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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
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.
Viremia Persists after Suppression by
Antiretroviral Therapy
Start Therapy (d4T/3TC/efavirenz)
107
107
106
106
105
105
104
104
103
103
102
102
101
101
100
100
Plasma HIV-1 RNA (copies/ml)
Start Therapy (d4T/3TC/efavirenz)
22 ± 6 c/ml
10-1
4 ± 2 c/ml
10-1
0
200
400
Time (days)
600
800
0
200
400
Time (days)
bDNA
bDNA <75 copies/ml
Palmer et al. JCM 2003
Maldarelli et al. PLoS Path 2007
Single-Copy Assay
Single-Copy Assay < 1 copy/ml
600
800
Biphasic decline in persistent viremia
over 7 years of treatment
Plasma HIV-1 RNA (copies/mL)
100
720 study
720 study assay limit
32
11.6 copies/ml
10
3.2
1.5 copies/ml
half-life=
1
half-life=39 weeks
0.32
0
60
120
180
Week
Palmer et al. PNAS 2008
240
300
360
∞
Persistent HIV Infection
The IAS Scientific Working Group on HIV Cure: Nature Reviews Immunology 2012
Palmer et al. JIM 2011
Persistent HIV Infection
www.aids2014.org
Measuring Persistent HIV
Where to Measure
Persistent Virus?
Peripheral Blood
Plasma
Cells: RNA versus DNA
Tissue Compartments
T cells
Other cell types
RNA versus DNA
Role of Replication
Defective HIV
www.aids2014.org
CNS/CSF
Measuring Persistent HIV
Culture assay : IUPM
www.aids2014.org
Lewin & Rouzioux, AIDS 2011
Rouzioux & Richman, 2012
Measuring Persistent HIV Infection
Measurement
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
Inexpensive, easy
Unintegrated HIV DNA
contributes to signal unless
patients are on HAART for 1-3
years. A lot of virus is defective.
excludes unintegrated HIV DNA,
less error than IUPM
Requires at least a million cells,
complex assay, defective provirus
(Peripheral Blood or Tissue
Compartments)
Integrated HIV DNA
(Peripheral Blood or Tissue
Compartments)
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
www.aids2014.org
Svicher et al. Curr HIV/AIDs Rep. 2014
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.
www.aids2014.org