A PD-L1 Nanobody-Engineered Synthetic RNA Virus Enhances Hepatocellular Carcinoma Immunotherapy by Interfering PCSK9 and Upregulating MHC-I.

Hepatocellular carcinoma (HCC) is characterized by low expression of major histocompatibility complex class I (MHC-I), which significantly limits the efficacy of immunotherapy. In this work, bioinformatic analysis finds that elevated PCSK9 in HCC correlates with reduced T cell activity and poor prognosis. Based on these discoveries, a PD-L1 nanobody-engineered synthetic RNA virus (αPDL1-VLPs/shPCSK9) is fabricated to inhibit PCSK9, thereby restoring MHC-I expression to enhance HCC immunotherapy. The αPDL1-VLPs/shPCSK9 is produced using MS2 virus-like particles (VLPs) in Escherichia coli (E. coli), displaying PD-L1 nanobodies and encapsulating PCSK9-downregulating shRNA. Notably, αPDL1-VLPs/shPCSK9 upregulates MHC-I to enhance cytotoxic T lymphocytes (CTLs) recognition of tumor cells while promoting M2-to-M1 macrophages polarization, thereby boosting immunotherapy. In vivo studies indicate that αPDL1-VLPs/shPCSK9 exhibits HCC tumor-targeting behavior, suppressing primary tumor growth while avoiding systemic toxicity. Immunological analysis confirms that αPDL1-VLPs/shPCSK9 enhances CTLs activation and infiltration, triggering systemic antitumor immunity to eradicate distant tumors. Overall, these findings highlight αPDL1-VLPs/shPCSK9 as a promising therapeutic strategy for reversing the multiple immunosuppressive characteristics of HCC, providing a streamlined yet comprehensive approach to potentiate immunotherapy.