Repurposing anti-viral subunit and mRNA vaccines T cell immunity for intratumoral immunotherapy against solid tumors.

Intratumoral (IT) immunotherapy can stimulate the tumor microenvironment and enhance anti-tumor immunity. We investigated IT delivery of three licensed viral vaccines-Shingrix (VZV shingles), Gardasil-9 (HPV), and Spikevax (SARS-CoV-2)-in prevaccinated mice using the murine tumor model TC-1, which expresses HPV16 oncogenes E6 and E7. Shingrix IT injection often induced tumor regression and resistance to secondary challenge. Injecting a VZV glycoprotein E (gE)-derived MHC-II-restricted peptide with polyI:C also led to durable remission, highlighting the role of gE-specific CD4⁺ T cells. While Gardasil-9 IT injection alone was ineffective, combining a HPV L1-derived MHC-I-restricted peptide with polyI:C or Shingrix enhanced tumor regression. Both approaches elicited CD8⁺ T cells against the E7 tumor viral oncoprotein. Tumor microenvironment analysis revealed remodeling of the myeloid compartment, significant induction of IFN-γ, TNF-α, and CXCL9 and broad gene expression reprograming. In a dual-flank model, IT injection of Shingrix with an MHC-I-restricted E7 tumor-specific peptide eliminated primary and non-injected tumors. Finally, Spikevax IT injection showed modest tumor growth delay, while improved control was observed with a SARS-CoV-2 spike-derived MHC-I-restricted peptide and polyI:C. These results demonstrate the potential of licensed vaccines as promising platforms for IT immunotherapy, either alone or combined with vaccine- or tumor-derived MHC-I-restricted peptide epitopes.