# Circular RNA-based HPV16 therapeutic vaccine elicits potent and durable antitumor immunity

## TL;DR

A new circular RNA vaccine targeting HPV16-related tumors shows strong immune responses and tumor regression in mice.

## Contribution

A novel circRNA-based therapeutic vaccine encoding HPV16 E7/E6 antigens is developed and shown to elicit durable antitumor immunity.

## Key findings

- Prime-boost vaccination with LNP-circRNAE7E6 induced functional antigen-specific cytotoxic T cells in mice.
- The vaccine caused significant changes in the tumor microenvironment, promoting immune activation and tumor regression.
- Vaccination sensitized non-inflamed tumors to immune checkpoint blockade therapy.

## Abstract

Human papillomavirus (HPV) 16 infection is associated with several human malignancies. Developing therapeutic vaccines holds great potential for patients who do not benefit from standard care. Circular RNA (circRNA) is an emerging next-generation platform for cancer vaccine development owing to its superior stability and convenient manufacturing process. Herein, we report development of a synthetic circRNA encoding fused HPV16 E7/E6 antigens encapsulated with lipid nanoparticles (LNP) to treat HPV16-related solid tumors.

The immunogenicity and anti-tumor immune response of the LNP-circRNA vaccine was determined in naïve C57BL/6 mice and TC-1 tumor-bearing mice, respectively. Changes in immune cells were examined using flow cytometry and immunofluorescence assay. RNA sequencing was used to identify differentially expressed genes and changes in the tumor microenvironment (TME) of tumors treated with LNP-circRNAE7E6 and empty LNP. Anti-tumor efficacy was further evaluated in LNP-circRNAE7E6 vaccine combined with anti-PD-L1 antibody treatment.

Prime-boost vaccination with LNP-circRNAE7E6 induced a large pool of functional antigen-specific cytotoxic T cells in both the peripheral blood and spleen. This immunization led to profound changes in the TME, characterized by the upregulation of immune activation genes, heavy infiltration of immune cells, and polarization toward a proinflammatory state. Consequently, circRNAE7E6 immunization could mediate complete tumor regression and prevent tumor growth. Moreover, vaccination sensitized non-inflamed tumors to immune checkpoint blockade therapy.

The present study results demonstrate that LNP-circRNAE7E6 vaccine is capable of eliciting robust anti-tumor immunity in the periphery and TME, highlighting the potential for treating HPV16-related cancers and preventing tumor recurrence.

The online version contains supplementary material available at 10.1186/s13046-026-03640-7.