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

ABSTRACT 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.