Synapses, cell-to-cell HIV transmission Julià Blanco FundacióirsiCaixaFundacióirsiCaixaFundacióirsiCaixa

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:

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 transmission HIV spread

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-1CD4 CXCR4 CCR5 ICAM-1 HIV ENV CD4 CXCR4 CCR5 HIV ENV LFA-1 ICAM-1 Morphologically similar to other synapses. Joly C. et al. JEM 2004, 199: T cell-t cell contacts. Virological synapses. CD4 CXCR4 Env Env Main determinant: gp120-CD4 interaction. Adhesion molecules, secondary role ( Puigdomènech et al RETROVIROLOGY, :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 contacts Conjugate Formation Cell-to-cell Fusion Hemifusion/ Target cell death Target cell infection A role for trogocytosis? Effect on inhibition/neutralization?

NL4-3 (X4)BaL (R5) Ctrl + Leu3a C34 IgGb12 4E10 2F5 Ctrl + Leu3a C34 IgGb12 4E10 2F5 * * * * Conjugated CD4 T Cells (%) Control Leu3a Shaking UNINF NL4-3 BaL CMRA FSC 1% 13% 8% 2% 1% 1% 1% 1% 1% * * * * Conjugated CD4 T Cells (%) NL4-3BaL Ctrl + Leu3a 3100 TAK779 C34 SHAKING Ctrl + 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

NL4-3BaL CD4-GFP+ MOLT Cells (%) 2h 293-CD4GFP+ MOLT NL4-3/BaL % MOLT CD4-GFP+ UNINFECTED INFECTED Transport of membranes. Trogocytosis Trogocytosis at the VS is Fusion-independent CD4-dependent

NL4-3 wt 41.2 NL4-3 wt h 293(Env) CD4 % CD4 DiI + 24h 293(Env+ env) CD4 % CD4 p24 + INFECTED UNINFECTED How to measure membrane transfer? No fusogenic activity to avoid hemifusion No virus production to avoid transfer of virus Expression of Env mutant 41.2 Transport of membranes. Trogocytosis

Infected - uninfected cellular contacts CD4 engagement Conjugate FormationMembrane ExchangeVirus Transfer Gp41 activation Cell-to-cell Fusion Hemifusion/ Target cell death Target cell infection CD4 blockade Coreceptor or gp41 blockade

Infection * 24h Real-Time PCR (probes for HIV and CCR5) To test active retrotranscription FundacióirsiCaixa

Virological Synapse Infected cell Target 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. Puigdomènech M. Massanella M. Curriu F. Cuñat E. García S. Marfil J. Carrillo C. Cabrera Margarita Bofill Nuria Izquierdo-Useros Javier Martínez-Picado Bonaventura Clotet Hospital Clínic (Barcelona) Manel Juan Hospital Germans Trias Maria T. Fernández IPBS (Toulouse) A. Aucher G. Gaibelet D. Hudrisier

Fundació irsiCaixa I. Puigdomènech M. Massanella M. Curriu F. Cuñat E. García S. Marfil J. Carrillo C. Cabrera Margarita Bofill Nuria Izquierdo-Useros Javier Martínez-Picado Bonaventura Clotet Hospital Clínic (Barcelona) Manel Juan Hospital Germans Trias Maria T. Fernández IPBS (Toulouse) A. Aucher G. Gaibelet D. Hudrisier