GLOBOTRIAOSYL CERAMIDE: A NATURAL RESISTANCE FACTOR TO HIV INFECTION

1
GLOBOTRIAOSYL CERAMIDE A NATURAL RESISTANCE
FACTOR TO HIV INFECTION

• Nicole Lund Darinka Sakac Clifford A.
  Lingwood Cyril Levene Åsa Hellberg Martin L.
  Olsson Donald R. Branch.
• Dept. of Laboratory Medicine Pathobiology,
  University of Toronto
• Canadian Blood Services, Toronto, Ontario,
  CANADA

2
HIV Entry Role of Glycosphingolipids

• Implicated in HIV/host cell membrane fusion
• Form lipid rafts which are central to HIV
  infection
• Bind HIVgp120 V3 loop via sphingolipid
  recognition motif
• GSL candidates include GC, SGC, GM3 and Gb3

Fantinis Model
T cell or Monocyte
GSL
CD4
CXCR4 or CCR5
3
Globotriaosylceramide HIV A contradiction in
terms

• Inhibit GSL biosynthesis in vitro block
  HIV-membrane fusion
• Reconstitute with Gb3 restore membrane
  fusion
• Hammache et.al .J.Virol (1999)
• A soluble Gb3 analogue inhibits HIV membrane
  fusion and infection, irrespective of viral
  tropism
• Lund et.al. AIDS (2006)
• Target cells with a genetic defect causing Gb3
  accumulation (Fabry disease), show significant
  resistance to HIV-1 infection
• Lund et.al. AIDS (2005)

4
Globotriaosylceramide (Gb3) or Pk Blood Group
Antigen
Sugar Moiety Recognition Function

• Pk blood group
• genetically defined differential Gb3 expression
• pp
• Inactive Gb3 synthase
• Lack Gb3
• P1k
• Inactive Gb4 synthase
• Accumulate Gb3

Gala(1-4) Galß(1-4) Glcß(1-1)
Sphingosine Alkyl chains
Ceramide Membrane Anchoring
Gb3, Pk, CD77, VT receptor
Pk (Gb3)
P (Gb4)
P1
p
5
HIV Susceptibility and Differential Gb3 Expression
6
PBMCs lacking Gb3 are highly susceptible to R5
HIV-1
HIV-1Ba-L Infection (P24 pg/ml)
Time (days)
plt0.05 plt0.005
FACS Analysis of surface receptors
HIV Infection
7
PBMCs lacking Gb3 are highly susceptible to X4
HIV-1
HIV-1IIIB Infection (P24 pg/ml)
Time (days)
plt0.05 plt0.005
FACS Analysis of surface receptors
HIV Infection
8
GM3 Expression potential facilitator in
infection?
7.7
1.8
GlcC GalC LC Gb3 Gb4 Gb5 GM3
Unactivated
3.4
3.0
PHA activated
p C p C p C
6.0
3.7
Unactivated
PHA activated
GSL Standards
PHA/IL2 activated
PHA/IL2 activated
Ctrl pp3
TLC of total GSL
FACS Analysis of surface GM3
9
PBMCs expressing high levels of Gb3 are less
susceptible to HIV-1
HIV-1Ba-L Infection (P24 pg/ml)
HIV-1IIIB Infection (P24 pg/ml)
Time (days)
plt0.05 plt0.005
HIV Infection
FACS Analysis of surface receptors
10
Gb3 Expression potential host resistance
factor?
15
29
GlcC GalC LC Gb3 Gb4 Gb5 GM3
PHA activated
7
13
PHA/IL2 activated
P1k C P1k C P1k C
Ctrl P1k
Unactivated
PHA activated
GSL Standards
PHA/IL2 activated
TLC of total GSL
FACS Analysis of surface Gb3
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Exogenous Gb3 Expression HIV-1 Infection
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Exogenous Gb3 Inhibits X4 HIV-1 Infection
HIV Infection
plt0.05 plt0.005
CD4 populations
PBS
Gb3 liposome
CXCR4
Gb3
Gb3
FACS Analysis of surface receptors
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In Conclusion

• Absence of surface expressed Gb3 (pp targets)
  enhances R5 and X4 HIV infection
• Higher surface expression of Gb3 (P1k targets)
  reduces R5 and X4 HIV infection
• Exogenously introduced Gb3 reduces X4 HIV
  infection, and mimics X4 infection of P1k targets

14
Gb3 Novel Host Resistance Factor
T cell or Monocyte
CD4
CXCR4 or CCR5
Gb3
Proposed Branch Model
15
Acknowledgements

• Supervisor Hospital for Sick Children
• Donald R. Branch Clifford A. Lingwood
• Muru Mylvaganam
• Committee Beth Binnington-Boyd
• Clifford A. Lingwood
• Stanley Read
• Branch Lab
• Darinka Sakac Funding
• Payman Bokaei CBS Graduate Student Fellowship
• Alison Foo CIHR Doctoral Research Award
• Garnet Suck OHTN Priority Initiative Grant
• Soad Fahim OHTN Operating Grant
• Simmy Wan
• Yulia Katsman
• Xue-Zhong Ma
• Elvisa Loshe
• Valerie McCann