2014 “Towards an HIV Cure” Symposium, Melbourne

“The Role of Therapeutic Vaccination in HIV Cure Strategies”

Viral Persistence: Obstacles and Opportunities in Overcoming AIDS Virus Infection

J.D. LifsonAIDS and Cancer Virus ProgramLeidos Biomedical Research, Inc.

Frederick National Laboratory AIDS and Cancer

Virus Program

http://www.nytimes.com/2011/11/29/health/new-hope-of-a-cure-for-hiv.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

• 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

• 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

• 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)

• 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 Necropsy

4 w

k

26-2

8 w

k

3 w

k3

wk

3 w

k

6-7

wk

3 w

k

3 w

k

5-6

wk

SAHA 45mg/kg/day

SAHA 57 mg/kg/day

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

• 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

• 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: Limitations of “Pharmacological Only” Approaches

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

http://tvtropes.org/pmwiki/pmwiki.php/Main/SomethingCompletelyDifferent

And now, for something completely different….

• 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!

Exploiting the Evolutionarily Acquired Immune Wisdom of CMV: Predicted Properties of T Cell Responses to

CMV-Vectored Vaccines

Kinetic Mismatch Barrier for AIDS Vaccines:“Too Little, Too Late”

Picker, LJ, Hansen, SG, and Lifson, JD, Ann Rev Med, 2011

Rh-rCMV

“Prophylactic” Rh-CMV/SIV Vaccination: Properties and Mucosal Challenge Cumulative Results

• 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, incl mucosal effector sites• No NAb responses• Post-acquisition control of infection

in > 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

• 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

;

Unusual Properties of CD8+ T Cell Responses to Rh-CMV/SIV Vaccines

130

130

RhCMV Vector-elicited CD8+ T Cell Responses: Epitope Recognition

• 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://wildlifeandbirdingdestinations.blogspot.com/2011/05/wildlife-rhesus-macaque.htmlhttp://www.nytimes.com/2011/11/29/health/new-hope-of-a-cure-for-hiv.html?pagewanted=all&_r=0

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*

*Del Prete, Keele BF. et al, J Virol. 2014 May 7

cART Rh-CMV/SIV

Rh-CMV/Empty

ATI

n=12

n=6

d 0 d 42 d 240 d 330 d ~ 600

Immunization

Therapeutic rhCMV/SIV Immunization of RM Started on cART in Early Chronic SIV Infection

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/SIVvaccinated (n=12)

RhCMV/emptyvaccinated (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*

*Del Prete, Keele BF. et al, J Virol. 2014 May 7

cART Rh-CMV/SIV

Rh-CMV/Empty

ATI

n=17

n=17

d 0 d 7-10 d 70 d 160 d ~ 550

• 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- orpharmacologic interventions to enhance/accelerate viral clearance

CMV-Vectored AIDS Virus Vaccines: Summary/Future

Viral Persistence in TFH in Follicles: A Potential Obstacle to Complete Viral Clearance

Fukazawa, et al, submitted

COLLABORATORS

Contract HHSN261200800001E

Louis PickerScott Hansen Afam OkoyeAbigail VenturaRoxanne GilbrideColette HughesJulia FordMatthew LewisAwbrey GilliamGeorge XuAndy SylwesterHaesun ParkShoko HagenYoshinori Fukazawa Richard Lum

LASP/LBRI/FNL/NCIJeremy SmedleyRhonda MacallisterMercy GathukaSolomon Wangari

Klaus FruhJonah SachaPatrizia CaposioJay NelsonEmily MarshallDaniel MalouliJennie HinesDan StreblowMichael Axthelm Alfred LegasseBen BurwitzShannon PlanerTonya SwansonJohn TurnerMichael JarvisChristoph Kahl

Mike Piatak, Jr.Jake EstesBrandon KeeleGreg Del PreteRandy FastKelli OswaldBecca ShoemakerYuan LIDoug SchneiderVicky CoalterAdam WilesRodney WilesBrandi FreemireWilliam BoscheBrian BerkemeierCarolyn ReidLaura NewmanLeslie Lipkey

RO1 AI060392; P01 AI094417; R01 AI095113; R01 DE021291

ACVP/LBRI/FNL/NCI VGTI/OHSU/ONPRC

Romas GeleziunasJoe HesselgesserJillian Hattersley Bei Li

DMSI/NCI-FGreg AlvordOctavio Quinones