Reduced IL7Ra expression in CD8 T cells from HIV patients is associated with Gfi1 and impaired STAT

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Reduced IL-7Ra expression in CD8 T cells from
HIV patients is associated with Gfi-1 and
impaired STAT activation in response to IL-7 but
not IL-2, IL-15, IL-4, and IL-10
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Cytotoxic T Lymphocytes

• Critical in the control of HIV replication
• Evidence that CTLs from HIV patients become
  defective
• Altered differentiation pattern
• Impaired cytotoxicity
• Increased susceptibility to apoptosis
• Cytotoxicity, growth, differentiation and
  maintenance controlled by cytokines

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Cytokines control T cell differentiation
Initiation
Contraction
Clonal expansion
Maintenance
IL-7
IL-15
IL-15
IL-15
IL-15
IL-2
IL-7
Peptide- MHC
TCR
IL-2
Cell death
Time
From Schluns and Lefrancois, Nat. Rev. Immunol.,
2003, 3 269.
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gc family cytokines
From Kovanen and Leonard Immunol Rev. 2004,
20267-83
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Increased IL7Ralow CTL in HIV Patients Off
therapy normalization under HAART

• Vingerhoets et al 1998, Macpherson et al 2001,
  Paiardini et al 2005, Rethi et al 2005, Boutboul
  et al 2005, Sasson et al 2006, Colle et al 2006,
  Read et al 2006.others

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Objectives1) Investigate the capacity of
IL-7Ralow CTLs to signal in response
cytokines2) Study the molecular mechanisms that
may downregulate IL-7Ra expression
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IL-2 Induced Signaling Pathways
Immunological Reviews 202/2004
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Cytokine dependent STAT activation in patient CTLs
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of patient CTLs unable to activate STAT5 in
response to IL-7
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Correlation between IL-7Ra expression and
IL-7-induced P-STAT5
IL-7 Stimulation
r ² 0.95
P-STAT5-positive cells
IL-7Ra - positive cells
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Transcriptional Regulators of IL-7R
Human IL-7Ra promoter
J. Kakal and P. Macpherson
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Relative mRNA Expression Levels IL-7Rahigh vs low
CTLs
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Silencing of GFI1 Leads to Enhanced Expression of
IL-7Ra
RT-PCR
24hrs
Fold Change
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Summary

• IL-7Ralow CTL failed to activate STAT5 pathway in
  response to IL-7 but recruited the STAT pathway
  in response to IL-2, IL-15, IL-10, and IL-4.
• Gfi-1 mRNA levels are reduced in IL-7Rahigh
  relative to IL-7Ralow CTL
• Silencing Gfi-1 expression lead to increased
  IL-7Ra mRNA expression in CTL
• GABPa mRNA levels did not significantly vary
  between IL-7Ralow and IL-7Rahigh CTL.
• Gfi-1B mRNA was not consistently detectable in
  these CTL populations (data not shown).

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Conclusions

• IL-7Ralow CTL appear to still be able to respond
  to other cytokines important for their
  maintenance in the periphery other than IL-7 at
  the level of STAT activation.
• Results provide support for a transcriptional
  repression mechanism involving Gfi-1 in the
  control of IL-7Ra expression in primary human
  CTL.

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Acknowledgements

• Ottawa Hospital
• Jonathan Angel
• Nancy Lamoureux
• Mary-Ellen Arsenault
• Paul Macpherson
• Juzer Kakal
• Study participants

• Childrens Hospital of Eastern Ontario
• Anita Benoit
• Khaled Abdkader
• Danylo Sirskyj
• Abdulkarim Alhetheel
• Nadia Sant
• Niranjala Gajanayaka
• Yuriy Yakubtsov
• Rita Frost
• Sue Aucoin

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PD-1 Protein Expression Increases on CD8 T Cells
from HIV patients