Modified peptides in anti-cancer vaccines: are we eventually improving anti-tumour immunity?

Area of Science:

• Immunology
• Oncology
• Vaccinology

Background:

• T cell-mediated anti-tumor immunity is a key cancer therapy strategy.
• Optimized peptides and altered peptide ligands (APLs) are used in cancer vaccines to enhance immunogenicity.
• Clinical efficacy of APLs has not met expectations despite preclinical promise.

Purpose of the Study:

• To investigate why altered peptide ligands (APLs) may not effectively translate preclinical success into clinical efficacy for cancer vaccines.
• To address the hypothesis that T cells primed by modified tumor peptides may exhibit impaired cross-recognition of tumor cells.
• To re-evaluate the utility of modified tumor peptides in light of current understanding and alternative strategies.

Main Methods:

• Review of existing preclinical and clinical studies on altered peptide ligands in cancer vaccines.
• Analysis of the impact of amino acid substitutions on HLA/peptide binding and T cell receptor (TCR) interactions.
• Evaluation of T cell cross-recognition capabilities following priming with modified tumor peptides.

Main Results:

• Amino acid substitutions in peptides can lead to unpredictable changes in the HLA/peptide interface.
• These changes can alter the T cell receptor repertoire, potentially reducing affinity for native tumor epitopes.
• Primed T cells may exhibit insufficient cross-reactivity with actual tumor cells, limiting therapeutic effect.

Conclusions:

• The potential for impaired cross-recognition by T cells primed with modified tumor peptides is a significant factor in their limited clinical success.
• Conservative amino acid changes can unpredictably affect TCR interactions and anti-tumor responses.
• Reconsideration of modified tumor peptides as a cancer vaccine strategy is warranted, exploring alternative approaches for boosting anti-tumor immunity.