Personalized Neoantigen Vaccine Combined with PD-1 Blockade Increases CD8 Tissue-resident Memory T-cell Infiltration in Preclinical Hepatocellular Carcinoma Models

Background: Personalized neoantigen vaccine could induce a robust antitumor immune response in multiple cancers, whose efficacy could be further enhanced by combining with programmed cell death 1 blockade (α-PD-1). However, the corresponding immune response and synergistic mechanisms remain largely unclear. Here, we aimed to develop clinically available combinational therapeutic strategy and further explore its potential antitumor mechanisms in hepatocellular carcinoma (HCC).

Methods: Neoantigen peptide vaccine (NeoVAC) for murine HCC cell line Hepa1-6 was developed and optimized by neoantigen screening and adjuvant optimization. Then the synergistic efficacy and related molecular mechanisms of NeoVAC combined with α-PD-1 in HCC were evaluated by orthotopic HCC mouse model, single-cell RNA sequencing, tetramer flow cytometry, immunofluorescence, etc. The tumor-killing capacity of CD8 tissue-resident memory T cells (CD8 T) was assessed by orthotopic HCC mouse model, and autologous patient-derived cells.

Results: NeoVAC, which consisted of seven high immunogenic neoantigen peptides and clinical-grade Poly(I:C), could generate a strong antitumor immune response in HCC mouse models. Significantly, its efficacy could be further improved by combining with α-PD-1, with 80% of durable tumor regression and long-term immune memory in orthotopic HCC models. Moreover, in-depth analysis of the tumor immune microenvironment showed that the percentage of CD8 T was remarkedly increased in NeoVAC plus α-PD-1 treatment group, and positively associated with the antitumor efficacy. In vitro and in vivo T-cell cytotoxicity assay further confirmed the strong tumor-killing capacity of CD8 T sorting from orthotopic mouse HCC or patient's HCC tissue.

Conclusions: This study showed that NeoVAC plus α-PD-1 could induce a strong antitumor response and long-term tumor-specific immune memory in HCC by increasing CD8 T infiltration, which might serve as a potential immune-therapeutic target for HCC.