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An In Vivo Screen to Identify Short Peptide Mimotopes with Enhanced Antitumor Immunogenicity
Xuedan He1, Shiqi Zhou1, Breandan Quinn1
1Department of Biomedical Engineering, University at Buffalo, State University of New York, Buffalo, New York.
Abstract:
Tumor-associated self-antigens are potential cancer vaccine targets but suffer from limited immunogenicity. There are examples of mutated, short self-peptides inducing epitope-specific CD8+ T cells more efficiently than the wild-type epitope, but current approaches cannot yet reliably identify such epitopes, which are referred to as enhanced mimotopes ("e-mimotopes"). Here, we present a generalized strategy to develop e-mimotopes, using the tyrosinase-related protein 2 (Trp2) peptide Trp2180-188, which is a murine MHC class I (MHC-I) epitope, as a test case. Using a vaccine adjuvant that induces peptide particle formation and strong cellular responses with nanogram antigen doses, a two-step method systematically identified e-mimotope candidates with murine immunization. First, position-scanning peptide microlibraries were generated in which each position of the wild-type epitope sequence was randomized. Randomization of only one specific residue of the Trp2 epitope increased antitumor immunogenicity. Second, all 20 amino acids were individually substituted and tested at that position, enabling the identification of two e-mimotopes with single amino acid mutations. Despite similar MHC-I affinity compared with the wild-type epitope, e-mimotope immunization elicited improved Trp2-specific cytotoxic T-cell phenotypes and improved T-cell receptor affinity for both the e-mimotopes and the native epitope, resulting in better outcomes in multiple prophylactic and therapeutic tumor models. The screening method was also applied to other targets with other murine MHC-I restriction elements, including epitopes within glycoprotein 70 and Wilms' Tumor Gene 1, to identify additional e-mimotopes with enhanced potency.
Insights
Researchers developed a new method to create enhanced mimotopes (e-mimotopes) from tumor antigens. These modified peptides show improved cancer vaccine potential by boosting T-cell responses against tumors.
Area of Science:
- Immunology
- Oncology
- Vaccine Development
Background:
- Tumor-associated self-antigens are promising cancer vaccine targets but often lack sufficient immunogenicity.
- Current methods struggle to identify mutated self-peptides (enhanced mimotopes or e-mimotopes) that can elicit stronger T-cell responses than wild-type epitopes.
Purpose of the Study:
- To present a generalized strategy for developing e-mimotopes.
- To demonstrate the efficacy of this strategy using the murine tyrosinase-related protein 2 (Trp2) peptide Trp2180-188 as a model.
Main Methods:
- A two-step screening method was employed using a novel vaccine adjuvant that promotes peptide particle formation and potent cellular immunity.
- Position-scanning peptide microlibraries were created by randomizing individual residues of the wild-type epitope.
- Subsequent testing involved substituting each of the 20 amino acids at the identified key position to find optimal e-mimotopes.
Main Results:
- Single amino acid mutations at specific positions significantly enhanced antitumor immunogenicity.
- Two e-mimotopes with single amino acid mutations were identified, exhibiting improved cytotoxic T-cell phenotypes and T-cell receptor affinity compared to the wild-type epitope.
- Immunization with e-mimotopes led to superior outcomes in prophylactic and therapeutic tumor models.
- The screening approach successfully identified e-mimotopes for other cancer targets (glycoprotein 70, Wilms' Tumor Gene 1) with different MHC class I restriction elements.
Conclusions:
- The developed generalized strategy effectively identifies potent e-mimotopes with enhanced immunogenicity.
- These e-mimotopes represent a promising advancement for developing more effective cancer vaccines with improved therapeutic and prophylactic potential.
- The method's applicability to multiple targets and MHC restriction elements highlights its broad utility in cancer immunotherapy research.
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