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Interactive Workshop “HIV Cure 101”: Challenges in identifying and targeting the HIV reservoir Sarah Palmer Centre for Virus Research Westmead Millennium Institute for Medical Research University of Sydney. Definitions. - PowerPoint PPT Presentation
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Interactive Workshop
“HIV Cure 101”:Challenges in identifying and
targeting the HIV reservoir
Sarah PalmerCentre for Virus Research
Westmead Millennium Institute for Medical ResearchUniversity of Sydney
Definitions
Residual Viremia: Persistent HIV RNA measured in plasma at levels below the limit of detection of the standard clinical assay (20-50 copies/ml).
Viral Reservoir: A viral reservoir is an anatomical site or cell type in which a replication-competent form of HIV persists, accumulating with more stable properties than the circulating pool of actively replicating virus. This HIV can persist even during effective therapy.
0 200 400 600 800Time (days)
107
106
105
104
103
102
101
100
10-1
0 200 400 600 800Time (days)
107
106
105
104
103
102
101
100
10-1
Pla
sma
HIV
-1 R
NA
(co
pie
s/m
l)
22 ± 6 c/ml 4 ± 2 c/ml
Viremia Persists after Suppression by Antiretroviral Therapy
Viremia Persists after Suppression by Antiretroviral Therapy
Start Therapy (d4T/3TC/efavirenz) Start Therapy (d4T/3TC/efavirenz)
bDNA
bDNA <75 copies/ml
Single-Copy Assay
Single-Copy Assay < 1 copy/ml Palmer et al. JCM 2003Maldarelli et al. PLoS Path 2007
0 60 120 180 240 300 360
Week
Pla
sma
HIV
-1 R
NA
(cop
ies/
mL)
0.32
1
3.2
10
32
100
Biphasic decline in persistent viremia over 7 years of treatment
11.6 copies/ml
half-life=39 weeks
1.5 copies/ml
720 study assay limit720 study
Palmer et al. PNAS 2008
half-life= ∞
Persistent HIV Infection
The IAS Scientific Working Group on HIV Cure: Nature Reviews Immunology 2012Palmer et al. JIM 2011
www.aids2014.org
Persistent HIV Infection
www.aids2014.org
Measuring Persistent HIV
Where to Measure Persistent Virus?
Peripheral BloodPlasmaCells: RNA versus DNA
Tissue CompartmentsT cellsOther cell typesRNA versus DNA
Role of Replication Defective HIV
CNS/CSF
www.aids2014.org
Measuring Persistent HIV
Culture assay : IUPM
Lewin & Rouzioux, AIDS 2011Rouzioux & Richman, 2012
www.aids2014.org
Measuring Persistent HIV InfectionMeasurement Advantages Disadvantages
HIV RNA in Plasma Relatively inexpensive Difficult to separate reservoir expression vs HIV replication, some positive samples undetectable,may not be representative of intracellular HIV RNA and DNA levels
Infectious Virus: estimates the number of infectious units of HIV per million mononuclear cells (IUPM)
Only direct measurement of replication competent virus or number of proviruses capable of productive infection
Requires large quantities of cells, $$$, large error, often impossible to detect changes in reservoir size
Total HIV DNA(Peripheral Blood or Tissue Compartments)
Inexpensive, easy Unintegrated HIV DNA contributes to signal unless patients are on HAART for 1-3 years. A lot of virus is defective.
Integrated HIV DNA(Peripheral Blood or Tissue Compartments)
excludes unintegrated HIV DNA, less error than IUPM
Requires at least a million cells, complex assay, defective provirus
www.aids2014.org
Persistent HIV Infection in Tissue
CNS/CSF
Lung 100 m2
Intestine 300 m2
Pinch Biopsy 0.000003 m2
www.aids2014.org
Persistent HIV Infection in Tissues
Svicher et al. Curr HIV/AIDs Rep. 2014
www.aids2014.org
Looking Ahead
Does a “cure” require the total absence of HIV RNA and DNA?
If not, then new more sensitive assays will be needed to differentiate between replication competent and non-replicating virus.
Must all potential reservoirs be analyzed? If not, are we confident that certain reservoirs are determinative of cure/remission?
With advances in curative strategies, will our current sensitive assays provide sufficient confidence to stop HIV therapy in patients showing a near absence of HIV RNA and DNA?
Looking ahead, to determine the effectiveness of curative strategies, our field will need to develop a more standardized assay system which is sensitive, efficient, less costly, and adoptable in local settings.
