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CTLA-4-Fas ligand functions as a trans signal converter protein in bridging antigen-presenting cells and T cells

J H Huang1, M L Tykocinski

  • 1Department of Pathology and Laboratory Medicine, University of Pennsylvania, 6 Gates Pavilion, 3400 Spruce Street, Philadelphia, PA 19104-4283, USA.

International Immunology
|April 3, 2001
PubMed

Insights

A novel fusion protein, CTLA-4-FasL, effectively suppresses pathogenic T cells by combining co-stimulator blockade and trans inhibitory signaling. This engineered protein is significantly more potent than existing therapies in inhibiting T cell proliferation.

Area of Science:

  • Immunology
  • Molecular Biology
  • Protein Engineering

Background:

  • Current strategies for suppressing pathogenic T cells include co-stimulator blockade (e.g., CTLA-4-Ig) and trans inhibitory signaling (e.g., Fas ligand [FasL]).
  • There is a need for novel therapeutic agents with enhanced efficacy in T cell suppression.

Purpose of the Study:

  • To design and characterize a novel hetero-bifunctional fusion protein, CTLA-4-FasL, combining both co-stimulator blocking and trans inhibitory signaling.
  • To evaluate the efficacy of CTLA-4-FasL in suppressing T cell activity compared to existing agents.

Main Methods:

  • A chimeric expression cassette was used to produce the CTLA-4-FasL fusion protein.
  • Binding affinities were assessed using immunofluorescence and flow cytometry.
  • Apoptosis induction and T cell proliferation inhibition were measured in vitro using co-culture systems and peripheral blood mononuclear cells.

Main Results:

  • CTLA-4-FasL demonstrated binding to both B7-1/B7-2-expressing B cells and Fas-expressing T cells.
  • The fusion protein's ability to induce apoptosis in T cells was enhanced by B cells presenting the necessary ligands.
  • CTLA-4-FasL exhibited approximately 1000-fold greater potency in inhibiting peripheral blood mononuclear cell proliferation compared to CTLA-4-Ig and surpassed the combination of CTLA-4-Ig and soluble FasL.

Conclusions:

  • CTLA-4-FasL is a novel fusion protein with combined co-stimulator blocking and trans inhibitory signaling functions.
  • This engineered protein, a 'trans signal converter protein', demonstrates significantly enhanced potency in suppressing T cell proliferation.
  • CTLA-4-FasL represents a promising new class of immunomodulatory agents.

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