Rapid Progression to AIDS in HIV Individuals With a Structural Variant of the Chemokine Receptor CX3

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Rapid Progression to AIDS in HIV Individuals
With a Structural Variant of the Chemokine
Receptor CX3CR1

• Sophie Faure, Laurence Meyer, Dominique
  Costagliola, Celine Vaneensberghe, Emmauelle
  Genin, Brigitte Autran, French ALT and Immunoco
  Study Group, David H. McDermott, Philip M,
  Murphy, Patrice Debre, Ioannis Theodorou,
  Christophe Combadiere.

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Factors That Affect the Progression of HIV or
Resistance

• CCR5?32 homozygous resistance to HIV-1.
• CCR5- powerful however accounts for a small
  proportion.
• CCR5 ?32 heterozygous slower disease
  progression.

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CX3CR1

• Its a leukocyte chemotactic
• Adhesion receptor for the chemokine fractalkine
• HIV coreceptor
• Expressed in many tissues especially the brain
  interleukin-2-activated peripheral blood
  lymphocytes.
• Interacts with HIV envelopes.

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What is a Fractalkine?

• Can efficiently block the HIV coreceptor activity
  of CX3CR1.
• Has unprecedented adhesion properties.
• It plays a role in the immune response by
  reinforcing cell contact.

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Rationale of Research Report

• To see whether CX3CR1 regulates HIV disease.
• Comparing genetic variants and outcomes of the
  altered disease.

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Method

• Searched genetic variants associated with altered
  disease outcome.
• Screened CX3CR1 coding sequence for mutations in
  78 random French Caucasians.
• Screening was performed by single stranded
  conformation polymorphism (SSCP) technique.

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Nonsynonymous Mutation

• A to G substitution changed Thr57 to Ala(T57A).
• Threonine has the genetic code
• ACU, ACC, ACA, ACG
• Converted to
• GCU, GCC, GCA, GCG

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Mutation Continued

• G to A substitution changed Val122 to Ile(V122I).
• Valine has the genetic code
• GUU, GUC, GUA, GUG
• Converted to
• AUU,AUC, AUA

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Mutation Continued

• G TO a substitution changed Val249 to Ile(V249I).
• Valine has the genetic code
• GUU, GUC, GUA, GUG
• Converted to
• AUU,AUC, AUA

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Mutation Continued

• G to A substitution changed Thr280 to MET(T280M).
• Threonine has the genetic code
• ACU, ACC, ACA, ACG
• The C in ACG is replaced and results in
• AUG for methionine

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Synonymous Substitution

• Happened in codon 255.
• Changed G to A.

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Frequency of Polymorphisms

• Positions 57 122
• Each found only once among 157 chromosomes.
• Other Nonsynonymous allelic variants
• V249I found in 25.7
• T280M found in 13.5
• Mutations specific to Caucasian population

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What is Restriction Fragment length Polymorphism
(RFLP)?

• Restriction fragment length analyses uses
  restriction enzymes (RE) to cut DNA at specific
  4-6 bp recognition sites.
• Sample DNA is cut (digested) with one or more
  REs and resulting fragments are separated
  according to molecular size using gel
  electrophoresis .

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RFLP Method

• Studied the distribution of V249I T280M among
  565 individuals.
• 3 HIV cohorts
• Immunoco patients with intermediate
  progression.
• ALT patients with asymptomatic long term
  progression
• SEROCO patients with a known date of
  seroconversion.

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Frequencies of CX3CR1Genotypes and Haplotypes

• Six genotypes observed.
• Separated into V249 T280, I249 T280, I249 M280.
• There was no significant difference between
  HIV-infected and uninfected individuals.

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Haplotypes and Genotypes?

• Haplotype
• A set of genetic determinants located on a single
  chromosome
• Genotypes
• Refers to the genetic make-up of an organism.

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Hardy-Weinberg Expectation (HWE)

• No deviation was found in uninfected individuals.
• Deviation more pronounced in CCR5 wild-type
  HIV-infected individuals.
• Neither CX3CR1-V249I, CCR5-?32, nor CCR2-64I
  alleles showed significant departure from HWE.
• Results suggest that I249 M280 Haplotype probably
  increases susceptibility to HIV infection.

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Disease Progression

• Higher frequency of the I249 M280 Haplotype in
  the Immunoco cohort compared with the ALT cohort.
• Protective CCR5-?32 allele was more frequent in
  the ALT cohort.
• Suggesting that CX3CR1 I249 M280 Haplotype
  adversely affects HIV disease progression.

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Predictive Values of CX3CR1 and CCR5 genotypes
for Immunoco Status.
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Kaplan-Meier Curves
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The Total SEROCO Cohort (426 patients)

• CX3CR1-M280 homozygous progressed faster to Aids
  than CX3CR1-T280.
• Disease progression was similar for heterozygotes
  and Wild-type homozygotes.
• Suggest that effects of CX3CR1-I249 M280
  haplotype is recessive.

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SEROCO patients Homozygous for CCR5 wild type.

• Patients are partially protected by the CCR5-?32
  allele.
• If this allele is excluded, acceleration to Aids
  or CD4 decline is pronounced.

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Compared Fractalkine Binding to Primary
Peripheral Blood mononuclear cells (PBMCs).
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Results of Comparison

• Revealed significantly reduced binding affinity
  of 125I-labeled Fractalkine.
• Indicated that two SNPs affect the integrity of
  the receptor.
• Binding sites per cell was dramatically reduced
  in CX3CR1-I249 M280 homozygotes vs. wild type
  controls.

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Conclusion

• CX3CR1 is polymorphic in the Caucasian
  population.
• CX3CR1 I249 M280, is associated with accelerated
  HIV disease.
• Potential mechanisms of action
• Regulation of HIV infection of target cells
• Regulation of antiviral immune responses.