Harnessing CD3 diversity to optimize CAR T cells | JoVE Visualize

Area of Science:

Immunology
Cell Biology
Biotechnology

Background:

Current chimeric antigen receptor (CAR) T cell therapies utilize the T cell receptor (TCR)-derived zeta (ζ) chain as an intracellular activation domain.
The functional roles of other TCR complex chains (CD3δ, CD3ε, CD3γ) within CARs remain largely unexplored.

Purpose of the Study:

To engineer and evaluate novel CAR T cells incorporating individual CD3 intracellular domains (CD3δ, CD3ε, CD3γ) as alternatives to the conventional ζ chain.
To investigate the mechanistic basis for enhanced anti-tumor efficacy observed with these novel CAR constructs.

Main Methods:

Systematic engineering of CAR T cells expressing single CD3 intracellular domains (CD3δ, CD3ε, CD3γ) or the conventional ζ chain.
In vivo efficacy studies comparing engineered CAR T cells against conventional CAR T cells.
Transcriptomic and proteomic analyses to assess T cell activation, metabolism, and dysfunctionality.
Investigation of CAR dimerization effects on functionality.
Identification of novel interaction partners for CD3 intracellular domains using CARs as surrogate TCRs.

Main Results:

CARs incorporating CD3δ, CD3ε, or CD3γ cytoplasmic tails demonstrated superior in vivo anti-tumor performance compared to conventional ζ CAR T cells.
Transcriptomic and proteomic analyses revealed distinct profiles of activation, metabolism, and reduced T cell dysfunctionality in the novel CAR T cells.
Dimerization of CAR constructs further enhanced overall T cell functionality.
The phosphatase SHP-1 was identified as a novel binding partner of CD3δ, interacting with the CD3δ-ITAM motif upon tyrosine phosphorylation.
SHP-1 binding to CD3δ was shown to attenuate T cell activation signals, potentially mitigating T cell exhaustion.

Conclusions:

CD3δ, CD3ε, and CD3γ intracellular domains represent viable and superior alternatives to the ζ chain for CAR T cell engineering.
These findings provide mechanistic insights into T cell activation and dysfunction, highlighting the role of SHP-1 in regulating CAR T cell responses.
The rational redesign of synthetic antigen receptors based on these insights holds promise for advancing cancer immunotherapy and overcoming T cell exhaustion.