CD4 Effector TCR Avidity for Peptide on APC Determines the Level of Memory Generated

Area of Science:

• Immunology
• T-cell Biology
• Vaccinology

Background:

• T-cell receptor (TCR) affinity for peptide antigens influences initial memory generation.
• The role of effector TCR affinity at a later "effector checkpoint" (5-8 days post-infection) in dictating memory formation and protective immunity remains unclear.
• Understanding this checkpoint is crucial for optimizing vaccine strategies and predicting immune responses.

Purpose of the Study:

• To investigate whether effector TCR affinity for peptide antigens at the effector checkpoint determines the extent of memory cell generation and protection against rechallenge.
• To elucidate the mechanisms by which TCR affinity influences memory formation, including the role of IL-2 signaling.

Main Methods:

• Generation of influenza A virus nucleoprotein (NP)-specific TCR transgenic mouse strain (FluNP).
• Creation of NP-peptide variants with varying affinities for the FluNP TCR.
• In vivo evaluation by priming naive FluNP T-cells, isolating effectors at the checkpoint, and adoptive transfer into uninfected hosts with peptide-pulsed antigen-presenting cells (APCs).

Main Results:

• Higher-avidity peptides resulted in significantly increased numbers of FluNP memory cells in spleen, lung, and draining lymph nodes.
• Higher avidity correlated with enhanced protection against lethal influenza challenge.
• Peptide avidity determined memory cell numbers and influenced IL-2 production by effector T-cells, with IL-2 receptor alpha (IL-2Rα) expression on APCs further enhancing memory formation.

Conclusions:

• Effector TCR affinity for peptide antigens at the effector checkpoint is a critical determinant of memory T-cell generation and protective immunity.
• The study highlights a regulatory pathway where peptide avidity modulates IL-2 production and availability, selecting high-affinity T-cells for memory development.
• These findings suggest that optimizing antigen affinity is key for enhancing vaccine-induced memory and long-term protection.