Fine mapping of hepatitis B virus pre-S deletion and its association with hepatocellular carcinoma

Background Naturally occurring pre-S deletion mutants have been identified in hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC). Aims This study investigated whether specific deletions within the pre-S region were associated with HCC development. Methods The virologic characteristics of 56 HBV chronic carriers and 112 age-matched patients with HBV-related HCC were examined. Results The HCC patients had a significantly higher frequency of high viral load, basal core promoter mutation and pre-S deletion than chronic carriers. Sequencing analysis showed that the deleted regions were clustered mainly in the C terminus of pre-S1 (70.5%) and the N terminus of pre-S2 (72.7%) in HCC patients. Immuno-epitope mapping of these pre-S deletion sequences showed that all the deletion regions encompassed T- and B- cell epitopes and the B-cell epitope at amino acid 16 of pre-S2 was significantly deleted in HCC patients (60.0% vs. 0.0%; P similar to=similar to 0.036). Functional mapping of these deletion mutants showed that most of HCC patients lost one or more functional sites and the deletion of site for viral secretion (aa 15 of pre-S2 domain) was significantly detected in HCC patients than chronic carriers (62.5% vs. 0.0%; P similar to=similar to 0.029). Computational protein function prediction indicated that these mutants may have different molecular functions and participate in other biological processes compared with wild-type pre-S. Conclusions Deletion of B-cell epitope at amino acid 16 of pre-S2 region and the site for virion secretion are significantly associated with the development of HCC in HBV carriers.