Regulatory T cells define affinity thresholds for CD8⁺ T cell tumor infiltration

Area of Science:

• Immunology
• Oncology
• Vaccinology

Background:

• Tumor-specific T cell receptor (TCR) repertoires often lack high-affinity TCRs.
• Regulatory T cells (Tregs) suppress anti-tumor immune responses, further limiting efficacy.
• Developing effective cancer vaccines targeting low-affinity T cells remains a challenge.

Purpose of the Study:

• To investigate if Treg depletion can enhance the anti-tumor efficacy of low-affinity T cells.
• To evaluate a vaccination strategy combining a weak agonistic peptide vaccine with Treg depletion.
• To assess the impact on T cell infiltration, functionality, and tumor progression.

Main Methods:

• Utilized a weak agonistic peptide (A4Y) derived from LCMV glycoprotein peptide p33 as a model antigen.
• Employed virus-like particles (VLPs) as a vaccine platform.
• Tested the approach in a B16F10 melanoma model, combining A4Y-VLP vaccine with Treg depletion.

Main Results:

• Limited in vivo lytic cross-reactivity was observed between A4Y and p33 peptides.
• The A4Y-VLP vaccine alone did not inhibit tumor progression.
• Combining the A4Y-VLP vaccine with Treg depletion induced robust CD8+ T cell infiltration, enhanced T cell function, and improved tumor-free survival.
• Treg depletion also enhanced anti-tumor responses in a separate low-affinity vaccine model.

Conclusions:

• Treg depletion can overcome the limitations of low-affinity T cells in anti-tumor immunity.
• This strategy holds promise for enhancing the efficacy of vaccines targeting tumor-associated antigens (TAAs).
• Combining Treg depletion with low-affinity vaccination represents a potential advancement in cancer immunotherapy.