Landscape of T-cell exhaustion heterogeneity and HBV integration in virus-related HCC revealed by whole-exome, transcriptome, and single-cell sequencing

Background & Aims: To enhance our understanding of the tumor immune microenvironment (TIME) in hepatocellular carcinoma (HCC), we investigated the heterogeneity of T-cell exhaustion and its association with HBV integrations and direct oncogenic potential in HCC. Methods: We conducted a multi-omics analysis, including single-cell RNA sequencing, whole-exome sequencing, whole-transcriptome sequencing, and next-generation sequencing (NGS)-based HBV integration analysis, in eight patients with virus-related HCC. For validation, bulk RNA sequencing and NGS-based HBV integration analysis were performed in an independent cohort (n = 106). Results: Based on the expression scores of exhaustion markers in effector CD8⁺ T cells, patients were classified into high (n = 2) and low (n = 6) exhaustion groups (p <0.001). The high-exhaustion group exhibited higher clonal expansion (Gini index: 0.83 vs. 0.48, p = 0.006) and sharing of CD8⁺ T effector memory and cycling T cells with elevated exhaustion markers. This group also showed increased clonal expansion of CD4⁺ regulatory T cells and follicular helper T cells (p <0.001) with higher PDCD1 expression. In addition, the high-exhaustion group had higher TP53 mutation rates and signature scores for proliferation subtypes compared with the low-exhaustion group, who predominantly harbored TERT mutations. Moreover, the high-exhaustion group demonstrated more pronounced HBV integrations with elevated intrahepatic covalently closed circular DNA (cccDNA) and pregenomic (pg)RNA levels. Similarly, in the validation cohort, the high-exhaustion group (n = 28) demonstrated stronger proliferation subtype signatures (p <0.001), along with higher HBV integrations, S-fusion transcripts, and an increased intrahepatic viral reservoir (cccDNA/pgRNA) (p <0.05) compared with the low-exhaustion group (n = 78). Conclusions: Our study revealed the heterogeneity in T-cell exhaustion in the TIME of HCC, along with differences in HBV integrations and molecular subtypes. These findings provide insight into the intricate relationship between high exhaustion, proliferation subtype, increased HBV integrations, and enhanced HBV-induced oncogenic potential in virus-related HCC. Impact and implications: This study provides a comprehensive immune landscape of T-cell exhaustion using multi-omics analysis, offering critical insights into T cell heterogeneity in virus-related HCC. It establishes a strong association between higher HBV integration, enhanced oncogenic potential, T-cell exhaustion, and proliferation subtypes in HCC. Our results also establish a basis for personalized therapies tailored to the immune-exhaustion status within the TIME of each patient with HCC.