Elevated tumor-associated antigen expression suppresses variant peptide vaccine responses

Area of Science:

• Immunology
• Cancer Research
• Vaccinology

Background:

• Variant peptide vaccines aim to broaden T cell reactivity against tumor-associated antigens (TAAs).
• Endogenous TAA expression and T cell tolerance can influence vaccine efficacy.
• Aging is associated with increased TAA expression and potential suppression of TAA-specific immune responses.

Purpose of the Study:

• To investigate how elevated endogenous TAA expression affects T cell responses elicited by variant peptide vaccines.
• To determine the impact of age-related changes in TAA expression on the cross-reactivity and functionality of vaccine-induced T cells.

Main Methods:

• Utilized a GP70 TAA model in BALB/c mice.
• Administered variant peptides to young and aging mice with varying GP70 expression levels.
• Assessed T cell cross-reactivity, binding affinity to AH1/MHC complexes, and ex vivo responsiveness.
• Analyzed precursor T cell phenotypes (PD-1, IL-7Rα) in naive mice.

Main Results:

• Elevated GP70 expression suppressed AH1 cross-reactive T cell responses in aging mice.
• Variant peptides elicited fewer AH1 cross-reactive T cells in older mice with detectable GP70.
• T cells expanded in aging mice showed reduced binding affinity and poor response to AH1 peptide.
• Tolerogenic administration of AH1 peptide before vaccination also suppressed responses.
• Naive T cells from mice with high GP70 expression exhibited anergic/deletion phenotypes (PD-1+, IL-7Rα-).

Conclusions:

• Increasing endogenous TAA expression diminishes the effectiveness of variant peptide vaccines in eliciting functional TAA cross-reactive T cells.
• Age-related increases in TAA expression contribute to immune tolerance and reduced vaccine efficacy.
• Complementary immunotherapies might enhance the expansion of T cells capable of recognizing TAAs, even with increased TAA expression.