Transcript SSD Presentation 2011x - ScholarWorks@GVSU

Amanda R. Antczak
Grand Valley State University
April 13, 2011
Faculty Mentor: Dr. Steven Hecht
HIV: An Overview
 Human Immunodeficiency Virus
 HIV-1 vs. HIV-2
 Discovered in 1981
 HIV vs. AIDS
 HIV statistics
HIV: Pathophysiology
 Transmission of the virus
 Lymphocytic attack
 T cells vs. B cells
 T “helper cells”
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CD4 glycoprotein expression
Macrophage/CD8 activation and B cell maturation
T- Cell Function and Cell
Mediated Immunity
HIV: Viral Entry
 The viral capsid
 Gp41 and gp120
 Chemokine receptor binding site
 CD4 binding
 Conformational changes
 Membrane fusion and viral entry
 Viral replication and “budding”
 T-cell destruction
 Normal: 1,000cells/mm3, AIDS: 400 – 800 cells/mm3
HIV: Viral Entry Mechanism
Chemokines
 Chemokines: small cytokine (cell signaling) molecules
 Chemoattractants
 2 classes:
 Pro-inflammatory
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Immune system recruitment
Activation of lymphocytes, monocytes, macrophages, etc.
 Homeostatic

Tissue maintenance
 CC chemokines (α) v. CXC chemokines (β)
Chemokine Receptors
 Cellular receptors for chemokines
 7-transmembrane structure
 Intracellular/extracellular loops
 On leukocyte surfaces
 Coupled to G-proteins
 Transmit signals to cell when coupled with G-proteins
 20 known chemokine receptors
 Two of interest: CCR5 and CXCR4
Chemokine Receptor Structure
C-C Chemokine Receptor 5
 A co-receptor for the HIV-1 virus (with CD4)
 Located on chromosome 3
 Structure:
 4 intracellular loops, 3 extracellular loops
 Viral tropism
 R5 strains: CCR5 entry
 X4 strains: CXCR5 entry
The Δ32 Base Pair Deletion
 A 32 base pair deletion in the CCR5 allele
 Shifts the open reading frame of the allele
 Deletion  a dysfunctional, truncated protein
 CCR5 not expressed on the cellular surface in individuals
with the BP deletion
Homozygosity vs. Heterozygosity
 Homozygous individuals:
 2 copies of the mutant allele
 Zero expression of CCR5 receptors on the cellular surface
 HIV resistance
 Heterozygous individuals:
 1 copy of the mutant allele
 Reduced levels of CCR5 receptors on the cellular surface
 Lowered risk of infection, delayed onset of AIDS (reduced
viral load)
CCR5 Δ32 Allele Frequencies
 1% homozygosity in Caucasians, up to 20%
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heterozygosity in some Northern European populations
The mutation is absent in those of African, Middle
Eastern, or Asian descent
Highest frequency observed among Ashkenazi Jews
High frequencies also seen in Iceland, Britain, Spain, Italy
and Russia
Absence in primates suggests the recent origin in the
mutation.
CCR5 Δ32 Allele Frequencies
Origins of the Δ32 Deletion
 Exact origin unknown
 Distribution/ spread of the mutation suggests recent origin
and a selective pressure in order to increase frequency
 HIV = not a possible selective pressure
 Bubonic Plague vs. Smallpox
 Bacterial vs. Viral
 Smallpox and chemokine receptors
 Endemic nature of smallpox
 Gene products and chemokine receptor inhibition
Potential Therapies Using CCR5 Δ32
 Chemokine inhibition
 Similar to Δ32 homozygotes
 CCR5 antagonists
 Maraviroc
 Vicriviroc
 Other research:
 Disrupting CCR5 synthesis
 RNA interference
 “Zinc fingers”
Maraviroc
 A CCR5 co-receptor antagonists
 Approved in Aug. 2007
 Inhibits CCL3 and CCL4 sub-type ligands from binding to
receptor
 Prevents interaction between gp120 and CCR5  no viral
entry
Vicriviroc
 A CCR5 co-receptor antagonist
 Not yet approved by FDA
 Similar MOA to Maraviroc
CCR5 Antagonist Concerns
 Tropism
 CCR5 antagonist resistance
 Blockade of maraviroc
 Use of CXCR4
 Conclusion: best when combined with ARV therapy
Δ32 Stem Cell Transplantation
 Allogenic stem cell transplantation
 From CCR5 Δ32 homozygous donor to HIV+ pt.
 Donor must be HLA matched (histocompatability)
 Only for R5 tropic strains of HIV-1
 ARV (HAART) therapy discontinued
 Pt. remained without viral rebound 20 mos. post
transplantation
 In rectal biopsy specimens, macrophages expressed CCR5,
but CD4 T cells did not
Other Clinical Potentials:
Multiple Sclerosis
 Multiple sclerosis
 Autoimmune disease
 T and B cell mediated
 Inflammation and demyelination of neuronal axons
 Chemotaxis mediated inflammation
 CCR5 on lymphocytes in actively demyelinating brain
lesions (and CSF fluid)
 CCR5 Δ32 deletion resulted in later age of onset in
clinical studies
Other Clinical Potentials:
Rheumatoid Arthritis
 Rheumatoid arthritis
 Autoimmune disease
 T cell infiltration into synovial joins
 Inflammation
 CCR5 found in synovial tissue from R.A. patients
 Fibroblasts upregulate CCL5 in response to TNF
 Δ32 deletion related to R.A. severity
 Carriers of allele more likely to fall into “non-severe”
category
Other Clinical Potentials:
Cancer
 Cancer
 Unregulated tumor growth
 Environmental and hereditary causes
 Inflammation induced via chemokines
 Increased tumor growth
 Increased metastasis
 CCR5 expression in cancer cells
 Multiple myeloma and CCR1
 Pancreatic cancer
CCR5 Δ32 individuals partially protected from diabetes
 CCR5 antagonists
 Block cellular signaling and inhibit tumor growth/metastasis

Other Clinical Potentials:
Autoimmune Myocarditis
 Autoimmune myocarditis
 Autoimmune disease
 Inflammation of the myocardium
 T cell mediated
 CCR5 expressing T cells in inflamed cardiac tissue
 CCR5 Δ32 allele results in reduced inflammation
 In mice, CCR5 antagonism resulted in a reduced
inflammatory response
Conclusions
 Future uses for the Δ32 B.P deletion
 HIV-1



CCR5 antagonists
Allogenic stem cell transplantation
Combined therapy
 Chemokine mediated disease


CCR5 antagonists
Role of chemokine ligands, possible sites for inhibition
Literature Cited
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QUESTIONS?