1. HIV-1 Vpu Exploits the Crosstalk Between BST2 and the ILT7 Receptor to Inhibit Innate Sensing of Infected T cells by pDCs
Mariana G. Bego1, Édouard A. Côté1, Nick Aschman2, Johanne Mercier1, Winfried Weissenhorn2 and Éric A. Cohen1,3
1Institut de Recherches Cliniques de Montréal (IRCM)
2 Unit of Virus-Host Interactions, Université Grenoble Alpes
3Department of Microbiology and Immunology, Université de Montréal
Poster : TUPDA0103

2. BST2/Tetherin: one gene (a few isoforms) and many roles
Vpu
1- BST-2 is an IFN-regulated host factor that restrict the release of HIV-1 by a process that is dependent on the Vpu accessory protein
2- The protein has also been shown to act as a sensor of progeny virus release and as such trigger the production of proinflammatory cytokine through activation of NFKB
3-Apart from these functions, BST-2 was reported to act as the ligands of an inhibitory receptor express on PDC, ILT7. Engagement of BST-2 with ILT-7 inhibits IFN production when PDC are activated via TLR 7/TLR9
NF-kB
Sauter, 2010

3. HIV-infected CD4+ T cells are more potent at stimulating pDCs
Sensing and antiviral responses:
1- Env-CD4 interaction
2- Membrane fusion 3-decapsidation and release of ssRNA into TLR7+ endosome
4-triggering of a
MyD 88/IRF7 signaling cascade that results in IFN-I and cytokine production
Weak
Most efficient way pDC sense HIV is via cell contacts
Strong
1-the most efficient way PDC sense HIV-1 is when they get in contact with virus infected cells, a condition that result in IFN production. This process requires Env/CD4 interaction, membrane fusion, decapsidation and release of ssRNA into TLR 7 endsomes
Env –dependent process
Sensitive to Fusion inhibitors but not RT inhibitors
Iwasaki, A., Immunity , 2012

4. Goal of the study To investigate whether HIV exploits
the BST2-ILT7 regulatory axis to
modulate pDC antiviral responses

5. HIV-1 Vpu suppresses sensing of HIV-1 infected cells by pDCs
Co-culture X4 infected MT4 T cells and PBMCs
TypeI IFN (U/ml)
PBMC
Stimuli TRL7 ago TLR9 ago
Coculture MT4-mock MT4-dU MT4-WT

6. HIV-1 Vpu suppresses sensing of HIV-1 infected cells by pDCs
Co-culture X4 infected MT4 T cells and PBMCs
TypeI IFN (U/ml)
PBMC
Stimuli TRL7 ago TLR9 ago
Coculture MT4-mock MT4-dU MT4-WT
Relative % of IFN released dU WT
Mean 52%
*** X4
Mean 57%
Mean 46% * ** ns
Relative % of IFN released
Primary T cells (X4/R5 infection) dU WT X4 R5

7. Two Working Models
1-In the absence of Vpu, tethered virions are more effectively presented at
the cell surface for transmission and sensing by pDCs
2- Vpu modulates the levels of BST2 that can engage and activate ILT7 on pDCs

8. Control of HIV innate sensing by Vpu is BST2-dependent
Relative % of particles released
HIV-1 release assay
BST2-depleted MT4 cell lines

9. ILT7 depletion in enriched pDCs
Control of HIV innate sensing by Vpu requires the ILT7 pDC inhibitory receptor A 9 81 64 12
Non pDCs (PBMCs)
pDCs (PBMCs)
Enriched pDCs
Enriched pDCs siILT7
% Max
ILT7-PE
ILT7 depletion in enriched pDCs B
Soluble ILT7

10. Interplay between Vpu and BST2
Vpu exploits the crosstalk between BST2 and ILT7 to dampen the antiviral response of PDCs
Through a sophisticated targeted regulation of specific BST2 isoforms, Vpu promotes HIV release while at the same time interfering with pDC antiviral responses through ILT7 activation
This mechanism of innate immune evasion is likely to be important for an efficient early viral dissemination during acute infection

11. Acknowledgements Other Lab Members Collaborators Reagents
Fadi Hajjar
Johanne Mercier
Collaborators
Wei Cao, MD Anderson Cancer Center
Yong-Jun Liu, MedImmune
Nick Aschman & W. Weissenhorn (Univ. Grenoble Alpes and UVHCI, UVHCI-CNRS, Grenoble)
Mariana Bego
Édouard Bérubé-Côté
Reagents
Idera Pharmaceuticals
AIDS Reagent Program
The IRCM Clinic staff and
healthy volunteers
IRCM Flow Cytometry and Microscopy Cores