HBV-specific T-cell reactivity for prediction of HBsAg loss

Chronic hepatitis B (CHB) represents a severe global public health concern. The immune status of CHB patients exhibits significant heterogeneity, which not only influences disease progression and treatment response but also determines patient eligibility for novel immunotherapies, thereby necessitating the development of more precise immunological indicators. Studies have demonstrated that HBV-specific T cells significantly impact the outcome of HBV infection, the efficacy of antiviral therapy, and disease relapse following treatment discontinuation. More importantly, the characteristics of HBV-specific T cell responses do not align with traditional CHB staging (immune-active, immune-tolerant, inactive carrier, and reactivation phases) based on viral load and ALT levels. No significant correlation has been observed between HBsAg levels and the frequency or function of HBV-specific T cells . Additionally, ALT levels have shown no positive correlation with the frequency of HBV-specific T cells in either peripheral blood or liver tissue. Consequently, virological and biochemical markers cannot predict the strength of HBV-specific T cell immunity, underscoring the need for direct assessment of HBV-specific T cells. Unfortunately, direct assessment of HBV-specific T cells is highly complex, thereby impeding their clinical application. Owing to the polymorphism of human leukocyte antigen (HLA) molecules and the lack of a well-defined broad-spectrum T cell epitope repertoire suitable for diverse populations, universal detection methods and kits for HBV-specific T cell responses remain unavailable. In research settings, ELISpot or FluoroSpot assays based on overlapping peptide libraries of HBV proteins are commonly employed. However, studies have shown that most overlapping peptides currently in use are not real-world T-cell epitope peptides, and in ELISpot assays, T cell responses induced by overlapping peptides are substantially weaker than those induced by functionally validated T-cell epitope peptides. In our prior research, we successfully constructed an HBV-specific T cell detection system comprising 103 functionally validated CD8+ T cell epitopes, which comprehensively cover the major protein, and are compatible with HLA polymorphisms in Chinese and Northeast Asian populations. Therefore, we further applied it to 200 CHB patients undergoing pegIFN-α treatments to systematically evaluate the predictive performance of HBV-specific T cell reactivity for HBsAg loss.