Dale and Betty Bumpers
Vaccine Research Center
National Institute of Allergy and Infectious Diseases
National Institutes of Health
Department of Health and Human Services
HIV Vaccine Enterprise: Progress in Basic Research
International AIDS Vaccine Meeting
2010
Atlanta, GA
Gary J. Nabel M.D., Ph.D.
Vaccine Research Center
NIAID, NIH
Sept. 28, 2010
Acquisition vs.Viral Load:
Independent Parameters
Vaccination to Control Viremia
Vaccination to Prevent Acquisition
X
X
X
Key Issues in AIDS Vaccine Development
1. Blocking infection vs. controlling viral load
2. Paradigm for HIV vaccine development differs
from all licensed vaccine: basic science drives
progress in rational vaccine design.
3. Basic science is done in clinical trials
Viral Load
How Might a Vaccine Prevent Infection?
Scenario 1: No Immune Protection
1
2
3
4
Time (months
5
Viral Load
How Might a Vaccine Prevent Infection?
Scenario 2: Broadly Neutralizing Antibodies
1
2
3
4
Time (months
5
Viral Load
How Might a Vaccine Prevent Infection?
Scenario 3: Highly Effective T Cell Vaccine
1
CD8 CTL
-
2
3
4
Time (months
5
Viral Load
How Might a Vaccine Prevent Infection?
Scenario 4: Partially Effective nAb Response
1
2
3
4
Time (months
5
CD8 CTL
CD8 CTL
Viral Load
How Might a Vaccine Prevent Infection?
Scenario 5: Partially Effective nAb and T Cells
1
2
3
4
Time (months
5
Basic Science and AIDS Vaccine Development
1. T cell vaccine vectors and concepts
2. Advances in B cell immunogen design
3. Modeling of HIV infection in the non-human
primate
Basic Science and AIDS Vaccine Development
1. T cell vaccine vectors and concepts
2. Advances in B cell immunogen design
3. Modeling of HIV infection in the non-human
primate
Next Generation T Cell Vaccines
New Vectors and Combinations
–
–
–
–
–
DNA prime + adenoviral vector boost
Heterologous rAd vector prime/boost
LCMV prime/boost
Chimp and simian Ads
Integrase-deficient lentiviral vectors
simian Ads
Human rAds
rAd5
rAd26
rAd28
rAd35
rAd41
Sim rAd ch rAd
non Ads
rLCMV rLVV
Next Generation T Cell Vaccines
New Vectors and Combinations
–
–
–
–
–
DNA prime + adenoviral vector boost
Heterologous rAd vector prime/boost
LCMV prime/boost
Chimp and simian Ads
Integrase-deficient lentiviral vectors
simian Ads
Human rAds
rAd5
rAd26
rAd28
rAd35
rAd41
Sim rAd ch rAd
non Ads
rLCMV rLVV
Next Generation Inserts: Expanding Breadth
Informatically
Mosaics (Env, Gag, Pol, Nef)
HIV/SIV Gag Chimeras and
Chimeric Mosaics
B. Korber, B. Hahn, Norm Letvin, Bart Haynes
Basic Science and AIDS Vaccine Development
1. T cell vaccine vectors and concepts
2. Advances in B cell immunogen design
3. Modeling of HIV infection in the non-human
primate
Neutralizing mAbs as of 2008
2F5, 4E10
(1993, 1994)
gp41
b12 (1994)
gp120
trimer
CD4bs
Co-receptor
bs
V3
447-D (1993)
2G12 (1996)

Until last year (2009) - No new
broadly NAb since 1996

NAbs were unable to explain the
potent neutralization found in
some sera
2009 – 2010: New Potent mAbs against HIV-1
• PG9/16 – Quaternary neutralization
epitope in regions of V2/V3
• VRC01, 02, 03 – target CD4bs
PG9/16
(V2/V3 region)
VRC01 - 03
HJ16
(CD4bs)
2G12
(glycan)
• Neutralize more potently, and with
far more breadth than prior mAbs
(80% - 90%); often < 1 ug/ml
• Additional new potent and broadly
reactive NAbs at this meeting
2F5, Z13, 4E10
MPER
Model of known neutralization epitopes based on
atomic level structure of gp120 and the
cryoelectron tomographic structure of trimeric Env
Laura M Walker and Dennis R Burton
Current Opinion in Immunology 2010
Liu/Subramaniam Nature 2008
Zhou/Kwong Nature 2007
A Proof of Concept for Vaccines?
Broad and Potent Neutralizing Antibodies are
Synthesized in Natural HIV-1 Infection
Viruses
Sera
ID50
> 150
> 500
15 - 25% sera display
significant cross-clade breadth
of neutralization-to what are
they directed?

Doria-Rose, Wyatt, Korber, Mascola, Connors et al. J Virol 83:188-199 (2009) – VRC/NIAID: 110 clade B sera

Sather/Stamatatos J Virol 83:757-769 (2009) – SBRI/Vanderbilt: 64 clade B sera

Simek, Burton, Koff et al; J Virol 83: 7337-7448 (2009) – IAVI protocol G: >1700 clade A, B, C, D, E sera

Gray, Montefiori, Mascola, Morris et al. J. Virol. 83:8925-37 (2009): SAAVI/CHAVI/CAVD 70 clade C sera
Strategy for Isolation of New Monoclonal Antibodies Based
On HIV Protein Structure
Designer Envelopes
Stabilizing the
inner/outer
domains
Stabilizing inner
domain and
bridging sheet
Core
Inner
Outer
Stabilized Core
Resurfaced Stabilized Cores (RSC)
Mascola et al. VRC Broadly Neutralizing Ab Isolation
Nabel, Schief, Kwong, Mascola
Resurfaced Stabilized Cores (RSC) as
Epitope-Specific Probes for B-Cell Isolation
Bill Schief
Gary Nabel (ZY Yang)
Peter Kwong (T Zhou
gp120 core
SA-PE
SA-APC
Biotin
X
resurfaced
residues
glycans
CD4 binding
site
RSC3
DRSC3
Kwong, Schief, Zhou, Nabel
Wu et al. Science (2010) 329:856
Strategy for Isolation of New mAbs Based on
Epitope Specific Protein Probes
epitope specific B cells
+
X
RSC3
(positive)
DRSC3
(negative)
Three mAbs bind to the RSC protein
RSC
RSC/d371I
OD450
VRC01
VRC02
VRC03
4
4
4
3
3
3
2
2
2
1
1
1
0
0.0001
0.001
0.01
0.1
mAb (g/ml)
1
10
0
0.0001
0.001
0.01
0.1
1
10
VRC02 g/ml
0
0.0001
0.001
0.01
0.1
1
10
VRC03 g/ml
• Two closely related somatic variants (VRC01, VRC02)
– bind to CD4bs region of gp120
– Neutralize ~90% viruses, often < 1ug/ml
• 1 additional mAb (VRC03)
– CD4bs directed
– Neutralizes ~ 60% viruses
Wu et al. Science (2010) 329:856
Panel of 190 Diverse Viral Isolates
b12
VRC01
IC50 < 1 μg/ml
IC50 1-50 μg/ml
IC50 > 50 μg/ml
D
B
gp160 protein distance
Neighbor-Joining tree
Mike Seaman
0.01
HXB2
HXB2
C
G
A
IC50 < 50 μg/ml
IC50 < 1 μg/ml
Virus clade
A
B
C
D
CRF01_AE
CRF02_AG
G
CRF07_BC
Number of
viruses
22
49
38
8
18
16
10
11
VRC01
100%
96%
87%
88%
89%
81%
90%
100%
b12
45%
63%
47%
63%
6%
19%
0%
27%
VRC01
95%
80%
66%
50%
61%
56%
90%
45%
b12
23%
39%
13%
25%
0%
0%
0%
9%
Other
18
83%
33%
78%
6%
Total
190
91%
41%
72%
17%
Crystal Structure of VRC01:gp120
Inner domain
gp120 outer domain
CD4 binding loop
Loop V5
CDR H2
Loop D
CDR H1
CDR H3
CDR L1
CDR L3
Light chain
Heavy chain
Zhou/Kwong Science (2010) 329;811
Mimicry of CD4 Receptor by Antibody VRC01
gp120
gp120
CD4
VRC01
heavy chain
V-domain
CD4 and VRC01 in highly similar positions
Why does VRC01 Work So Well?
1. Partial mimicry
of CD4 binding
to gp120
2. Binding
focused on the
conformational
ly invariant site
of initial CD4
attachment.
gp120
outer domain
gp120
inner domain
bridging sheet
Structural Models of Alternative Forms of HIV-1 Envelope
Induction of CD4 BS Antibodies by Trimeric Immunogens
in Rabbit
Resurfaced Stabilized Cores: Probes for Human Abs and
Templates for Immunogens
Cores
CD4
binding site
Resurfaced Stabilized Cores
Alter surface
residues to eliminate
reactivity with nonneutralizing
antibodies
1.
Probe to isolate B cells and clone broadly neutralizing abs
2.
Prototype immunogens to elicit antibodies to the highly
conserved CD4 binding site
Nabel, Schief, Kwong, Mascola
Scope of Clinical Applications of
Anti-HIV Neutralizing Antibodies
Scope
• Prevention
• Therapy
• Eradication of
reservoir
Anti-HIV Neutralizing Antibodies
Scope
• Prevention
- Topical microbicides
- Regulated gene expression
(e.g. AAV, lentiviral vectors)
- Passive infusion (systemic)
• Therapy
• Eradication of
reservoir
Anti-HIV Neutralizing Antibodies
Scope
• Prevention
• Therapy
− Passive infusion - antiviral
• Combination of antibodies
• Combination of drugs/antibodies
• Eradication of reservoir
Anti-HIV Neutralizing Antibodies
Scope
• Prevention
• Therapy
• Eradication of reservoir
- Fc mediated: Virolysis, ADCC
- Targeting viral reservoirs
• Ab-toxin chimeras
Basic Science and AIDS Vaccine Development
1. T cell vaccine vectors and concepts
2. Advances in B cell immunogen design
3. Modeling of HIV infection in the non-human
primate
Vaccine-Mediated Protection Against
SIVsmE660 Infection
Acquisition of Established Infection
Peak Viral Load
p = 0.31
Vaccine
Plasma log10 RNA copies/mL
Control
Control
Vaccine
Letvin, Mascola et al., VRC NHP Studies
The Three Pillars of a Highly Effective AIDS Vaccine
Clinical Efficacy Trials
Neutralizing Antibodies
and T cell immunogens
Non-human Primate
Models
mAb Isolation Acknowledgments
VRC and NIAID
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Xueling Wu
Yuxing Li
Rich Wyatt
Mark Connors
Nicole Doria-Rose
Krisha McKee
Mark Louder
Sijy O’Dell
Steve Schmidt
Diane Wycuff
Mario Roederer
Carl Hogerkorp
Tongqing Zhou
Zhi-Yong Yang
Peter Kwong
John Mascola
Collaborators
•
Bill Schief
The Neutralizing Antibody Vaccine Concept
A broad and potent neutralizing antibody response will prevent
HIV infection or control HIV disease through inactivation of virus
and/or by mobilization of antibody-dependent or innate immune
responses to virus infected cells .
Cell-free virus
Neutralizing antibodies
HIV-infected cells
External Viral Protein
• Envelope
CD4
Env
ADCC, Complement
Provirus
Structure Based Vaccine Design
Recessed receptor binding sites:
Decoy effects from monomer and V regions:
CD4 and CCR5
induction of non-neutralizing antibodies
Major Conformational Alterations of HIV Env
Upon Engaging the CD4 Receptor
Unbound
CD4-bound conformation
Chen et al. & Harrison, Nature 2005
The coreceptor binding domain is only formed
after CD4 engagement.
Structure Assisted Vaccine Design:
Constraint of Conformational Flexibility
Mutagenic stabilization of the CD4-bound conformation of
gp120: have engineered four domain-stabilizing disulfides
and three cavity-filling mutants.
(Zhou, et al. & Wyatt, Nabel & Kwong)
Overall Structure of b12:gp120 Complex
b12 binds to gp120
conformational
invariant surface.
Tongqing Zhou et al. Nature 445,732-737 (2007)
A Site of Vulnerability on HIV-1
b12-Epitope Structure-Base Design
•Trimers
• Monomeric gp120 (core) and cloaks
gp120 core
“cloaked core”
• Outer domain of gp120
Outer Domain
• Scaffolding
CD4-binding
loop
Complex epitope
b12-Epitope Structure-Base Design
•Trimers
• Monomeric gp120 (core) and cloaks
• Outer domain of gp120
• Scaffolding
Modeled HIV-1 Env Trimer and Glycan Shield
90° rotation
Kwong et al. J Virol 2000.
b12-Epitope Structure-Base Design
•Trimers
• Monomeric gp120 (core) and cloaks
gp120 core
• Outer domain of gp120
• Scaffolding
“cloaked core”
“Cloaking” of Irrelevant HIV gp120 Surface
Determinants with SIV
Inner domain
Outer domain
Cloak siv_8b_11_2a
180o
CD4 binding
loop
Bridging Sheet
Core (8B)
Wild type HXB2
Cloak 2NXY-11b-comp-6e_0007
Designs: View from CD4
Binding Face
2nxy_11b_1
2nxy-11bcomp-2g_0017
siv_8b_sg_11b
siv_8b_11_2a
2nxy-11bcomp-6e_0007
2nxy-11bredes-8_0105
2nxypolar1pt5_0177
2nxy-11bredes-8_0105
Designs: View from Backside
2nxy_11b_1
2nxy-11bcomp-2g_0017
siv_8b_sg_11b
2nxy-11bredes-8_0105
siv_8b_11_2a
2nxypolar1pt5_0177
2nxy-11bcomp-6e_0007
2nxy-IIc25_0188
Model of Free Trimer
b12 Trimer Structure Model
Model of Free Trimer
“Cloaking” of Irrelevant HIV gp120 Surface
Determinants with SIV
Inner domain
Outer domain
Cloak siv_8b_11_2a
180o
CD4 binding
loop
Bridging Sheet
Core (8B)
Wild type HXB2
Cloak 2NXY-11b-comp-6e_0007
Structural Models of Alternative Forms of HIV-1 Envelope
Competition of CD4 BS Antibodies in Rabbit Antisera
by IgG1 b12 and b13