Synapses, cell-to-cell HIV transmission
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Synapses, cell-to-cell HIV transmission
Julià Blanco
www.irsicaixa.org
Fundació irsiCaixaFundació irsiCaixaFundació irsiCaixa
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One virus + one cell = ?
?
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Por qué sinapsis??
• Las sinapsis son uniones estables de dos células mediadas por interacciones específicas que permiten el intercambio de material o información
• El tejido linfoide es el principal lugar de replicación del VIH
• Alta concentración de células presentadoras (DC, infectadas) y células diana.
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Synapses in the immune system
MAIN MECHANISM OF COMMUNICATION IN THE IMMUNE SYSTEM
- Antigen presentation
Threshold for activation
- Activation induced death
Only cell-surface expressed FAS Is relevant for in vivo cell killing.
- CTL recognition of target cells
- NK recognition of target cells
…
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Synapses and viruses
Viruses are professional cellular hijackers:
VIRUSES EXPLOIT CELLULAR COMUNICATION IN ITS OWN BENEFIT
For many viruses, cell-to-cell virus transmission is the most efficient mechanism of viral spread.
HTLV-1, first virological synapse defined.
Igakura et al. Science 2003, 299:1713-1716.
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A role for synapses in HIV infection
T cell-T cell contact
For HIV, cell-to-cell contacts are involved in 90% of infection events in vivo. (Dixit and Perelson, 2004, J Virol)
DC-T cell contact
T cell-Epithelial cell contact
HIV
tra
ns
mis
sio
n
H
IV s
pre
ad
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1. T cell-Epithelial cell contacts
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2. DC-T cell contacts. Infectious synapse.
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DC-SIGN independent HIV capture.
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Virus and exosomes.
Izquierdo-Useros N, Naranjo M et al, BLOOD 2009
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LFA-1 CD4CXCR4CCR5
ICAM-1 HIV ENV CD4CXCR4CCR5
HIV ENVLFA-1
ICAM-1
Morphologically similar to other synapses. Joly C. et al. JEM 2004, 199:283-293
3. T cell-t cell contacts. Virological synapses.
CD4 CXCR4
Env Env
Main determinant: gp120-CD4 interaction. Adhesion molecules, secondary role(Puigdomènech et al RETROVIROLOGY, 2008. 5:32)
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Pero las cosas no son fáciles…
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Trogocytosis…
Active process of cellular communication, different from proteolitic cleavage or exosome transfer.
Intercellular exchange of antigens/membranes.
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Infected - uninfected cellular contactsInfected - uninfected cellular contacts
Conjugate Formation
Cell-to-cell FusionHemifusion/Target cell death Target cell infection
A role for trogocytosis?Effect on inhibition/neutralization?
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NL4-3 (X4) BaL (R5)
Ctrl +
Leu3a C34
IgGb12
4E10 2F
5
Ctrl +
Leu3a C34
IgGb12
4E10 2F
5
** *
*
0
5
10
15
20
Co
nju
ga
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CD
4 T
Ce
lls
(%
)
Control
Leu3a
Shaking
UNINF NL4-3 BaL
CMRA
FS
C
1% 13% 8%
2% 1% 1%
1% 1% 1%
**
**
0
5
10
15
20
Co
nju
ga
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CD
4 T
Ce
lls
(%
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NL4-3 BaL
Ctrl +
Leu3a
3100
TAK779
C34
SHAKING
Ctrl +
Leu3a
3100
TAK779
C34
SHAKING
Formation of cellular conjugates.
Infected cells Target cells
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Transport of viral materials (p24)
X4
R5
CD4+CXCR4+CCR5-
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Transport of viral materials (p24)
INFECTON(TRANSMISSION)
PASSIVE TRANSFER
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*
*
*
*
*
**
*
Accumulation of HIV into endosomes
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Ctrl +
Leu3a C34
IgGb12
4E10 2F
5
Ctrl +
Leu3a C34
IgGb12
4E10 2F
50
5
10
15
*
*
*
*
**
% M
OL
T G
FP
+
NL4-3 BaL
CD
4-G
FP
+ M
OL
T C
ell
s (
%)
2h
293-CD4GFP+
MOLT NL4-3/BaL
% MOLT CD4-GFP+UNINFECTED INFECTED
Transport of membranes. Trogocytosis
Trogocytosis at the VS isFusion-independent CD4-dependent
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Ctrl+
Leu3a C34
Ctrl+
Leu3a C34
0
2
4
6
8
10
DiI
CD
4+
T c
ells
(%
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* *
NL4-3 wt 41.2
NL4-3 wt 41.2
0
5
10
15
20
25
* *p24+
CD
4 T
Cells
(%
)
24h
293(Env)
CD4 % CD4 DiI +
24h
293(Env+env)
CD4 % CD4 p24 +
INFECTED UNINFECTEDHow to measure membrane transfer?
No fusogenic activity to avoid hemifusionNo virus production to avoid transfer of virus
Expression of Env mutant 41.2
Transport of membranes. Trogocytosis
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Infected - uninfected cellular contactsInfected - uninfected cellular contacts
CD
4 en
gag
emen
t Conjugate Formation Membrane ExchangeVirus Transfer
Gp
41ac
tiva
tio
n
Cell-to-cell FusionHemifusion/Target cell death Target cell infection
CD4 blockade
Coreceptor orgp41 blockade
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InfectionInfection
CD
4
MO
LT
Ctr
l
MO
LT
Ctr
l t=
0
Ctr
l
Leu
3a
C34
AZ
T
IgG
b12
4E10
2F50
5
10
15
NL4-3Uninf.
* * * * *
2^(-
Ct)
*
24h
Real-Time PCR (probes for HIV and CCR5)
To test active retrotranscription
FundacióirsiCaixa
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Virological SynapseVirological Synapse
Infected cellInfected cell
Target cellTarget cell
FundacióirsiCaixa
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Synapses increase the efficiency of HIV transmission/spread.
Two major synaptic mechanisms are involved in HIV spread: Infectious (DC-T cell) (virus hides in DCs)Virological (T cell-T cell) synapses (virus-driven)
For virological synapses:Cell-to-cell HIV transmission requires an extracellular neutralization-sensitive step.
Implications for vaccine design.
Pathophysiological consequences…
Conclusions.
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Fundació irsiCaixa
I. PuigdomènechM. MassanellaM. CurriuF. CuñatE. GarcíaS. MarfilJ. CarrilloC. Cabrera
Margarita Bofill
Nuria Izquierdo-UserosJavier Martínez-Picado
Bonaventura Clotet
Hospital Clínic (Barcelona)
Manel Juan
Hospital Germans Trias
Maria T. Fernández
IPBS (Toulouse)
A. AucherG. GaibeletD. Hudrisier
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Fundació irsiCaixa
I. PuigdomènechM. MassanellaM. CurriuF. CuñatE. GarcíaS. MarfilJ. CarrilloC. Cabrera
Margarita Bofill
Nuria Izquierdo-UserosJavier Martínez-Picado
Bonaventura Clotet
Hospital Clínic (Barcelona)
Manel Juan
Hospital Germans Trias
Maria T. Fernández
IPBS (Toulouse)
A. AucherG. GaibeletD. Hudrisier
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