Genetic variability of HIV-2 LTR regionsimpact transcriptional activities

Le Hingrat QuentinLaboratoire de Virologie

Hôpital Bichat-Claude BernardINSERM UMR 1137- IAMEUniversité Paris Diderot

Abst#_O_#06

HIV-2: a « mild » retrovirus

• Slower progression towards AIDS than HIV-1 1

• HIV-2 viral loads frequently undetectable even before ART initiation 2

• Epidemic restrained to a smallernumber of countries: West Africa 3

• Longer viral cycle (2 vs 1 day)

This slower evolution of HIV-2 is still unexplained:– Level of HIV-2 reservoir controversial

– Reduced reactivation of HIV-2 proviruses?

1 Grassly et al., 1998; 2 Popper et al., 1999 ; 2 Visseaux et al., 2016. 2

Long Terminal Repeat regions

• Organized in 3 sub-regions: U3, R and U5 1

• Involved in transcription of proviral DNA

• HIV promoter– Activated by cellular transcription factors (TF) 2

– And by the viral protein Tat 3,4

1 Krebs et al., 2001; 2 Leiden et al., 1992; 3 Rhim et Rice, 1995; 4 Pagtakhan et al., 1997. 3

Objectives

• To assess genetic diversity of HIV-2 LTR

• To determine its potential impact on:

– HIV-2 cellular reservoir

– LTR transcriptional activities

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Patients & methods

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Plasma

PBMCFicoll®

Red blood cells

Extraction ofviral DNA

HIV-2 plasmaticviral load

Quantification of HIV-2 total DNA

Sequencing of HIV-2 LTR regionby Sanger technology

99 antiretroviral-naive HIV-2 infected patients, enrolled in the

French ANRS CO5 cohort

PBMC availableduring the year 2015

HEK293T and Jurkat cells

Transcriptional activitiesof different HIV-2 LTR

Clinical and biologicaldata collected

HIV-2 LTR mutations

• Higher variability of group B sequences (15.0% versus 13.2% for group A)

• Deletion of PuB1 and pets binding sites in all group B LTR

– Both sites are activated by the transcription factor Elf-1

– Elf-1 is expressed only in activated T lymphocytes 1

• 4 group B-infected patients (11%) also had a deletion of one Sp1 binding site

– Sp1 = ubiquitous TF involved in basal level of LTR transactivation 2

• Numerous unique insertions and/or deletions in group B regulatory regions(42% versus 7% in group A; p=0.002)

61 Leiden et al., 1992; 2 Ross et al., 1991.

HIV-2 cellular reservoir

• Quantification of HIV-2 total DNA in PBMC– Less frequently quantifiable for group B (16% vs 67%; p<1.10-3)

– And lower level of cellular reservoirs when quantifiable (1.75 log10 c/106 CSMP vs 2.11 log10 c/106 CSMP; p=0.03)

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No specific mutation associated to this lower level

of cellular reservoir

LTR transactivation

– Basal activity lower if deletion of one Sp1 binding site

– PMA: Lower response to cellular activation of group B LTR

– Addition of Tat to PMA is not sufficient to overcome lower cellular transactivation of group B LTR

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LTR transactivation

– Basal activity lower if deletion of one Sp1 binding site

– PMA: lower response to cellular activation of group B LTR

– Addition of Tat to PMA is not sufficient to overcome lower cellular transactivation of group B LTR

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LTR transactivation

– Basal activity lower if deletion of one Sp1 binding site

– PMA: lower response to cellular activation of group B LTR

– Addition of Tat to PMA was not sufficient to overcome lower cellular transactivation of group B LTR

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Discussion

• High variability in the U3 sub-region– Previously observed in HIV-1 1

– Inter-group differences for HIV-2 with variations in TF binding sites

• Impact of those differences on LTR transactivation– Deletion of one Sp1 site has a slight impact on basal activity

– Deletion of PuB1 and pets decreases response to cellular activationElf-1 is expressed in activated T lymphocytes 2

• May it block or limit HIV-2 group B reactivation?– Contribution to the lower cellular reservoir?

– Impact on pathogenesis?

1 Alteri et al., 2015; 2 Leiden et al., 1992. 11

Acknowledgements

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▪ Lise Chauveau▪ Olivier Schwartz▪ Françoise Porrot▪ Florence Guivel

▪ Harry Kemble

▪ Mélanie Bertine

▪ Charlotte Charpentier

▪ Diane Descamps

▪ Benoit Visseaux

▪ Gilles Collin

▪ Sophie Matheron

▪ Fidéline Collin

▪ Clinicians and techniciansinvolved in the French ANRS CO5 cohort

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