Synapses, cell-to-cell HIV transmission

Julià Blanco

www.irsicaixa.org

Fundació irsiCaixaFundació irsiCaixaFundació irsiCaixa

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.

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

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

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)

Pero las cosas no son fáciles…

Trogocytosis…

Active process of cellular communication, different from proteolitic cleavage or exosome transfer.

Intercellular exchange of antigens/membranes.

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?

NL4-3 (X4) BaL (R5)

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Leu3a C34

IgGb12

4E10 2F

5

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Leu3a C34

IgGb12

4E10 2F

5

** *

*

0

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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%

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**

0

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CD

4 T

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(%

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NL4-3 BaL

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Leu3a

3100

TAK779

C34

SHAKING

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Leu3a

3100

TAK779

C34

SHAKING

Formation of cellular conjugates.

Infected cells Target cells

Transport of viral materials (p24)

X4

R5

CD4+CXCR4+CCR5-

Transport of viral materials (p24)

INFECTON(TRANSMISSION)

PASSIVE TRANSFER

*

*

*

*

*

**

*

Accumulation of HIV into endosomes

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Leu3a C34

IgGb12

4E10 2F

5

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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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Leu3a C34

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0

2

4

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DiI

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4+

T c

ells

(%

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* *

NL4-3 wt 41.2

NL4-3 wt 41.2

0

5

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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

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

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

Virological SynapseVirological Synapse

Infected cellInfected cell

Target cellTarget cell

FundacióirsiCaixa

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.

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

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