2014 “Towards an HIV Cure” Symposium, Melbourne
Viral Persistence:
Obstacles and
Opportunities
“The Role of Therapeutic
Vaccination
in in
Overcoming
AIDS
Virus Infection
HIV Cure
Strategies”
J.D. Lifson
AIDS and Cancer Virus Program
Leidos Biomedical Research, Inc.
Frederick National Laboratory
AIDS and Cancer
Virus Program
http://www.nytimes.com/2011/11/29/health/
new-hope-of-a-cure-forhiv.html?pagewanted=all&_r=0
http://www.advocate.com/news/2009/01/24/
aids-hero-martin-delaney-dies-california
Definitions
Reservoir: Virus that persists despite apparently effective
suppressive cART, and is capable of giving rise to recrudescent
infection if/when cART is stopped
Cure (definitive treatment beyond lifetime cART):
Eradication: Elimination through treatment of all virus capable
of giving rise to recrudescent infection if/when cART is stopped
Functional Cure (sustained off treatment remission): Not
complete elimination of reservoir, but reduction of reservoir to
levels sufficiently low, with sufficient host control, to
limit/abrogate pathogenesis and minimize/eliminate risk of
transmission
Challenges for HIV Cure
•
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Residual virus replication (“active reservoir”)
Long lived/self renewing infected cells
Latent reservoirs
– Epigenetic and transcriptional mechanisms of
latency
– Anatomic and cell lineage compartments
Pharmacological or immunological sanctuary sites
Must eliminate or control “last virus” capable of
initiating recrudescence
Approaches to HIV Cure:
Mechanism Based and Empirical
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cART intensification
Transcriptional activators
Epigenetic modulators
Immune modulators
– Cytokines
– Immune checkpoints
Immune targeting (require viral expression)
– mAbs
– Adoptive cell therapy (engineered cells; effector, resistance)
– Therapeutic vaccination
Combinations
Dr. Lifson will
see you now….
Animal (NHP) Models in HIV Cure Research:
Strengths, Role, Limitations
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Experimental Control and Flexibility
Identity, timing, route, amount of viral inoculum;
sequence tagged “synthetic swarm”
Flexibility for sampling: Blood (incl ‘pheresis),
tissues
- Longitudinal
- Scheduled euthanasia/necropsy
cART regimen: Compliance, flexibility for
initiation, interruption
Flexibility for experimental interventions:
Preliminary proof of concept, risk/benefit
Monkeys are not people, HIV is not SIV/SHIV
cART in NHP
•
Drug Considerations
• Activity/potency vs. SIV
• Drug delivery: Dosage, Route (“compliance”)
• Bioavailability, PK (plasma and tissue levels!)
• Toxicity
• Sustainability over experimental duration
• Drug availability/cost
• 2012-14: Regimens able to achieve and sustain
suppression of SIVmac239 to < 30 RNA copies/mL
Evaluation of Pharmacologic Interventions
(HDACi/SAHA) in cART Suppressed NHP (Merck)
•
•
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Test SAHA, establish NHP model
cART regimens
In vitro/Ex vivo validation
– SIV vs. HIV, macaque cells vs. human cells
Safety
In vivo activity
SIVmac239
cART
SAHA
45mg/kg/day
SAHA
57 mg/kg/day
Necropsy
Ex Vivo SAHA Treatment Increases Histone Acetylation and
Induces SIV Expression from CD4+ T Cells From SIV-Infected
Macaques on Suppressive cART
cART + SAHA in NHP
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cART treatment for > 1 yr
SAHA safe; cumulative 84 doses
Treatment effects; histone acetylation, SIV transcriptional
ratio (vRNA:vDNA)
Results complex; PK/PD; decr. response with repeat dosing
Despite activity, extensive dosing, no viral clearance
HDACi may have role, but alone unlikely to meaningfully
impact reservoirs without other interventions
Romidepsin also studied (Gilead); histone acetylation, incr
PVL, but not viral clearance
Similarities to emerging clinical data support
utility/relevance of NHP models
HIV Cure: Limitations of
“Pharmacological Only” Approaches
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Activity (potency, specificity)
PK/PD
Fractional hit rate per dose/cycle
Interpretation/significance of readouts
Fate of “induced” cells
Toxicity/off target effects
Must eliminate/control “last virus”; potential role for
immune surveillance, immune clearance
Role for therapeutic vaccination? Cellular vs. Ab
HIV Cure: Therapeutic Vaccination (TVX)
Limitations of conventional TVX:
• Kinetics:
– Transient vaccine Ag
– Later responses depend on Ag from infection;
responses chase the virus
• Specificity:
– Limited breadth vs. sequence diversity, viral
plasticity
– MHC allele dependence
– Potential boosting of responses to already escaped
epitopes
And now, for something
completely different….
Exploiting the Evolutionarily Acquired Immune Wisdom
of CMV: Predicted Properties of T Cell Responses to
CMV-Vectored Vaccines
• Extremely high frequency of CD4+ and CD8+ T cell
responses
• Effector memory biased
• Indefinitely persistent
• Widely distributed, incl mucosal effector sites,
viral portals of entry
• Capable of locally containing, aborting infection?
• Clearly different from other approaches; even if it
doesn’t protect, likely to learn something!
Kinetic Mismatch Barrier for AIDS Vaccines:
“Too Little, Too Late”
Rh-rCMV
Picker, LJ, Hansen, SG, and Lifson, JD, Ann Rev Med, 2011
“Prophylactic” Rh-CMV/SIV Vaccination:
Properties and Mucosal Challenge Cumulative Results
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•
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No superinfection block
Uniquely broad CD4 + (TNF+, IFN-g+, IL-2+, MIP-1b+ ) and
CD8+ (TNF+, IFN-g+, MIP-1b+, CD107+) TEM responses
Maintained indefinitely
Widely
distributed, inclcontrol
mucosalof
effector
sites
•
Post-acquisition
infection
No NAb
in > responses
50% of vaccinated macaques
rRh-CMV Vectored SIV Vaccines: Additional Findings
•
•
•
•
•
Unusual breadth of CD4+ and CD8+ T cell responses, but
missing responses to immunodominant epitopes
“Protected animals” (i.r., ivag) clearly infected; repeat
challenged until transient viremia, immune responses to
non-vaccine SIV antigens
SIV specific CD4 cells not lost
Control of infection, not “sterile protection”
Durable control with extended follow up
Zinkernagel-D’Oh-erty Revisted
http://www.nobelprize.org/nobel_prizes/medicine/laureates/1996/
“…when you have eliminated the impossible,
whatever remains, however improbable, must be
the truth…”
S. Holmes, The Sign of the Four
Unusual Properties of CD8+ T Cell Responses to
Rh-CMV/SIV Vaccines
• Extremely broad CD8 responses; no canonical immunodominant
epitopes, indefinitely persistent
• 2/3 of CD8 responses restricted by MHC-II, NOT MHC-I
• Promiscuous Supertopes: Epitopes presented by multiple MHC-II
allomorphs; Multiple peptides presented by individual MHC-II
allomorphs
• Atypical MHC-I restricted responses presented by minimally
polymorphic MHC-I-E, not MHC-I A,B (nef resistant)
• RhCMV 68.1 vector dependent alternative antigen priming:
• Rh189 (US11)
• Rh157.5, Rh157.4, and Rh157.6 (UL128, UL130, and UL131)
• Mechanism? Importance for protection?
• Vectors provide opportunities for response customization
RhCMV Vector-elicited CD8+ T Cell Responses:
Epitope Recognition
130
130
• Viral control after i.r, i.vag., i.v. challenge
• Control of disseminated infection, not just at portal of entry
• Progressive decline of infection dependent T cell responses,
clearance of virus over time, including from tissue sites
• “Functional cure” and apparent eradication
Longitudinal Analysis of Rh-CMV/SIV Mediated
Protection After Intravaginal Infection
Longitudinal Analysis of Rh-CMV/SIV Mediated Protection
After Intravaginal Infection: Tissue Viral Load
SIV RNA
SIV DNA
Adoptive Transfer to Naïve Hosts:
No Evidence of Residual Infectious Virus
?
http://www.nytimes.com/2011/11/29/health/new-hope-of-a-cure-for-hiv.html?pagewanted=all&_r=0
http://wildlifeandbirdingdestinations.blogspot.com/2011/05/wildlife-rhesus-macaque.html
Implications of Apparent Viral Clearance for
Therapeutic Vaccination
• Can TVX with RhCMV/SIV clear infection in SIVmac239
infected macaques on cART?
• Indefinitely persistent immune surveillance, broad, atypical
T cell responses
• Considerations for evaluation of therapeutic vaccination
• Effective, sustainable cART in NHP
• Timing of cART initiation
• Duration of cART
• Vaccine immunogenicity in infected NHP on cART
• Virological readouts (Bx vs. Nx)
- qPCR/qRT PCR
- Virus recovery culture
- Adoptive transfer
- cART interruption
Therapeutic rhCMV/SIV Immunization In RM
Started on cART in Early Chronic SIV Infection
SIVmac239X* cART
Rh-CMV/SIV
ATI
n=12
d0
d 42
d 240
d 330
Rh-CMV/Empty
n=6
*Del Prete, Keele BF. et al, J Virol. 2014 May 7
d ~ 600
Therapeutic rhCMV/SIV Immunization of RM
Started on cART in Early Chronic SIV Infection
Log RNA copies/ml
8
Immunization
Plasma viral loads
ART
RhCMV/SIV (n=12)
RhCMV/empty vector (=6)
6
4
2
Limit of detection
0
0
50
100
150
200
250
Time post SIV infection (Days)
300
350
Rh-CMV/SIV Vaccination of SIV-Infected Macaques on cART
Increases CD4+ and CD8+ T Cell Responses to Vaccine (gag) but
Not Non-Vaccine (vif) SIV Antigens
RhCMV/SIV
vaccinated (n=12)
RhCMV/empty
vaccinated (n=6)
Timing of cART Initiation Profoundly Influences
“Reservoir” Establishment
Okoye, et al, submitted
Rebound Competent Reservoir Established Early
Okoye, et al, submitted
Therapeutic rhCMV/SIV Immunization of RM
Started on cART in Acute SIV Infection
SIVmac239X*
cART
Rh-CMV/SIV
ATI
n=17
d 0 d 7-10
d 70
d 160
Rh-CMV/Empty
n=17
*Del Prete, Keele BF. et al, J Virol. 2014 May 7
d ~ 550
Plasma viral loads
Log SIV RNA copies/ml
5
RhCMV/SIV (n=17)
RhCMV/empty vector (n=16)
4
3
2
1
0
14
28
42
56
Time post SIV infection (Days)
70
84
CMV-Vectored AIDS Virus Vaccines: Summary/Future
• Unusual immunology; vector dependent alternate priming
• Control after infection via i.r., i.vag., i.v. routes
• Control infection disseminated to tissues, not just portal of
entry
• Indefinitely persistent immune surveillance; progressive
viral clearance to functional cure, apparent eradication
• Extremely broad epitope coverage; epitopes not recognized
in natural infection, including promiscuous supertopes;
advantages for both prophylactic and therapeutic vaccination
• Timing of cART initiation
• Future plans (addtl NHP studies, clinical development):
- Prophylactic vaccination
- Therapeutic vaccination, with addtl immuno- or
pharmacologic interventions to enhance/accelerate
viral clearance
Viral Persistence in TFH in Follicles:
A Potential Obstacle to Complete Viral Clearance
Fukazawa, et al, submitted
COLLABORATORS
ACVP/LBRI/FNL/NCI
Mike Piatak, Jr.
Jake Estes
Brandon Keele
Greg Del Prete
Randy Fast
Kelli Oswald
Becca Shoemaker
Yuan LI
Doug Schneider
Vicky Coalter
Adam Wiles
Rodney Wiles
Brandi Freemire
William Bosche
Brian Berkemeier
Carolyn Reid
Laura Newman
Leslie Lipkey
Contract
HHSN261200800001E
VGTI/OHSU/ONPRC
Louis Picker
Klaus Fruh
Jonah Sacha
Scott Hansen
Afam Okoye
Abigail Ventura
Roxanne Gilbride
Colette Hughes
Julia Ford
Matthew Lewis
Awbrey Gilliam
George Xu
Andy Sylwester
Haesun Park
Shoko Hagen
Yoshinori Fukazawa
Richard Lum
LASP/LBRI/FNL/NCI
Jeremy Smedley
Rhonda Macallister
Mercy Gathuka
Solomon Wangari
RO1 AI060392; P01 AI094417;
R01 AI095113; R01 DE021291
Patrizia Caposio
Jay Nelson
Emily Marshall
Daniel Malouli
Jennie Hines
Dan Streblow
Michael Axthelm
Alfred Legasse
Ben Burwitz
Shannon Planer
Tonya Swanson
John Turner
Michael Jarvis
Christoph Kahl
Daria Hazuda
Chris Tan
John Wai
Rosa Sanchez
Romas Geleziunas
Joe Hesselgesser
Jillian Hattersley
Bei Li
DMSI/NCI-F
Greg Alvord
Octavio Quinones