HIV Cure Research Training CurriculumNicolas Chomont, University of MontrealRichard Jefferys, Treatment Action Group

The HIV CURE training curriculum is a collaborative project aimed at making HIV cure research science accessible to the community and the HIV research field.

CONCEPTS IN BASIC SCIENCE AND TRANSLATIONAL RESEARCH

• Basic science: Laboratory studies that aim to further understanding of the mechanisms involved in phenomena e.g. the mechanisms of HIV persistence

• Translational research: Research that aims to translate knowledge gained from basic science into the clinic (sometimes referred to as “bench-to-bedside”)

Definitions

From Han et al, Nat Rev, 2007

HIV life cycle

Limit of detection

Antiretroviral drugs (HAART) are capable of suppressing HIV, even to undetectable

levelsCi

rcul

ating

viru

s

Time

START STOP

HAART

However, the virus rebounds after

cessation of therapy

HIV hides in reservoir that are not sensitive to current therapies

HIV infection is characterized by high levels of circulating viruses

in the blood

Current anti-HIV drugs do not eradicate HIV

HIV persists during ART

• Proliferation: Reservoir cells, like other memory T cells, divide very slowly to maintain the memory of the immune system.

• T cell survival: Reservoir cells are memory T cells. These cells, which are generated after infection or vaccination, keep the memory of the immune system for decades.

Ongoing viral replication

Active reservoir

Latent reservoir

How does HIV persist during ART?

Where is the HIV reservoir?

From http://textbookofbacteriology.net

HIV latency

From Siliciano et al. Cold Spring Harb Perspect Med 2011

IL-2IFN-g

SurvivalApoptosis

Self renewalActivation

Sallusto et al. Nature 1999 ; Riou et al. J Exp Med. 2007 ; Ahmed et al. Nat. Rev Immunol 2009 ; Gattinoni et al. Nat Med 2011 ; Farber et al. Nat. Rev Immunol 2014

Naïve Central memory

Transitionalmemory

Effectormemory

Terminally differentiated

Ag

“Stem cell” memory

CD4 T cells

HIV persists in central, transitional and effector memory CD4 T cells

Chomont et al. Nat Med 2009

Contribution of CD4 T cells to the HIV reservoir

• At the anatomical level: Potential “hiding places”• Brain• Lymph nodes (inc. B cell follicles)• Peripheral blood• Gut• Bone marrow

Adapted from A. Fauci

Where does HIV persist during ART?

« Size » of the HIV reservoir

Ho et al. Cell 2013

The « real reservoir » ?

The frequency of cells harboring HIV integrated DNA is 10-1000 per 106 CD4 T cells 0.1-0.001% of CD4 T cells contain HIV integrated DNA

Among these cells, 0.1-1% are able to produce infectious viral particles upon stimulation (Finzi, Siliciano Nat. Med. 1999)

=> 0.001-0.000001% of CD4 T cells harbor infectious HIV

The total number of CD4 T cells in humans is estimated to 200X109

(Gasunov and De Boer, Trends in Immunology, 2007)

This calculation does not include additional reservoirs such as tissue macrophages

The total number of « reservoir CD4 T cells » in suppressed individuals may be 100,000 -10,000,000

Estimated HIV reservoir size

Minimal decay of the HIV reservoir

HIV persistence

Siliciano et al. Nat Med 2003

Half life of the HIV reservoir

Siliciano et al. Nat Med 2003

Reservoir established rapidly after infection

Early ART restricts the size of the HIV reservoir (RV254)

Very early ART (<2 weeks after infection) dramatically reduces the size of the HIV reservoir

Absolute CD4 count

CD4 count (cells/µl)

Inte

grat

ed H

IV D

NA

copi

es

per 1

06 CD

4 T

cells

= -0.38p = 0.03

200 700 12001

10

100

1000

10000

CD4/CD8 ratio

CD4/CD8 ratio

> 1< 1

p < 0.0001

1

10

100

1000

10000

Higher CD4 count, smaller reservoir

Two strategies to eliminate the reservoir:

• Reactivation of HIV replication from its latent reservoir

• Interfering with the immunological mechanisms that contribute to HIV persistence

HIV-induced cell death

Uninfected cells

Cytokines, chemical compounds…

T cell survival ProliferationAntibodies, cytokines,

gene therapy, chemotherapy

Translating basic science into interventions

• Histones• Cellular proteins that encase genes and prevent their

transcription• HIV genes can be freed form histone entrapment by

drugs called histone deacetylase (HDAC) inhibitors• HDAC inhibitors promote production of HIV RNA (and

maybe proteins) by latently infected cells • Vorinostat, panobinostat and romidepsin being evaluated

in clinical trials

Targeting molecular mechanisms of HIV latency

Targeting molecular mechanisms of HIV latency

Targeting molecular mechanisms of HIV latency

Richman et al. Science 2009

PKC agonists: ProstratinBryostatin

Gamma-c Cytokines:IL-7IL-15

Bromodomain inhibitorsJQ1I-BET

HDAC inhibitorsSaha (vorinostat)PanobinostatRomidepsin

Targeting molecular mechanisms of HIV latency

T-cell activation PKC Cytokines HDACi other

Spina et al., Plos Pathogens 2013 Dec;9(12):e1003834

Targeting molecular mechanisms of HIV latency

• CD4 T cells respond to signals from their environment via receptors on the cell surface

• The receptors expressed on a CD4 T cell also fluctuate in response to signaling from the environment

• HIV latency in CD4 T cells is associated with the expression of receptors that are involved in maintaining the CD4 T cell in a resting state

• These receptors are referred to as “negative regulators” or “immune checkpoints” as they are also involved in preventing immune reactions to self (autoimmunity)

Targeting molecular mechanisms of HIV latency

PD-1

• Negatively regulates T cell responses (Freeman J Exp Med 2000, Wei PNAS 2013)

• Two known ligands: PD-L1 and PD-L2, mostly expressed by myeloid cells (Freeman J Exp Med 2000, Latchman Nat Immunol 2001)

• Blocking PD-1 interaction with its ligands restores HIV specific T cell functions (Day Nature 2006, Trautmann Nat Med 2006, Porichis Blood 2011)

r = 0.61p < 0.0001

The frequency of cells harboring integrated HIV DNA correlates with PD-1 expression

Hatano et al. JID 2013

PD-1 and the HIV reservoir

Chen L, Nat Rev Imm. 2013

PD-1 and more

R. Fromentin, Means +/-SD from 5 ART subjects

CD4 T cells expressing multiple negative regulators are highly enriched for integrated HIV DNA

CD4 Memory CD4

0 1 2 3 Number of negative regulators expressed

Expression of multiple negative regulators

Blocking PD-1 in vitro induces a modest but significant increase in viral production in latently infected CD4 T cells

Reactivation of the latent HIV reservoir

R. Fromentin

• The negative regulators PD-1, LAG-3 and TIGIT identify CD4 T cells harboring integrated HIV DNA

• Blocking these receptors may revert HIV latency and possibly also enhance HIV-specific T cell responses

• A clinical trial of an antibody to PD-L1 is ongoing (ACTG A5326)

• PD-1 blockade may also be studied

Targeting immunological mechanisms of HIV latency

• Manipulating the tight regulation of the immune system has to be carefully evaluated (autoimmunity?)

• So far, clinical studies with ICBs have been performed in patients with cancer

• Possible additional side effects in HIV-infected individuals?

Risk consideration of immune checkpoint blockers

Gelao et al. Toxins 2014

• Other approaches with the potential to interfere with the proliferation and/or survival of latently infected CD4 T cells also being explored (e.g. mTOR inhibitors, auranofin)

Targeting immunological mechanisms of HIV latency

• Basic research findings on molecular and immunological mechanisms of HIV persistence are being translated into clinical trials of possible interventions

• These are many other examples of translational research in the HIV cure field, trials of gene therapies, therapeutic vaccines and immune-based therapies also based on basic research discoveries

• Additional CUREiculum modules provide more information on all these approaches: http://www.avac.org/cureiculum

Translational research

CRCHUMRémi Fromentin

VGTI FloridaClaire VandergeetenFrancesco ProcopioMariam LawaniWendy BakemanAmanda McNultyJessica BrehmDeanna KulpaRafick-Pierre Sékaly

MHRPJintanat AnanworanichJerome KimMerlin RobbNelson Michael

Institut PasteurAsier-Saez-Cirion

MerckDaria HazudaMike MillerRichard Barnard

UCSFHiroyu HatanoMa SomsoukPeter HuntElisabeth SinclairRick HechtRebecca HohLorrie EplingMike McCuneSteven Deeks

Westmead InstituteSarah PalmerEunok Lee

McGillJean-Pierre Routy

VRCDanny DouekEli Boritz

AcknowledgmentsUNCKarine Dubé

AVACJessica Handibode

Collaborators

The study participants!