Subgenotype and genetic variability in the precore/core regions of hepatitis B virus in Korean patients with chronic liver disease

CD8+ T-Cell Response-Associated Evolution of Hepatitis B Virus Core Protein and Disease Progress

Under the immune pressure of cytotoxic T cells (CTLs), hepatitis B virus (HBV) evolves to accumulate mutations more likely within epitopes to evade immune detection. However, little is known about the specific patterns of the immune pressure-associated HBV mutation of T-cell epitopes and their link to disease progression. Here, we observed a correlation of the accumulated variants on HBV core protein (HBc) with the disease severity of HBV infection. Further analysis indicated that these substitutions were mostly located within CD8⁺ T-cell epitopes of HBc protein, which were systematically screened and identified in an unbiased manner in our study. From individual peptide level to the human leukocyte antigen I (HLA-I)-restricted population level, we elucidated that the mutations in these well-defined HLA-I-restricted T-cell epitopes significantly decreased antiviral activity-specific CTLs and were positively associated with clinical parameters and disease progression in HBV-infected patients. The molecular pattern for viral epitope variations based on the sequencing of 105 HBV virus genomes indicated that the C-terminal portion (Pc), especially the Pc-1 and Pc-2 positions, have the highest mutation rates. Further structural analysis of HLA-A*02 complexed to diverse CD8⁺ T-cell epitopes revealed that the highly variable C-terminal bulged peak of M-shaped HBc-derived epitopes are solvent exposed, and most of the CDR3βs of the T-cell receptor hover over them. These data shed light on the molecular and immunological mechanisms of T-cell immunity-associated viral evolution in hepatitis B progression, which is beneficial for designing immunotherapies and vaccines.IMPORTANCE The specific patterns of sequence polymorphisms of T-cell epitopes and the immune mechanisms of the HBV epitope mutation-linked disease progression are largely unclear. In this study, we systematically evaluated the contribution of CD8⁺ T cells to the disease progress-associated evolution of HBV. By evaluation of patient T-cell responses based on the peptide repertoire, we comprehensively characterized the association of clinical parameters in chronic hepatitis B with the antiviral T-cell response-associated mutations of the viruses from the single-epitope level to the overall HLA-I-restricted peptide levels. Furthermore, we investigated the molecular basis of the HLA-A2-restricted peptide immune escape and found that the solvent-exposed C-terminal portion of the epitopes is highly variable under CDR3β recognition. Our work may provide a comprehensive evaluation of viral mutations impacted by the host CTL response in HBV disease progression in the context of the full repertoire of HBc-derived epitopes.

Hepatitis B virus genotypes: epidemiological and clinical relevance in Asia

Hepatitis B virus (HBV) is characterized by a high genetic heterogeneity since it replicates via a reverse transcriptase that lacks proofreading ability. Up to now, ten genotypes (A-J) have been described, with genotype A and D being ubiquitous but most prevalent in Europe and Africa, genotype B and C being confined to Asia and Oceania. Infections with other genotypes such as E, F, G and H are also occasionally observed in Asia. Genotype I is rare and can be found in Laos, Vietnam, India and China, whereas genotype J has been described in Japan and Ryukyu. Novel variants generated by recombination and co-infection with other genotypes have gradually gotten worldwide attention and may be correlated with certain clinical features. There are substantial differences in HBV infection regarding prevalence, clinical manifestation, disease progression and response to antiviral therapy. Due to the complex interplay among viral, host and environmental factors, the relationship between HBV genotypes and clinical profiles remains incompletely revealed. In general, genotype A is associated with better response to interferon therapy; genotype C, and to lesser extent B, usually represent a risk factor for perinatal infection and are associated with advanced liver diseases such as cirrhosis and hepatocellular carcinoma; genotype D may be linked with poor response to interferon therapy. Future studies with better design and larger sample size are warranted to further clarify the controversial issues and guide the day-to-day clinical practice.