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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
4
Patients & methods
5
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)
7
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
10
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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