Download Sinapsis Virológicas

Synapses,
cell-to-cell HIV transmission
Julià Blanco
Fundació
irsiCaixa
www.irsicaixa.org
One virus + one cell = ?
?
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.
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
…
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.
DC-T cell contact
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)
HIV spread
T cell-Epithelial cell contact
HIV transmission
A role for synapses in HIV infection
1. T cell-Epithelial cell contacts
2. DC-T cell contacts. Infectious synapse.
DC-SIGN independent HIV capture.
Virus and exosomes.
Izquierdo-Useros N, Naranjo M et al, BLOOD 2009
3. T cell-t cell contacts. Virological synapses.
Morphologically similar to other synapses. Joly C. et al. JEM 2004, 199:283-293
Main determinant: gp120-CD4 interaction. Adhesion molecules, secondary role
(Puigdomènech et al RETROVIROLOGY, 2008. 5:32)
CD4
CXCR4
Env
Env
ICAM-1
LFA-1
CD4
HIV ENV
CXCR4
CCR5
HIV ENV
CD4
CXCR4
CCR5
ICAM-1
LFA-1
Pero las cosas no son fáciles…
Trogocytosis…
Intercellular exchange of antigens/membranes.
Active process of cellular
communication, different from
proteolitic cleavage or exosome
transfer.
Infected - uninfected cellular contacts
Conjugate Formation
A role for trogocytosis?
Effect on inhibition/neutralization?
Cell-to-cell Fusion
Hemifusion/
Target cell death
Target cell infection
Conjugated CD4 T Cells (%)
Formation of cellular conjugates.
20
Infected cells
Target cells
15
10
NL4-3
Control
1%
5
*
*
*
0
BaL
13%
8%
Conjugated CD4 T Cells (%)
UNINF
*
20
NL4-3
BaL
15
FSC
Leu3a
10
2%
1%
1%
Shaking
1%
1%
CMRA
1%
5
*
*
*
*
0
NL4-3 (X4)
BaL (R5)
Transport of viral materials (p24)
CD4+
CXCR4+
CCR5-
X4
R5
Transport of viral materials (p24)
INFECTON
(TRANSMISSION)
PASSIVE TRANSFER
Accumulation of HIV into endosomes
*
*
*
*
*
*
*
*
Transport of membranes. Trogocytosis
UNINFECTED
% MOLT CD4-GFP+
INFECTED
2h
293-CD4GFP+
MOLT NL4-3/BaL
10
*
*
5
*
*
*
*
0
C
tr
Le l +
u3
a
C
Ig 34
G
b1
4E 2
10
2F
5
C
tr
Le l +
u3
a
C
Ig 34
G
b1
4E 2
10
2F
5
Cells (%)
MOLT
CD4-GFP+
% MOLT
GFP+
15
NL4-3
BaL
Trogocytosis at the VS is
Fusion-independent
CD4-dependent
Transport of membranes. Trogocytosis
UNINFECTED
293(Env+Denv)
No fusogenic activity to avoid hemifusion
No virus production to avoid transfer of virus
Expression of Env mutant 41.2
24h
24h
% CD4 p24 +
25
20
CD4
10
5
*
*
NL4-3 wt
tr
Le l
u3
a
C
34
C
tr
Le l
u3
a
C
34
0
41.2
% CD4 DiI +
10
DiI CD4+ T cells (%)
15
C
p24+ CD4 T Cells (%)
293(Env)
8
6
4
2
* *
0
NL4-3 wt
C
tr
Le l +
u3
a
C
34
CD4
How to measure membrane transfer?
C
tr
Le l +
u3
a
C
34
INFECTED
41.2
Infected - uninfected cellular contacts
CD4 blockade
Virus Transfer
Membrane Exchange
CD4
engagement
Conjugate Formation
Coreceptor or
gp41 blockade
Gp41
activation
Cell-to-cell Fusion
Hemifusion/
Target cell death
Target cell infection
Fundació irsiCaixa
Infection
24h
Real-Time PCR (probes for HIV and CCR5)
To test active retrotranscription
10
5
Uninf.
NL4-3
2F5
4E10
* * *
IgGb12
AZT
C34
Leu3a
Ctrl
Ctrl t=0
MOLT
Ctrl
0
MOLT
* * *
CD4
2^(-DD Ct)
15
Virological Synapse
Target cell
Infected cell
Fundació irsiCaixa
Conclusions.
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…
Fundació irsiCaixa
Hospital Clínic (Barcelona)
I. Puigdomènech
M. Massanella
M. Curriu
F. Cuñat
E. García
S. Marfil
J. Carrillo
C. Cabrera
Manel Juan
Margarita Bofill
IPBS (Toulouse)
Nuria Izquierdo-Useros
Javier Martínez-Picado
Bonaventura Clotet
Hospital Germans Trias
Maria T. Fernández
A. Aucher
G. Gaibelet
D. Hudrisier
Fundació irsiCaixa
Hospital Clínic (Barcelona)
I. Puigdomènech
M. Massanella
M. Curriu
F. Cuñat
E. García
S. Marfil
J. Carrillo
C. Cabrera
Manel Juan
Margarita Bofill
IPBS (Toulouse)
Nuria Izquierdo-Useros
Javier Martínez-Picado
Bonaventura Clotet
Hospital Germans Trias
Maria T. Fernández
A. Aucher
G. Gaibelet
D. Hudrisier