Michael Imbeault, Michel J' Tremblay

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Characterization of early interactions between
primary CD4 lymphocytes and HIV-1

• Michael Imbeault, Michel J. Tremblay
• CRI CHUL Quebec, Canada

AIDS 2006 Toronto
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Experimental design
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Determination of infection rate in the studied
population
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Infection rates in primary cells is low
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Results

• An overview

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So many genes lets focus

• We chose to focus on p53 because of many reasons
• p53 is regulated post-transcriptionally by HDM2
  at the time of analysis, no transcriptional
  regulation pathway was known
• The literature on it is abundant, as its involved
  in many cancers, cell cycle control, dna repair
  and apoptosis
• Its activation have been implicated in HIV-1 Env
  mediated apoptosis
• p53 binds to multiple viral proteins such as nef,
  tat, vpr RT
• NF-kappaB and p53 are the dominant
  apoptosis-inducing transcription factors elicited
  by the HIV-1 envelope. Perfetinni al, 2004
• The only other HIV-1 study (Corbeil al, 2001)
  based on microarrays stated that no p53
  upregulation was observed upon exposure of CD4 T
  lymphocytes to HIV-1. However, it used a
  transformed cell line (CEM-GFP).
• We found that HIV-1 modulated the transcription
  of several p53-related genes (PP1R15A, p53BP2)

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qRT-PCR Western blot confirmations of p53
upregulation
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p53 can be transcriptionally regulated
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Nice but

• CD4 T lymphocyte dont produce type I
  interferons in response to HIV-1

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FACS analysis cell purity
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Could CD14 cells in our population produce type
I interferons?
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Interferon ? production
Detection limit
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Interferon a / bNeutralization assay
2.4 fold
0.8 fold
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Working model

• HIV-1 cause type I interferon production by CD14
  cells present in the culture.
• Presence of IFNs could be responsible for the low
  rate of infection observed in primary cells as
  compared to cell lines.
• Interferon leads to a transcriptional increase of
  p53 in CD4 T cells.
• Increased presence of p53 inhibit Tat, limiting
  viral synthesis and promoting latency early on, a
  key to survival of HIV-1 (Li al, 1995 Harrod
  al, 2003)
• Controversial, as a recent study (Pauls al,
  2006) states that p53 is necessary for viral
  replication.

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Working model

• p53 is also bound by nef, which inhibits env
  mediated p53 mediated apoptosis (Greenway al,
  2002).
• p53 enhance reverse transcriptase activity,
  thereby facilitating the infection process in
  other cells (Bakhanashvili, 2001).
• Because of IFNs mediated p53 surexpression,
  uninfected, bystander cells are more susceptible
  to undergo p53-mediated apoptosis, a
  well-described phenomenon.
• Our results show that multiple proteins
  implicated in p53 regulation were also
  differentially regulated by HIV-1.

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Summary

• HIV-1 disrupts multiple cellular pathways, all of
  which are consistent with retroviral infection
• cell cycle
• dna repair
• rna metabolism
• apoptosis
• No significant difference was observed between
  the wild type virus and the ICAM-1 bearing one.
• HIV-1 adapted to take advantage of the type I
  interferon mediated antiviral response, notably
  by taking advantage of p53 surexpression.

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Thanks

• Dr Michel J. Tremblay the team
• Special thanks to
• Dr Michel Ouellet
• Dr Corinne Barat
• Canadian Institutes
• of Health Research
• (CIHR) for funding

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