The HIV Epidemic · infected with HIV and the average life span has declined by ~ 20 years • It...
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• Over 50 million HIV/AIDS cases have occurred worldwide • Over 40 million people are currently living with HIV/AIDS • 95% of all cases are in developing countries • Highest prevalence in Africa • In some African countries 30% of adult population is infected with HIV and the average life span has declined by ~ 20 years • It is currently estimated that there are over 11 million orphans worldwide due to the HIV/AIDS epidemic • In the US over 700,000 people have been infected and over 400,000 people are currently infected. The HIV Epidemic
Transcript of The HIV Epidemic · infected with HIV and the average life span has declined by ~ 20 years • It...
• Over 50 million HIV/AIDS cases have occurred worldwide
• Over 40 million people are currently living with HIV/AIDS
• 95% of all cases are in developing countries
• Highest prevalence in Africa
• In some African countries 30% of adult population is infected with HIV and the average life span has declined by ~ 20 years
• It is currently estimated that there are over 11 million orphans worldwide due to the HIV/AIDS epidemic
• In the US over 700,000 people have been infected and over 400,000 people are currently infected.
The HIV Epidemic
Opportunistic Diseases in AIDS
Opportunistic Diseases in AIDS (cont.)
A Crash Course in Immunology
To activate a T cell you need:Foreign AntigenAntigen Presenting Cell (APC)
T Cell Activation
ActivatedT Cell
CD3
Quiescent
CD28
T Cell
CD3
Quiescent
CD28
T Cell
CD3 Stimulation
Co-Stimulation
AnergicT Cell
HIV
CD4
CXCR4
Binding
Fusion & Entry
Nuclear localization & entry
Reverse transcription
Integration
Infection
gp120p24
Viral RNA
RT & othervirionproteins
CCR5
Expression
gp120p24
Viral RNA
RT & othervirion prteins
Budding
Assembly
Viral Gene Transcription
Translation
Post-translationalprocessing
Cellular Activation
The “dogma” in the AIDS field is that CD4 cells are lost
However CD8 T cells can also be depleted.
01234567
% CD8+CD4dimof Total CD3+
% CD8+CD4dimof CD3+, CD8+
CD4/CD8 Ratio
CD8+CD4dim Cells in the Peripheral Blood
Num
ber o
f Cel
ls
Stimulation of CD8 cells By APC Induces
CD4 ExpressionCD45RO+ CD8+ CD45RA+ CD8+TOTAL CD8+
CD4
7% 38%28%
Costimulated CD8+ T cells Unsorted PBL
Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
10
100
500
p24
ng/m
l
Ada-M
Bal
89.6
HTLV-IIIB
Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
10
100
500
p24
ng/m
l Ada-M
Bal
89.6
HTLV-IIIB
HIV Replication in CD8+ T cells
The HIV Long Terminal Repeat (LTR)
HIV Infection in the Lymph Node
There is poor peripheral human cell reconstitutionIn SCID-hu mice
How can we improve in vivo modeling to model pathogenesis andassess efficacy of drugs?
BLT (bone marrow-liver-thymus) mouse
-Better peripheral reconstitution than Thy/Liv alone (Spleen, Lymph node, Peripheral blood etc.)
-Can we establish efficacy for stem cell-based TCR approaches?
%CD45+mean=53% ± 29%
range 19%-80%
n=12
Multilineage Hematopoiesis in BLT mice
CD34+CD34+
CD34+CD34+
CD34+
1. Sort CD34+
6. Analyze TCR
Expression/ Function
6‐12 weeks
Fetal Liver
2. Transduce withAnti‐HIV TCR or Control TCR
HLA‐A*0201+Tissue
3. Combine with fetal thymus tissue and
liver stroma, implant under kidney
capsule
2a. Viably freeze fraction
CD34+CD34+
CD34+
4. Thaw and Transduce withAnti‐HIV TCR
Or Control TCR
3 weeks
5. Tail Vein Inject
Humanized Mouse Model of HIV Infection:The Modified BLT Model
Infect with HIV-1NL4-3HSA-HA
NSG NSG
Irradiate
Kitchen et al, PLoS Pathogen 2012
0
5
10
15
20
25
30
35
SL9-TCR ControlTCR
Uninfected SL9-TCR ControlTCR
Uninfected
%C
D45
+HIV
(HSA
-HA
)+ C
ells
Week 2 Week 6
Suppression of HIV Replication by HIV-specific TCR
Control of Plasma Viral RNA
Why Do Current Therapies Fail?
Toxicity mandates cesssation of therapyDrug resistance (mutation)Failure to clear all reservoirs
Mutation causes:
Drug resistanceEscape from immune responseAltered tropismIncreased replication potential
Effect of NVP on Viremia
Wei et. al., Nature 373, 1995
The Anti-Viral immune response/Escape By Virus
Antibodies to viral proteins are madeThey are poorly neutralizingViral env protein mutates, and escapes from antibody responsesRelevant epitopes are physically hidden from immune response
buried by other regions of envblocked by glycosylation
CD4 cells respond, but CD4 numbers are lowCD8 cells are present
Up to 50% can be virus-specific as assessed by tetramer bindingEscape mutants have been demonstratedNef causes down-regulation of MHC I A and B (not C)
This results in decreased CD8-mediated killingCD8 cells can be infected (CD4-mediated)
APC function is perturbed The physical demand to replace lost T cells may alter BM functionHIV infection perturbs myeloid and erythroid hematopoiesis
CD4/gp120 Interaction
Is There Hope For A Vaccine?
Attenuated viruses can elicit protective immunity
However, these can cause disease in immunocompromisedIndividuals
Phase III trials of recombinant env have failed
DNA vaccines or viral vectors hold much promise
Phase III trials of viral vector plus recombinant env have Shown a small amount of efficacy.
A successful vaccine will most likely need to generate:Strong T cell-mediated responsesIgA responses to protect mucosal surfaces
Stevenson, M. Nature Med 9:853-860, 2003
AddHAART
RemoveHAART
Effect of Cessation of TherapyOn Viral Load
Limit ofDetection
Vire
mia
Years
HAART eliminates productively infected cells
HAART eliminates productively infected cells
HAART eliminates productively infected cellsBut does not eliminate latently infected cells
HAART eliminates productively infected cellsBut does not eliminate latently infected cells
We must eliminatelatent virusto “cure” HIV disease
0.000010.00010.0010.010.1
110
1001000
10000
0 1 2 3 4 5 6 7 8
Time on HAART (years)
Freq
uenc
y(I
UPM
)Frequency of Latently Infected CD4+
T Cells as a Function of Time on HAART
-
t 1/2 = 44.2 months73.4 years
R. Siliciano
Vaccines may be decades away
Vaccines may be decades away
Can we target viral reservoirs to deplete virus?
Targeting The Latent Reservoir
Low-level activation signals should stimulate expression of latent virus, without compromizing the function of other cells
This might allow the immune system to kill the infected cell
A specific anti-viral approach (immunotoxin) may also killcells now producing virus, so that the latently infected cellis eliminated.
An immunotoxin is an antibody linked to a toxic molecule
The antibody binds to virus proteins on the cell, causing the toxin To kill the cell before new virus is made.
The Rationale
Prostratin or IL-7
Minimal activation plus immunoxin results in:
1. Elimination of 80% of the latent virus2. No effect on normal, uninfected cells
AddHAART
RemoveHAART
Effect of Cessation of TherapyOn Viral Load
Limit ofDetection
Vire
mia
Years
IL-7/Prostratin
We have developed improved activators that inducevirus to express from latently infected cells
In normal mice, we can activate 50% or more of splenocyteswith a single dose of these activators
Studies are ongoing to test these systems, coupled withimmunotoxins or anti-HIV CTL, in humanized mice to determine if we can eliminate the latent reservoir in vivo
If successful, we may have a new form of therapy which could be used to provide a “functional cure” for HIV disease.
What is ongoing now?
