CD59
Bora et al., Seminars in Immunopathol, 2008
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CD59 -/- mice developed CNV complex early in the
disease process
A
B
C
D
G
F
E
H

J of Immunology, 1781783-1790, 2007
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PBS
rsCD59-Fc
Intra-peritoneal
(100 mg)
Intra-vitreal
(50 mg)
Administration of rsCD59-Fc inhibited the
development of CNV complex.
J of Immunology,
1781783-1790, 2007
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rsCD59 injected
PBS injected
716 bp 512 bp
716 bp 512 bp
VEGF
VEGF
684 bp
TGF-ß2
TGF-ß2
684 bp
298 bp
ß-FGF
ß-FGF
298 bp
ß-actin
ß-actin
746 bp
746 bp
N 1 3 5
7
N 1 3 5 7
Day Post-Laser
Day Post-Laser
Hatched Bar rsCD59-Fc Solid Bar PBS
Hatched Bar rsCD59-Fc Solid Bar PBS
J of Immunology, 1781783-1790, 2007
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• Conclusions (Part 1)
• The presence of complement system is essential
  for the development of ocular angiogenesis
  (choroidal neovascularization, CNV).
• Complement components C3 is crucial for the
  development of laser-induced CNV.
• MAC formation via the activation of alternative
  pathway is essential for the release of growth
  factors that drive the development of
  laser-induced CNV.

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Implications

Control of complement activation at the level of
MAC formation has important clinical implications
for AMD. For example, complement inhibitors
could be administered to the eyes with AMD to
inhibit the inflammatory response and may
provide a new therapeutic alternative to current
treatment.
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Acknowledgements
Collaborators Puran Bora Paul Morgan, Cardiff,
United Kingdom Claire Harris, Cardiff, United
Kingdom Stephen Taylor, Queensland, Australia

• 
  Purushottam
  Jha
• John Sohn
• Bharati Matta
• Valeriy Lyzogubov
• Ruslana Tytarenko
• Jose M. Cruz
• Scott Simpson
• Hiroki Nishihori
• Yali Wang
• Saori Nishihori
• Bala Manickam
• Juan Liu

NIH/NEI Jones Eye Institute Arkansas
Biosciences Institute
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Thank You!