Restoring tumor antigenicity activates the "bystander" T cell immune cycle

Area of Science:

• Immunology
• Oncology
• Biotechnology

Background:

• Tumor-specific T cells are crucial for immunity but often exhausted in the tumor microenvironment (TME).
• The TME contains abundant virus-specific "bystander" T cells (T_BYS) with anti-tumor potential.
• Limited efficacy of current cancer immunotherapies necessitates novel strategies.

Purpose of the Study:

• To develop a method for redirecting pre-existing T_BYS cells to recognize and eliminate tumor cells.
• To enhance anti-tumor immunity by leveraging the functional memory characteristics of T_BYS cells.
• To investigate the potential of intracellular delivery systems for cancer immunotherapy.

Main Methods:

• Designed an intracellular delivery system (ASCP) encoding a T_BYS epitope to redirect T cell specificity.
• Administered ASCP-antigen peptide to restore tumor cell antigenicity and induce epitope spreading.
• Incorporated unnatural amino acids (p-nitrophenylalanine, NiraTh) into MHC-II epitopes to stimulate CD4+ T cell immunity.

Main Results:

• ASCP effectively redirected T_BYS cells, leading to significant tumor inhibition in preclinical models.
• The strategy restored tumor cell antigenicity and induced broader T cell responses through epitope spreading.
• Stimulation of CD4+ T cell immunity via NiraTh-containing MHC-II epitopes aided CD8+ T cell tumor clearance.

Conclusions:

• ASCP-mediated tumor antigen reprogramming is a promising strategy for cancer immunotherapy.
• This approach can harness pre-existing T_BYS cells, particularly in individuals with prior viral infections.
• The findings offer new insights into enhancing T cell-mediated anti-tumor responses.